Seasonal changes in the distribution and abundance of marine cladocerans of the Northwest Alboran Sea (Western Mediterranean), Spain

The annual cycle of marine cladocerans was studied over six years from 1994 to 1999 within the frame of the monitoring Project ECOMALAGA at a nine stations in the NW of the Alboran Sea, with the aim of assessing seasonal patterns and interannual trends in distribution and abundance of marine cladocerans. Seven species (Penilia avirostris, Evadne nordmanni, Evadne spinifera, Pseudoevadne tergestina, Pleopis polyphemoides, Podon leuckarti and Podon intermedius) were detected in the northwest Alboran Sea. Total cladoceran relative abundance varied from 0 to 89 percent of the total cladocerans. The abundance of cladocerans was higher in summer-autumn than in winter-spring (7012 - 4711.100 and 743 - 217.100m-3 , respectively). The species composition was very different in terms of seasonality. P. polyphemoides, P. leuckarti and P. intermedius appeared mostly during the spring. P. tergestina, E. spinifera and E. nordmanni predominantly occurred during the winter. P. avirostris occurred mostly during the summer and autumn.

Reproductive aspects of marine cladocerans Penilia avirostris and Pseudevadne tergestina (Crustacea, Branchiopoda) in the outer part of Guanabara Bay, Brazil

The objective of this study was to report on some aspects of marine cladoceran reproduction in Guanabara Bay. Samples were collected during 1985 using a conical net with 200 mm mesh. Two species were identified: Penilia avirostris and Pseudevadne tergestina. Both species disappeared from the plankton in winter. Two months before this phenomenon, parthenogenetic females displayed reduction in brood size, while gamogenetic individuals appeared among the populations. This sequence of events is generally typical of marine cladoceran populations in temperate waters.

O objetivo do presente estudo foi registrar alguns aspectos da reprodução das espécies de cladóceros marinhos que ocorrem na Baía de Guanabara. As amostras foram obtidas durante o ano de 1985, com o auxílio de uma rede cônica de 200 mm de diâmetro de poro. As duas espécies identificadas (Penilia avirostris e Pseudevadne tergestina) são comuns à baía, mas desaparecem do plâncton no inverno. Dois meses antes desse fenômeno, as fêmeas partenogenéticas apresentam redução no tamanho da ninhada, enquanto os animais gametogenéticos surgem na população. Essa seqüência de eventos, em geral, é típica para as populações de cladóceros marinhos que ocorrem em regiões temperadas.