ABSTRACT
A infestação por poliquetas do gênero Polydora em ostras C. gigas de cultivo foi acompanhada por meio de coletas mensais enquanto os parâmetros físico-químicos da água do mar foram monitorados semanalmente. Foi determinada a área total ocupada pelas bolhas e tubos na superfície interna das valvas, observando os possíveis danos às principais características fisiológicas da ostra. Houve prevalência do anelídeo Polydora sp. (Polychaeta: Spionidae) em todos os meses amostrados, chegando a 100% no período de águas mais frias. As análises histológicas mostraram que os tecidos e órgãos estavam intactos, ocorrendo a formação de gametas. Nas ostras severamente infestadas, foi possível observar intensa fibrose na região do manto, mostrando reparo do tecido.
The infestation of polychaetes Polydora in oyster C. gigas within cultivation was accompanied by monthly samples whereas the physical and chemical parameters of seawater were monitored weekly. The total area occupied by bubbles and tubes in the inner surface of the valve was determined, indicating the possible damage to the main physiological characteristics of oysters. It was observed prevalence of annelid Polydora sp. (Polychaeta: Spionidae) in all samples each month, reaching 100% in the period of cooler waters. The histological analysis showed that the tissues and organs were intact, occurring the formation of gametes. In oysters severely infested, it was possible to observe intense fibrosis in the mantle, showing repair of the tissue.
Subject(s)
Animals , Ostreidae/physiology , Annelida , PolychaetaABSTRACT
We examined the spat availability the oyster Pteria colymbus at 6-8 and 19-21 m depths for 15 months (March 1993-June 1994) in Turpialito, Golfo de Cariaco, Venezuela. Spats were trapped using artificial collectors (plastic filaments in bags, 30 x 60 mm), suspended from a long line. Each collector was replaced by a replica monthly to analyse abundance, shell dimension and mass of P. colymbus. Intraweekly, the temperature, salinity, oxygen and food availability (Chlorophyll a, total seston, organic and inorganic seston) were determinated. There is juvenile recruitment all year, suggesting continuous reproduction. Spat counts were higher at 6-8 m (generally 50-230 juveniles per collector) with peaks in August and December 1993 (April and June 93 at 19-21 m). The length-weigh mass relation was higher at 19-21 m, suggesting greater food availability because of lower organism density (including P. colymbus) and a greater water flux. Phytoplanktonic abundance and temperature were correlated (r2=0.38) with juvenile abundanc; this relationship and the association of juvenile abundance with higher temperature and Chlorophyll a levels, suggest that spat abundance was higher at the beginning of the water stratification period, when phytoplankton biomass is high.
Subject(s)
Animals , Ecosystem , Ostreidae , Seawater , Ostreidae/anatomy & histology , Ostreidae/physiology , Population Density , Reproduction , Seasons , VenezuelaABSTRACT
The Mexican oyster fishery, 90% supported by the coastal lagoons of the Gulf of Mexico, has decreased drastically in the last six years as a result of anthropogenic pollution and improper management. The mussel Ischadium recurvum has proliferated and competes with oysters for space and probably food. Crassostrea virginica and Ischadium recurvum were studied to evaluate somatic production with biometry and physiological condition indices (PCI's) during an annual cycle. A random sample of 200 organisms was taken montly for each species. Condition indices wet flesh weigth: wet shell weight ratio (WFW/WSW), dry flesh weight: wet flesh weight ratio (DFW/WFW), dry flesh wet: dry shell weight ratio (DFW/DSW), and ash free dry weight: tissue dry weight (AFDW/TDW) were calculated. In order to stablish physiological condition and temporal variability, these indices were compared between species and months. The somatic production of mussels was higher than in oysters. This enhancement in production could be explained by: 1) Mussel uses less energy for shell production, 2) a constant recruitment of mussel almost year-round, and 3) the mesohalin lagoon was more favourable to the mussel.