Hot in Here: Local and Global Temperature Tolerance of Coral Reefs Based On Location

One of the biggest problems facing coral reef ecosystems is coral bleaching, a condition which occurs when the symbiotic algae inside coral expels itself from the host coral. This condition leads to the deterioration of the reef and possible death. This is very concerning for a country  like Belize as coral reefs provide a coastal barrier to currents and an entire ecosystem for fish.  Coral Reefs also mean big money. In 2007, Ninety percent (US$150-$195 million) of Belize’s tourism revenue came from snorkeling and reef related activities (Belize,United Nations).

The main culprit for this phenomenon is increasing ocean temperatures due to a creeping change in climate.  The year 2016 is shaping up to be a real nasty year for coral reefs with climatologists predicting it to be the hottest year on record. Considering the importance of temperature in coral reef sustainability, my travels in the Belize Barrier Reef made me curious about local and global differences in coral thermotolerance determined by their location in the sea.  I hypothesize there is little variation in temperature tolerance in local coral populations but great variation in distant populations.

I began my thermotolerance investigation looking at potential differences between reefs that are closer to channels versus reefs that are farther away.  Snorkeling in the warm channel of Hol  Chan inspired this hypothesis; however, no literature was found.  So, I went back to books and researched if there are temperature tolerance differences between coral that resides in the shallow water (inshore) where it might heat up quicker versus deep water (offshore) coral where the sun’s influence is less potent. Turns out that at least in the Florida Keys, there is a noticeable difference between the two groups. To get to this conclusion, a group from the University of Texas, led by Dr. Matz, performed a common garden experiment where they took samples of mustard hill coral from an inshore patch reef and an offshore reef and placed them into a communal lab environment where they experienced heat stress. After six weeks of heat stress, it was found that coral inshore experiences less instances of bleaching and faster growth compared to their offshore kin (Kenkel et. al 2013).  

(Mustard Hill Coral, photo courtesy of Wikimedia Commons)

Take note:  the coral species the researchers used were exactly the same.  Although they might look identical to the naked eye, differences in genetic expression or long term acclimation may have been the cause for the significant differences in the two populations. A similar experiment  looking at in- and offshore thermotolerance differences was conducted in the Vietnam reef.  Like Matz et al, this report produced similar results with inshore Porites lutea coral displaying greater energy production than their offshore counterparts (Faxneld, et. al 2011).  On the flipside, these reports do not necessarily mean inshore coral is inherently the thermotolerant one since in another species these researchers looked at (Galaxea fascicularis), the inshore variant displayed lower energy output compared to the offshore coral.

(location of all known reefs on earth, photo courtesy of NOAA)

We have  observed thermotolerance on a local level but what about a global scale?  Is there any variation if they share the same great sea and longitudinal lines?  Unsurprisingly there are differences in thermotolerance with a specific research interest in the Arabian Gulf, the hottest coral reef in the world. The average coral reef temperature ranges from  73° to 84° Fahrenheit (23°–29°Celsius) while the Arabian Gulf coral tolerates temperatures as hot as 97° Fahrenheit (36° Celsius)  (NOAA).  Because the symbiont algae is what determines if they will expel themselves from the coral, researchers have taken increased interest in discovering if the algae in Arabian Gulf coral  has any genetic similarities to other algaes.

Arabian Gulf, courtesy of Wikimedia commons

Out of seven species of coral sampled from an Abu Dhabi  reef, all of the symbiont algae belonged in the same phylogenetic clade C3, suggesting they all come from a similar common ancestor (Hume et. al 2013). This brings the possibility of propagating gulf coral into other parts of the sea but like every other biological puzzle, the phylogenetic similarity is not a silver bullet into cracking the global bleaching problem.  A recent report in Nature has shown that if you took the temperature-hardy Arabian Gulf coral into less saline environments that are common outside of the gulf, they perish faster than if they were in their native environment (D’Angelo et. al 2015).   

The bottom line is that yes, there are significant thermotolerance differences between coral reefs that are only miles from each other and corals that are oceans away.  Although the research is only in it’s infancy, there is a spark of promise that coral may exhibit some resistance to the rising temperature in the oceans.  The question, and controversy, still begs the question can or even should humans find a way to intervene with the rising coral bleaching rates? It is not the heaviest concern for me right now. Ask again later when my Old Kentucky Home becomes a beach house in 2500.

 

Sources:

Belize. United Nations. UN Secretary. Belize Country Report on The Protection of Coral Reefs As It Relates to The UN Secretary General Report.

D’Angelo, Cecilia, Benjamin CC Hume, John Burt, Edward G. Smith, Eric P. Achterberg, and Jörg Wiedenmann. “Local adaptation constrains the distribution potential of heat-tolerant Symbiodinium from the Persian/Arabian Gulf.” The ISME journal (2015).

Faxneld, Suzanne, Tove Lund Jörgensen, Ngai D. Nguyen, Magnus Nyström, and Michael Tedengren. “Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam.”Marine environmental research 71, no. 3 (2011): 225-233.

Hume, B., C. D’angelo, J. Burt, A. C. Baker, Bernhard Riegl, and Joerg Wiedenmann. “Corals from the Persian/Arabian Gulf as models for thermotolerant reef-builders: prevalence of clade C3 Symbiodinium, host fluorescence and ex situ temperature tolerance.” Marine pollution bulletin 72, no. 2 (2013): 313-322.

Kenkel, C. D., G. Goodbody‐Gringley, D. Caillaud, S. W. Davies, E. Bartels, and M. V. Matz. “Evidence for a host role in thermotolerance divergence between populations of the mustard hill coral (Porites astreoides) from different reef environments.” Molecular ecology 22, no. 16 (2013): 4335-4348.

NOAA. “In What Types of Water Do Corals Live?” In What Types of Water Do Corals Live? Accessed May 22, 2016. http://oceanservice.noaa.gov/facts/coralwaters.html.

Leaf-Cutters

While walking through the trails of La Milpa, everyday we came upon cleared paths in the forest, with small ants carrying leaves on their backs, on trails that seemed like they never ended. We learned that these were made by different species of leaf-cutter ants. Leaf-cutter ants forage for a variety of leaves and, “Culture a fungus on them, the specialized hyphae of which serve as their sole food source (Weber 1966, Hubbell and Rockwood 1980)” (Hubbell et al. 1980). This fungus lies within their large nests and they carry these leaves back to their nest to be cleaned, fertilized, and integrated for the fungus (Howorth, Paige). Everyday these leaf cutters forage for leaves since there is no storage form for the fungus and it must always be cultivated (Shepard 1982). The ants choose newer leaves and flowers over mature, as well as plants with a high water content (“Texas Leaf Cutting Ant, Atta Texana”) to better cultivate this fungus. If they choose the wrong leaves, the fungus can develop a parasite and will die within days, leaving the ants without a food source. This mutualistic relationship allows the fungus to grow and the ants feed off of the sprouting tips of the fungus (Howorth, Paige).

One thing you notice when you look at these trails, is that the ants are in a uniform line, and they do not stray from the path. After witnessing these ants in the forest and learning about their extensive job, I began to wonder how all of them stay so uniform while foraging. During a group project in Belize, I studied the way leaf cutter ants react to objects placed on their trails. One of the specific tests we performed was to take our shoe and rub part of the trail they were on and observe its effects. When we erased this trail, it was amazing to see the ants hesitate for so long whether to turn back or continue on their path. This made me think that there has to be a chemical component involved in the trail making process. I wanted to try and figure out if the ants lay down some sort of chemical when making a trail, and what the chemical composition is.

Since these leaf cutter ants appear to have such an imperative role to this fungus, they must be resourceful and efficient when foraging. Stephen Hubbell performed a study to watch the trails that these ants forage on. Leaf cutter ants lay down a, “Trail

-Fig A: Alternate route formed from main trail (heavy black) to the breadcrumbs (black dot) Source: Hubbell et al. 1980.

