1972 年 33 巻 4 号 p. 92-96
This paper deals with the seasonal variation of body length of Sinodiaptomus volkanoni KIEFER, collected from small ponds near Miki City, Hyogo Prefecture, from August, 1967 to July, 1970. With regard to its body length, two different types could be found i. e., a small-sized group occurring in the warm season (autumn) and a large-sized group in the cold season.
The seasonal changes in length of the head, thorax and abdomen were also found. The maximum percentage of head length to body length was met with in the warm season and the minimum in the cold season. On the contrary, the maximum percentage of abdomen length to body length was found in the cold season and the minimum in the warm season.
However, the thorax length to body length, regarding its maximum percentage, was sporadic to some extent.
In the specimens collected in winter it was observed that reddish orange oil drops were deposited in the body, but, as the season progressed, they gradually decreased and entirely disappeared in summer.