Long‐term adaptation to low salinities in the euryhaline shrimp Crangon franciscorum (Stimpson)

Abstract

The euryhaline shrimp Crangon fi.anciscorum is a hyper-hypoosmotic regulator, its hemolymph being iso-osmotic with the medium near 27 0100 salinity. Shrimp collected from low salinity environments are physiologically very distinct from those collected from high salinity environments. Individuals from low salinity habitats exhibit better survival, a lower water content and apparent permeability to water, and a decreased rate of sodium loss in low salinities when compared to shrimp from high salinity habitats. These differences persist after several days of adaptation to low salinity, however after acclimation to a low salinity for a longer time (5-6 weeks in this study), these differences disappear.Some studies concerning the acclimation of crustacea to a salinity change show that, after transfer to a new salinity, the osmotic concentration of the hemolymph (or concentrations of ions) reaches a new level within a relatively short time, usually between a few hours to a week (Flugel, '60; Grimm, '68; Haefner, '69; Hagerman, '71; Horlyck, '73; Thompson and Pritchard, '69; Williams, '60). After transfer to a lower salinity, the osmotic concentration of the hemolymph often stabilizes at a new level, and remains unchanged for several days. However, there is also evidence of a long term component of acclimation, one that requires considerably more time to complete. For example, several investigators have observed that animals collected from high salinities differ in osmoregulatory abilities from animals collected from low salinities (Anderson and Prosser '53; McLusky, '79; McLusky et al., '82; Segal and Burbanck, '63: Tagatz, '71; Theede, '69; Weber and Spaargaren, '70). This effect could be due to 1) genotypic differences between animals inhabiting high and low salinity habitats or, alternatively 2) incomplete acclimation in the lab of the high salinity animals to low salinity. McLusky et al. ('82) have shown that in the European shrimp Crangon crangon this effect is phenotypic, and not a result of genetic differences between populations. We have attempted to distinguish between these two possibilities in the study described in this report, and we will show that, at least for Crangon fi-anciscorm, a euryhaline shrimp and the subject of the present studies, shrimp transferred from high to low salinity rapidly lower the osmotic concentration of their hemolymph. This concentration then remains unchanged for several days and is very different from that of shrimp from low salinity habitats. This difference is in part due to differences in water content, apparent permeability to water, and rate of sodium loss between shrimp acclimated short term to high and low salinities. However, after a longer period of acclimation in the low salinity, the former high salinity animals become physiologically more similar to those collected from low salinity. MATERIALS AND METHODS Sources of shrimpShrimp were collected by trawl from two localities: 1) a system of sloughs north of Suisun Bay in the Sacramento -San Joaquin Delta,...

Discarding Norway lobster (Nephrops norvegicus L.) through low salinity layers – mortality and damage seen in simulation experiments

“…reduced tail-flipping on stimulation and slow movements). Similar symptoms of low salinity exposure have been reported in other stenohaline marine crustaceans (Dall, 1974;Shaner et al, 1985). In some studies, mortality was described as being due to ''bursting'' where bulk fluid losses through the exoskeleton occurred.…”