 

pheromone [which] helps to guide the workers between nest and food source (Wilson 1971, Moser and Blum 1963)” (Hubbell et al. 1980). They placed a species of breadcrumbs called, bursera iimaruba, a preferred tree species for Atta cephalotes, one meter from an established trail (Figure A) (Hubbell et al. 1980). The black dot is where the breadcrumb was placed, and illustrates how a trail was formed off of the main trail (heavy black line) (Hubbell et al. 1980). What they observed is that the ants were able to diverge from their path, but also get back to it as well. This was because they observed that the ants were touching the abdomen of their bodies to the ground repeatedly; which is a behavioral sign that means they are depositing a pheromone on the ground (Hubbell et al. 1980).

Fig B: Anatomy of a leaf cutter ant for pheromone detection and production. Source: Leaf Cutter Ant Communication. (n.d.). In AntARK. Retrieved May 21, 2016.

This is the way ants can start new trails and allow them to get back to their nest without confusion. By laying down this pheromone, they communicate with the rest of the worker ants the quality and direction of the patch (Shepard 1982). One study also found a strong correlation (r= 0.940, P< 0.01) that the more developed a trail is, the higher the input of substrate (leaves) will be for the nest (Fowler 1978).

This pheromone trail is how these ants can form extensive trails without losing their way from the nest. They can extend more than 100 meters from the nest and they’re visible on the forest floor (Wetterer et al.). Leaf Cutter ants completely clear a trail for them to forage on and ensure they get back to their nest. It’s incredible to see the distance in the forest itself, because they stick out so much in the surroundings. We experienced a lot of these while hiking at La Milpa, since you can see the ants

Figure C: Leaf cutter ant trail in La Milpa. Taken by: Marissa Coutinho

actively carrying leaves on their backs to and from their nest.  Above, is a picture of just a small portion of a trail I saw while hiking at La Milpa.

Once I determined that there is a chemical component to these trails, I began researching the breakdown of the pheromone. However, my results were a bit inconclusive due to the hundreds of different species of leaf-cutter ants as each species has their own chemical makeup for the different pheromones they lay down (Attygalle & Morgan 1985). While this was frustrating, when I thought further about it, every species will have different pheromone so that different species don’t cross paths and interfere nests while foraging.

So what we were experiencing while at La Milpa was the extensive trail development process leaf-cutter ants go through so they can cultivate and protect the fungus in their nest. Disrupting even a small portion of that pheromone trail will disrupt the whole process, and this can ultimately lead to the fungus dying in their nest. Pheromones play such a vital role in helping these leaf-cutter ants thrive in these dense forests.

 

Works Cited

Attygalle, A., A., & Morgan, D., E. (1985). Ant Trail Pheromones. Advances in Insect Physiology, 18, 3-20..

Fowler, H. (1978). Foraging Trails of Leaf-Cutting Ants. Journal of the New York Entomological Society, 86(3), 132-136.

Howorth, P. (n.d.). A Leaf Cutter Ant Playlist. Retrieved May 22, 2016.

Hubbell, S., Johnson, L., Stanislav, E., Wilson, B., & Fowler, H. (1980). Foraging by Bucket-Brigade in Leaf-Cutter Ants. Biotropica, 12(3), 210-213

Leaf Cutter Ant Communication. (n.d.). In AntARK. Retrieved May 21, 2016.

Shepherd, J. (1982). Trunk Trails and the Searching Strategy of a Leaf-Cutter Ant, Atta colombica. Behavioral Ecology and Sociobiology, 11(2), 77-84.

Texas Leaf Cutting Ant, Atta texana. (n.d.). Retrieved May 20, 2016.

Wetterer, J., Shafir, S., Morrison, L., Lips, K., Gilbert, G., Cipollini, M., & Blaney, C. (1992). On- and Off-Trail Orientation in the Leaf-Cutting Ant, Atta cephalotes (L.) (Hymenoptera: Formicidae). Journal of the Kansas Entomological Society,65(1), 96-98.

Taste and See: Flamingo Tongues Take Over Sea Fans

The Flamingo Tongue looks beautiful attaching ever so gently to the Sea Fan as it sways back and forth in the current, catching plankton. Do not be fooled! There is a lot more going on besides the pretty snail attaching to the Sea Fan. Flamingo Tongues are gastropod mollusk’s that feed on Sea Fans.

Flamingo Tongue on Sea Fan off the coast of Belize. Photo taken by Claire Mielcarek.

 

Known as the “gorgonian specialist,” Cyphpoma gibbosum, or “The Flamingo Tongue” is an occupant of the common Sea Fan (Slattery, 1999). The orange, white and black coloration serves as a warning to predators. In other words, it is aposematic. On the other hand, predators of the snails are protecting the gorgonians and Sea Fans because, according to Burkepile and Hay (2007), when the large predators were removed from parts of the Florida Keys the Flamingo Tongue snail population increased and damage to gorgonian corals was more often and extensive (Shapiro, L).

The Common Sea Fan (Gorgonia ventalina) is within the order Gorgonacea and category Gorgonians (Caribbean Reefs). Gorgonians are apart of the Order Alcyonacea, which include soft corals and leather corals, and subclass Octocorallia, which are coral with the structural feature being eight: eight tentacles or septae (Brough). Therefore, the common Sea Fan is an octocoral, fan-shaped, and composed of calcite and gorgonian. It is a filter feeder with tissue that contains dinoflagellates to photosynthesize so the host coral can obtain the organic carbon compounds (Gorgonia ventalina). In terms of responding to stress, Gorgonia ventalina responds to temperature and fungal stress by increasing ameobocytes. They use cellar defenses to survive during stressful climate events (Mydlarz et al. 2008). Gorgonia ventalina is found in the Western Atlantic and Caribbean Sea where there is a strong current (Gorgonia ventalina).

Chiappone et al. studied the distribution of gorgonians occupancy of Cyphpoma gibbosum (Flamingo Tongue Snails) in terms of not only the habitat of the region, but also the spatial distribution of the gorgonians. The paper wanted to know if the occupancy of gorgonians by Flamingo Tongues was due to having a preferred host, or simply the gorgonian’s availability. It was not a question of if the Flamingo Tongue preferred the Sea Fan, because of 129 snails all but one were on gorgonian colonies (Chiappone et al. 2003). In terms of the first question they addressed, habitat of the region, more Flamingo Tongues were found in fishing areas rather than protected areas. In terms of the second question addressed in the paper, (availability of gorgonians and preference of snails) the Sea Fan (G. ventalina) was occupied with the Flamingo Tongues in proportion to the abundance of the Sea Fans. Even though 20% of the gorgonians sampled was Plexauridae, over 60% of the Flamingo Tongue spotting were on this family of coral (the most common spotting). Furthermore, when they were spotted, 58% of them were individuals (38% in pairs) on gorgonians (Chiappone et al. 2003).

Flamingo Tongue feeds on sea Fan. Photo Courtesy of Diego Ávila of Peachin & Peachin.

 

The snails do not just live and feed on the Sea Fans, but they raise juvenile snails there as well. After the snail has fed on a coral, eggs will be laid on the coral and about a week later they hatch. After hatching they usually fall onto other gorgonian coral and remain on the underside of the coral branches until they are visible adults. The adults, when feeding, scrape off the polyps of the coral, but this is not lethal to the host (Shapiro). Corals that are damaged by grazers have the ability to regenerate. Henry and Hart found that coral regeneration impairs the coral’s ability to defend themself and reduces parts of its sexual reproduction. Furthermore, smaller, older corals regenerate less well than others (Henry & Hart 2005). If a coral is small, old and regenerating, then it is extremely vulnerable to the Flamingo Tongues grazing and reproduction behaviors. Although not all of the snails grazing kill the coral, over time the coral cannot regenerate and protect its polyps from the snails.

