向宇品におけるケガキ・マガキの生態学的研究

抄録

This paper deals with the distribution of the two oysters, Ostrea echinata and Ostrea laperousei, based upon the ecological and physiological methods. 1) Materials used for this investigation are O. echinata and O. laperousei which were attached on the rocks in Mukoujina, Hiroshima City. In their habitats, these oysters often populate densely the high levels in the ravines of rocks in which rainwater flows temporarily into the sea. O. laperousei is situated on the rock of the high water level, on the other hand O. echinata is found on the rock of the low water level, the difference of vertical distributions of the two species of oyster was generally seen in the field and their habitats showed perfect segregation. On the contrary the area where no ravine was found is populated only by O. echinata (Figs. 1,2 and 3) 2) The oysters of the two species used for the experiment of the ciliary activity were collected from same water level in adjacent areas. The ciliary activity of the gills showed different results between the two species. Namely, in normal sea water obtsined from their habitat, gill cilia of O. echinata showed a higher activity than that of O. laperousei. While in dilute sea water, O. laperousei showed a higher activity than O. echinata (Fig. 4). 3) Seasonal changes of glycogen and fat contents were measured in the two species collected from same water level. Glycogen content decreased in both species as the season progressed, from May to August, thereafter it increased slowly. Fat content in O. echinata showed a minimum in August, thereafter it increased gradually. But fat content in O. laperousei fluctuated in great degrees from April to June (Fig. 5).