title: The nerve ring in cnidarians: its presence and structure in hydrozoan medusae.
abstract: In our previous studies of the Hydra nerve ring, we proposed the following hypothesis: "The nerve ring in the hypostome of Hydra is a central nervous system (CNS)-like neuronal structure." Related to this hypothesis, we have started to survey the nerve ring immunocytochemically using antibodies against neuropeptides throughout the whole phylum of cnidarians. In the present study, we describe nerve rings in hydrozoan medusae. We examined the medusae of five hydrozoan species belonging to three orders: Eirene sp. (order Leptomedusae), Craspedacusta sowerbyi (order Limnomedusae), Sarsia tubulosa, Turritopsis nutricula, and Cladonema radiatum (order Anthomedusae). We observed a well-developed nerve ring in all species. The nerve ring runs circumferentially around the margin of the bell. In all cases, the nerve ring was visualized by plural antibodies, suggesting that it contains different neural subpopulations. In C. radiatum, antibodies against four different neuropeptides labeled the nerve ring. We established clear (without undesirable cross-reactions) double-staining procedures with two rabbit primary antibodies. Using the double-staining method, three neural subsets visualized by three antibodies revealed completely separate neural populations. The results show that the nerve ring is a common feature in hydrozoan medusae and has a complex heterogeneous structure composed of different neural subsets.
authors.affiliation: Department of Environmental Science, Fukuoka Women's University, Kasumiga-oka 1-1-1, Higashi-ku, Fukuoka 813-8529, Japan. Electronic address: koizumi@fwu.ac.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Koizumi
authors.affiliation: Department of Environmental Science, Fukuoka Women's University, Kasumiga-oka 1-1-1, Higashi-ku, Fukuoka 813-8529, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Hamada
authors.affiliation: Department of Environmental Science, Fukuoka Women's University, Kasumiga-oka 1-1-1, Higashi-ku, Fukuoka 813-8529, Japan.
authors.forename: Sumiko
authors.initials: S
authors.lastname: Minobe
authors.affiliation: Department of Environmental Science, Fukuoka Women's University, Kasumiga-oka 1-1-1, Higashi-ku, Fukuoka 813-8529, Japan.
authors.forename: Kayoko
authors.initials: K
authors.lastname: Hamaguchi-Hamada
authors.affiliation: Department of Environmental Science, Fukuoka Women's University, Kasumiga-oka 1-1-1, Higashi-ku, Fukuoka 813-8529, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Kurumata-Shigeto
authors.affiliation: Okinawa Churashima Foundation, Ishikawa 888, Motobu-cho, Okinawa 905-0206, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Zoology, National Museum of Nature and Science, Amakubo 4-1-1, Tsukuba-city, Ibaraki 305-0005, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Namikawa
mesh_terms: D000818:Animals; D002490:Central Nervous System / Q000033:anatomy & histology / Q000166:cytology; D037402:Hydrozoa / Q000033:anatomy & histology* / Q000166:cytology
keywords: Cnidaria; Hydrozoa; Medusa; Nerve ring; Nervous system