DefenseMechanisms

From coraldigest
Jump to: navigation, search

Defense Mechanisms

The Importance of Defense Mechanisms

Corals are sessile, colonial organisms, forever fixed in a certain position by attaching as young polyps to a substrate such as a rock or existing coral. This makes the ocean a very dangerous place for these immobile animals. However, in an effort to combat their immobility, many corals have developed different types of defense mechanisms to protect themselves from the ocean's looming dangers--leading to the production of some of the most lethal toxins found in nature. [1][2] In this sense, chemical defense is vital to the life of the coral, whose life depends upon its ability to protect itself from predators and invasive species. In fact, some 73% of all coral is toxic to fish, and most of the other species of coral maintain some physical type of defense mechanism to protect against fish predation. [3]

Chemical Defense Mechanisms

Bioluminescence

History

(Genetic Evolution as a defense mechanism. This phenomenon draws unwanted attention to predators or can frighten them.)

How it works/ why different colors

We will elaborate on the chemical processes such as the reaction--Compound Luciferin is either synthesized by the bioluminescent organisms or it is absorbed from an other organisms through a symbiotic relationship. Luciferase, an enzyme, then catalyzes oxidized luciferin to produce oxyluciferin, and through this exothermic reaction, light is given off.

-=Difference in bioluminescence and fluorescence=- (light is absorbed and reemitted-not created

-=Uses in nature==- Most aquatic organisms bioluminesce. Communication and defense

-=Locations where the organisms that bioluminesce live.=- Majority of complex, bioluminescent organisms live deep in the ocean

-=Applications to science=- (ex. reporter gene for staining or biobulb)

-=Quorum sensing communication in general with cells and application in reefs=-

Sources: Brönmark, Christer, and Lars-Anders Hansson. Chemical Ecology in Aquatic Systems. Oxford: OUP Oxford, 2012. Print [4].

Harvey, E. Newton. 1957. A history of luminescence from the earliest times until 1900. Philadelphia: The American Philosophical Society. (Volume 44 of the Memoirs.)

Roda, Aldo. Chemiluminescence and bioluminescence : past, present and future . Cambridge, UK: Royal Society of Chemistry, 2011. 590 . Print.

"The Bioluminescence Web Page." National Geographic . N.p., 23, 2014 Jan 2014. Web. 25 Feb 2014. <http://biolum.eemb.ucsb.edu/>.

Winans, Stephen, and Bonnie Bassler. Chemical communication among bacteria . Washington, DC: ASM Press, 2008. Print.

Toxins

Many corals possess toxic defense mechanisms for protection. Toxicity levels of different corals were naturally selected for, which has resulted in a direct relationship between how toxic a particular type of coral is and how much nutrition it provides to those who prey upon it. For instance, fish began preying more often upon those corals that had more nutritional benefits, so those corals had to increase their levels of toxicity in order to protect themselves and survive. Corals that had lower nutritional values were less susceptible to predation, so they did not adapt and increase their toxicity levels the way other types had to. [5]


Fire Coral
Blade Fire Coral [6]

Despite their toxic defense mechanisms, most corals are relatively harmless to humans, with one exception: fire coral. The particular type of proteinaceous toxin in fire coral affects humans, but only mildly — most reactions just involve stinging pain and inflammatory effects, and the more severe, but rare, side effect is nausea or vomiting [7]. The most common toxins are neurotoxins, and there are three main types. Saxitoxins block sodium channels in the body of species it comes in contact with, causing paralysis and respiratory failure. [8] Palytoxins act on the antiporters that control cell membrane activity, thus disrupting the proper functioning of kidneys and red blood cells and leading to kidney, respiratory and heart failure. The third common type of toxin, the lophototoxin, causes muscle contractions and potential paralysis or respiratory failure by blocking the synapses where nerves connect with muscles.[9]

Physical Defense Mechanisms

Nematocysts [10]

Discharge of a Nematocyst [11]

In a cross between a chemical and physical defense mechanism, most corals also have nematocytes for protection — stinging cells on the end of coral tentacles that are used to sting, capture and kill off small prey and neighboring coral in a continuous battle for space. The nematocytes look like double-walled structures that each contain a coiled, venomous thread with a barb at the end, so that when the nematocyte is stimulated either physically or chemically, the thread releases, penetrates its victim's skin and releases poison. [10]

Nematocysts are incredibly efficient, especially for their small size and relatively simple structure. When the nematocysts are activated, they fire a barb into the potential victim, which is the physical defense aspect. Then, the barb burrows through the skin of the prey and leaves a hollow filament in its wake, and poison is injected into the new space. The poison then immobilizes the prey, protecting the reef. [12].

Diagram of a Cnidocyte[13]

Cnidocyte

A cnidocyte is the explosive, stinging cell that contains the nematocyst. While cnidarians are incredibly diverse in form, every cnidarian has a cnidoycte for protection. Cnidocytes help the usually quite defenseless cnidarians, like coral, capture prey and defend against predators. When the cnidocyte is stimulated, it fires the nematocyte — the coiled, threadlike structure that contains the toxic — through the cnidocyte wall and into the prey.[[14]]

Other Marine Organisms with Unique Defense Mechanisms

The Glaucus nudibranch steals the stinging nematocysts of some cnidarians like jellyfish and uses them against the jellyfish and the nudibranch's own predators. Watch this cool video: http://vimeo.com/84585526

References

  1. Van Der Weijden, Sander. "Chemical Defense Mechanisms." Chemical Defense Mechanisms. Coral Publications, n.d. Web. 27 Feb. 2013 [1]
  2. "NOAA's Coral Reef Information System (CoRIS) - About Coral Reefs." Coral Ecosystem Publications RSS. National Oceanic and Atmospheric Administration, n.d. Web. 27 Feb. 2013.
  3. Chemical Defense Mechanisms on the Great Barrier Reef, Australia – Gerald J. Bakus. Science. New Series, Vol. 211, No. 4481 (Jan. 30, 1981). pp. 497-499
  4. Brönmark, Christer, and Lars-Anders Hansson. Chemical Ecology in Aquatic Systems. Oxford: OUP Oxford, 2012. Print.
  5. Daniels, Ethan. "Reefs of Poison and Venom." Alert Diver. Dan Holdings, Inc., 2013. Web. 23 Apr. 2013. <http://www.alertdiver.com/Poison_and_Venom>.
  6. Personal photograph by author. 2013. By Brian Naess
  7. Moats, William E. "Fire Coral Envenomation." Wilderness and Environmental Medicine 3.3 (1992): 284-87. Print.
  8. Ferrer, Ryan P., and Richard K. Zimmer. "Neuroecology, Chemical Defense, and the Keystone Species Concept." The Biological Bulletin 213.3 (2007): 208-25. Print.
  9. Marcus, Erin N. "Marine Toxins." Marine Toxins. Ed. James F. Wiley, II. UpToDate, Inc., 17 Dec. 2012. Web. 27 Feb. 2013.
  10. 10.0 10.1 Kass-Simon, G., and A.A. Scappaticci, Jr. "The Behavioral and Developmental Physiology of Nematocysts." Canadian Journal of Zoology 80.10 (2002): 1772-794. Print.
  11. Nematocyst Discharge. N.d. Photograph. National Oceanic and Atmospheric Administration. Web.
  12. ???????
  13. Cnidocyte Diagram. Digital image. Pearson Education, Inc, n.d. Web.>.
  14. "Cnidarian Characteristics." Animals / Wildlife. About.com, n.d. Web. 4 Apr. 2013.
Cookies help us deliver our services. By using our services, you agree to our use of cookies.