Marine Cladoceran Research Articles

伊勢湾・浦神湾の底土中の海産枝角類耐久卵の分布

伊勢湾・浦神湾の底土中の海産枝角類耐久卵の分布

Diurnal vertical migration of an estuarine cladoceran, Podon polyphemoides, in the Chesapeake Bay

Populations of the marine cladoceran Podon polyphemoides (Leuckart) in the Chesapeake Bay (USA) zooplankton typically occur in large patches, extending the length of the estuary. These patches are characterized by well defined maxima, which do not move seaward during a given season. During the day, the bulk of the population is situated in the upper part of the two-layered estuarine circulation, where it is subjected to transport by net non-tidal seaward current. One mechanism for maintaining the population within the estuary is provided by the diurnal behavior of the podonids, which migrate to deeper water during the night. The landward advection of the deeper currents, thus, helps to counterbalance seaward population loss during the day. The extent of the vertical movement of the population can be modified by various environmental factors, but a suggestive correlation with light was found. It is thought that the downward component of the migration is due to passive sinking.

Penilia avirostris DANA in the Indian Ocean (Cladocera)

AbstractThe records of the marine cladoceran Penilia avirostris DANA in the Indian Ocean are discussed as a further contribution to studies on the features of its world distribution. The review has pointed out different aspects of the life cycle of the species and the influence of biological and environmental factors upon the mechanisms of the cycle itself. Production of P. avirostris is considered on a trophic basis. Observations carried out elsewhere are also discussed.

Distribution of marine cladocerans in the Indian Ocean

Cladocera of the Indian Ocean have been studied, on the basis of samples collected during the International Indian Ocean Expedition (IIOE). Out of a total of 1927 samples, 552 contained Cladocera. Although the distribution of this group is mainly coastal, one species, Evadne tergestina, has been found in oceanic waters also, where it may establish seasonal populations. Evadne spinifera was recorded off the Australian and South African coasts in the southern hemisphere, and in the Northeastern part of the Arabian Sea coastal waters in the northern hemisphere. Podon polyphemoides was reported from a single station in South African waters. Penilia avirostris was found in coastal waters throughout the Indian Ocean. Short-term distribution patterns of E. tergestina and P. avirostris are discussed. The possible value of this group as food for pelagic fishes has been indicated. This work makes clear that adequate sampling in space and time is required along the Continental Shelf of the Indian Ocean in order to obtain more comprehensive information on this group.

海産枝角類ウスカワミジンコ耐久卵の海底における存在の確認

海産枝角類ウスカワミジンコ耐久卵の海底における存在の確認

Marine Cladocerans in the Chesapeake Bay Estuary1)

Marine Cladoceren (Crustacea, Branchiopoda) konnen wahrend der Saison reiche Planktonelemente in der Chesapeake Bay (U.S.A.) darstellen. Podon polyphemoides ist in der Bay weit verbreitet. Penilia avirostris und Evadne tergestina befinden sich gelegentlich im oberen Teil der Bay. Die letztgenannte Art ist noch nicht von dieser Gegend gemeldet worden, obwohl sie zusammen mit den beiden anderen Arten seit 1942 in der Chesapeake Bay lebt.

The Marine Cladoceran Penilia avirostris Dana in the American Waters of the Pacific Ocean

THE marine cladoceran Penilia avirostris Dana has been recognized as the only species of the genus1–3, and to this species belong the many specimens collected on April 11, 1953, at Bingham Station No. 70, at 04° 42′ S., 81° 22′ W., near the Peruvian coast.