Adam Holena Physiology Venom Research Paper 5/2/2013 Crown of Thorns Starfish To many tourists the Great Barrier Reef is an exciting and relaxing destination to travel to. It holds beauty in its waters that are difficult to find anywhere else. Within the beauty however lies many varieties of marine organisms that all can inflict great harm to humans. One such organism is the Crown of thorns starfish (Acanthaster planci). When most people hear of the organism starfish, they think of this barely mobile, harmless creature that lives on the bottom of the ocean.
This specific species of starfish, however; is quite different from those commonly referred to. The crown of thorns starfish lives predominantly in the Great Barrier Reef, but can also be found in along sea beds, and intertidal zones of tropical and subtropical latitudes. The shaping of the crown of thorns starfish is the same as most starfish, including the traits of having a center mass with protruding appendages used for movement. This starfish differs from the normal Asteroidea family of starfish in that it is not limited to the five arms, and is heavily armed with spines covering its dorsal surface.
An adult of this species ranges from 25 to 35cm in size and is seen with up to 21 arms. The coloration of these animals is usually on the dull side of pale brown, but depending on their location, are often seen with a vivid color scheme. Figure 1: A picture of a Acanthaster planci depicting an example with a vivid color scheme. (“Acathancaster planci”, 2011) If the spines were removed from this organism, the surface of it would be very soft, as the majority of the shape this organism has comes from the water that is contained within it.
The crown of thorns starfish is known to thrive off of the coral reef that it lives amongst, where it digests the coral using its gastric juices to liquefy the coral to a state for consumption (“Crown-of-thorns Starfish”, 2013). Because of the manner that these starfish live off of the coral reefs, there has within the recent years been an increase in the numbers of these organisms living on the reef beds, causing great devastation when they all begin to feed.
One adult starfish can be known to consume on average, 478 cm2 of coral within one day alone. It is easy to see then how these creatures become an extreme threat to the coral ecosystems present in the oceans. In addition to feeding on the coral reefs, these creatures are known to feed off of other sessile animals and dead organisms as well, classifying them as opportunistic carnivores (Ault, 2011). Many different attempts have been made to limit the number of these starfish in areas faced with an over-abundance of them.
These attempts include physically moving them, placing up barriers to prevent them from reaching the reefs, or even studies to see whether or not there are any valuable components within the starfish that could be used as a resource in some way (“Acathanster planci, 2011). Contrary to much knowledge of the starfish family, this species contains within it deadly venom that is uses mostly in a protective manner. The spines of these creatures are sharpened to be able to penetrate the skin. Once in the skin of is predator, the spines will break off leaving some of the tissue with glands in them behind.
This initial penetration itself is known to be very painful, but that is not the end of the damage that the starfish will do to its attacker. The glands that the tissues hold in the spines are known to produce different compounds that are venomous to other organisms. Some of these compounds include hemolytic and myotoxic PLA2 enzymes, anticoagulants, and plancitoxins. The combination of all of these different compounds provides ample protection from the predators that this creature faces when conduction its feeding, which usually requires little movement leaving this organism subject to attack.
The hemolytic and myotoxic PLA2 (phospholipase A2) enzymes act to initiate pain and inflammation at the site of penetration. This inflammation is caused by the build-up of arachidonic acid which is governed by a pathway that the breakdown of phospholipids due to the PLA2 action. It is the build-up of the arachidonic acid that facilitates the production of several thrombogenic molecules which initiate the actual inflammatory response. The mechanism by which this PLA is initiated involves a HIS-48/ASP-99/calcium complex on the active site.
The calcium portion of this complex act in order to polarize a sn-2 carbonyl oxygen while the His-48 bridges two water molecules necessary to travel the distance between the histidine and the ester of the molecule (Argiolas, 1983). Once this phospholipase is initiated, it can be converted into the arachidonic acid which will produce the leukotrienes and prostaglandins that are key parts of the inflammatory response. In addition to the phospholipases that are produced, the glands of the crown of thorns starfish will produce anticoagulants that act in the system by preventing blood clotting.
One of the common anticoagulants found in venoms produced by organisms is Batroxobin. This is a proteolytic enzyme that acts by splitting bonds in the alpha chain of fibrinogen which normally releases fibrinopeptide A that will start the formation of the clot (Kawakami, 1992). By decreasing the level of fibrinogen in the blood, it will directly inhibit the production of the blood clot which is initiated by the presence of fibrinogen.
If an organism is successful at preventing the clotting of the blood of either its attacker or its prey, then inflicting what would normally be a simple flesh wound, would actually turn out to be a fatal event by allowing extreme amounts of blood to be lost. This mechanism also allows for the continuation of blood to flow around the site of damage, passing any other compound that needs to travel elsewhere in the organism, to be able to successfully enter the blood stream without getting block at the wound. The final component of the crown of thorns starfish venom is a plancitoxin.
According to several studies found, this toxin is a very close match to the known DNase II already present in human systems. When these plancitoxins enter the attackers system, they go into action by beginning to cleave the DNA molecules within in the attacker. The major region that receives the damage when these plancitoxins do the damage they are set out to do is the liver. In one test conducted using purified plancitoxin from the crown of thorns starfish injected into mice, found that this toxin greatly increased the glutamic oxaloacetic transaminase and glutamic pyruvic transaminase evels produced within the mice (Shiomi, 2004). This led the researchers to conclude that the plancitioxin is are extremely hepatotoxic, or damaging to the liver. When all of these different components of the venom produced by the crown of thorns starfish work together to protect it, they become very effective at doing so. However deadly and threatening these all seem on the surface, there have been no known fatalities of humans due to these creatures. The main disturbance that is observed from an encounter with these animals is painful swelling of the wound caused by the spines.
Figure 2: Aproximately 10 Stab wounds caused by the crown of thorns starfish. Each wound has visible bleeding and swelling surrounding the spine. (Sato, 2008) References: “Acanthaster Planci. ” GoldenMap. N. p. , 23 Oct. 2011. Web. 02 May 2013. Argiolas, A. , and JJ Pisano. “Facilitation of Phospholipase A2 Activity by Mastoparans, a New Class of Mast Cell Degranulating Peptides from Wasp Venom. ” The Journal of Biological Chemistry 258. 11 (1983): 13697-3702. PubMed. Web. 01 May 2013. <http://www. ncbi. nlm. nih. gov/pubmed/6643447>. Ault, Larissa, Julie Macardle, and Caitlin Sussman. Acanthaster Planci Crown of Thorns Starfish. ” ADW: Acanthaster Planci: INFORMATION. N. p. , 2011. Web. 02 May 2013. Birkeland, Charles, and John S. Lucas. Acanthaster Planci: Major Management Problem of Coral Reefs. Boca Raton: CRC, 1990. GoogleBooks. “Crown-of-thorns Starfish. ” BBC News. BBC, 2013. Web. 01 May 2013. Kawakami, Michiro, Kazuo Makimoto, Hirofumi Yamamoto, and Hiroaki Takahashi. “The Effect of Batroxobin on Cochlear Blood Flow. ” Acta Oto-Laryngologica 112. 2 (1992): 991-97. PubMed. Web. 01 May 2013. <http://www. ncbi. nlm. nih. gov/pubmed/1481670>. Luch, Andreas.
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