биота российских вод японского моря - Materials of Alexey Shipunov

plankton of the north-western part of the Sea of Japan and the Inland Sea of Japanfrom early spring till early summer. Records from the Chukchi, Bering and Japan seastestify that P. leuckarti is a neritic, eurythermal, and euryhaline species with a temperaturerange from 4 to 21˚C and a salinity range from 4 to 34‰ (average seawater salinity)(Kos, 1977).In the western part of Peter the Great Bay (Alekseev Bight of Amursky Bay) thefirst appearance of P. leuckarti was recorded for April, when temperature rose abovezero; in June the density was maximal, and in August, when water temperaturereached 21˚C, the species disappeared (Mikulich & Biryulina, 1977).In the south-western part of Peter the Great Bay P. leuckarti is also found onlytill August. In mid-July, when water temperature varied from 14 to 17˚C, the speciesgenerally occurred in bights and adjacent areas, with a mean density of 500 sp./m 3(Shkoldina & Shevchenko, 2001). Sporadic occurrences were recorded from the openpart of the Bay, and only for the cold near-bottom water layer.In Vostok Bay P. leuckarti appears in early June at a water temperature of 12–13˚C, but by the end of June and later, at a temperature above 20˚C, it is not found(Shkoldina, 2001, 2002).Seasonal dynamics of P. leuckarti is studied thoroughly for the Inland Sea of Japan(Onbe, 1974). The species appears there in early May, reaches maximum densityin late June, and disappears in August. Other evidence (1974–1977) point out that thespecies is present in the plankton from February-March till June (Onbe, 1985), and itsabundance is not more than 0.6–0.7 thousand sp./m 3 .Near the eastern coast of Hokkaido Island (43˚N, south of Sakhalin Island) P.leuckarti dominated among the podonids in mid-October. Parthenogenetic femalescomprised from 36 to 52.4% of all females in the population; gamogenetic femalescomprised from 39.8 to 52.8%. Most females had one resting egg; only one femalehad two eggs. Observations showed that in the daytime these cladocerans near the bottomor the surface may gather into assemblages, dissipating at night. Females withresting eggs mostly accumulate near the bottom and don’t rise up to the surface, thusprotecting themselves from predators (Saito & Hattori, 2000).Among the contents of the intestine of P. leuckarti mostly centric diatoms includingSkeletonema costatum were found (Kim et al., 1989).4. Genus Evadne Loven, 1836Type species: Evadne nordmanni Loven, 1836.Shell elongated, with pointed apex. Head not clearly separated from shell. Nuchalorgan situated on top of head. Branches of swimming antennae with 6 setae. Thoraciclimbs biramous, with relatively long exopods. Each exopod of limbs 1–2 bears twosetae; each exopod of limbs 3–4 bears one seta. Exopod of limb 1 equal in length tofirst segment of endopod. Cauda in shape of 2 conical pointed outgrowths.KEY TO THE SPECIES OF THE GENUS EVADNE1 (2). Exopod of limb 3 has 2 setae. Apex of shell produced into pointed peak .......................................................................................................... 1. E. spinifera (p. 22)21