Baby sea lilies

Rudimentary details of the life cycle of the stalkless crinoids (feather stars) — derived from stalked forms and readily collectible from the water column — have been worked out. By contrast the embryos and larvae of stalked crinoids — considered the most basal and ancient living echinoderms having arisen 500 million years ago — have been poorly studied. In the January 9 Nature, Hiroaki Nakano and colleagues at the University of Tokyo, Japan, describe for the first time the larval stages of a living sea lily (Nature, 421:158-160, January 9, 2003).

Nakano et al. used gill nets to collect mature adults of the sea lily Metacrinus rotundus from Suruga Bay, Japan, and fertilized eggs with sperm obtained by dissecting the male testes. They observed that from fertilization to larval settlement there were two successive larval stages. The first was a non-feeding auricularia stage with partly longitudinal ciliary bands (similar to ...