Ecological studies of a fresh water copepod, Sinodiaptomus vodkanoni Kiefer

II. Metamorphosis, growth, seasonal and geographical distribution

Abstract

This study deals with Sinodiaptomus volkano Kiefer concerning its metamorphosis growth and its seasonal distribution in Japan.
1. Fourteen stages are observed in metamorphosis, two nauplius, six metanauplius and six copepodid stages. In ecdysis new segments are inserted in frout of the ventral process, i. e. anamorphosis (Fig. 1). The duration between hatching and sex discernible stage varies according to the temperature of water and kind of foods, showing 22-23 days at 17.-18 °C on average. Body length in sex discernible individuals is about 1.3mm.
2. The larva of 0.13mm in body length just after hatching attains 1.08 mm on average after 18 days in summer populations, while that of 0.12 mm long attains 0.70 mm after 22 days in winter populations (Table 1).
3. Growth rate from minimum sex discernible individual to adult is expressed as _??_Y=0.1036X+0.7360 in summmer populations, and _??_Y=0.0719X+0.7693 _??_Y=0.1005X+0.6430 _??_Y=0.0689X+0.5650 in winter populations, where X is days and Y is body length in mm (Fig. 2).
4. This species is eurythermal, occurring in small ponds throughout the year. The winter population is larger in size than those of summer, spring and autumn populations (Fig. 3).
5. The summer populations prefer temperature range from 15 °C to 30 °C, while the winter populations have a preference for a range between 5 °C and 10 °C.
6. It occurs abundantly in ponds on the northern and southern coasts of the Seto Inland Sea covering the prefectures of Fukuoka and Oita, as well as Yamaguchi, Hiroshima, Okayama, Ehime, Tottori and the southern part of Hyogo (Table 2 and 3, Fig. 4).
7. Its common habitats are ponds lying at 50-100 m above sea level. The habitat water is neutral or slightly alkaline and oligotrophic in nutritive conditions.