Stenosemus exaratus (G.O. Sars, 1878 )

Sirenko, Boris, 2023, A small collection of rare and new chitons (Mollusca: Polyplacophora) from the Tasmanian Museum and Art Gallery, Zootaxa 5325 (3), pp. 359-392 : 378-381

publication ID	https://doi.org/10.11646/zootaxa.5325.3.3
publication LSID	lsid:zoobank.org:pub:A1FD8DA8-A72C-41B9-8FD7-E0DCE2A1D3BD
DOI	https://doi.org/10.5281/zenodo.8247062
persistent identifier	https://treatment.plazi.org/id/03CD7E00-6848-696A-44FE-61E0FC24EB5B
treatment provided by	Plazi (2023-08-13 15:47:55, last updated 2024-11-26 23:49:33)
scientific name	Stenosemus exaratus (G.O. Sars, 1878 )
status

Treatment

Stenosemus exaratus (G.O. Sars, 1878) View in CoL

( Figures 23A, B View FIGURE 23 24–26 View FIGURE 24 View FIGURE 25 View FIGURE 26 )

Lophyrus exaratus G.O. Sars, 1878: 113 View in CoL , pl. 8, fig. 1, pl. II, fig. 1.

Lepidopleurus dorsuosus Haddon, 1886: 18 , pl. 1, fig. 5, pl. 3, figs. 5a–i.

Lepidopleurus dallii Haddon, 1886: 19 , pl. 1, fig. 6, pl. 3, figs. 6a–i.

Ischnochiton (Chondropleura) affinis Thiele, 1906 View in CoL , 334, pl. 29, figs. 17–20.

Lepidopleurus (Leptochiton) nicomedes Dall, 1919: 501 .

Ischnochiton johnstoni Cotton, 1937: 11 View in CoL , figs. 10–18.

Lepidopleurus nicomedes ; Leloup, 1956: 15 (bibliography).

Ischnochiton exaratus View in CoL ; Leloup, 1956: 41, fig. 21; Kaas, 1972: 92, figs. 195–199, pl. 6, fig. 9.

Ischnochiton dorsuosus View in CoL ; Dell, 1964: 114 (bibliography); Kaas, 1979: 29; Ferreira, 1980: 59.

Ischnochiton (Stenosemus) exaratus View in CoL ; Kaas, 1979: 29; Kaas & Van Belle 1990: 62, fig. 25. maps 1, 23 (synonymy and bibliography).

Stenosemus exaratus View in CoL ; Ferreira, 1981: 327.

Type material. Two syntypes ( NHMO D33573 ). Type locality. Norway, Bodö (67°17’N, 14°25’E) GoogleMaps and Florö (61°36’N, 5°0’E), 180–360 m. GoogleMaps

Material examined. Southern Ocean, Macquarie Islands , R/V Dmitry Mendeleev, cruise 16, stn 1294, 54°56.5’S, 158°49.7’E, 320 m, Sigsby trawl, 4 spms, BL 11.0–14.0 mm, 25.01.1976 GoogleMaps ; Macquarie Islands , offshore to W, 54.7119°S, 158.7679°E, 200–468 m, stn SS1999_01_060Lot_60, Benthic dredge, CSIRO, 1 spm (TMAG, E 45537 View Materials ) BL 16.0 mm, 22.01.1999 GoogleMaps . Macquarie Islands , offshore to E, 54.5959°S, 158.9433°E, 250–500 m, stn SS1999_093Lot_093, Benthic dredge, CSIRO, 28 spm (TMAG, E 45535 View Materials ) BL 10.5–17.0 mm, 26.01.1999 GoogleMaps ; Southern Tasmania Slope: Southern Sirveyor , 44.0306°S, 147.5796°E, 830–1030 m, stn SS0207_08_Lot_8, Sherman sled, CSIRO, 2 spm (TMAG, E 45526 View Materials ) BL 11.0–12.0 mm, 31.03.2007 GoogleMaps .

Distribution. Wide-spread species. It inhabits the Atlantic Ocean from Greenland, Iceland, Norway up to Terra del Fuego, South Shetlands and South Orkney Islands, Pacific Ocean near Southern Chile, Indian Ocean near Prince Edward, Kerguelen and Amsterdam Islands. The four above mentioned samples of this species are the first find for South Australia and Macquarie Islands. The species lives at depths from 23 up to 2580 m ( Kaas & Van Belle 1990; Schwabe & Sellanes 2010).

Remarks. The specimen (TMAG, E 45526, BL 11.5 mm) studied under SEM has 21 gills on each side arranged from valve IV to the anus; radula 4.1 mm long with 31 transverse rows of mature teeth. Gut content contains detritus (50%), foraminifera (40%, about 100% calcareous shells) and sand (10%).

The studied specimen collected south of Tasmania, as well as individuals collected from Macquarie, differs from Norwegian individuals in the almost complete absence of radial grooves on the postmucronal area of the tail valve and the presence of granules on the top of the dorsal calcareous corpuscles (not metioned in the description by Kaas & Van Belle 1990).