There are still remaining questions about preference and patterns of Flamingo Tongues occupancy. Lasker et al. researched patterns of the Flamingo Tongue on octocorals. Movement patterns, host selection, feeding patterns, and resident time on the host are all factors of snail occupancy that were studied. This paper mentioned that there might be a preference of the snail because of mating and egg laying behavior of the Flamingo Tongues. Also, this paper found no difference in picking prey or feeding pattern of snails to gorgonians that were toxic (Lasker, Coffroth & Fitzgerald 1988). Mark Slattery found that Sea Fans with a fungal infection had a greater amount of Flamingo Tongues on them than uninfected Sea Fans (Slattery 1999).

The findings of these papers beg future research on if there is a preference of the snails egg laying specifically if the gorgonian is toxic or infected by a fungus. If there is not, then the research needs to be taken one step further to figure out if the snail has a certain enzyme that allows it and its larvae to handle toxic substances and why the snail prefers the infected coral. Maybe on gender of the snail has the ability to fight off the toxin while the other doesn’t so one protects the larvae while the other goes to mate again and find another gorgonian.

Questions remain with the mating patterns and population of predator fish. When predators are around there are going to be fewer Flamingo Tongues and therefore less damage to Sea Fans. When fish are around that avoid the snails because of their aposematic features, then there are going to be more snails and damage to the Sea Fans. In which situation is there going to be more mating competition? When there are fewer snails around because of the predators, or when there are more Sea Fans being occupied by the snails and their larvae and therefore less availability of places to raise the juvenile? There is room for future research in the mating behaviors in the presence of certain predators.

In conclusion, it is not just the shape of the Sea Fan that attracts the Flamingo Tongue, but social interactions, grazing time, reproduction habits, and abundance of gorgonians. The snails use the Sea Fans to not just graze and damage polyps, but to lay their eggs and for their juvenile to grow up and live. They have species preference, according to Chiappone et al. and even habitat preference because their predators are being extracted in fishing areas.

References

Brough, C. What Are Gorgonians. http://animal-world.com/aquarium-coral-reefs/what-are-gorgonians.

Caribbean Reefs. http://reefguide.org/carib/commonfan.html.

Chiappone, M., Dienes, H., Swanson, D.W. & Miller, S.L. (2003) Density and Gorgonian host-occupation patterns by Flamingo Tongue snails (Cyphoma gibbosum) in the Florida keys. Caribbean Journal of Science, 39, 116–127.

Gorgonia ventalina. 2013, March 22. Wikimedia Foundation. https://en.wikipedia.org/wiki/gorgonia_ventalina.

Henry, L.A. & Hart, M. (2005) Regeneration from injury and resource allocation in sponges and corals – A review. International Review of Hydrobiology, 90, 125–158.

Lasker, H.R., Coffroth, M. a & Fitzgerald, L.M. (1988) Foraging patterns of Cyphoma gibbosum on octocorals: the roles of host choice and feeding preference. The Biological Bulletin, 174, 254–266.

Mydlarz, L.D., Holthouse, S.F., Peters, E.C. & Harvell, C.D. (2008) Cellular responses in Sea Fan corals: Granular amoebocytes react to pathogen and climate stressors. PLoS ONE, 3.

Peachin, M., and D. Ávila. 2014. FLAMINGO TONGUE ON SEA FAN DIEGO AVILA. SCUBA DIVING IN SANTA MARTA, COLOMBIA. photographPeachin & PeachinSanta Marta.

Shapiro, L. Flamingo Tongue Snail – Cyphoma gibbosum – Overview – Encyclopedia of Life. http://eol.org/pages/593724/overview.

Slattery, M. (1999) Fungal pathogenesis of the Sea Fan Gorgonia ventalina : direct and indirect consequences. Chemoecology, 9, 97–104.

 

Medicinal Miracles?

        Evidence of Mayan nutritional and medicinal use of plants has been found from as early as the Classical Mayan Period (Abramiuk 2011). In many areas of Central America, there are still large communities that rely of this traditional medicine and medicine men that are highly valued. However, it seems that if these miracle cures were actually as effective as are claimed to be, there would be much more integration of them into Western medicine. Traditional Mayan medicinal plants, such as Moringa oleifera and Datura stramonium, may help to alleviate symptoms of various diseases, but will do so by creating a euphoric effect, not by curing the disease.
As recently as 2000, 75-80% of the world population relied heavily on herbal medicine (Kamboj 2000). This type of health care was (and is) most prominent in developing countries where there is better cultural acceptability as well as better observed compatibility with the human body and lesser side effects. While many people trust these types of medicine, are there any scientific findings to support their beliefs?
One of the most widely used medicinal plants is Moringa oleifera. Called the “miracle plant” by some, Moringa is biologically known to have very high quantities of minerals, protein, vitamins, beta-carotene, amino acids and phenolics (Anwar 2007). All of these properties have many nutritional values and cures for many illnesses have been scientifically recorded. One of the most impressive uses is for cardiovascular disorders. Moringa acts as a diuretic and this along with its lipid and blood pressure lowering chemical constituents have been shown to greatly stabilize blood pressure. Researchers believe that isolating more chemical compounds and components in this plant is crucial to fully understanding its medicinal value. There has been much speculation that Moringa has tumor inhibitor components which could be crucial to advancement of modern cancer treatment.
Another commonly used plant Datura stramonium, or Angel’s Trumpet, is a highly toxic and hallucinogenic plant that is illegal in most parts of the world. In some places, it is used by traditional medicine men for pain relief. While there is no evidence that this plant cures the source of the disease, there is no doubt that it is highly toxic. There have been many reported hospitalizations from ingestion, both accidental and intentional, of Angel’s Trumpet (Wiebe 2006). Symptoms include decreased level of consciousness, visual hallucinations, dilated pupils, and agitation. The euphoric high received by consuming this plant has been compared to the effects of marijuana.

Often, there is a strong belief that herbal medicines have only positive effects, and no negative ones. The idea that natural compounds, specifically plants, can be ingested and act as a miracle cure is a dangerous myth. While there has been evidence of its ability to alleviate symptoms of a wide variety of illnesses, there is still little understanding of how these interactions occur in the body, and taking them without approval from a doctor can be dangerous (Miller 1998). The idea that natural is best only applies under observations from a doctor, especially when taken with other medicines.
While I strongly believed there was little legitimate evidence for the effectiveness of traditional herbal medicine, there has been research done that shows successful treatment. Part of my doubts may have come from unfair beliefs that western medicine is better than other traditional medicines. However, there is still a lot that is unknown about herbal medicine and research could lead to many great discoveries.

Anwar, F., Latif, S., Ashraf, M., & Gilani, A. H. (2007). Moringa oleifera: a food plant with multiple medicinal uses. Phytotherapy research, 21(1), 17-25.
Abramiuk, M. A., Dunham, P. S., Cummings, L. S., Yost, C., & Pesek, T. J. (2011). Linking Past and Present: A preliminary paleoethnobotanical study of Maya nutritional and medicinal plant use and sustainable cultivation in the Southern Maya Mountains, Belize. Ethnobotany Research and Applications, 9, 257-273.
Kamboj, V. P. (2000). Herbal medicine. CURRENT SCIENCE-BANGALORE-, 78(1), 35-38.
Miller, L. G. (1998). Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Archives of internal medicine, 158(20), 2200-2211.
Wiebe, T. (2008). Angel’s Trumpet (Datura stramonium) poisoning and delirium in adolescents in Winnipeg, Manitoba: Summer 2006.

Evading the Toxic Takeover

Lionfish, Photo by NOAA.

Jumping off the back of the large pontoon boat, Goliath,  in seas off the coast of Belize, the guides have their snorkel gear on, mindset, and a two-pronged spear in hand.  These locals were ready, but for what exactly? After their first spear in between the crevices of the bright coral, I finally figured out that they were hunting lionfish, which have invaded the waters and wrecked havoc on the surrounding ecosystem.

