Abstract
Recently, the species richness of provannid gastropods inhabiting chemosynthetic ecosystems in the northwestern Pacific has been reassessed, revealing a much higher diversity than previously realized. Here, we describe four further new species, two in the genus Desbruyeresia and two in the genus Provanna. Their generic placement was confirmed by both shell and radula morphology, as well as phylogenetic reconstruction using the mitochondrial cytochrome c oxidase subunit I gene. Desbruyeresia armata n. sp. from vent fields in the Izu-Ogasawara Arc is characterized by a stout shell with numerous tubercles or short spines and marginal teeth coarsely serrated into only four denticles. Desbruyeresia costata n. sp. from Okinawa Trough vents is distinguished from other congeners by an elongate shell with strong axial ribs and obsolete spiral ribs. These represent the first Desbruyeresia species from Japanese waters. Provanna fenestrata n. sp. discovered from two vent fields in the Okinawa Trough is instantly recognizable from its uniquely regular rectangular lattice sculpture; Provanna stephanos n. sp. is a surprising new discovery from the supposedly well-explored ‘Off Hatsushima’ hydrocarbon seep site in Sagami Bay, and is highly distinctive with two characteristic rows of strongly spinous spiral ribs. The discovery of these new species in relatively well-explored chemosynthetic ecosystems in Japan indicates that the biodiversity of such systems remains poorly documented.
Highlights
Since the first discovery of hydrothermal vents in the Galápagos Rift in 1977 [1], intensive investigations have revealed hundreds of deep-sea chemosynthetic ecosystems in a variety of forms including vents and methane seeps and organic falls [2]
The Japanese waters are in the vicinity of four tectonic crust plates converging together, a tectonic setting leading to very active plate motion which fuels more than 50 chemosynthetic sites relatively close to land [4]
Remarks: Desbruyeresia costata n. sp. is distinct from other described Desbruyeresia species from its shell sculpture, in which the spiral ribs are obsolete in the adult whorls
Summary
Since the first discovery of hydrothermal vents in the Galápagos Rift in 1977 [1], intensive investigations have revealed hundreds of deep-sea chemosynthetic ecosystems in a variety of forms including vents and methane seeps and organic falls [2]. These ecosystems host lush communities of organisms energized by bacterial chemosynthetic production and contain largely endemic taxa not found in nonchemosynthetic environments, with 71% out of 712 species in hydrothermal vents, for example [3]. These four novel taxa are characterized and formally described, and new biogeographic insights gained through their discovery are discussed
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