ACTION OF HYDROSTATIC PRESSURE ON SEA URCHIN CILIA

¹ Department of Zoology, University of Toronto, Toronto, Canada and Marine Biological Laboratory, Woods Hole, Massachusetts

The effects of hydrostatic pressure on the cilia of sea urchin embryos (Arbacia and Strongylocentrotus) were investigated. At a pressure of 10,000 psi the swimming blastula and early gastrula embryos became less active. They lost their translational movement and began to rotate slowly on the bottom of the chamber; in about 10 min all movement stopped and essentially all cilia had fallen from the embryos. At lower pressures and with longer durations the embryos were differentially affected and there was considerable variation in the number of cilia removed from individual embryos. With pressures of 6000 psi for 60 min the majority of the embryos lost more than 50% of their cilia. Arbacia embryos were more pressure-sensitive than Strongylocentrotus embryos.

Following deciliation with hypertonic seawater, hydrostatic pressure above 5000 psi was found to block regeneration for the duration of the pressure treatment. At 6000 psi and above the regeneration delay was in excess of the duration of pressure treatment; the regeneration delay was directly proportional to the duration of treatment. At pressures lower than 5000 psi sea urchin cilia were able to regenerate under pressure but at a reduced rate relative to controls. Pressure treatment does not affect regeneration rate following decompression.

The results are discussed in terms of the known effects of pressure on cellular systems.