The lionfish, with its flowing, fancy pectoral fins and visually enticing, red zebra stripe pattern, is one of the most dangerous fish in the ocean due to its seemingly delicate, yet highly venomous spines on the dorsal.  They have become one of the main nuisances for reef life as well as citizens of the Caribbean area to the point that they are being hunted as a sport.  The invasion of the lionfish has been attributed, via genetic and dispersal studies, to the introduction of the Indo-Pacific species in the 1990s to the Atlantic ocean by humans, which created an unfortunate founders effect with low genetic diversity (Ricardo, et al. 2011). The lionfish are now found along the eastern coast of the United States all the way down to South America in high density, especially against the barrier reef systems (Morris, et al. 2009).

The invasion of Indo-Pacific lionfish are thriving by outcompeting for resources and decimating native reef. The question that I had as I was watching the terrifying slaying actions of the guides, though, is, what makes the lionfish so successful? After a bit of research, I decided that despite their charming, seductive looks, the spikes of the lionfish, which are extremely toxic must decrease the ability of predators to create a natural bio-control. As a result, their population densities are increasing further, and becoming unmanageable, especially for the sake of reef conservation.

The lionfish contains a total of 18 spines (13 dorsal, 3 anal, and 2 pelvic) to provide a 360-degree protection from predation. Envenomation occurs when the glandular tissue encasing the spine is depressed, exposing the venom producing tissue (Morris).  Venom encompassing acetylcholine and variable neurotoxins diffuse through the devised puncture wound to enter the victim’s body and, eventually, bloodstream to cause effects as minor as swelling to as serious as paralysis (Cohen, et al. 1989).  This would definitely be a red flag to avoid at all cost, especially as a fish trying to survive in the incredibly competitive reef system.

Known predators of the lionfish are few to none after they have entered into the juvenile stage of the fish development cycle. The female lionfish lays thousands of eggs at a time, which are carried by the current until they are large enough to swim (Morris).  Many of the eggs are eaten before hatching, but the survivors have a much better chance of life continuation due to their toxic spikes as protective mechanisms.

There are a few studies on possible predation of the lionfish. For starters, lionfish have been found in the stomachs of some Caribbean grouper, but surveys have shown that the biomass of groupers is less than a seventh of the lionfish, making the odds of being an actual bio-control practically impossible (Mumby et al. 2011). Mumby’s actual results were vague and not as promising for the conservation of the reefs as “grouper predation of lionfish… as a biocontrol of the invasive species is unknown.” A second study attempted to observe sharks and other top of the food chain area-native predators and their interactions with lionfish (Hackerott et al 2013). However,  Bruno’s results showed that “native predators do not influence the colonization or post-establishment population density of invasive lionfish on Caribbean reefs.”  Unfortunately, other research regarding lionfish and predation for bio-control has concluded no different from Mumby’s or Bruno’s.  Locals are extremely worried and discouraged about the ecological aspect of  the continued destruction of the reefs and decimation of native fish.  The future of these reefs and species inhabitants is unclear at the rate that the population of lionfish is growing (Morris).

Due to the lack of predation, the lionfish population is running amok with its strong defenses to outcompete the native species of the reefs. Albins conducted multiple separate studies to compare the lionfish to native predators of the coral-reef fish communities, and showed that the lionfish correlated to a reduction almost 3 fold to similar sized coney grouper, creating a deleterious effect on the reef system by decreasing forage fish recruitment by approximately 79% (Albins, Hixon 2008; Albins 2013). So, fewer native fish are remaining in the vicinity where the lionfish reside, which affects not only the food chain but also the symbiotic and mutualistic relationships between the various fish and corals, such as small fish that aid in cleaning the coral or even the gobies guarding the blind shrimp’s sand door. Ultimately, the entire ecosystem is being affected by the invasion of the lionfish.

The Lionfish Derby is a sporting competition that is supported by the government to aid in the ever-growing population of lion fish. Photo by GoPro Julianne Smith.

In order to combat the extremity of the situation, fishermen, conservationists, divers, and locals have come together with a common goal of killing these organisms upon detection.  Local markets and restaurants in the Caribbean are using them for meals rather than other local fishes to prevent further depletion of the native populations (Hackerott). The authorities have even stepped in to create lionfish derbies to see who can kill the most lionfish within a set time period—basically creating a new sport in both their and the reef’s best interest.  After visiting Belize, seeing some of the local sales and menus of fish, and talking to the guides, I can put this research into perspective with how destructive the lionfish have been to the intricate reef ecosystem, and to my (and anyone else concerned about ecology) dismay, it is only getting worse. Locals and visiting researchers have been oh so careful throughout the years studying in the reefs to leave it as they found it, and having a single species come in and leave a path of destruction is catastrophic at best. The venom contained in the spines of the lionfish may be the reason for the lack of predators and bio-control. Further research and observations would need to be conducted in order to see the actual correlation and determine other variables that may affect the predation of lionfish. But, at this point, I am all for becoming a “lion slayer” just to help reverse the effects of the invasion!

References

Albins, M. A. (2013). Effects of invasive Pacific red lionfish Pterois volitans versus a native predator on Bahamian coral-reef fish communities. Biological Invasions, 15(1), 29–43. doi:10.1007/s10530-012-0266-1

Albins, M. A., & Hixon, M. A. (2008). Invasive Indo-Pacific lionfish Pterois volitans reduce recruitment of Atlantic coral-reef fishes. Marine Ecology Progress Series, 367, 233–238. doi:10.3354/meps07620

Cohen, A. S., & Olek, A. J. (1989). An extract of lionfish (Pterois volitans) spine tissue contains acetylcholine and a toxin that affects neuromuscular transmission. Toxicon, 27(12), 1367–1376. doi:10.1016/0041-0101(89)90068-8

Hackerott, S., Valdivia, A., Green, S. J., Cote, I. M., Cox, C. E., Akins, L., Layman, C.A., Precht, W.F.,  Bruno, J. F. (2013). Native Predators Do Not Influence Invasion Success of Pacific Lionfish on Caribbean Reefs. PLoS ONE, 8(7). doi:10.1371/journal.pone.0068259

Morris Jr, J., Akins, J., & Barse, A. (2009). Biology and ecology of the invasive lionfishes, Pterois miles and Pterois volitans. Proceedings of the Gulf …, 61, 1–6. Retrieved from http://www.tflats.com/app/webroot/userfiles/66/File/morrisetal_2009.pdf

Mumby, P. J., Harborne, A. R., & Brumbaugh, D. R. (2011). Grouper as a natural biocontrol of invasive Lionfish. PLoS ONE, 6(6). doi:10.1371/journal.pone.0021510

NOAA Center for Coastal Fisheries and Habitat Research.  Lionfish Picture. Retrieved from http://www.noaanews.noaa.gov/stories2004/s2227.htm

Ricardo, B. R., Hines, A., Arturo, A. P., Orto, G., Wilbur, A. E., & Freshwater, D. W. (2011). Reconstructing the lionfish invasion: Insights into Greater Caribbean biogeography. Journal of Biogeography, 38(7), 1281–1293. doi:10.1111/j.1365-2699.2011.02496.x

Hummingbird Feeders: A blessing and a curse?

Caitlin Raley

Before going to Belize I thought of hummingbirds as docile little creatures who went through life serenely sipping nectar from flowers, but upon arriving at La Milpa Ecolodge I was quickly shown how aggressive and territorial these little guys can be. There were three species clamoring for a location at one of the many feeders around the dining area, and it amused me to no end to see them give chase to each other. Of the three species found two were identified as the White Necked Jacobin, and the Buff Bellied Hummingbird, while the third, given its very common coloration and tendency to not sit still, went unidentified. These interactions sparked an interest in how these feeders could potentially cause conflict between species that normally would never come into contact with each other, and how these conflicts can have impacts on the energy expenditures for them.

Buff Bellied Hummingbird at Feeder

White Necked Jacobin at Pond

But first it may be pertinent to start with why animals, with such similar life histories, would actually never meet, or at the very least never fight. Even though all hummingbirds drink nectar, not all hummingbirds use the same flowers due to physical constraints like beak size, or perhaps they use them at different times of the day, or even they forage in different habitats, as is the case for the White Necked Jacobin, and the Buff Bellied hummingbird, two of the three species found at La Milpa’s feeders. The Jacobin is primarily a canopy dweller, except when there are feeders to be found. And the Buff Bellied prefers open woodlands, and second growth clearings.