Stenosemus exaratus View in CoL and S. beui ( O’Neill, 1987) View in CoL have a very similar sculptured tegmentum but S. exaratus View in CoL differs from S. beui View in CoL by having slightly striated dorsal calcareous corpuscles (vs. coarse lattice-like sculptured, longitudinally ribbed corpuscles in S. beui View in CoL ), the head of major lateral teeth lacks a small appendix at its outer side (vs. head of major lateral teeth with small appendix at outer side in S. beui View in CoL ).

References

Cotton, B. C. (1937) Loricata. Reports of the British Australian and New Zealand Antarctic Research Expedition, Series B, 4 (1), 9 - 19, figs. 1 - 29, pl. 1. [1929 - 1931]

Dall, W. H. (1919) Descriptions of new species of chitons from the Pacific coast of America. Proceedings of the United States National Museum, 55, 499 - 516. https: // doi. org / 10.5479 / si. 00963801.55 - 2283.499

Dell, R. K. (1964) Antarctic and subantarctic Mollusca: Amphineura, Scaphopoda, and Bivalvia. Discovery Reports, 33, 93 - 250, figs. 1 - 4, pls 2 - 7.

Ferreira, A. J. (1980) A new species of Lepidopleurus Risso, 1826 (Mollusca: Polyplacophora) in the deep waters of the Eastern Pacific. The Veliger, 23 (1), 55 - 61, figs. 1 - 6.

Ferreira, A. J. (1981) A new species of Stenosemus Middendorff, 1847 (Mollusca: Polyplacophora) in the abyssal Northeastern Pacific. The Veliger, 23 (4), 325 - 328, figs. 1 - 9.

Haddon, A. C. (1886) Report on the Polyplacophora collected by H. M. S. Challenger during the years 1873 - 76. Challenger Reports, 15, 1 - 50, pls. 1 - 3.

Kaas, P. (1972) Polyplacophora of the Caribbean region. Studies on the fauna of Curacao and other Caribbean islands, 41 (137), 1 - 162, figs. 1 - 247, pls. 1 - 9. https: // doi. org / 10.5962 / p. 283216

Kaas, P. (1979) On a collection of Polyplacophora (Mollusca, Amphineura) from the Bay of Biscay. Bulletin du Museum National d'Histoire Naturelle. Paris, 4 (A), A (1), 13 - 31, pls. 1 - 5.

Kaas, P. & Van Belle, R. A. (1990) Monograph of living chitons (Mollusca: Polyplacophora). Vol. 4 Suborder Ischnochitonina: Ischnochitonidae: Ischnochitoninae (continued). Additions to Vols. 1 - 3. E. J. Brill, Leiden, 298 pp. https: // doi. org / 10.1163 / 9789004431706

Leloup, E. (1956) Polyplacophora. Reports of the Lund University Chile expedition 1948 - 1949. Acta Universitatis Lundensis, New Series, 52, 1 - 94, figs. 1 - 53.

O'Neill, M. H. B. (1987) Lepidozona beui n. sp. (Mollusca: Polyplacophora) from New Zealand. New Zealand Journal of Zoology, 14, 131 - 134, figs. 1 - 3. https: // doi. org / 10.1080 / 03014223.1987.10422690

Sars, G. O. (1878) Mollusca regionis Arcticae Norvegiae, Christiania, i-xiii, 466 pp.

Schwabe, E. & Sellanes, J. (2010) Revision of Chilean bathyal chitons (Mollusca: Polyplacophora) associated with cold-seeps, including description of a new species of Leptochiton (Leptochitonidae). Organisms Diversity & Evolution, 10 (1), 31 - 55. https: // doi. org / 10.1007 / s 13127 - 009 - 0002 - 6

Thiele, J. (1906) Uber die Chitonen der deutschen Tiefsee-Expedition. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition, 9 (2), 327 - 334, pl. 29.

Figures

FIGURE 23. Stenosemus exaratus, Southern Ocean, South Tasmania slope, (TMAG, E 45526), BL 11.5 mm: (A, B) and Stenosemus simplicissimus, Southern Ocean, Heart Island, (TMAG, E 26179) BL 20.0 mm (C, D).

FIGURE 24. Stenosemus exaratus, Southern Ocean, South Tasmania slope, (TMAG, E 45526), BL 11.5 mm: A. Valve I, dorsal view; B. Valve II, dorsal view; C. Valve V, dorsal view; D. Valve VIII, dorsal view; E. Valve V, detail of tegmentum in central area; F. Valve V, rostral view; G. Valve VIII, lateral view.

FIGURE 25. Stenosemus exaratus, Southern Ocean, South Tasmania slope, (TMAG, E 45526), BL 11.5 mm: A, C. Dorsal corpuscles; B, D. Ventral scales

FIGURE 26. Stenosemus exaratus, Southern Ocean, South Tasmania slope, (TMAG, E 45526), BL 11.5 mm: A. Middle part of radula; B. Central and first lateral teeth of radula.

Abbreviations

CSIRO	Australia, Commonwealth Scientific and Industrial Research Organisation
NHMO	Natural History Museum, University of Oslo
CSIRO	Australian National Fish Collection

Copyright notice

No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.

Taxonomy

Kingdom	Animalia
Phylum	Mollusca
Class	Polyplacophora
SubClass	Neoloricata
Order	Chitonida
Family	Ischnochitonidae
Genus	Stenosemus