.”Activity of Na+K+-ATPase in a “freshwater shrimp”, Palaemonetes argentinus (Caridea, Palaemonidae): Ontogenetic changes and effects of salinity”

ITUARTE, R.; LOPEZ MAÑANES A.A.; SPIVAK, E.; ANGER, K.

Coquimbo, Chile

Congreso; The Crustacean Society Mid-Year Meeting 2007; 2007

Embryos, larvae and adults of the shrimp Palaemonetes argentinus tolerate a wide range of salinities, but osmoregulatory capacities have been demonstrated only in post-embryonic stages. Like in many other crustaceans, little is known about osmoregulation during the embryonic phase. In the present investigation, ontogenetic changes in the activity of one of the key enzymes involved in the osmoregulation of crustaceans, Na+-K+-ATPase, were studied in the following life-history stages: (1) in embryos at an early (soon after egg laying; SI), an intermediate (SII), and a late stage of embryonic development (near larval hatching, SIII); (2) after hatching (Zoea-I stage, ZI); (3) in adult shrimps; (4) in isolated gill tissues from adults. All stages were abruptly transferred to 1, 15 and 25 PSU, and Na+-K+-ATPase activity was determined after 24 (embryos, larvae) or 48 hs (adults, gill tissues). Na+-K+-ATPase activity was lowest in SI and SII, maximum in SIII, and intermediate values were measured in the ZI and in adults. Increasing Na+-K+-ATPase activity during late embryonic development, with highest levels just prior to hatching (SIII), suggest that the osmoregulatory functions of P. argentinus are expressed during a late embryonic stage. Comparing different salinity treatments, late embryonic Na+-K+-ATPase activity (in SIII) was always higher at 15 PSU than at 1 and 25 PSU. By contrast, the enzyme activity in isolated gill tissues was higher at both 15 and 25 PSU than at 1 PSU. Changes in Na+-K+-ATPase activity under hyperosmotic conditions indicate that gill tissue are involved in the osmoregulation of adult shrimps. As these tissues are absent in embryonic and early larval stages, ion-transporting cells must be located elsewhere during these early ontogenetic phases.Palaemonetes argentinus tolerate a wide range of salinities, but osmoregulatory capacities have been demonstrated only in post-embryonic stages. Like in many other crustaceans, little is known about osmoregulation during the embryonic phase. In the present investigation, ontogenetic changes in the activity of one of the key enzymes involved in the osmoregulation of crustaceans, Na+-K+-ATPase, were studied in the following life-history stages: (1) in embryos at an early (soon after egg laying; SI), an intermediate (SII), and a late stage of embryonic development (near larval hatching, SIII); (2) after hatching (Zoea-I stage, ZI); (3) in adult shrimps; (4) in isolated gill tissues from adults. All stages were abruptly transferred to 1, 15 and 25 PSU, and Na+-K+-ATPase activity was determined after 24 (embryos, larvae) or 48 hs (adults, gill tissues). Na+-K+-ATPase activity was lowest in SI and SII, maximum in SIII, and intermediate values were measured in the ZI and in adults. Increasing Na+-K+-ATPase activity during late embryonic development, with highest levels just prior to hatching (SIII), suggest that the osmoregulatory functions of P. argentinus are expressed during a late embryonic stage. Comparing different salinity treatments, late embryonic Na+-K+-ATPase activity (in SIII) was always higher at 15 PSU than at 1 and 25 PSU. By contrast, the enzyme activity in isolated gill tissues was higher at both 15 and 25 PSU than at 1 PSU. Changes in Na+-K+-ATPase activity under hyperosmotic conditions indicate that gill tissue are involved in the osmoregulation of adult shrimps. As these tissues are absent in embryonic and early larval stages, ion-transporting cells must be located elsewhere during these early ontogenetic phases.