White Necked Jacobin at Feeder

Buff Bellied Hummingbird taking flight

These hummingbirds under normal circumstances would never come into contact with each other due to these differences in habitat preference, but the feeders draw them in together. Feeders lack some of the things that can exclude certain species from capitalizing on certain flowers. The Sword Billed Hummingbird, whose bill is longer than the rest of its body, can capitalize on flowers such as the Passiflora mixta, which has an extremely long corolla. While this species was not observed at La Milpa feeders, it does serve to illustrate the specificity that hummingbirds exhibit with their food resources. Birds with much shorter bills will not be able to get to the nectar at the bottom of the corolla, which would mean that those short billed hummingbirds would not compete with the Sword Billed for that food source. Feeders do away with this kind of exclusion by providing easily accessible sugar water at all times. Any kind of hummingbird can use it, not just ones with extraordinarily long bills or ones that feed high in the trees as is the case with the Jacobin.

Passiflora mixta with Sword Billed Hummingbird. Note the extremely long bill in comparison to the body.

All hummingbirds walk a razor thin line between energy gained and lost. They must enter a hibernation like state called torpor every night just to survive without eating. If they are unable to do this, or go too long without eating they will die because their metabolism is so fast, and they do not store much energy because it hampers flight. It was intriguing to think about how the constant availability of a high quality food source such as the La Milpa sugar water would alter the number of defense activities of the hummingbirds, and how that might alter their energy requirements.

Research has shown that when the resource value for a territory increases, the territory defenses will increase as well. This was shown in the the Dearborn 1998 study, and the Camfield 2006 study. In the Dearborn study increased resource value by injecting extant flowers with sucrose solution increasing the yield. The other study had three different solution concentrations, 10%, 20%, and 30%. Both of these studies all looked at territorial species just like the Jacobin.So it stands to reason that the Jacobin would behave in much the same way when presented with a high value resource such as a near infinite supply of food from a feeder. That should mean that Jacobins choosing to utilize the feeders at La Milpa are spending more time chasing away rivals, of which there were many, than Jacobins that do not have access to feeders which are easily defensible, and are a limitless resource when compared to flowers that can only provide a small amount of nectar at a time. This would cause them to increase their energy output due to burning calories by chasing or fighting with other hummingbirds.

For the Dearborn study, the intruder’s size was also examined, and it was found that the size of the intruder had a negative correlation with the number of territory defenses. However, this negative correlation lessened when the resource value of the territory was increased by injecting extant flowers with sugar solution to increase their yield.

The Powers and McKee 1994 study, the territoriality was investigated in response to changing food availabilities for a Blue Throated Hummingbird’s territory. Sucrose solution in syringes was left out consistently without limit to the amount or the territory was only given 32mL of solution per day. On restricted days 48% of interspecific intruders were chased, while on unrestricted days only 11% were chased. Intraspecific intruders were chased 81% and 80% of the time on unrestricted and restricted days respectively, giving a new element to the intricacies of hummingbird interactions where intraspecific and interspecific intruders will be treated differently.

In the Tiebout 1993 study two species of hummingbirds were evaluated to see the costs of competition between them. One was the territorial Amizilia saucerottei, and the other was the trapline feeding Chlorostilbon canivetii. They were monitored for many variables that can indicate dominance, and energy expenditure. These birds were paired in heterospecific and conspecific pairs, and the activities of these pairs was compared to individuals that served as controls. For paired birds there was a 25% increase in hovering, and an overall 13% increase in energy expenditure, which illustrates that the presence of rivals has a marked impact on the energy balance of these birds. These costs can be offset by taking in larger meals, which is afforded to the bird who wins control of the feeder. Normally the winner is the territorial species, which, in the case of La Milpa is the Jacobin.

Another study focusing on the habits of a territorial hummingbird species was the Lyon, Crandall, and McKone 1977 study. A territory was artificially increased to an area of 85m2 by moving feeders out further away from one another making it more difficult for the resident male Blue Throated Hummingbird to defend the boundaries of his territory. As the territory got larger the male spent more time chasing, and foraging to make up for the increased energy expenditure. Another interesting factor to this study was that as the territory size increased the number of different species allowed to forage increased as well, mostly due to the fact that it was impossible for the male to chase all of them off. I suspect that this is one of the reasons we see multiple species at the La Milpa feeders. For the very few territorial hummingbirds that reside in the area, there are too many feeders spaced too far apart to adequately defend all of them.

Hummingbird feeders are a great way to draw in many types of hummingbirds, but they do cause conflict between species that may never come into contact with one another. These conflicts can have significant effects on the energy allocation of the birds, and will result in altered behavior be it increased agonistic activities, increased food intake, or both. For endangered species having access to feeders like these has the potential to increase their survivorship, and reproductive output because it lessens the burden of finding enough food, but there is a downside to these feeders as we have seen.

 

References:

Camfield, A. F., 2006. Resource Value Affects Territorial Defense by Broad-Tailed and Rufous Hummingbirds. Journal of Field Ornithology. 77:120-125.

Dearborn, D. C. 1998. Interspecific Territoriality by a Rufous-Tailed Hummingbird ( Amazilia tzacatl ): Effects of Intruder Size and Resource Value. Biotropica. 30:306–313.

Lyon, D. L., Crandall, J., and McKone, M. 1977. A Test of the Adaptiveness of Interspecific Territoriality in the Blue-Throated Hummingbird. The Auk. 94:448–454.

Powers, D. R., and T. McKee. 1994. The Effect of Food Availability on Time and Energy Expenditures of Territorial and Non-Territorial Hummingbirds. The Condor. 96:1064-1075.

Tiebout, H. M. 1993. Mechanisms of Competition in Tropical Hummingbirds : Metabolic Costs for Losers and Winners. Ecology. 74:405–418.

Jaws of Life: The powerful suction mechanism of the nurse shark

The time spent in Ambergris Caye was truly incredible. For me, it was not just because of all the beautiful coral or colorful and intriguing fish, but the intensity and gentleness of the nurse shark. The nurse shark is a moderately sized shark, which makes it hard to believe that it uses suction feeding, rather than other feeding tactics typically thought of when the “shark” is in conversation. Their power led me to wonder how such a large animal could feed in this particular way, when their relatives fed so differently. From my curiosity, I hypothesized that nurse sharks evolved to be bottom feeders due to competition and therefore, their feeding mechanism evolved as well.

The anatomy of the shark is to be contributed to cause this suction feeding. Nurse sharks have a downward facing mouth that is positioned slightly lower on the face when compared to several other sharks. This allows them to be better equipped to feed along the ocean floor as bottom dwellers. The teeth of these sharks are broader and serrated, which especially allows them to tear, crush, and hold on to their prey, unlike great whites, who simply rip large chunks of flesh from the animal with incredibly large and sharp teeth. Nurse sharks have independent arrangement of teeth, as most sharks do, meaning that there is no overlap in the teeth and that shedding is not dependent on other teeth (FLMNH). Moss (1965) states that the sharks adaptations allows for a suction pump technique and the mouth possess thick lips that are removed from the jaw. The nurse shark possess all of the qualities primarily used for suction feeding. Each of these being a small, laterally enclosed gape, reduced tooth arrangement, rapid expansion of the cheeks/ sides of mouth, and top hyoid depression after peak gape. Motta et al. (2001) found that nurse sharks couple head elevation with depression of the jaw in order to open the mouth as much as possible as well as direct the prey toward the back of the opening, allowing the mouth to envelop the prey entirely. Although they do not exactly exhibit inertial suction feeding (the type of feeding used by bony fish), their tactics are extremely close to functionally replicating those found in bony fish. Motta also explains that when the nurse shark approaches a food source, the jawbone is rapidly depressed as the lips move back to laterally close the mouth. Often we believe that the larger the shark, the faster the attack may be. However, Robinson (1999) found that smaller nurse sharks tend to perform the same kinematic feeding more quickly than their larger counterparts. This is thought to be due to the physiological constraint on muscular contraction dynamics. It was observed to take approximately thirty-two milliseconds for the shark to open its mouth! One of the fastest recorded feedings of any shark.

