KUBOKAWA, K.; UCHIDA, K.; KURATANI, S.; AGATA, K.; Ocean Res. Inst., Unive. of Tokyo, Tokyo; Sado Marine Biol. Station, Niigata Univ., Sado; Center for Dev. Biol., RIKEN, Kobe; Center for Dev. Biol., RIKEN, Kobe: Novel RFamide-like peptide in amphioxus

The amphioxus, cephalochordate is the closest living invertebrate relative of vertebrates, and study of amphioxus genes would provide important information on the evolution from invertebrate to vertebrate. For this interesting animal, extensive morphological and developmental biological studies have been conducted, but limited information has been available on endocrinology and physiology of amphioxus. We surveyed neuropeptides genes in nerve code of adult amphioxus by constructing a cDNA library of nerve code removed from five hundred animals. A homologue of the RFamid like peptide gene was obtained from the library by using the EST method. RFamid is one of evolutionary primitive neuropeptides and exists in a variety of animal species. The precursor gene of RFamid like peptide encoded five type peptides which show different amino acid sequences. The expression of RFamid like peptide gene in amphioxus was examined by means of the whole mount in situ hybridization method. The nerve cord of adults, late neurulas, and early larvae of amphioxus were used as material. The expression in adults was observed in dorsal ocelli cells in the nerve code. In late neurula, the expression was detected in several cells which were considered to be dorsal ocelli cells although pigment has not yet appeared in them. These cells existed in front and back of a dorsal ocelli cell which was already pigmented. In early larva, the number of expressed cells increased approximately twice although the number of the pigmented dorsal ocelli cell is still one. These results suggest that physiological role of RFamid concerning to the development of embryo is suspicious, and the non-pigmented dorsal ocelli cells may be important to regulate neural activity even though they have no pigment.