Development and Growth of the Feather Star Oxycomanthus japonicus to Sexual Maturity

Abstract

Crinoids, including feather stars, are the most basal group among extant echinoderm classes and share a basic body plan. In spite of their importance for evolutionary developmental study, information on the development of crinoids has been limited, because there are not many species whose spawning season is known, and artificial spawning is impossible. Therefore, it is not easy to obtain fertilized eggs of crinoids. We have observed the spawning and development of the feather star Oxycomanthus japonicus for 7 years. We have established a cultivation system that has enabled us to culture large numbers of O. japonicus from eggs through to sexually mature adults. In the present study, we show that (1) individuals take 2 years to reach sexual maturity; (2) the skeleton of the theca of a stalked juvenile consists of five orals, five basals, five radials, five infrabasals, and an anal plate; and (3) the onset of spawning has shifted by about two weeks since 60 years ago. Our cultivation system can provide enough embryos, larvae, juveniles, and adults for further experiments, extending the possibilities for crinoid research.

Nervous system development of two crinoid species, the sea lily Metacrinus rotundus and the feather star Oxycomanthus japonicus

“…They are the only two species of crinoids in which eggs and larvae are reliably accessible annually and where useful data on their morphology and gene expression during development are available (Hara et al 2006;Holland 1991;Nakano et al 2003;Shibata et al 2008). The ancestral pattern of nervous system development in echinoderms is inferred from our data and suggestions on the early evolution of deuterostome life cycles put forward based on the basiepithelial nerve cells formed in M. rotundus doliolaria larvae.…”

Ciona intestinalis and Oxycomanthus japonicus, Representatives of Marine Invertebrates

“…In comparison, feather stars are more accessible, since there are those that live in shallower waters. The feather star O. japonicus inhabits shallow rocky seashores around Japan, and can be collected by scuba divers near the Misaki Marine Biological Station (MMBS), the University of Tokyo, situated at the tip of the Miura Peninsula facing Sagami Bay, at around 5 m depth [52]. Such wild specimens are maintained in cages hung at a depth of 3 m in the cove of the MMBS.…”

“…These studies also used the specimens from the MMBS. Recently, Shibata et al reported that sexually mature females and males captured at MMBS spawn naturally on a neap-tide day in middle to late October [52]. Eggs and sperm were collected and fertilized eggs were reared into larvae, from which juveniles were obtained.…”

“…Eggs and sperm were collected and fertilized eggs were reared into larvae, from which juveniles were obtained. They could be further reared until sexual maturity [52]. Thus, the complete cultivation method for O. japonicus on a large scale, from larvae up to sexually mature adults, has been established.…”

“…Recently, a cultivation system and inland culture of two marine invertebrates, a basal chordate Ciona intestinalis and an echinoderm Oxycomanthus japonicus, were reported [21,52]. A constant supply of wild-type animals of these species has been achieved with these cultivation systems.…”