DCIM100GOPRO

Suction feeding of these sharks is characterized by an expansive, compressive, and recovery phase. Motta et al. (2008) found that during the expansive phase, depression of the lower jaw is effected by jaw muscles. There is also depression of the hyoid and expansion of the gill arches which are driven by contraction. The loose connection between a part of the hyoid arch (ceratohyal) and jaw allows for substantial cheek depression, unlike in most other sharks. Muscle activity by inner hyoid and inner jaw show that the hyoid and jaw are moved and the muscle from the mandibular arch move the jaws during the compressive phase. During what is thought to be the recovery phase, cartilage elements return to initial positions.

Two small barbels located near the mouth are used to search for prey by brushing them along the ocean floor. Some nurse sharks have even been found hovering over the ocean floor by resting on their pectoral fins. This creates a possible false cave in which to lure in crabs, lobsters, etc.. The power of their suction feeding is so intense that it has been known to dismember their prey. While nurse sharks would rather feast on the finer things such as fish, shrimp, and squid, their strong jaws are able to capture and crush shellfish and even coral. These sharks are typically nocturnal creatures and tend to “sleep” during the day under coral. However, their small mouths prevent them from consuming large fish. They hunt for their prey along the ocean floor and have even been seen grazing for algae and ground corals. Robinson and Motta (2001) also examined the effects of growth patterns on the scale of feeding kinematics. They found that a nurse shark’s feeding mechanism grows isometrically (same scale of growth).Their findings conclude that kinematic feeding will not differ with physiological growth and/or change of the shark.

DCIM100GOPRO

It’s safe to say that nurse sharks are unique in many ways; from their suction technique primarily used for feeding, to the slurping/sucking sound this method produces. While nurse sharks are generally not hunted, a slight decline in population has still been found. Education programs such as TREC and even the worldwide phenomena Shark Week, all contribute to helping the world understand the beauty, rather than terror, of all sharks, not only the nurse. To me, they are such beautiful creatures and give a very different view of sharks than the one JAWS seemed to captivate. They are such a great contradiction by way of the incredible power of the jaws and feeding tactics, coupled with their docile nature to educated visitors.

 

References:

Florida Museum of Natural History n.d. Ginglymostoma cirratum. Ichthyology Collection.

Motta, P.J., R.E. Hueter, T.C. Tricas, A.P. Summers 2002. Kinematic Analysis of Suction Feeding in the Nurse Shark, Ginglymostoma cirratum (Orectolobiformes, Ginglymostomatidae). Copeia 2002:24-38.

Motta, P.J., R.E. Hueter, T.C. Tricas, A.P. Summers, D.R. Huber, D. Lowry, K.R. Mara, M.P. Matott, L.B. Whitenack, A.P. Wintzer 2008. Functional Morphology of the Feeding Apparatus, Feeding Constraints, and Suction Performance in the Nurse Shark Ginglymostoma cirratum. Journal of Morphology 269:1041-1055.

Motta, P. J., C.D. Wilga. 2001. Advances in the study of feeding behaviors, mechanisms, and mechanics of sharks. Environmental Biology of Fishes 60:131-156.

Robinson, M.P., P.J. Motta 2001. Patterns of growth and the effects of scale on the feeding kinematics of the nurse shark (Ginglymostoma cirratum). The Zoological Society of London 256:449-462.

Snyderman, M. n.d. More Than a Mouthful: How Fishes Use Their Mouths. Dive Training Magazine.

Tanaka, S.K. 1973. Suction Feeding by the Nurse Shark. Copeia 60:606-608.

 

Get Cancer For Coral

When going to the beach, the one thing no one forgets is sunscreen. It is the saving grace of all fair skinned homosapiens who have to apply religiously after the ocean washes it all off their body. However,there is a problem that few people think about. What happens to all that sunscreen that gets washed off your body? Is it harmful to coral reefs and the marine life they support?

Coral and sponges

Coral reefs make up less than 1% of the ocean floor but are home to an estimated one million species of fish, invertebrates, and algae (Gilbert et al. 2009). The actual corals belong to the phylum Cnidaria and are made up of animals called polyps. Zooxanthellae or symbiotic algae, live in the polyps and provide the coral with food through photosynthesis. So already we can see some problems sunscreen might have on the lives of coral. If sunscreen from your body washes off and gets on the coral that have to receive sunlight in order to produce food, then the coral will not be able to get the proper sunlight, which will lead to death. Over 60% of coral reefs are under threat from a variety of sources including marine pollutants (Gilbert et al. 2009). You may not think that sunscreen amasses for a lot of marine pollutants, but 10% of the coral in danger is just because of sunscreen-induced bleaching (Than 2008). In 2005 sunscreen product sales reached over half a billion dollars (Shaath and Shaath 2005). The United States National Park Service claims that 4,000 to 6,000 tons of sunscreen enters reef areas annually (Than 2008). Unfortunately these concentrations of sunscreen do not spread out evenly over the entire ocean and it is estimated that 90% of tourists are concentrated on only 10%  of the world’s reefs (Gilbert et al. 2009). That means reef areas with high tourist rates get much more exposure to sunscreen than most.

Tourist destroying coral and spreading sunscreen all around the reef.

Interestingly, some of the chemicals in sunscreens interact with the coral in strange ways. One study found that sunscreen promoted coral bleaching by promoting viral infections (Danovaro et al. 2008). In the study, even very low concentrations of sunscreen (i.e., 10 µL/L), was enough to cause large amounts of coral mucus (composed of zooxanthellae) to be released within 18-48 hours (Danovaro et al. 2008). In hard corals, low concentration amounts of 10 µL/L caused complete bleaching within 96 hours (Danovaro et al. 2008). The controls used throughout the experiment didn’t show any change, but the experimental groups bleached faster when larger quantities were used (Danovaro et al. 2008). Further experiments were done on seven specific compound found in most common sunscreens in order to better understand the exact cause of coral bleaching. They found that butylparaben, ethylhexyl- methoxycinnamate, benzophenone-3 and 4-methylbenzylidene camphor caused complete bleaching even at very low concentrations (Danovaro et al. 2008). However, octocrylene, ethylhexyl salicylate, and 4-tert-butyl-4-methoxydibenzoylmethane, and the solvent propylene glycol, which are all common ingredients in sunscreen, had little or no effects on the coral (Danovaro et al. 2008). They also found that after hard corals were exposed to sunscreen, the seawater surrounding the coral branches increased in viral abundance significantly and even reached values that were fifteen times greater than the controls (Danovaro et al. 2008). The samples from all around the world showed that latent infections are common in symbiotic zooxanthellae. Once the coral is exposed to sunscreen, the lytic cycle in the viruses are activated (Danovaro et al. 2008). They believe that sunscreen among other things like pesticides are both contributing to promoting the lytic cycle in viruses that leads to coral bleaching.

Further studies have been done with Benzophenone-2 (BP-2), another common ingredient in sunscreen, to try and pin down the more specific effects that it has on coral. They found that BP-2’s effects were more severe in the light than in the dark (Downs et al. 2014). This surprised me since at Trek we were told that most coral are nocturnal. But in the dark and light, BP-2 caused coral planulae to change from a motile planktonic state to a more deformed and sessile state (Downs et al. 2014). However, in the light, BP-2 caused necrosis in the coral’s epidermis and gastrodermis layers while in the dark it caused autophagy and autophagic cell death (Downs et al. 2014). What is really amazing is how little amount of BP-2 causes this kind of reaction. The LC50 of BP-2 in light for 24 hour exposure was 165 parts per billion and in the dark 548 parts per billion (Downs et al. 2014). It doesn’t take a whole lot of sunscreen at all for it to cause damage to the coral.

