RESUMO
Salinity in the oceans is changing due to climate change and global warming. Intense rainfalls and freshwater runoff decrease salinity along the coastal areas. In contrast, intense drought seasons and river damming have certainly increased salinity in lagoons and estuaries. Few studies have focused on aspects of the biology and culture of oyster Crassostrea corteziensis, but until now, physiological and immunological responses in this species have not been assessed under acute hypo- and hypersaline stress conditions. Oysters obtained from a local farm were acclimated for three weeks in laboratory conditions. To avoid closure of oyster valves during salinity induced-stress conditions, a notch was done on each organism shell not only to facilitate oyster tissue exposure to rearing water but also for sampling hemolymph. Oysters (N = 180) were abruptly exposed to three salinity treatments: (HO) hypo-, (C) control, and (HP) hypersaline stress conditions (10, 35, and 50 PSU, respectively). Four oysters per treatment were sampled at 1, 2, 3, 6, 12, 24, and 48 h after exposure. Hemolymph osmolality, water content and total protein concentration in tissues, metabolic and immune responses were assessed for each organism. Oyster survival was not different among treatments and was maintained above 96% at the end of the experimental trial. Hemolymph osmolality reached the value of rearing water at 6 and 48 h of exposure to HP and HO stress conditions, where oysters exposed to salinity increase showed less resilience than those to decrease. Higher glucose levels in plasma and lower ones of hemocyanin were assessed in the oysters exposed to HP compared to HO conditions, suggesting more stressful conditions or susceptibility of oysters during salinity increase. Total hemocyte (THC), hyalinocyte (HC), and granulocyte (GC) counts decreased in oysters exposed to HP condition, while total and differential hemocyte counts were similar among oysters exposed to HO and control conditions. Despite hemocyte phagocytosis was not different among treatments, viability decreased in those exposed to HP condition. Contrastingly, superoxide anion (SOA) production (oxidative capacity) increased in oysters exposed to both induced salinity-stress conditions, which suggest susceptibility increase in oysters, particularly during salinity increase. The results show that HP condition is particularly stressful for C. corteziensis. In turn, this condition could increase both their vulnerability to other environmental stressors, such as temperature and/or acidification or susceptibility to opportunistic pathogenic microorganisms that cause the most common oyster diseases.
Assuntos
Crassostrea , Salinidade , Estresse Fisiológico , Animais , Crassostrea/imunologia , Crassostrea/metabolismo , Crassostrea/fisiologia , Estuários , Hemócitos , Imunidade , Pressão OsmóticaRESUMO
The clam Megapitaria squalida is a fishing resource with increasing importance in Northwestern Mexico. Nevertheless, this fishery has shown important variations that could be related to environmental factors. To assess this, monthly landings of M. squalida were analyzed during 2002-2005 for Bahía de La Paz, B.C.S., and were related with monthly time series of sea surface temperature, derived from MODIS-Aqua Sensor. The results showed a positive and significant relationship between sea surface temperature and clam landings. The likely impact of anomalous conditions of sea temperature on this resource is discussed.
Assuntos
Bivalves/classificação , Pesqueiros , Temperatura , Animais , México , Oceanos e Mares , Densidade Demográfica , Dinâmica Populacional , Estações do AnoRESUMO
Megapitaria squalida (Bivalvia: Veneridae) fishery landings and temperature relationship in Bahía de la Paz, México. The clam Megapitaria squalida is a fishing resource with increasing importance in Northwestern Mexico. Nevertheless, this fishery has shown important variations that could be related to environmental factors. To assess this, monthly landings of M. squalida were analyzed during 2002-2005 for Bahía de La Paz, B.C.S., and were related with monthly time series of sea surface temperature, derived from MODIS-Aqua Sensor. The results showed a positive and significant relationship between sea surface temperature and clam landings. The likely impact of anomalous conditions of sea temperature on this resource is discussed. Rev. Biol. Trop. 59 (1): 151-157. Epub 2011 March 01.
La almeja chocolate Megapitaria squalida es un recurso pesquero con creciente importancia en el noroeste de México al registrarse un incremento en los volúmenes de captura. Sin embargo, esta pesquería ha observado variaciones importantes en las capturas que podrían estar relacionadas con factores ambientales. Se obtuvieron datos mensuales de producción de M. squalida durante 2002- 2005 y se estimaron series de tiempo de temperatura superficial del mar en la Bahía de La Paz B.C.S. a partir de imágenes mensuales derivadas del sensor MODIS-Aqua. Los resultados indican una relación positiva significativa entre la temperatura superficial del mar y los volúmenes de captura, razón por la cual nuestro trabajo tiene como objetivo estudiar las relaciones entre capturas de Megapitaria squalida (Bivalvia: Veneridae) y la temperatura superficial del mar en La Bahía de la Paz, Baja California Sur, México.
