Deep-sea 'test-tube babies.' (sea urchin research)

By mixing eggs and sperm of sea urchins that live deep in the sea, marine biologists have produced embryonic sea urchins and have obtained a new glimpse into the life cycle of animals that inhabit the ocean depths.

The lives of these animals have been well hidden from scientific scrutiny, because specimens caught in dredges or nets generally arrive at the sea surface dead or severely damaged. But researchers from the Harbor Branch Foundation in Ft. Pierce, Fla., recently used a submersible vessel with a collecting device that resembles a vacuum cleaner to bring healthy animals to the surface, to a shipboard laboratory.

Eggs and sperm removed from specimens of two sea urchin species and one starfish species successfully developed into embryos. Embryos of solely deep-dwelling echinoderms (the phylum including starfish and sea urchins) had never previously been observed by scientists, says Craig Young of Harbor Branch.

In the fertilization experiment, the scientists removed gonads from the adult animals they had collected. They used a hormonelike chemical, 1-methyladenine, to make the eggs mature before mixing them with the sperm. In an expedition planned for this spring, the researchers hope to produce embryos of more species.

An unexpected lifestyle for deep-sea echinoderm larvae has been postulated from the observation of the eggs of 21 species recovered by Young and his colleagues Lane Cameron of Harbor Branch and Larry McEdward of the University of Alberta in Edmonton. In shallow-water-dwelling echinoderms, the size of the egg correlates with larval behavior: In species with small eggs, larvae begin swimming and feeding on plankton early in life; in species with large eggs, larvae survive for long periods on the yolk. Marine biologists had predicted that, because plankton is scarce at great depths, animals there would be found to have large, yolky eggs. But Young and Cameron report that most of the echinoderms they collected have small, transparent eggs, only 90 to 150 microns in diameter. They speculate that the newly hatched larvae undertake an epic journey. To find food they must swim more than 2,000 feet upward, propelled only by their minute, hairlike cilia.