Differential adjustment in gill Na+/K+- and V-ATPase activities and transporter mRNA expression during osmoregulatory acclimation in the cinnamon shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae)

Abstract

We evaluate osmotic and chloride (Cl(-)) regulatory capability in the diadromous shrimp Macrobrachium amazonicum, and the accompanying alterations in hemolymph osmolality and [Cl(-)], gill Na(+)/K(+)-ATPase activity, and expression of gill Na(+)/K(+)-ATPase α-subunit and V-ATPase B subunit mRNA during salinity (S) acclimation. We also characterize V-ATPase kinetics and the organization of transport-related membrane systems in the gill epithelium. Macrobrachium amazonicum strongly hyper-regulates hemolymph osmolality and [Cl(-)] in freshwater and in salinities up to 25‰ S. During a 10-day acclimation period to 25‰ S, hemolymph became isosmotic and hypo-chloremic after 5 days, [Cl(-)] alone remaining hyporegulated thereafter. Gill Na(+)/K(+)-ATPase α-subunit mRNA expression increased 6.5 times initial values after 1 h, then decreased to 3 to 4 times initial values by 24 h and to 1.5 times initial values after 10 days at 25‰ S. This increased expression was accompanied by a sharp decrease at 5 h then recovery of initial Na(+)/K(+)-ATPase activity within 24 h, declining again after 5 days, which suggests transient Cl(-) secretion. V-ATPase B-subunit mRNA expression increased 1.5-fold within 1 h, then reduced sharply to 0.3 times initial values by 5 h, and remained unchanged for the remainder of the 10-day period. V-ATPase activity dropped sharply and was negligible after a 10-day acclimation period to 21‰ S, revealing a marked downregulation of ion uptake mechanisms. The gill epithelium consists of thick, apical pillar cell flanges, the perikarya of which are coupled to an intralamellar septum. These two cell types respectively exhibit extensive apical evaginations and deep membrane invaginations, both of which are associated with numerous mitochondria, characterizing an ion transporting epithelium. These changes in Na(+)/K(+)- and V-ATPase activities and in mRNA expression during salinity acclimation appear to underpin ion uptake and Cl(-) secretion by the palaemonid shrimp gill.

Osmoregulation in the Hawaiian anchialine shrimpHalocaridina rubra(Crustacea: Atyidae): expression of ion transporters, mitochondria-rich cell proliferation, and hemolymph osmolality during salinity transfers

“…While H. rubra acts as an osmoconformer at oceanic salinities (32‰), it transitions to osmoregulation at lower salinities, similar to previously studied marine euryhaline crustaceans (e.g. Zanders, 1980;Henry and Watts, 2001;Chung and Lin, 2006;Faleiros et al, 2010), including another atyid species (Born, 1968). However, 'strong' osmoregulating crustaceans with a marine ancestry such as the blue crab (Callinectes sapidus) maintain an osmotic gradient between the external medium and their hemolymph of 600 mOsm kg −1 H 2 O (Cameron, 1978;Henry, 2001).…”

“…In euryhaline crustaceans, expression of these genes usually increases dramatically in the osmoregulatory gills during comparable salinity transfers (reviewed by Havird et al, 2013). For example, NKA expression in C. granulatus increased 25-to 55-fold after transfer from SW to 45‰ and 2‰ (Luquet et al, 2005), with similar results for Scylla paramamosain (Chung and Lin, 2006), Pachygrapsus marmoratus (Jayasundara et al, 2007), C. sapidus (Serrano et al, 2007), C. maenas (Serrano and Henry, 2008;Jillette et al, 2011), Macrobrachium amazonicum (Faleiros et al, 2010) and Litopenaeus vannamei (Wang et al, 2012). Although utilized in fewer studies, CAc (but not CAg) (see Serrano and Henry, 2008), NKCC, HAT and AK (e.g.…”

Understanding the molecular basis of adaptation to freshwater environments by prawns in the genus Macrobrachium

“…Several studies have identified specific genes involved in osmoregulation in crustacean species that include NKA, NKCC, VTA, CA and Cystic fibrosis transmembrane regulator (CFTR) (Pongsomboon et al, 2009;Faleiros et al, 2010;Havird et al, 2013). Functional roles of these genes are known to be: NKA establishes an electromechanical gradient across the gill cell membrane; NKCC transports ions into gill cells from the blood or the environment depending on salinity level; VTA pumps protons to influence HCO 3 -and Cl -exchange, and Na + uptake; CA produces H + and HCO 3 -that are needed to drive Na + and Cl -exchange; and CFTR is the Cl -channel regulator for osmoregulation in crustaceans (Singer et al, 1998;Hwang and Lee, 2007;Moshtaghi et al, 2016 (Foster et al, 2010;Havird et al, 2013;Scott and Brix, 2013).…”

“…All experimental tanks were maintained at 6‰ (a level that we considered as control salinity) for two weeks to minimize environmental impacts on gene expression and body physiology (hemolymph). Previous investigations have shown that crustaceans can acclimate well to different salinity conditions within 1-3 days depending on the relative salinity stress level (Lovett et al, 2006;Roy et al, 2007;Charmantier et al, 2009;Faleiros et al, 2010;Havird et al, 2014). While this strategy may not rule out all environmental effects completely, we consider that it will provide a robust foundation for assessing the impact of salinity level on experimental individuals.…”

“…It is now widely accepted that acclimation to low ionic freshwater is more energetically costly than to brackish or seawater because freshwater organisms need to conserve internal ions, absorb ions from food and their surrounding environment while restricting water gain (Lovett et al, 2006;Faleiros et al, 2010;Havird et al, 2013;Havird et al, 2014). Conversely, organisms need to restrict water loss and limit ion accumulation in high saline environments (Henry et al, 2002;Brennan et al, 2015).…”