抄録
The population of the green mussel Perna viridis (L.) at Enoshima Island (Sagami Bay, Kanagawa, Japan: lat. 35°30′N) was sampled monthly from April, 1999, to September, 2001, and the annual reproductive cycle was determined by histological examination. In this species, genital tubules containing germ cells occur in the mantle tissue as well as in the body tissue. Already specified above testicular and ovarian activity peaked during August and September in 1999, but from mid-June to August in 2000. We suggest that warmer water in early summer in 2000 compared to that in 1999 caused this shift in the reproductive season. After the end of the spawning season, some gonadal recrudescence occurred in late autumn in both sexes; however, the gonads did not mature and regressed during the winter months, possibly due to low water temperature (10-13°C). In spring, male and female gonads developed once again, and spawning occurred from summer to early autumn. These results indicate that although P. viridis was originally a subtropical species, the Enoshima population of P. viridis is established there throughout the year and is able to reproduce.
