Research into tolerance for the environment salinity in sea starfish Asterias rubens L. from populations of the White Sea and Barentz Sea

Abstract

Adaptive responses to salinity changes in three groups of sea starfish Asterias rubens L. at different ontogenetic stages were studied. These three groups are the starfish from the White-Sea population, the starfish from the Barentz-Sea population, and the starfish from the Barentz-Sea population experienced a year acclimatization period, the gametes and larvae produced by these three groups of starfish were studied as well. One hundred percent of eggs survived in the following conditions: the White-Sea starfish with the salinity ranged from 24‰ to 26‰; the Barentz-Sea ones survived at salinity of 34‰; the Barentz-Sea ones acclimatized in the White Sea survived within a range of 24–26‰. One hundred percent of gastrulae survived within the following salinity ranges: for the White-Sea starfish it is 18–26‰, for the Barentz-Sea ones—32–34‰; for the Barentz-Sea ones acclimatized in the White Sea—22–26‰. One hundred percent of bipinnaria larvae survived within the following salinity ranges: 12–28‰ for the White-Sea starfish, 20–38‰ for the Barentz-Sea ones; and 18–28‰ for the Barentz-Sea ones acclimatized in the White Sea. For the Barentz Sea starfish acclimatized in the White Sea, the preferred salinity range was shifted towards brackishwater too. The most narrow limits of tolerance for salinity is typical for initial ontogenetic stages of the starfish, i.e. the stage of fertilizing the egg, and the stage of the gastrula. For bipinnariae of the White-Sea starfish, the critical value of salinity, at which 100% of them survived, appeared to be 12‰, in comparison with 16‰ for the adult starfish. The population of the starfish from the White and Barentz Seas appeared to have some physiological differences revealing in different resistance of the animals, their gametes and larvae for the salinity influence. The White-Sea population might be considered as an example of the initial stage of the physiological race isolation in the terms of salinity. However, according to the observed results, the revealed physiological differences are not hereditary. For the Barentz-Sea starfish, the shift of their salinity tolerance towards brackishwater was observed, and the range of their salinity tolerance became similar to the range for the White-Sea starfish.