RESUMO
This study evaluated the influence of different microalgae diets on gonadal tissue maturation in the native oyster Crassostrea gasar in the laboratory, between March and May 2010, totalizing 60 days. Ninety-six oysters, collected from an experimental farm located on Florianópolis/SC, were transferred to the laboratory and maintained in three different diet treatments: Isochrysis galbana, Chaetoceros müelleri and a mix diet of both species in a 1:1 ratio. The oysters were conditioned in 3 L experimental units at a water flow rate of 300 mL min-1 and constant aeration. Food was provided in a continuous flow system, at a density of 16 x 104 cells mL-1. The mean water temperature and salinity during the experimental period were 24.36 ± 1.23 ºC and 29.4 ± 3.08, respectively. Fortnightly, six oysters randomly sampled from each treatment were examined for histological analysis. The condition index was analyzed at the beginning and the end of the experiment. The initial mean height and weight of the oysters were 68.25 ± 6.73 mm and 60.89 ± 14.19 g, respectively, and the final mean height and weight were 69.20 ± 5.97 mm and 70.04 ± 17.42 g, respectively. The sex ratio for the treatments was 1.2 males for each female and 19.5% of the oysters were considered indeterminate. The condition index was not affected by treatments and there was no improvement on the gonadal tissue maturation of t
Este estudo avaliou a influência de diferentes dietas microalgais sobre a maturação do tecido gonádico da ostra nativa Crassostrea gasar em laboratório, entre março e maio de 2010, totalizando 60 dias. Noventa e seis ostras, coletadas em cultivo experimental localizado em Florianópolis/SC, foram transferidas para o laboratório e submetidas a três tratamentos de alimentação: Isochrysis galbana, Chaetoceros müelleri e uma dieta mista das duas espécies na proporção de 1:1. As ostras foram acondicionadas em unidades experimentais de 3 L com vazão de 300 mL min-1 de água e aeração constante. A alimentação foi fornecida em sistema de fluxo contínuo, na densidade de 16 x 104 células mL-1. A temperatura e salinidade média da água durante o período experimental foram 24,36 ± 1,23 ºC e 29,4 ± 3,08, respectivamente. Quinzenalmente, foram realizadas análises histológicas de seis indivíduos amostrados aleatoriamente de cada tratamento. O índice de condição foi calculado no início e no fim do experimento. A altura e peso inicial das ostras foram 68,25 ± 6,73 mm e 60,89 ± 14,19 g, respectivamente, e a altura e peso final foram 69,20 ± 5,97 mm e 70,04 ± 17,42 g, respectivamente. A proporção sexual dos tratamentos foi 1,2 machos para cada fêmea e 19,5% das ostras foram consideradas indeterminadas. O índice de condição não foi afetado pelos tratamentos e não houve melhora na maturação do tecido
RESUMO
Crassostrea rhizophorae is a euryhaline oyster that inhabits mangrove areas, which are widely distributed along the Brazilian coast. The aim of this study was to investigate the effects of salinity (9, 15, 25, and 35ppt) on the activities of glutathione S-transferase (GST), glucose 6-phosphate dehydrogenase (G6PDH), catalase (CAT), and acetylcholinesterase (AChE) in the digestive gland of this species after exposure to diesel oil for 7 days at nominal concentrations of 0.01, 0.1, and 1mlL(-1) and after depuration for 24h and 7 days. GST activity increased in a diesel oil concentration-dependent manner at salinities 25 and 15ppt and remained slightly elevated even after depuration periods of 24h and 7 days. No changes were observed in the activities of G6PDH, CAT, and AChE in the oysters exposed to diesel and depurated. Based on these results, GST activity in the digestive gland of C. rhizophorae might be used as a biomarker of exposure to diesel oil in sites where the salinity is between 15 and 25ppt, values usually observed in mangrove ecosystems.