биота российских вод японского моря - Materials of Alexey Shipunov

Great Bay, but no one specimen has been recorded from the Sea of Okhotsk and theBering Sea.Biology and ecology. P. polyphemoides is an exceptionally neritic species in theFar East seas. It prefers surface waters, but may occur to a depth of about 100 m. InPeter the Great Bay of the Sea of Japan it is found at a temperature from 6 to 26°C andfrom low (several ‰) to normal seawater salinity (Kos, 1977). Maximum density hasbeen recorded for autumn. In the southwestern part of Peter the Great Bay the specieshas two peaks of density, in July and in September. Thus, in Sivuchya Bay its densityreached 500 sp./m 3 in July, then in August at a surface water temperature of 20–22°Cthe population declined, and in September (at a temperature of 17–19°C) it reached1047 sp./m 3 (18.3% of the total density of zooplankton) (Shkoldina & Shevchenko,2001). In the western part of Peter the Great Bay P. polyphemoides appears in July at18°C temperature and 33–34‰ salinity. Maximum density, 616 sp./m 3 , was recordedfor mid-October at 14.1°C, and specimens were found singly until January, when temperaturefell below zero (Mikulich & Biryulina, 1977). In Vostok Bay the species isusually found during a period from June till October. Substantial desalination of theinner part of the bay stimulates its mass development (Shkoldina, 2001). It appears insmall numbers in June at a temperature of 13.4–13.8°C (Shkoldina, 2002) and attainspeak density (over 7.6 thousand sp./m 3 ) twice: in August at 21.3°C and in October at14.3°C.P. polyphemoides is abundant in the coastal waters of Korea in the Sea of Japan.Its density reaches 10% of the total density of the zooplankton in July. In Novemberand December males and gamogenetic females comprise 30–40% of the total densityof the population (Yoo & Kim, 1990). The species occurs in the coastal waters of Koreaall the year round excluding February (Yoo & Kim, 1987). The seasonal dynamicsand ecology of the species were most thoroughly studied for the Inland Sea of Japan(Onbe, 1974). P. polyphemoides is found there in the plankton from April-May untilearly August. Its density widely varies from year to year; it is highest (2–38 thousandsp./m 3 ) from late May till early July, at a temperature of 12–26.8°C. The species disappearsat a temperature between 22.8 and 26.8°C, depending on a mean temperatureof a year. It inhabits the upper 20 m deep layer of water, being most abundant to 10 m.The fecundity of P. polyphemoides is two to ten embryos per female; it is maximalin April (four–ten); in late June the number of embryos decreases to two–six.Small amounts of males and females with resting eggs occur in mid-June. The newlyhatched specimen of P. polyphemoides has well developed eye and limbs, and weaklydeveloped brood pouch (Onbe, 1974).Observations of P. polyphemoides in the ports of the Mediterranean Sea andChesapeake Bay show that it is relatively tolerant to pollution; under conditions ofeutrophication it even increases in numbers (Mordukhai-Boltovskoi & Rivier, 1987;Rivier, 1998).2. Genus Pseudevadne Claus, 1877Type species: Pseudevadne tergestina Claus, 1877.Body oval or triangular, with rounded apex. Shell narrowing to apex or inflated,depending on size of embryos and their number, as in members of genus Evadne.Shell with strongly pronounced crests of fornix, and with pigment cells of hypodermis17