Summer osmoregulatory capacity of the world's northernmost living salmonid

Abstract

Anadromous Arctic charr (Salvelinus alpinus L.) were caught on their way to and from the sea with the use of a fish trap placed in the Dieset watercourse located on the Spitsbergen Island (79 degrees 10' Northern latitude) within the high-Arctic Svalbard archipelago. When subjected to a seawater challenge test (34 parts/thousand at 4-5 degrees C), charr on their way to the sea showed only minor and temporary changes in blood plasma osmolality and Na+ and Mg2+ concentrations. The seawater tests also revealed good hypoosmoregulatory capacity for Arctic charr returning from the marine environment 4 wk later. A progressive decrease in seawater tolerance was first documented 7-11 days after their return to the freshwater habitat. Thus the Svalbard charr, being the northernmost anadromous salmonid and probably a direct descendant from the first Salvelinus immigrants to freshwater systems, undergoes a preparatory increase of hypoosmoregulatory capacity (smoltification) before entering the oceanic water bodies. Furthermore, the termination of their short annual seawater stay is probably elicited by factors controlling body systems other than osmoregulation.

Environmental influences on regulation of blood plasma/serum components in teleost fishes: a review

“…These times differed significantly between the two populations. This transient improvement in hypoosmoregulatory capability supported the conclusions of Finstad et al (1989), Arnesen et al (1992Arnesen et al ( , 1995Arnesen et al ( , 1998, Halvorsen et al (1993), Nilssen et al (1997), that acquiring hypoosmoregulatory capacity did not depend on a previous exposure to sea water. It was assumed that photoperiod was the essential environmental cue initiating increased hypoosmoregulatory capacity.…”

“…Salvelinus alpinus from the high-Arctic Svalbard Archipelago (79°10 0 N) are said to be ''the world's northernmost living salmonids'' (Nilssen et al 1997). Fresh waters in the area are ice-free for only a short period, 23.5-32.5 days, in the late summer.…”

Unique arylalkylamine N-acetyltransferase-2 polymorphism in Salmonids and profound variations in thermal stability and catalytic efficiency conferred by two residues

“…In favor of this is the observation that Arctic charr recombinant AANAT2 isoforms display high stability at 45°C (see below), a temperature fatal to melatonin secretion irrespective of the experimental conditions. Whatever it may be, the time-keeping system of the Arctic charr displays a range of tolerance above what is experimented by the fish in its natural habitat, where temperatures above 15°C are seldom experienced and are far above the temperature that the strain of charr used in the present study experiences (0 to 5°C) at 80°N (Nilssen et al, 1997). On the contrary, it is noteworthy that melatonin secretion remained relatively high in Experiment 2 at the temperatures Arctic charr experience in the cold range, e.g.…”

Intermediary metabolism of Arctic char Salvelinus alpinus during short-term salinity exposure

“…Many studies report similar changes in Arctic char plasma ion content and gill Na + ,K + -ATPase activity during salinity acclimation (e.g. Arnesen et al, 1992;Nilssen et al, 1997). The observed rise in gill Na + ,K + -ATPase activity is very characteristic of the acclimation of euryhaline fish to seawater (McCormick, 1996).…”