DefenseMechanisms
From coraldigest
Defense Mechanisms
The Importance of Defense Mechanisms
- Corals are sessile
- Fixed at a certain position, attached to a substrate (such as a rock, or between sand)
- Corals are sessile, colonial animals — remaining stationary for most of their life cycle — which makes the ocean a very dangerous place
- Their vulnerability has lead to some of the most lethal toxins found in nature today
- chemical defense is vital
- Toxicity was naturally selected for
- Corals that were often preyed upon by fish now have higher toxicity levels, for their own protection
- The low nutritional value of some corals made them less susceptible to predation, so the lower the nutritional value, the lower the toxicity level
Chemical Defense Mechanisms [1][2]
- Toxins
- Harmless to humans (except fire coral – can cause pain, inflammatory effects)
- Most toxins are neurotoxins
- Interfere with signal transmission in animals’ nervous systems
- Three main types
- Saxitoxin – causes paralysis and respiratory failure
- Palytoxin - causes kidney, respiratory and heart failure
- Lophototoxin – causes muscle contractions, possibly paralysis and respiratory failure
- Symbiotic Relationships
- Nematocytes
- Stinging cells used to capture small prey, kill of neighboring corals in a continuous battle for space
- Most corals possess these in addition to everything else
Physical Defense Mechanisms
- Cnidocils
- Activated when a predator touches it
- Discharges a nematocyst
- Nematocysts [6]
- Discharge by firing a barb into the predator, leaving a hollow filament through which poisons are injected to immobilize the prey
- Tentacles move the prey to the polyp mouth
Notes
- ↑ Van Der Weijden, Sander. "Chemical Defense Mechanisms." Chemical Defense Mechanisms. Coral Publications, n.d. Web. 27 Feb. 2013 [1]
- ↑ 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
- ↑ Rosenberg, Eugene, Omry Koren, Leah Reshef, Rotem Efrony, and Ilana Zilber-Rosenberg. "The Role of Microorganisms in Coral Health, Disease and Evolution." Nature Reviews Microbiology 5.5 (2007): 355-62. Print.
- ↑ Lema, Kimberley A., Bette L. Willis, and David G. Bourne. "American Society for MicrobiologyApplied and Environmental Microbiology." Corals Form Characteristic Associations with Symbiotic Nitrogen-Fixing Bacteria. American Society for Microbiology, 17 Feb. 2012. Web. 27 Feb. 2013.[2]
- ↑ *Stewart, Hannah L., Sally J. Holbrook, Russell J. Schmitt, and Andrew J. Brooks. "Symbiotic Crabs Maintain Coral Health by Clearing Sediments." Coral Reefs 25.4 (2006): 609-15. Print.[3]
- ↑ 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.