Temperature and pressure tolerances of embryos and larvae of the Antarctic sea urchin Sterechinus neumayeri (Echinodermata : Echinoidea): potential for deep-sea invasion from high latitudes

Early embryos, blastulae, prisms and 4-arm plutei of the Antarctic shallow-water echinoid Sterechinus neumayeri were subjected to a temperature/pressure regime from -1.2 to + 2.5 degrees C and from 1 to 250 atm. Early embryos were able to tolerate pressures up to 150 atm at +2.5 to +0.9 degrees C and 100 atm at -1.2 degrees C. Blastulae and prisms showed an increasing sensitivity to pressure with decreasing temperature. Four-arm plutei were more sensitive than early larval stages to pressure and were also more sensitive to pressure at lower temperatures. These data suggest that the embryonic and larval stages of S, neumayeri are capable of surviving low temperatures in surface waters, but only tolerate higher pressures when water column temperatures are > 0 degrees C. Such a pattern of temperature increase is seen in the formation of Antarctic Bottom Water in the Weddell Sea and we infer that the larvae of S, neumayeri are capable of penetrating the deep sea through the agency of this deep water formation.