ECOLOGY OF THE MURRAY ISLAND CORAL REEF. 



37 



temperature and to the effects of silt. They must have clean, cool water in 

 which to live. Only forms which can withstand both high temperature and 

 muddy water can live within 500 feet of the shore. This suggests that high 

 temperature may produce death through asphyxiation and, as is well known, 

 Winterstein' concluded that heat depression in frogs is a form of fatigue due 

 to the oxygen being insufficient to support the accelerated metabolism of 

 the animal. 



Doubt has been cast upon this conclusion by Babak^ and by Amerling,^ 

 who showed that certain frogs which are resistant to heat paratysis are easily 

 paralyzed by lack of oxygen, while others (such as Rana fused) are resistant 

 to lack of oxygen but readily paralyzed by heat. Finally, Becht^ found that 

 in the isolated cord, and in the isolated nerve of frogs, and in the automatic 

 ganglion of the Limulus heart, recovery from heat paralysis can take place 

 in the absence of atmospheric oxygen. There may, however, be sufficient 

 oxygen generated in the tissues to cause recovery. See Carlson.^ 



Table 10. — Death temperatures and relative resistance to asphyxiation in various 

 species of corals from the Bahamas and from Florida. 



In view of this conflict of results, experiments were conducted upon 

 corals from the Bahamas and the Tortugas. It was found that those corals 

 which are resistant to being smothered under the mud are correspondingly 

 resistant to the effects of carbon dioxide in the sea-water. 



Thus, Acropora muricata is least resistant and is killed by being buried 

 10 hours under the mud, whereas Siderastrea radians is the most resistant 

 coral and is only about half killed by being buried 73 hours. The death 

 temperatures of various Atlantic corals and their relative ability to resist 

 smothering by mud or asphyxiation by CO2 is given in table 10. 



Vaughan several years ago observed that Siderastrea radians and 

 Mceandra areolata were corals of the inner flats where the bottom was apt to 

 be muddy; on the other hand, Acropora muricata requires pure water in a 



'Winterstein, 1902, Zeit. fiir allgemeine Physiologie, Bd. l; alio Bondy, 1904, Ibid., Bd. 2; also Verworn, 



1913, Irritability, pp. 240-243. 

 'Babak, 1907, Centralblatt fiir Physiol., Bd. 21, pp. 6-8. 

 'Amerling, 1908, PflUger's Archiv fiir Physiologie, Bd. 121, pp. 263-269. 

 *Becht, 1908, American Journal Physiol., vol. 22, pp. 456-476. 

 'Carlson, 1906, American Journal Physiol., vol. 15, p. 232. 