Zooxanthellae in coral

So what can we do? Probably the best thing for the coral reefs is to just leave them alone. Whenever humans get involved, it typically means that the environment suffers. But since this will never happen, the next best thing is to educate people who are going to be swimming around the reefs to not wear sunscreen. This sounds like a bad idea, but there are other options besides sunscreen that will keep you protected. The United States National Park service recommends covering up in rash guards and other similar clothing. Sorry this won’t give you a tan, but it will protect you and the coral reefs from harm.

So what have we learned? Sunscreen can cause harm to coral in a number of different ways. First, it can block the sun which is needed for the coral to get their energy. Second, a lot of chemicals in sunscreen lead to coral bleaching due to them activating the lytic cycle in viruses. Third, it doesn’t take a whole lot of sunscreen to cause these harmful effects and the chemicals, specifically BP-2, have worse effects in light. Lastly, this is an easy fix if we want to keep our coral reefs, just cover up with clothes.

References

Blitz, J. B., & Norton, S. A. (n.d.). Possible environmental effects of sunscreen run-off. Journal of American Dermatology, 59, 897–898. doi:10.1016/j.jaad.2008.06.013

Danovaro, R., Bongiorni, L., Corinaldesi, C., Giovannelli, D., Damiani, E., Astolfi, P., … Pusceddu, A. (2008). Sunscreens cause coral bleaching by promoting viral infections. Environmental Health Perspectives. doi:10.1289/ehp.10966

Downs, C. A., Kramarsky-Winter, E., Fauth, J. E., Segal, R., Bronstein, O., Jeger, R., … Loya, Y. (2014). Toxicological effects of the sunscreen UV filter, benzophenone-2, on planulae and in vitro cells of the coral, Stylophora pistillata. Ecotoxicology, 23(2), 175–191. doi:10.1007/s10646-013-1161-y

Gilbert, D. T., & Ferry Center, H. (2009). Protect Yourself, Protect The Reef! Discovering an underwater wonderland.

Than, K. (2008). Swimmers’ Sunscreen Killing Off Coral. National Geographic. National Geographic Society, n.d. Web.

Shaath NA, Shaath M. 2005. Recent sunscreen market trends. In: Sunscreens, Regulations and Commercial Development (Shaath NA, ed). Third ed. Boca Raton, FL:Taylor & Francis, 929–940.

 

Strangler Fig Germination in Palm Trees

 

During a recent stay at La Milpa Ecolodge and Research Center in Belize I noticed that there was variation in the amount of dead leaves retained by palms. Some of the palm trees had retained a large clump of dead leaves right under their productive leaves while other palms seemed to be discarding their dead leaves and had at most three dead fronds hanging onto their trunks. Having learned about epiphytes (a plant that grows on another plant such as a tree without being parasitic) a few days prior in my tropical ecology class and how these epiphytes germinate in pockets of nutrients up in the canopy of the forest I began to wonder if the clumps of dead leaves could be collecting the nutrients needed by the epiphytes. If this is the case does that mean that I would find more epiphytes and ferns growing on the palm trees that retained their leaves than on the palm trees that dropped their leaves on a regular basis? In order narrow the range of my question I chose to focus on one type of epiphyte and one trait that influenced their growth. In my research I have come across three types of epiphytes: obligate epiphytes, secondary epiphytes and primary epiphytes. Obligate epiphytes are those that live on a host tree, or phorophyte, and never come in contact with the ground (Tsutsumi 2006). Secondary epiphytes are those that start their lives on the ground and then climb up the trunk of a phorophyte and eventually lose their connections with the ground (Tsutsumi 2006). Finally the primary epiphytes are those that begin life on a phorophyte and then send roots down into the ground and can eventually win out the competition with their phorophyte killing it and becoming freestanding (McPherson 1999). I chose to focus on primary hemiepiphytes because the strangler fig, which is a very successful epiphyte and the topic of many research projects, is a primary hemiepiphyte.

A Strangled Tree, Photo by Laurel Lietzenmayer

Many factors need to align for a primary hemiepiphyte to successfully germinate and eventually reach the ground from a tree. First the seeds much reach the tree, this is often accomplished by frugivores (animals that eat the fruit containing the epiphytes seeds) desiccating in the tree (Male 2005, Todzia 1986). In order for these seeds to then germinate there must be enough moisture and nutrients which are often derived from pockets of humic soil (or humus) that has collected on a tree. This humus can collect at branching points, wounds on the tree, hollows in the tree, on rough bark, and in the case of palm trees marcescent leaf bases (clusters of dead leaves) (Kramer 2011, Male 2005, McPherson 1999, and Todzia 1986). The seeds and subsequent primary hemiepiphytes also must be protected from getting knocked out of their phorophyte and be in a position where the phorophyte will be capable of supporting the epiphytes’ increasing weight (whether it be the strength of a branch or the peeling nature of a tree’s bark) (McPherson 1999). Due to the large amount of factors influencing the success of an primary hemiepiphyte many studies have had trouble locating the source of a correlation. For example it has been shown that primary hemiepiphytes are more likely to be found on larger trees but this could be because they have more humus pockets than smaller trees, because they are home to more frugivores and or because they are sturdier and their branches don’t break under the increasing weight of an epiphyte (Male 2005).

Studying palm trees, due to their lack of branches, has allowed researchers to focus more on a couple of variables. The two that I have found are the presence or absence of a crown shaft ( a portion of smooth trunk right below the leaves of a palm tree) and whether the palm tree has a marcescent leaf base or senescing leaves (also referred to as a self cleaning tree where the dead leaves fall off the tree). By far the strongest correlations I have seen in the current research between phorophyte traits and primary hemiepiphyte presence has been that the epiphytes grow on palms with marcescent leaves and not on those palms that have senescing leaves. Kramer found that palm trees with no crown shafts and marcescent leaf bases were the most susceptible to epiphytes and that out of the 697 self cleaning palms observed (across 34 species) none of them held primary hemiepiphytes (2011). McPherson also found that out of the groups studied palms with marcescent leaf bases held the most primary hemiepiphytes (1999)

Learning about Strangler Figs, photo by Laurel Lietzenmayer

While looking at larger categories like all palms with marcescent leaf bases, correlations appear. However, these correlations are not always accurate predictors of whether or not a specific species will serve as a phorophyte because there are many other factors involved. For example, in Kramer’s study only 1 of 156 Thrinax radiata palms (no crownshaft with marcescent leaf base) was observed to contain a primary hemiepiphyte but 6 out of 7 hyphaene petersiana (no crownshaft with marcescent leaf base) contained primary hemiepiphytes (2011).

In palms, discarding dead leaves excludes the palm from becoming a primary hemiepiphyte’s phorophyte. However, it cannot yet be said that the palms developed the ability to senesce in reaction to epiphytes and so further research needs to be done in order to find an answer (Kramer 2011). This research could perhaps involve development of phylogenetic trees for the origin of senescing palms and phylogenies for the origin of primary hemiepiphytes. If the two developed in similar places at similar times then it would be a good start in saying that senescing was in reaction to the epiphytes (although it wouldn’t confirm the theory). Another avenue of research that I would like to pursue is deciduous versus evergreen trees as phorophytes for primary hemiepiphytes. In research that has been done trees that drop leaves, like senescing palm trees, and trees that shed their bark (Male 2005) have fewer counterparts that do not, therefore it would make sense if deciduous trees had fewer epiphytes than their evergreen counterparts. However, this is not the case and researchers in Australia have found that primary hemiepiphytes prefer deciduous trees to evergreen trees (McPherson 1999). When looking at research for primary hemiepiphytes, although there are a few gaps as pointed out, research is plentiful but there needs to be a lot more research done on other types of epiphytes to fully understand their dynamics. 

