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Since 2000, a well‐established population of the invasive oriental shrimp Palaemon macrodactylus has been present in fully marine conditions in the southwestern Atlantic Ocean (~38° S). To assess the physiological performance of this atypical population restricted to fully marine conditions, we conducted a laboratory experiment in which individuals were transferred from 35 ‰S (local seawater) to 2 ‰S; 5 ‰S; 10 ‰S; 20 ‰S; 50 ‰S and 60‰ for short (6 h), medium (48 h), and long (>504 h) acclimation periods. We measured the time course response of relevant parameters in the shrimp's hemolymph; activity of Na+, K+‐ATPase (NKA), and V‐H+‐ATPase (VHA); and muscle water content. Shrimp showed great osmoregulatory plasticity, being able to survive for long periods between 5 ‰S and 50 ‰S, whereas no individual survived after transfer to either 2 ‰S or 60 ‰S. Shrimp hyper‐regulated hemolymph osmolality at 5 ‰S and 10 ‰S, hypo‐regulated at 35 ‰S and 50 ‰S, and isosmoticity was close to 20 ‰S. Compared to 35 ‰S, prolonged acclimation to 5 ‰S caused a decrease in hemolymph osmolality (~34%) along with sodium and chloride concentrations (~24%); the NKA and VHA activities decreased by ~52% and ~88%, respectively, while muscle water content was tightly regulated. Our results showed that the atypical population of P. macrodactylus studied here lives in a chronic hypo‐osmo‐ion regulatory state and suggest that fully marine conditions contribute to its poor performance at the lower limit of salinity tolerance (<5 ‰S). [ABSTRACT FROM AUTHOR]

Studies on molecular characteristics and modulation of expression of [alpha]-amylase and trypsin in the hepatopancreas of intertidal euryhaline crabs are lacking. In this work, we cloned and studied by in silico approaches the characteristics of cDNA sequences for [alpha]-amylase and two trypsins isoforms, as well as the effect of environmental salinity, on gene expression and protein activities in the hepatopancreas of Neohelice granulata (Dana, 1851), which is a good invertebrate model species. The cDNA sequence of [alpha]-amylase is 1637 bp long, encoding 459 amino acid residues. Trypsin 1 and 2 are 689 and 1174 bp long, encoding 204 and 151 amino acid residues, respectively. Multiple sequence alignment of deduced protein sequences revealed the presence of conserved motifs found in other invertebrates. In crabs acclimated at 37 psu (hyporegulation), [alpha]-amylase mRNA level and total pancreatic amylase activity were higher than at 10 psu (hyperregulation) and 35 psu (osmoconformation). Trypsin 1 mRNA levels increased at 37 psu, while trypsin 2 levels decreased at 10 and 37 psu. Total trypsin activity was similar in all salinities. Our results showed a differential modulation of [alpha]-amylase and trypsin expression and total amylase activity by salinity acclimation, suggesting the occurrence of distinct mechanisms of regulation at different levels that could lead to digestive adjustments in relation to hyperregulation and (or) hyporegulation. Key words: [alpha]-amylase, trypsin, cloning, digestive flexibility, hepatopancreas, Neohelice granulata. Les etudes des caracteristiques moleculaires et de la modulation de l'expression de l'[alpha]-amylase et de la trypsine dans l'hepatopancreas de crabes euryhalins intertidaux sont rares. Nous avons clone et etudie par des approches in silico les caracteristiques de sequences d'ADNc pour l'[alpha]-amylase et deux isoformes de la trypsine, ainsi que l'effet de la salinite ambiante sur l'expression genique et l'activite proteique dans l'hepatopancreas de Neohelice granulata (Dana, 1851), une bonne espece modele d'invertebre. La longueur de la sequence d'ADNc de l'[alpha]-amylase fait 1637 pb, codant 459 residus d'aminoacides. Les trypsines 1 et 2 font 689 et 1174 bp de longueur, codant 204 et 151 residus d'aminoacides, respectivement. L'alignement de sequences multiples de sequences proteiques deduites revele la presence de motifs conserves presents chez d'autres invertebres. Chez des crabes acclimates a 37 psu (hyporegulation), la concentration d'ARNm de l'[alpha]-amylase et l'activite de l'amylase pancreatique totale etaient plus elevees qu'a 10 psu (hyperregulation) et qu'a 35 psu (osmoconformation). Les concentrations d'ARNm de la trypsine 1 augmentaient a 37 psu, alors que les concentrations de trypsine 2 diminuaient a 10 et a 37 psu. L'activite totale des trypsines etait semblable a toutes les salinites. Nos resultats font ressortir une modulation differentielle de l'expression de l'[alpha]-amylase et des trypsines et de l'activite de l'amylase totale par l'acclimatation a la salinite, ce qui indiquerait l'intervention de differents mecanismes de regulation selon la concentration pouvant se traduire par des ajustements digestifs associes a l'hyperregulation et l'hyporegulation. [Traduit par la Redaction] Mots-cles: [alpha]-amylase, trypsine, clonage, souplesse digestive, hepatopancreas, Neohelice granulata., Introduction Phenotypic flexibility involves changes in attributes atdifferent levels (from molecular to organismal) in response to variations in external stimuli. These reversible changes can increase probability of survival particularly in [...]

In spite of its inherent physiological importance, studies on the occurrence, characteristics, and modulation of amylase in euryhaline crabs are lacking. We investigated the occurrence of amylase forms and the effect of acclimation to different salinities on their number and made a partial purification and characterization of the major form present in the hepatopancreas of Neohelice granulata. Zymogram analysis revealed 5 amylase forms in crabs acclimated to 35 psu (seawater) and 37 psu, and an additional band at 10 psu, but with a major form (29 kDa) in all cases, which was partially purified and characterized. Amylolytic activity was maximal between 30 and 40 °C; maintained at high NaCl concentrations (up to 4 M); increased by 5 mM K+, Li+, Co2+, and Mg2+ (36%-45%); inhibited by Cu2+, Zn2+, Cd2+, Fe2+, and Mn2+ (92.4% and 23.7%); not affected by Ni2+ or Ba2+; and enhanced almost 100% by Ca2+. Amylase exhibited Michaelis-Menten kinetics (starch: Km = 1.24 mg mL-1; glycogen: Km = 16.19 mg mL-1). The potential physiological significance and relationship to habitat conditions of the extra form in low salinity and the biochemical characteristics of the partially purified amylolytic activity (halotolerant, differential sensitivity to ions, capability to hydrolyze starch and glycogen) are discussed. [ABSTRACT FROM AUTHOR]