Koichi Ara

Daily egg production rate of the planktonic calanoid copepod Acartia lilljeborgi Giesbrecht in the Cananéia Lagoon estuarine system, São Paulo, Brazil

Seasonal variation in daily egg production rate of the planktonic calanoid copepod Acartia lilljeborgi Giesbrecht in relation to temperature, salinity and chlorophyll a concentration was studied in the Cananéia Lagoon estuarine system, from March 1995 to January 1996. Recently captured A. lilljeborgi adult females were individually incubated in bottles filled with surface water screened through a 40-μm mesh, containing a natural assemblage of phytoplankton in the laboratory, at temperatures corresponding to ambient. Daily egg production rate ranged from 13.8±3.5 to 66.8± 15.1 eggs female−1 d−1 (mean ± 95% CL). The mean and maximum rates of daily egg production increased with temperature from 19.5 to 25.2 °C but then decreased with further increase in temperature at 28.4 through 29.1 °C, attaining the highest rates at approximately annual mean ambient water temperature (ca. 24–25 °C). The egg production rates increased linearly with chlorophyll a <40 μm fraction. Hatching success varied from 68.6 to 91.9%. Cannibalism varied from 1.4±0.7 to 7.1±3.3 nauplii female−1 d−1 (mean ± 95% CL). These results suggest that water temperature and phytoplankton concentration are important factors affecting the egg production rate of A. lilljeborgi in the Cananéia Lagoon estuarine.

Temporal variability and production of Euterpina acutifrons (Copepoda: Harpacticoida) in the Cananéia Lagoon estuarine system, São Paulo, Brazil

Diel and seasonal variations in abundance, population structure, biomass and production rate of the harpacticoid copepod Euterpina acutifrons were studied in the Cananeia Lagoon estuarine system, Sao Paulo, Brazil. Zooplankton samples were collected at 4-h intervals during multiple 24-h periods, from February 1995 to January 1996. Copepodites and adults of E. acutifrons were present in the plankton throughout the year (temperature, 18.6–29.4°C; salinity, 4.5–33.0 psu; chlorophyll-a concentration, 1.32–20.42μg 1−1) Abundance of E. acutifrons showed considerable diel variations. On most sampling dates, higher abundances were recorded at times when salinity was higher. Biomass varied from 0.044+-0.046 (daily mean+-SD) to 5.264+-3.425 mg C m−3The estimated production rates (minimum +- SD-maximum +- SD) were 0.034+-0.035−4.95+-3.25 (Ikeda-Motoda model), 0.035+-0.036−5.123+-3.347 (Huntley-Lopez model), and 0.016+-−2.101+-1.372 mg C m−3 d−1 (Hirst-Sheader model).

Deep-sea whale fall fauna from the Atlantic resembles that of the Pacific Ocean

Whale carcasses create remarkable habitats in the deep-sea by producing concentrated sources of organic matter for a food-deprived biota as well as places of evolutionary novelty and biodiversity. Although many of the faunal patterns on whale falls have already been described, the biogeography of these communities is still poorly known especially from basins other than the NE Pacific Ocean. The present work describes the community composition of the deepest natural whale carcass described to date found at 4204 m depth on Southwest Atlantic Ocean with manned submersible Shinkai 6500. This is the first record of a natural whale fall in the deep Atlantic Ocean. The skeleton belonged to an Antarctic Minke whale composed of only nine caudal vertebrae, whose degradation state suggests it was on the bottom for 5–10 years. The fauna consisted mainly of galatheid crabs, a new species of the snail Rubyspira and polychaete worms, including a new Osedax species. Most of the 41 species found in the carcass are new to science, with several genera shared with NE Pacific whale falls and vent and seep ecosystems. This similarity suggests the whale-fall fauna is widespread and has dispersed in a stepping stone fashion, deeply influencing its evolutionary history.

Feeding of the planktonic shrimp Lucifer faroni Borradaile, 1915 (Crustacea: Decapoda) in the laboratory

O comportamento alimentar de especimens jovens de Lucifer faxoni Borradaile, em laboratorio, sob condicoes de luz e escuro, foi estudado utilizando-se como alimento nauplios recem-eclodidos e metanauplios de Artemio. Neste estudo a taxa de alimentacao de L. faxoni foi influenciada pelo tamanho e concentracao da presa, bem como pelo tempo de contato com a mesma. A atividade alimentar de L. faxoni foi maior em condicoes de luz, quando comparado com as condicoes de escuro. f- taxa maxima de ingestao calculada foi de 17,28 e 13,40 nauplios.L. faxoni .d- para as condicoes de luz e escuro, respectivamente.