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Morphology of chloride cells was studied in embryos, larvae and juveniles of ayu (Plecoglossus altiuelis), carp (Cyprinus carpi01 and flounder (Kareius bicoloratus). Chloride cells of seawater-adapted fishes interdigitated to neighboring cells and linked each other with leaky junctions. No such interdigitation or a leaky junction was found in those of freshwater fishes. Larval ayu were able to tolerate direct transfer from fresh water to seawater even immediately after hatching. Juvenile flounder reared in seawater for 60 days were able to adapt to fresh water. Their chloride cells started developing or degenerating interdigitations and leaky junctions within 3 h after the transfer. Juvenile ayu of landlocked form caught in Lake Biwa survived in seawater for no longer than 6 h. Juvenile carp died within 12 h after transfer to 15%, seawater. Newly hatched flounder did not survive in fresh water for longer than 48 h. Their chloride cells did not show any morphological change, although the epithelial cells were severely damaged. Thus, the ability of chloride cells to modify their intercellular organization and junctional structure appears to play a critical role in salinity adaptation.

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Abstract. Caprella danilevskii Czerniavski, an epifaunal amphipod crustacean, was successfully reared for two generations under laboratory conditions. Amphipods were maintained in pairs or fours in a Petri dish. Temperature and photoperiod were maintained at 20 °C, and 14 h light: 10 h dark, respectively. Colonies of the diatom Cylindrotheca closterium (Ehrenberg) Reumann and Lewin were provided as food source. The red alga Gelidium amansii (Lamouroux) Lamouroux was used to provide an attachment substrate for the caprellids. Juveniles that emerged from the brood pouch were described as instar I. Subsequent instars were identified by molts. Juveniles molted successively at 2.5 to 6.5 d intervals. The body length of males at each instar increased exponentially, while that of females followed a sigmoid curve. A different pattern of flagellar segment addition in the antenna I of males and females was revealed. At the age of 20.8 d, females reached instar VII, and produced their first embryos. After 5.1 d, juveniles emerged from the brood pouch. On average, females produced 5.4 clutches successively at 5.0 d intervals. The number of offspring per spawning increased from 6.3 at instar VII to 22.0 at instar XII. The total number of offspring was 69.0 for a female throughout her life span.