REPRODUCTION IN SEA ANEMONE 477 



samples contained no males (possibly a sampling artifact), males with 

 mature sperm were present in July, and by August some of the 

 population had spawned. Residual gametes persisted until October. 

 In 1975, no gonads could be found until April, when anemones with 

 only early spermatogonia occurred along with those with ripe 

 gonads. Mature sperm remained through July, but by Aug. 8 there 

 were no identifiable males. This situation remained until May 1976, 

 when again a variety of stages of maturity appeared at once. 

 Although only residual gametes were found on July 13 (this 

 indicated that some of the population had spawned), the August 

 sample again contained ripe anemones, as well as some which were 

 spawning. By September, only residual sperm were found. 



Outfall temperatures were significantly higher than those of the 

 control area throughout the project, except during April and May 

 1975 (Fig. 5). Control temperatures showed a rise through the spring 

 to a summer plateau in all 3 years and a subsequent drop-off each 

 winter. Outfall temperatures showed a similar pattern, but at a 

 considerably higher level. Fluctuations in outfall temperatures were 

 caused by variations in power-plant activity and occasionally by high 

 spring tides, which backflushed the outfall canal to some extent. 



Of the anemones collected on Mar. 25, 1976, from the transplant 

 cages, the size-frequency histograms (Fig. 6) of outfall (where five of 

 the six anemones examined had gonads) and outfall caged but not 

 transplanted (three of seven had gonads) animals were very similar to 

 those of unmanipulated anemones from the Morro Bay control site 

 (where five of six had gonads). Of the control-site anemones 

 transplanted to the outfall, however, two showed a much larger 

 average oocyte diameter, and three more had spawned. Unfor- 

 tunately, the transplant cages hung in the intake area became silted 

 up, and the anemones were lost. 



DISCUSSION 



Numerous studies have correlated seasonally changing sea tem- 

 peratures with the timing of reproductive events in marine inver- 

 tebrates (see Kinne, 1970; Giese and Pearse, 1974, for reviews). 

 Hedgpeth and Conor (1969) suggested that temperature is the major 

 environmental factor controlling reproductive cycles of benthic 

 marine invertebrates, but they added that photoperiod and other 

 factors are also important. Thorson (1946), Giese (1959), and others 

 cautioned that a distinction must be made between the effect of 

 gradual temperature changes on gametogenesis and that of a sharp 

 temperature change on spawning. 