Kat

Works Cited

 

Tsutsumi C, Kato M. Evolution of epiphytes in Davalliaceae and related ferns. Botanical Journal Of The Linnean Society [serial online]. August 2006;151(4):495-510. Available from: Academic Search Complete, Ipswich, MA. Accessed May 20, 2016.

McPherson J. Studies in Urban Ecology: Strangler Figs in the Urban Parklands of Brisbane, Queensland, Australia. Australian Geographical Studies [serial online]. November 1999;37(3):214. Available from: Academic Search Complete, Ipswich, MA. Accessed May 19, 2016.

Male T, Roberts G. Host associations of the strangler fig Ficus watkinsianain a subtropical Queensland rain forest. Austral Ecology [serial online]. April 2005;30(2):229-236. Available from: Academic Search Complete, Ipswich, MA. Accessed May 20, 2016.

Todzia C. Growth Habits, Host Tree Species, and Density of Hemiepiphytes on Barro Colorado Island, Panama. Biotropica [serial online]. March 1986; 18(1): 22-27.  Available from WIley.

Kramer G. Palm Tree Susceptibility to Hemi-epiphytic Parasitism by Ficus. Thesis from the Graduate School of Environmental Horticulture at the University of Florida. August 2011.

Black Spot Disease in Sand Tilefish and Other Species

Figure 1: From Belize Google Drive Folder

In the week that I spent at Ambergris Caye in San Pedro, Belize, I had the experience of a lifetime. I was able to explore and make predictions about my observations that I encountered each day in various parts of the coral reef. Many of my experiences were truly once in a lifetime such as jumping into a shark filled ocean, swimming with stingrays and sea turtles, and holding various sea creatures such as squid and sea stars. But throughout the various snorkels each day, there was a lingering question that struck me as I swam through the reef patches. How have we affected the reef dynamic as humans? As we saw dead or bleached sections of coral, I thought about the various ways in which humans have had an impact on the degradation of one of the most diverse ecosystems in the world. My questions were further expanded during one of our lectures with Kenny, in which we learned about some of the common fish we would likely see throughout the reef. The fish that stood out to me the most was the sand tilefish, not for aesthetic reasons, but for its susceptibility to illness. It is often found in the water covered with black spots, often so severe that the fish’s coloration appears black. Until further research on the disease, I assumed that the disease was an evolutionary tool to promote the genes of the most fit of the species, while destroying the weakest. After much exploration into the disease, I found an answer to my question as to just how involved humans are in the major changes happening in the coral reef systems.

Figure 2.  From “Sand Tile Fish Builds Nest” by Cyndee and Alex,2015, Waterlogged: Something’s Fishy Here.  Available https://waterloggedfishblog.wordpress.com/2015/05/24/sand-tilefish/

As I was researching Black Spot Disease, I found stark differences in how disease arises in these ecosystems compared to human transmission. The cause of most human diseases are viruses and bacteria from infected areas which are transmitted by contact with others. In fish, although contact with other organisms is a common method of transmission, the creation of most of their diseases is more likely to be attributed to changes in the environment. My new hypothesis is that in response to changes in temperature of the water and the degradation of the fish’s habitat, the fish become more susceptible to contracting BSD.

Figure 3. From ” What’s Bugging our Critters”. By Alberta Government Fish and Wildlife, 2014, Black Spot Fish in Alberta. Available at: http://aep.alberta.ca/fish-wildlife/wildlife-diseases/documents/Blackspot-Feb-2015.pdf

The parasitic Black Spot Disease is amongst those that arose from changes in the water’s ecosystem dynamic. “SD is caused by the metacercariae (larvae) of a trematode (worm) which induces the black spots on the body surface of the fish” (Bush et al 2001). BSD is found in salt and freshwater habitats and it has been known to affect organisms such as sand tilefish, salmon, parrotfish and various types of bass. Researchers started to test the presence of BSD in water that has recently suffered a substantial change in temperature and they found that they are correlated. In response to the increase in core temperature of the earth’s surface, there is an increase in the prevalence of black spot disease. Rising temperatures of the waterways create an increased metabolic demand due to higher energy expenditures, thus resulting in decreased resistance to disease and increased susceptibility to parasites (Lavigne et Davis 2005: 1471). The water’s temperature is is very important for maintaining optimal feeding and metabolic conditions. When the fish are exposed to a “new” environment, they will be stressed causing decreased immunity. The parasites can easily attach if the fish’s immune system is compromised. Not only are temperatures giving BSD a more hospitable habitat to host on the resident fish, but other environmental changes such as habitat degradation by urban development and a decrease in biotic integrity can cause a surplus of BSD to be found on fish. Biotic integrity is a collection of factors that contribute to determining overall fish health in areas of water. From different samples of various waterways, researchers measured the intensity of BSD against size of the waterway, gradient, and level of urbanization. They found that, “ habitat degradation accompanying agricultural and urban development is associated with increased incidence of black spot in a variety of fish species (Steedman 2011:494). Through this experiment, we understand that there is a correlation between this disease and environmental destruction through urbanization.

In terms of fish health, the Black Spot Disease can decrease physical health including irreversible anatomical deformations especially in juvenile fish. Severe infections of juveniles can cause spinal curvature, abnormal muscle development, or death. In adult fish it causes below average adult size and susceptibility to secondary infections.  (Harrison et Hadley 1982: 106). Not only can BSD cause changes in fish health, but it also ultimately changes the dynamics of fish behavior. According to the Tobler and Schlupp article “Influence of Black Spot Disease on Shoaling Behavior…”, this disease creates a deterrent for other fish to form a school with the infected fish. The authors suggest, “ the presence of infected fish may detract from the benefits of group living by reducing the levels of coordination, regularity, and homogeneity in the shoal” (Tobler et Schlupp 2006:29). It is directly beneficial for fish to form schools because they are at heightened level of protection with a larger group. If a member of the group is less likely to be able to keep up, is less coordinated, or decreased vision from Black Spot, then the shoal will be less likely to form a shoal with the infected fish. The cost of losing a group of fish to a predator because of one fish’s inability to fully contribute to the shoal is too high.

In conclusion, the controversy surrounding Black Spot Disease is not the deniability of the prevalence of the disease, but its effect on humans. The fish markets and the portions of mass consumerism that are associated with seafood production and marketing have concerns about the fish’s eat ability due to the Black Spot Disease. Some buyers are skeptical if the fish are safe to eat because of the parasitic nature of the disease. Although all sources are suggesting it is safe to eat when cooked, it is important to notice the domino effect that is being formed here. The inflated number of fish that are being exposed to BSD is highly correlated with the various changes in environment discussed above such as changes in temperatures and habitat degradation. These changes in environment are highly attributed to human interventions such as the warming of the earth caused by the burning of the ozone layer attributed to the release of CFC’s into the atmosphere. Habitat degradation is likely caused by the mass production of urban areas that are replacing the natural habitats of various aquatic and terrestrial organisms. The destruction of these habitats creates a domino effect for other relating ecosystems that were interdependent on them for various resources. From this, it can be suggested that humans can have a large influence in the increase of this disease in various fish habitats.

1. 1. Bush AO, Fernández JC, Esch GW, Seed JR. Parasitism: the diversity and ecology of animal parasites. Cambridge University Press, Cambridge (2001)
   2. Cairns, M. a. et al. Influence of Summer Stream Temperatures on Black Spot Infestation of Juvenile Coho Salmon in the Oregon Coast Range. Am. Fish. Soc. 134, 1471–1479 (2005).
   3. Harrison, E. J. & Hadley, W. F. Possible effects of black-spot disease on northern pike. Trans Am Fish Soc 111, 106–109 (1982).
   4. Steedman, R. J. et al. Influence of Summer Stream Temperatures on Black Spot Infestation of Juvenile Coho Salmon in the Oregon Coast Range. Am. Fish. Soc. 81, 106–109 (1991).
   5. Steedman, R. J. Occurrence and Environmental Correlates of Black Spot Disease in Stream Fishes near Toronto, Ontario. Transactions of the American Fisheries Society 120, 494–499 (1991).