REPRODUCTIVE CYCLES OF SOME WEST COAST 



INVERTEBRATES ' 



ARTHUR C. GIESE 



Hopkins Marine Station of Stanford University, Pacific Grove, California 



That many marine animals breed in a restricted part of the year 

 (MacGinitie and MacGinitie, 1949) as do many fresh-water and 

 terrestrial forms (Bullough, 1951), is evident to all who have collected 

 them for use in the laboratory. Sometimes the spawning is timed by 

 phases of the moon to a remarkable degree, as in the case of the 

 grunion which spawns during the spring months (Thompson and 

 Thompson, 1919), or the palolo worm which will spawn only after a 

 certain phase of the moon, in two months of the year (Clark, 1941). 

 In most marine invertebrates spawning is less spectacular and, in fact, 

 seldom seen, yet the breeding season is marked. Furthermore, spawn- 

 ing may be triggered by factors, such as the phases of the moon, 

 which may have little to do with the overall growth of the gonads and 

 the annual gonadal cycle. The latter may be the result of the operation 

 of one or more of a number of possible factors, e.g., supply of food, 

 temperature, or photoperiod. 



It is the purpose of the program outlined below to survey the breed- 

 ing cycles in as many of the invertebrates of the central California 

 coast as is feasible with the following objectives in mind: ( 1 ) to deter- 

 mine for each species whether an annual breeding cycle occurs, (2) 

 to obtain a quantitative measure of the cycle, with the aim of finding 

 some very clearly demarcated ones, (3) to ascertain with which 



1 This paper covers work done in collaboration with a group of associates: 

 John Bennett, Richard Boolootian, Allahverdi Farmanfarmaian, Leonard Green- 

 field, Reuben Lasker, and John Tucker. Data for each of the species will be pub- 

 lished in detail elsewhere. The studies were supported by Grant GS 482 from 

 the National Science Foundation and Grant RG 4578 from the Public Health 

 Service, and funds from the Rockefeller Foundation. We are indebted to Drs. 

 L. R. Blinks, D. P. Abbott, and R. L. Bolin for interest in the studies and for 

 provision of facilities. 



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