Four New Species of Provanna (Gastropoda: Provannidae) from Vents and a Seep off Nansei-shoto Area, Southwestern Japan

Abstract

Members of the genus Provanna are abundant and widely distributed in deep-sea chemosynthetic environments. Around Japan provannids inhabit a wide range of depths and substrates. In this study, we report additional species of Provanna from vents and a seep in the Nansei-shoto area. Shell morphological and molecular phylogenetic analyses showed that there are four new species: (1) P. subglabra is characterized by an inflated smooth shell and is most abundant in vent fields in the Okinawa Trough; (2) P. clathrata has a roughly sculptured shell and is distributed in vents in the southern Okinawa Trough; (3) P. lucida possesses a thin smooth shell with a deep suture and is limited to vents on the Minami-Ensei Knoll in the northern Okinawa Trough; and (4) P. kuroshimensis, which is distinguished by an olive-colored periostracum and is endemic to a seep site on the Kuroshima Knoll. In contrast to shell and molecular characters, radula morphology does not show clear differences among these species. The present study revealed a high species diversity of Provanna in a relatively limited area in southwestern Japan. The diversification of the genus might be correlated with complex topographic features in the Nansei-shoto area including the Okinawa Trough and Ryukyu Arc.