Temperature and pressure tolerance of embryos and larvae of the Atlantic seastars Asterias rubens and Marthasterias glacialis (Echinodermata: Asteroidea): potential for deep-sea invasion

Abstract

Eggs of the shallow-water asteroids Asterias rubens and Marthasterias glacialis were fertilized in vitro and incubated through the early embryonic cleavages until the larval stage. Early embryos, blastulae, gastrulae, and swimming bipinnaria were subjected to a temperature/pressure matrix of 5, 10, 15 and 20°C and 1, 50, 100, 150 and 200 atm. Early embryos of both species were able to tolerate pressures up to 150 atm at 15°C and 100 atm at 10°C. Survivorship of A. rubens swimming bipinnaria remained high (>70%) after incubation at all the temperature/pressure combinations. Swimming larvae ranged from 100% survival at 10°C/50 atm to 72% at 15°C/200 atm. For M. glacialis the highest survival of swimming larvae was 100% at 5, 15 and 20°C/1 atm and 15 and 20°C/50 atm, but decreased to 56.85% at 5°C/200 atm. In general, survivorship decreased as pres- sure increased; nevertheless larvae generally tolerated pressures of 200 atm. Data for the tempera- ture and pressure effects on the later stages of development suggest that all the larval stages are more temperature/pressure tolerant than the early embryos and survivorship increases with larval age. All the developmental stages of both species have a potentially wider depth distribution than their respective adults. Therefore, the larvae of shallow-water species A. rubens and M. glacialis could survive transport to deeper waters and may be capable of acting as colonists in the deep sea.