Isosmotic points and their ecological significance for juvenile Chinese sturgeon Acipenser sinensis

Abstract

Serum osmolality and ion concentrations were measured in juvenile Chinese sturgeon Acipenser sinensis at different salinities to determine the isosmotic point. Isosmotic and isoionic concentrations were calculated from the regressions for serum and ambient osmolality, with Na(+) , Cl(-) and K(+) as salinities 9·19, 8·17, 7·89 and 9·70, respectively. These values were consistent with the salinity of the habitat where juvenile A. sinensis occur in the Yangtze Estuary, suggesting that an isosmotic salinity is an important factor driving their habitat choice.

Adaptive alterations on gill Na+, K+-ATPase activity and mitochondrion-rich cells of juvenile Acipenser sinensis acclimated to brackish water

“…As has been observed previously by He et al (2009) and Zhao et al (2011, 2015, juveniles of this age/size class were able to acclimate to salinities greater than FW. In the present study, serum osmolality was significantly increased in sturgeon acclimated to BW, relative to those in FW (Table 1).…”

“…This increase in osmolality was also observed in juvenile green sturgeon (A. medirostris) of similar size (Allen and Cech 2007;Sardella and Kültz 2009). The average serum osmolality (284.50 ± 7.97 mOsmol kg -1 ) of juvenile Chinese sturgeon acclimated to BW was similar to their isosmotic concentration, i.e., 275.8 mOsmol kg -1 (Zhao et al 2015). It seems that this would be an osmoregulatory strategy for juvenile Chinese sturgeon.…”

“…It seems that this would be an osmoregulatory strategy for juvenile Chinese sturgeon. Generally, juvenile Chinese sturgeons migrated to the Yangtze Estuary in early May and spend 4-5 months (Wei et al 1997;Zhao et al 2009), in where the salinity level does not excess salinity 15 % and there is abundant food Zhao et al 2015). Juveniles of this age/size regulating their serum osmolality at nearly isosmotic level could save more energy to grow for preparation of entry to sea.…”

“…Mature adults swim upstream to middle and upper reaches of the Yangtze River to spawn in October and November, and juveniles migrate downstream in the following year to the estuary in preparation for their seaward migration (Wei et al 1997;Zhao et al 2009). Although they are considered to be the most anadromous of the sturgeons (Wei et al 1997), few studies have investigated their osmoregulatory mechanisms Zhao et al 2011Zhao et al , 2015.…”

Copper and Zinc Toxicity Estimates for Juvenile Chinese Sturgeon Acipenser sinensis in the Yangtze River Estuary

“…As the life history of the Chinese sturgeon includes a transition from birth in freshwater to saltwater for maturity, juveniles concentrate in the Yangtze River estuary from May through September annually to develop osmoregulatory capacity (He et al, 2009;Zhao et al, 2015). The Chinese sturgeon population has declined drastically in recent years as a result of many activities, including heavy metal contamination as a contributing stressor restricting survival fitness (Zhuang et al, 2016).…”