DefenseMechanisms: Difference between revisions
From coraldigest
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* Symbiotic Relationships | * Symbiotic Relationships | ||
** A close relationship between two species | ** A close relationship between two species | ||
** Corals | ** Corals either have their own toxins, or live in symbiosis with bacteria and protists that produce toxins | ||
*** The symbiotic relationships help protect coral that cannot produce the toxins themselves | |||
***Coral probiotic hypothesis <ref>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.</ref><ref>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.[http://aem.asm.org/content/78/9/3136.abstract]</ref> | ***Coral probiotic hypothesis <ref>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.</ref><ref>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.[http://aem.asm.org/content/78/9/3136.abstract]</ref> | ||
**Some corals maintain symbiotic relationships with small animals | **Some corals maintain symbiotic relationships with small animals | ||
***Trapeziid crabs and stony coral <ref> *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.[http://link.springer.com/article/10.1007%2Fs00338-006-0132-7] </ref> | ***Trapeziid crabs and stony coral <ref> *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.[http://link.springer.com/article/10.1007%2Fs00338-006-0132-7] </ref> | ||
**** Reefs worldwide are experiencing increasing sedimentation, or larger amounts of sediment deposited on coral reefs | |||
**** The sediment inhibits growth of the coral and accelerates tissue bleaching | |||
**** In a field experiment conducted at UC-Santa Barbara, all corals outplanted with crabs survived, while 45-80 percent of those outplanted without crabs died within a month. | |||
*Nematocytes | *Nematocytes | ||
**Stinging cells used to capture small prey | **Stinging cells on the coral's tentacles used to capture small prey and kill off neighboring corals in a continuous battle for space | ||
**Double-walled structures each containing a coiled, venomous thread with a barb at the end | |||
**Tiny sensors on the outside of each nematocyte, when stimulated physically or chemically, will release the threat, penetrate its victim's skin and release poison | |||
**Most corals possess these in addition to everything else | **Most corals possess these in addition to everything else | ||
Revision as of 22:55, 15 April 2013
Defense Mechanisms
The Importance of Defense Mechanisms[1][2]
- 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 [3]
- Toxins
- Relatively harmless to humans
- Exception: Fire coral – contain a cocktail of toxins than can cause pain, inflammatory effects
- Most toxins are neurotoxins
- Interfere with signal transmission in animals’ nervous systems
- Three main types of toxins, all neurotoxic in origin
- Saxitoxin – causes paralysis and respiratory failure
- Palytoxin - causes kidney, respiratory and heart failure
- Produced by a dinoflagellate
- Acts on the sodium/potassium antiporters that control cell membrane activity essential for proper functioning of the kidneys and red blood cells
- So potent that a dose large enough to kill an adult human is invisible to the human eye
- Lophototoxin – causes muscle contractions, possibly paralysis and respiratory failure
- Blocks the connections, or synapses, where nerves connect with muscles
- Disruption of these receptors causes muscle contractions
- Relatively harmless to humans
- Symbiotic Relationships
- A close relationship between two species
- Corals either have their own toxins, or live in symbiosis with bacteria and protists that produce toxins
- Some corals maintain symbiotic relationships with small animals
- Trapeziid crabs and stony coral [8]
- Reefs worldwide are experiencing increasing sedimentation, or larger amounts of sediment deposited on coral reefs
- The sediment inhibits growth of the coral and accelerates tissue bleaching
- In a field experiment conducted at UC-Santa Barbara, all corals outplanted with crabs survived, while 45-80 percent of those outplanted without crabs died within a month.
- Trapeziid crabs and stony coral [8]
- Nematocytes
- Stinging cells on the coral's tentacles used to capture small prey and kill off neighboring corals in a continuous battle for space
- Double-walled structures each containing a coiled, venomous thread with a barb at the end
- Tiny sensors on the outside of each nematocyte, when stimulated physically or chemically, will release the threat, penetrate its victim's skin and release poison
- Most corals possess these in addition to everything else
Physical Defense Mechanisms
- Cnidocils
- Activated when a predator touches it
- Discharges a nematocyst
- Nematocysts [9]
- 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
- ↑ "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.
- ↑ 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
- ↑ Ferrer, Ryan P., and Richard K. Zimmer. "Neuroecology, Chemical Defense, and the Keystone Species Concept." The Biological Bulletin 213.3 (2007): 208-25. Print.
- ↑ Marcus, Erin N. "Marine Toxins." Marine Toxins. Ed. James F. Wiley, II. UpToDate, Inc., 17 Dec. 2012. Web. 27 Feb. 2013.
- ↑ 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.