Occurrence of an unidentified harrimaniid acorn worm in the genus Stereobalanus (Hemichordata: Enteropneusta) from the Japan Trench hadal zone
Kajihara, H.; Abato, J.; Matsushita, M. (2023). Occurrence of an unidentified harrimaniid acorn worm in the genus Stereobalanus (Hemichordata: Enteropneusta) from the Japan Trench hadal zone. Deep-Sea Res., Part 1, Oceanogr. Res. Pap. 198: 104075. https://dx.doi.org/10.1016/j.dsr.2023.104075
In: Deep-Sea Research, Part I. Oceanographic Research Papers. Elsevier: Oxford. ISSN 0967-0637; e-ISSN 1879-0119, more
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| Keywords |
Stereobalanus Spengel, 1901 [WoRMS]
Marine/Coastal |
| Authors | | Top |
- Kajihara, H.
- Abato, J.
- Matsushita, M.
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| Abstract |
A number of soft fragments of uncertain identity, mostly taking a form of a disk or button, were found among trawled material from the hadal zone (7426–7654 m in depth) in the Japan Trench during the cruise KH-22-8 of the R/V Hakuho-maru in October 2022. These enigmatic ‘disks’ subsequently turned out to be the proboscides of enteropneusts severed from the collar. A molecular phylogenetic analysis based on the mitochondrial 16S rRNA and nuclear 18S rRNA gene sequences determined from one of the fragments along with others available in public databases indicated that the species in question was sister to the harrimaniid enteropneust Stereobalanus canadensis (Spengel, 1893). Some morphological features of the fragments—the proboscis longitudinal musculature arranged in radial plates, the four tubular ovaries, and the absence of synapticula on the gill bars—support that the Japan Trench species would belong to Stereobalanus Spengel, 1902. This study represents the deepest record of Stereobalanus and the first report of enteropneusts from the Japan Trench hadal zone, albeit identified to the genus level. While the species is putatively undescribed, a formal taxonomic description should await intact specimens in future studies. |
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