New Locality for the Deep-Sea Acorn Worm Quatuoralisia malakhovi (Hemichordata: Enteropneusta)

Abstract

The torquaratorid enteropneust Quatuoralisia malakhovi Ezhova et Lukinykh in Ezhova, Lukinykh, Galkin, Krylova, et Gebruk, 2022 has been known only by the type material from the bathyal zone at depths of 1957–2289 m on the slopes of the submarine Piip Volcano in the Volcanologists Massif, southwestern Bering Sea. In this study, fragments of soft-bodied animals were obtained among trawled material from the bathyal zone in the Japan Trench, about 41.51° N, 144.13° E, at depths of 1987–2007 m during the cruise KH-22-8 of the R/V Hakuho-maru in October 2022. Partial sequences of the mitochondrial 16S rRNA gene from two fragments showed a 100% match with the ones determined from the type series of Q. malakhovi, suggesting conspecificity among them. This study broadens the known geographic distribution range of Q. malakhovi by ~2500 km southwestward. This is also the first record of the species as well as the family Torquaratoridae from Japanese waters. In total, the Hakuho-maru cruise KH-22-8 yielded four species of acorn worms in the Japan Trench (all represented by body fragments), including Q. malakhovi and two unidentified species in the family Harrimaniidae (briefly reported in this paper, about 40.80° N, 144.51° E, 6800 m, and 40.70° N, 144.68° E, 7000 m) in addition to Stereobalanus sp. (previously reported in another paper, about 40.80° N, 144.65° E, 7400 m). The phylogenetic positions of the two unidentified harrimaniids are inferred based on partial sequences of the 16S rRNA gene.