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Populations of Pseudevadne tergestina were studied in Guanabara Bay, southeastern Brazil, to

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ABSTRACT. A frrst record of Pleopis schmackeri (Poppe, 1889) (Branchiopoda, Onychopoda) in the Guanabara Bay, Rio de Janeiro, Brazil is described. This marine cladoceran species occurred in zooplanktonic samples obtained on June 26, 2000, with densities =: 4.0 ind.m-3 Its presence may be related with inflow of coastal waters to the bay. KEY WORDS. Cladocera, Pleopis schmackeri, zooplankton, Guanabara Bay, Brazil Cladocerans are small crustaceans that mainly inhabit fresh water, with only eight truly marine species (ONBÉ 1999). As compared with the rest of eladoceran species, the ecological characteristics of Pleopis schmackeri (Poppe, 1889) are unknown. This is probably due to its very rare presence and low abundance in temperate and tropical waters . Its occurrence has been described mainly in waters from the South China Sea through northern Honshu (Japan); and sporadic records from the Agaba Bay (Red Sea) and Madagascar (lndian Ocean). According to these reports, P. schmackeri may be considered warm water, coastal and oceanic species.ln Brazilian waters, a single record was made by ROCHA (1985) in the coastal waters of São Paulo (24°27'S-47°05 ' W), on 24 th June 1983.The presence of P. schmackeri in the Guanabara Bay is an unexpected fact, because this eladoceran species had never been recorded before in spite of intense investigations in previous decades . This fact suggests that P. schmackeri does not participate in the zooplanktonic community of this bay. Guanabara Bay, Rio de Janeiro, southeastern Brazil (22°41' -23°56' S and 43°02' -43°18'W), has been elassified as a coastal estuary with shallow and partially mixed waters.The occurrence of P. schmackeri was observed during research about the dynamics of planktonic communities of the Guanabara Bay. The zooplanktonic samples were obtained in surface water, at a fixed station on the entrance of the bay. ln a time series of sampling (from February 2 to August 1, 2000 with 3-4 day intervals), P. schmackeri was detected only in the triplicate samples taken on June 26, with mean densities == 4.0 ind.m-3 . Water temperature and salinity were 21 .6°C and 35.2 respectively. Population was composing by parthenogenetic females only. Mean body length and fecundity of individuaIs were 420 Ilm and five embryos.female-1 respectively . On that day, a strong intrusion of clearer and more saline

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 microm 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.

The aim of this study was to determine the development time of embryos and to estimate the hatching rates of resting eggs of cladocerans found in the sediment of Guanabara Bay, Rio de Janeiro, Brazil, under experimental conditions. Eggs were sorted by species (Penilia avirostris -Sididae; Pleopis polyphemoides and Pseudevadne tergestina -Podonidae) and incubated at a temperature of 25 °C, salinity 35 and photoperiod 12 hours light/ 12 hours dark. Hatching rates were about 38% for Pseudevadne tergestina and 28% for Pleopis polyphemoides. Embryos of resting eggs of Penilia avirostris developed comparatively slowly (hatching after 86 days of incubation), with a hatching rate of only 5%. It was observed that development and hatching of resting eggs of marine cladocerans suggest that pulses of recruitment may exist, thus contributing to the rapid appearance and maintenance of planktonic populations of these crustaceans in Guanabara Bay.Keywords: Cladocera, resting eggs, hatching, Guanabara Bay, Brazil. Taxas de eclosão de ovos de resistência de 'Cladocera' (Crustacea; Branchiopoda) em uma baía tropical, BrasilResumo O objetivo do presente estudo foi determinar o tempo de desenvolvimento de embriões e estimar as taxas de eclosão de ovos de resistência de cladóceros encontrados no sedimento da baía de Guanabara, Rio de Janeiro, Brasil, sob condições experimentais. Os ovos foram separados por espécie (Penilia avirostris -Sididae; Pleopis polyphemoides e Pseudevadne tergestina -Podonidae) e incubados a 25 °C, salinidade 35 e fotoperíodo 12 horas claro/ 12 horas escuro. As taxas de eclosão foram de aproximadamente 38% para Pseudevadne tergestina e de 28% para Pleopis polyphemoides. Os embriões dos ovos de resistência de Penilia avirostris desenvolveram-se de forma relativamente lenta (eclodindo apenas 86 dias após o início da incubação), com uma taxa de eclosão de apenas 5%. Foi observado que o desenvolvimento e a eclosão dos ovos de resistência de cladóceros marinhos sugerem que podem ocorrer em pulsos, contribuindo assim para o rápido aparecimento e manutenção destes crustáceos na baía de Guanabara.Palavras-chave: Cladocera, ovos de resistência, eclosão, baía de Guanabara, Brasil.