THE EFFECTS OF TEMPERATURE UPON TROPICAL MARINE ANIMALS. 



By Alfred Goldsborough Mayer. 



CONCLUSIONS. 



Tropical marine animals commonly live within 5° C. of their temperature 

 of maximum activity and within 10° to 15° C. of their upper death temper- 

 ature. In marine animals of the temperate or arctic regions a considerable 

 range of temperature above or below the normal produces relatively little 

 difference in their activities, but in tropical forms even a few degrees of 

 heat or cold cause a marked depression in movement. In tropical Scypho- 

 medusse this depression of movement appears to augment about as the square 

 of the change in temperature from that of the optimum. Thus it is more 

 depressant than one would expect were it due to a simple chemical reaction. 



As was shown by Harvey (191 1), the rate of nerve-conduction in the 

 subumbrella tissue of Cassiopea varies as the increment of temperature, 

 increasing in a linear ratio as the temperature is raised. 



Experiments conducted at the Murray Islands, Australian Great Bar- 

 rier Reef, show that those corals which die at temperatures below 36.5° 

 are killed by being buried 11 hours under the mud, but those which resist 

 37°, and above, are proportionally less sensitive to the smothering effects 

 of mud and may survive being buried for 30 to 40 hours. This suggests 

 that high temperature produces death by causing asphyxiation, the oxygen 

 of the sea-water being insufficient to sustain the increased metabolic activity 

 of the animal. 



OBSERVATIONS AND EXPERIMENTS. 



The literature upon the effects of temperature on animal life and activi- 

 ties is both extensive and widely scattered, although Davenport and 

 Castle (1895), in their paper in the "Archiv fiir Entwicklungsmechanik der 

 Organismen," Bd. 2, have given a list of all previous papers treating of 

 experiments upon the maximum temperature which can be endured by 

 aquatic organisms; and Bachmetjew (1899), in the "Zeitschrift fur wissen- 

 schaftliche Zoologie," Bd. 66, presents a complete resume of researches upon 

 the subject of the temperature of insects in relation to that of their sur- 

 roundings. Also a review of works upon the physiological effects of temper- 

 ature is given by Demoll and Strohl (1909). 



Probably no single factor is a more effective barrier to the extensive 

 geographical range of marine animals than is that of temperature. This 

 fact has long been recognized and there are many striking examples of its 



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