EFFECTS OF THERMAL EFFLUENTS 

 ON REPRODUCTION 

 IN A SEA ANEMONE 



BRIAN L. JENNISON* 



Department ol" Zoology, University of California, Berkeley, California 



ABSTRACT 



Reproduction of the sea anemone Anthopleura elegantissima was studied in the 

 thermal-outfall canal of a large (1350-MW) Pacific Gas and Electric Company 

 power plant and at an adjacent control site at Morro Bay, San Luis Obispo 

 County, California. Female reproductive cycles, determined by oocyte diam- 

 eters, were similar at both sites for 3 years; oocytes appeared in the fall, and 

 spawning occurred in the late summer. Outfall females spawned as much as 1 

 month before control females, however. Spermatogenesis of outfall males was 

 delayed and compressed compared with control populations, but outfall males 

 developed quickly and spawned before control males. Anemones transplanted 

 from the control to the outfall in November 1975 spawned by the end of March 

 1976; undisturbed animals from both sites did not spawn until the end of the 

 summer. It is suggested that this species of sea anemone spawns during the 

 summer period of highest annual temperature and that anemones in the outfall 

 have become acclimated to the temperatures there, which are often 10 C above 

 ambient. 



The sea anemone Anthopleura elegantissima is a conspicuous and 

 abundant intertidal animal along the central California coast (Hand, 

 1955), It occurs in large numbers in the thermal-outfall canal of the 

 Pacific Gas and Electric Company's large (1350-MW) power plant at 

 Morro Bay, San Luis Obispo County, California. 



Ford (1964) showed that A. elegantissifna exhibits an annual 

 reproductive cycle in central California, with gametogenesis begin- 

 ning in the winter, oocytes increasing in size through the spring and 



*Prisent Address: Harbor Branch Foundation, Inc., Fort Pierce, Florida. 



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