Meeting Abstract

57.3  Tuesday, Jan. 6  Phylogeny of early vertebrates based on evidence from developmental study of hagfish OTA, K.G.*; KURATANI, S; RIKEN CDB; RIKEN CDB ota_kinya@cdb.riken.jp

Hagfish is still located on the most basal position in the morphological phylogenetic tree of vertebrates, even though the monophyletic relationship between this animal and lamprey was confirmed by a large amount of molecular sequence data. This discrepancy between morphological and molecular data is mainly due to the apparently primitive features of this animal. To solve this problem, knowledge of the developmental and morphological study of hagfish is required. We attempted to collect the embryos from a shallow water hagfish, the Japanese inshore hagfish (Eptatretus burgeri), and succeeded to obtain several embryos. The result of our histological study implied the presence of the vertebrae in the hagfish embryo, although it is absent in the adult. The comparison between the embryo and the adult showed that the subcutaneous sinus, which is recognized as open blood-vascular system and representative primitive traits, evidently originate from the embryonic blood vessels. In addition, the morphology of the semicircular canal having two ampullars indicates that the degeneration has occurred in the inner ear of this animal during the evolution. These results suggested that most of primitive morphological traits could be regarded as derived condition. Based on these evidences, we will discuss the phylogenetic relationship of early vertebrates.