REPRODUCTION IN SEA ANEMONE 



479 



6 (5) 



3 spawned 



Fig. 6 Oocyte size-frequency histograms from the Mar. 25, 1976, 

 transplant collections. N is the number of animals examined, and the 

 numbers in parentheses are those having gonads. 



Although temperatures are significantly higher in the Morro Bay 

 outfall than at the control site (Fig. 5), the reproductive cycles of 

 females appear to parallel each other well, except for the timing of 

 spawning. The observed early spawning of outfall animals was 

 consistent from one year to the next and suggests a possible effect of 

 the warm-water regime on this critical aspect of reproduction. 

 Comparing the timing of spawning of outfall anemones (Fig. 3) with 

 the temperature data shows that, in 1974 and 1975, anemones 

 spawned within 2 weeks of the time that mean temperatures first 

 exceeded 25° C. In both years this temperature was reached abruptly. 

 In 1976, spawning did not occur until the mean temperature had 

 stabilized at 26° C; earlier brief fluctuations above this point did not 

 bring about spawning. It is possible that anemones are unable to 

 retain and nourish oocytes at sustained temperatures above this 

 threshold level because of the metabolic demands placed upon them 

 by these high temperatures. 



