Ultracytochemical location of Na+/K+-atpase activity and effect of high salinity acclimation in gill and renal epithelia of the freshwater shrimpMacrobrachium olfersii (Crustacea, Decapoda)

Abstract

Accumulation sites of lead phosphate reaction product consequent to Na+/K+‐ATPase activity in gill and renal epithelia of the freshwater shrimp Macrobrachium olfersii were located ultracytochemically by para‐nitrophenyl‐phosphate hydrolysis and lead precipitation, and quantified per unit membrane area and cytoplasmic volume. In shrimps in freshwater (<0.5‰ S, 20 mOsm/kg H2O, 0.7 mEq Na+/liter), numerous sites of electron‐dense, Na+/K+‐ATPase reaction product accumulation were demonstrated in the membrane invaginations of the mitochondria‐rich, intralamellar septal cells (12.5 ± 1.7 sites/μm2 membrane, 179 ± 22 sites/μm3 cytoplasm, mean± SEM, N ≤ 7) and in the basal region of the medial renal tubules (19.8 ± 1.8 sites/μm2 membrane, 437 ± 53 sites/μm3 cytoplasm), but not in the pillar cells whose apical flanges form the primary interface with the external medium. A putative, ouabain‐insensitive Na+‐ or H+‐ATPase was found in the apical microvilli of the medial renal tubules (17.4 ± 1.7 sites/μm2 membrane, 629 ± 101 sites/μm3 cytoplasm). This restricted location of Na+/K+‐ATPase activity within the gill epithelium suggests that during uptake, Na+ moves across the apical pillar cell membrane, passes through specialized, basolateral coupling junctions into the septal cell cytoplasm and is pumped into the hemolymph via the Na+/K+‐ATPase in the invagination membranes. In shrimps acclimated to a high‐salinity medium (21‰ S, 630 mOsm/kg H2O, 280 mEq Na+/liter) for 2 and 5 days, the mean number of sites of para‐nitrophenylphosphatase activity/μm2 membrane and /μm3 cytoplasm for both epithelia increases markedly by 83 and 163%, respectively. However, after 10 days acclimation, the number of sites declines dramatically, attaining values far below those for shrimps in freshwater. These acclimation‐induced alterations in numerical density/μm3 cytoplasm cannot be accounted for by corresponding changes in membrane surface density (μm2 membrane/μm3 cytoplasm) and reflect a real alteration in the number of Na+/K+‐ATPase reaction product sites/unit membrane area. These data suggest that neither the gill nor the renal Na+/K+‐ATPase systems function at maximal activity in shrimps in freshwater, possibly due to the low Na+ concentration, and are initially stimulated by the increase in external ionic concentration. However, these powerful Na+ transport systems respond to salt loading by a notable reduction in the number of hydrolysis sites, possibly through the incorporation of the Na+/K+‐ATPase into isolated membrane vesicles in the basal invaginations of the medial renal tubules, together with ultrastructural alterations like the spatial isolation of the mitochondria by multiple membrane stacks in the intralamellar septal cells. J. Exp. Zool. 284:617–628, 1999. © 1999 Wiley‐Liss, Inc.

Increasing the illumination slowly over several weeks protects against light damage in the eyes of the crustacean Mysis relicta

“…Thermal and photic stress has been found to change fatty acid composition and the ultrastructure of photoreceptive membranes in crayfish eyes (Kashiwagi et al, 1997). Under salinity acclimation, reported responses range from changes in epithelial Na + /K + -ATPase activity (shrimp: McNamara and Torres, 1999;frog: Wu et al, 2014) to whole-organism effects on development (frog tadpoles: Wu and Kam, 2009). In fact, it appears as remarkable that acclimation of eyes and visual function to variations in light levels on the time scale of seasonal changes has not been reported before.…”

A kinetic characterization of the gill V(H+)-ATPase in juvenile and adult Macrobrachium amazonicum, a diadromous palaemonid shrimp

“…Of these enzymes, the evolution of function in the V(H + )-ATPase and (Na + , K + )-ATPase has been considered critical for the colonization of fresh water (Morris, 2001;Tsai and Lin, 2007). The (Na + , K + )-ATPase is restricted to the basal membrane of the gill ionocytes and provides part of the driving force for the trans-epithelial movement of monovalent ions across the gill epithelia in brachyuran Crustacea (Towle and Kays, 1986;McNamara and Torres, 1999;Lignot and Charmantier, 2001;Lucu and Towle, 2003;McNamara and Faria, 2012). In freshwater shrimps, a V(H + )-ATPase located apically in the gill pillar cell flanges may complement the intralamellar septal cell (Na + , K + )-ATPase in energizing osmoregulatory NaCl uptake from fresh water (McNamara and Lima, 1997;Faleiros et al, 2010;McNamara and Faria, 2012).…”

Kinetic Analysis of Gill (Na+,K+)-ATPase Activity in Selected Ontogenetic Stages of the Amazon River Shrimp, Macrobrachium amazonicum (Decapoda, Palaemonidae): Interactions at ATP- and Cation-Binding Sites

“…,K ? )-ATPase located in the basal membrane of ion-transporting, septal cell ionocytes to which the pillar cells are structurally coupled McNamara and Torres 1999;Belli et al 2009;Faleiros et al 2010). H ?…”