Meeting Abstract

69.3  Sunday, Jan. 6  Developmental evolutionary study of the hagfish embryo OTA, K.G.*; KURATANI, S; CDB RIKEN; CDB RIKEN ota_kinya@cdb.riken.jp

Although hagfishes and lampreys are clustered as a monophyletic group by recent molecular phylogenetic analyses, the phylogenetic position of hagfishes is still a matter of debate for their apparently primitive morphological features such as the absence of vertebrae. To resolve the contradiction between morphological and molecular data, embryology of the hagfish will give us important information. We have succeeded to obtain some embryos of Japanese inshore hagfish, Eptatretus burgei. Using these embryos, we observed the expression pattern of Collagen type II alpha 1 (Col2A1) gene, which is known as molecular marker of cartilage cells, to provide a clue to the origin of vertebra. We isolated two different Col2A1 genes, EbCol2A1a and EbCol2A1b, showing high similarity with the lamprey Col2A1a and Col2A1b in the amino acid sequence, respectively. In the late hagfish embryo, EbCol2A1a was expressed in overall mesenchymal cells including the putative meninges of the spinal cord, and EbCol2A1b in the notochord. Taking into account that Col2A1b was also expressed in the notochord of the lamprey embryo, it seems likely that the latter expression uniquely evolved in the common ancestor of hagfishes and lampreys, namely as a synapomorphy of cyclostomes. Based on these data, the origin of the vertebra and early evolution of vertebrates will be discussed.