Effects of salinity on larval tolerance and early developmental rates of four species of echinoderms

Abstract

Larval tolerances and developmental rates of four species and one hybrid cross of echinoderms were determined as a function of salinity. Fertilization and development of Strongylocentrotus droebachiensis (O.F. Muller, 1776), Strongylocentrotus purpuratus (Stimpson, 1857), Strongylocentrotus pallidus (G.O. Sars, 1871), and Pisaster ochraceus (Brandt, 1835) larvae were observed. A hybrid was created by fertilizing eggs of S. droebachiensis with sperm from S. pallidus. Fertilized eggs were placed in filtered, natural seawater (30‰ S) diluted to 30, 27.5, 25, 22.5, and 20‰ S and cleavage and larval development were observed over 32 days. Developmental rates differed among salinity treatments within each species. For each species, embryos and larvae at lower salinities (20, 22.5, and 25‰ S) tended to develop more slowly than those at higher salinities (27.5 and 30‰ S). Pisaster ochraceus and S. droebachiensis larvae survived all salinity treatments throughout the experimental period. The hybrid larvae exhibited salinity tolerances and developmental rates intermediate between values reported for the more stenohaline larvae of S. pallidus and those for the more euryhaline larvae of S. droebachiensis. The interaction of a secondary stressor (food availability) with salinity was examined; algal concentration did not influence the survival, developmental rate, or length of P. ochraceus or S. droebachiensis larvae.

The Effects of Salinity and pH on Fertilization, Early Development, and Hatching in the Crown-of-Thorns Seastar

“…Although we did not rear our cultures to the larval stage, delayed hatching in COTS due to low salinity is likely to be associated with larval abnormality, as shown for Pisaster ochraceus and Echinaster sp. [49,53]. Despite our finding of delayed hatching of COTS, no signs of changes in stage at hatching were observed, as has been found in some echinoids [29].…”

“…In general, decreased salinity is well known to delay or retard development in echinoderms [26,28,29,45,47,[49][50][51][52]. For COTS, hatching was significantly delayed in embryos reared from fertilization at 27 ppt.…”

Cryptic species diversity and reproductive isolation among sympatric lineages ofStrongylocentrotussea urchins in the northwest Atlantic

“…Laboratory studies have demonstrated that S. droebachiensis is one of the most tolerant echinoderms to hyposalinity (Russell 2013). Roller and Stickle (1985) showed that in the Pacific, larvae of S. pallidus failed to develop, and cultures experienced 100% mortality at salinities below 27.5‰. In contrast, although cultures of S. droebachiensis developed slowly at salinities ≤22.5‰ and below, survival was 100% at salinities as low as 20‰.…”

Influence of temperature and salinity on embryonic development ofParacentrotus lividus (Lmk, 1816)

“…Based on the results of hybridation experiments between two morphs of Echinaster modestus, Watts et al (1982) drew the conclusion that varying thermosaline requirements are genetically controlled and not environmentally influenced; similar results were obtained by Roller & Stickle (1985) by means of hybrid-cross experiments between two species of Strongylocentrotus. Our data agree with the latter conclusions.…”

“…Several studies demonstrate that earlier embryonic stages are more sensitive than adults to these abiotic factors (Runnstrom, 1927;L/3nning, 1959;Calabrese, 1969;Gorodilov, 1969;Roller & Stickle, 1985, 1993. Furthermore, the tolerance limits of embryos are probably responsible for the relatively fixed thermo-saline range of reproduction (Andronikov, 1975;Fujisawa, 1989).…”