биота российских вод японского моря - Materials of Alexey Shipunov

oping in the brood pouch have a full reserve of nutrients for embryos. But in membersof the genus Penilia and the Onychopoda (Polyphemoidea) parthenogenetic eggs donot have the same reserve and get nutrients from the inner hypodermic wall of thebrood pouch. Eggs develop in the brood pouch into tiny young cladocerans, whichhatch out and grow into adults, going through several ecdyses. The young of the Polyphemoidaehatch out by the destruction of female’s brood pouch; these young are bornsexually mature.The appearance of males in populations depends on unfavourable conditions. Afterfertilization the ovicell begins to accumulate yolk in the ovary. After the period oftrophoplasmatic growth in the ovary, resting eggs having only an elastic membraneflow to the brood pouch where dense chitinous membranes are formed. In the podonidsat complete ripening of the eggs the death of a female follows, and the restingeggs sink to the bottom (Swammerdam, 1685). Unlike the Cercopagidae, amongwhich particular gamogenetic females appear, in the Podonidae the resting eggs aredeveloped in parthenogenetic females after fertilization. The resting egg, covered withthick chitinous membranes protecting it from unfavourable environment conditions,rests on oozy sediments.The present work is based on the taxonomic system, by which the superorderCladocera includes three orders: Ctenopoda (two families), Anomopoda (ten families),and Onychopoda (three families) (Dumont & Negrea, 2002). The superorder Cladoceracontains more than 450 species belonging to 52 genera. Most cladocerans (95%) arefound in freshwater habitats, 3% (about 30 species) – in brackish water habitats (includinglandlocked seas, e.g. the Caspian and the Aral), and only eight species occurin marine environments (Bowman & Abele, 1982). One of these species belongs to thefamily Sididae (Penilia avirostris Dana, 1849), and other seven to the family Podonidae.All eight species occur in the Sea of Japan, and seven of them, excluding Podonintermedius Lilljeborg, 1853, are found in its northwestern part (Peter the Great Bay).Most cladocerans, including Sididae, are filter feeders; they feed on algae, bacteria,and detritus. Species of the order Onychopoda (Polyphemoidea) are mostly predators,feeding on larger organisms (small crustaceans, rotifers, protozoans, and algae).Cladocerans represent the important trophic part of plankton communities, being consumersof organic matter and food for other organisms, particularly for fishes.Cladocerans are typical neritic species of the Sea of Japan. The coastal zone inhabitedby various neritic animals is 3–5 miles wide in the northern part of the Sea ofJapan, narrowing southward to a width of 0.5–1 mile within the Korea Strait and expandingto 7–10 miles in the eastern part of the sea near the Korea Strait (Kun &Meshcheryakova, 1954; Kun, 1975). Currents may bring cladocerans to the open sea(Brodsky, 1955; Meshcheryakova, 1960; Miklukhina, 1967). Some species of the superorder(Pseudevadne tergestina, Podon leuckarti, Pleopis polyphemoides, and Peniliaavirostris) are indicators of coastal surface water conditions (Biryulin et al., 1970).In summer cladocerans may be abundant in the neritic zone. They are common andoften dominate and subdominate in the plankton of Peter the Great Bay.Specimens for drawing some missing biological stages of four species of the podonids(Podon leuckarti, Pleopis polyphemoides, Evadne nordmanni, and Pseudevadnetergestina) were picked out from the plankton samples collected in 1996–2002in Vostok Bay (Peter the Great Bay) and in the south-western part of Peter the GreatBay.10