REPRODUCTIVE CYCLES 633 



adequate food, are spawning (Feder, 1956). It is therefore obvious 

 that it requires food for maintenance of its gonads. This is interesting 

 in view of the fact that the ochre star in the intertidal area near the 

 Hopkins Marine Station hves a marginal existence and consumes only 

 a relatively small mass of food in a year (Feder, 1956). Its food con- 

 sists primarily of mussels, but it eats a variety of snails and limpets, as 

 well as bivalves other than mussels. 



In view of the small amount of food taken in and the paucity of 

 organic compounds in the body fluid, ^ the rapid rise in size of the 

 gonads is remarkable. However, it was noticed that the hepatic caecae 

 shrink as the gonads increase in size. The relationship was almost 

 quantitatively reciprocal, suggesting that the hepatic caecae continually 

 store the food as it comes from the gut (Farmanfarmaian et al., 1959). 

 Further, it was found that when glucose and amino acids are injected 

 into the body fluid, they are rapidly removed (Giese, Huang, and Woo, 

 unpublished). Presumably the hepatic caecae rapidly remove the 

 nutrients and store them until needed by the gonad. The gonad is 

 therefore not so dependent upon the immediate food supply. Something 

 other than food must therefore trigger the development of the gonads. 



The purple sea urchin also fails to develop sperm or eggs in the small 

 number of animals that have been starved; in fact, the gonads shrink to 

 a small fraction of their initial size. The major part of the food storage 

 in this case seems to occur in the gonads. One might therefore suspect 

 that the sea urchin would be more dependent upon the food supply and 

 its variations than the starfish possessing hepatic caecae. However, 

 whereas the ochre star is restricted to eating live animals, the purple 

 sea urchin is quite omnivorous in the laboratory and apparently will 

 take in quite a variety of live and dead food in the field, judging from 

 the varied contents of its intestines, although its main food consists of 

 algae. An omnivorous habit would tie an animal less firmly to the 

 variations in the supply of any one type of food, e.g., the algae which 

 have their own seasonal growth cycle. However, it is possible that the 

 nutrient value of the food available varies. For example, young ac- 

 tively growing algae have a higher proportion of protein and would 



^ For example, monthly samples for a year showed an average of less than 

 2 mg % of nonprotein nitrogen, usually less than 1 mg % of reducing sugar 

 and protein detectable only in traces (by paper electrophoresis). 



