Leptochiton subantarcticus (Iredale & Hull, 1930)
publication ID |
https://doi.org/ 10.11646/zootaxa.4851.3.1 |
publication LSID |
lsid:zoobank.org:pub:D5837E58-53D6-4C51-A5C0-C96A31F26BC4 |
DOI |
https://doi.org/10.5281/zenodo.4488138 |
persistent identifier |
https://treatment.plazi.org/id/03B2CD3F-FFC7-0C29-BD99-27E8CAC33EB9 |
treatment provided by |
Plazi |
scientific name |
Leptochiton subantarcticus (Iredale & Hull, 1930) |
status |
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Leptochiton subantarcticus (Iredale & Hull, 1930) View in CoL
( Figures 36–43 View FIGURE 36 View FIGURE 37 View FIGURE 38 View FIGURE 39 View FIGURE 40 View FIGURE 41 View FIGURE 42 View FIGURE 43 , 44E, F View FIGURE 44 , 46F, G View FIGURE 46 )
Lepidopleurus columnarius View in CoL ; Ashby 1929b: 372, pl. 32, fig. 9. (non Hedley & May 1908).
Parachiton subantarcticus Iredale & Hull, 1930: 157 View in CoL , pl. 16, figs. 6–7; Kaas 1977: 85; Powell 1979: 22.
Lepidopleurus subantarcticus ; Beu 1977: 39.
Leptochiton (Leptochiton) subantarcticus View in CoL ; Kaas & Van Belle 1985: 160, fig. 73, map 29.
Leptochiton subantarcticus View in CoL ; Kaas & Van Belle 1994: 24, fig. 8.
Syn. nov. Leptochiton (Leptochiton) deecresswellae Anseeuw & Terryn, 2002: 77 View in CoL , figs. 1–3.
Type material. Holotype ( AM C149662 ), a single eroded intermediate valve.
Type locality. New Zealand, off Auckland Island , 171 m.
Material examined. Photographs of the type material ( AM C 149662 ); New Zealand, Papanui Canyon, off Otago Heads, South Island, 45°50’S, 171°1’E, stn. Mu 70–45, 540– 490 m, 9 spms ( ZISP 2384 View Materials ), BL 5.0– 7.5 mm, 22.10.1970, leg. A.G. Beu; off Dunedin, 540– 490 m, 3 spms GoogleMaps ( ZISP 2385 View Materials ), BL 5–7 mm, 22.10.1970, leg. A.G. Beu; New Zealand, South Island , shelf NE of Tiaroa Head, 45°41’S, 170°53’E, R / V Munida, stn 1975008, 50 m, 30 spms, BL 4.0– 5.7 mm GoogleMaps ( NMNZ M 319795 View Materials ), 08.10.1975; shelf NE of Taiaroa Head , 45°42’S, 170°51’E, R / V GoogleMaps Munida, stn 1975009, 44 m, 1 spm, BL 8.0 mm ( NMNZ M 319796 View Materials ), 08.10.1975; Crooked Arm Sill, Doubtful Sound, Fiordland , 45°21.42’S, 167°1.78’E, R / V GoogleMaps Munida, stn 1997104, 54– 60 m, 2 spms, BL 2 mm, ( NMNZ M 319788 View Materials ), 25.05.1997; Crooked Arm Sill, Doubtful Sound, Fiordland , 45°21.42’S, 167°1.78’E, R / V GoogleMaps Munida, stn 1997104, 54– 60 m, 6 spms, BL 4.0–5.0 mm, ( NMNZ M 319792 View Materials ), 25.05.1997; North Island, stn 81833, 143– 153 m, 11 spms, BL 2.5–7.0 mm, ( NMNZ M 149934 View Materials ), 22.01.1981; Head of Pegasus Canyon, Pegasus Bay , R / V Acheron, stn 1976558, 446 m, mud, 5 spms, BL 3.5–6.0 mm, ( NMNZ M 152576 View Materials ), 27.09.1976; Campbell Island , 52°43.9’S, 169°32.5’E, R / V GoogleMaps Dmitriy Mendeleev, 16 cruise, stn 1279, Sigsby trawl, 186 m, dead bryozoans and brachiopods, 9 spms, BL 3–6 mm, 16.01.1976; wall of Pegasus Canyon, stn 76559, 512– 1006 m, 5 spms, BL 5.0–9.0 mm, ( NMNZ M 052841 View Materials ), 27.09.1976; North Island, stn 56081, 796 m, 1 spms, BL 8.0 mm, ( NMNZ M 100811 View Materials ), 23.12.1981; Pegasus Canyon , NE of Banks Peninsula, 43°26.90’S, 173°29.50’E, R / V GoogleMaps Acheron, stn 1985940, 505 m, 4 spms, BL 5.0–7.0 mm, ( NMNZ M 319763 View Materials ), 13.04.1985. All samples without registered numbers of the NMNZ are kept in the ZISP.
Distribution. All around New Zealand, Auckland and Campbell Islands, 44– 796 m.
The type material of this species comprises a single intermediate valve. The present study attempts to improve the re-description by Kaas and Van Belle (1994). The new observations are based mainly on a specimen from South Island, stn. Mu 70–45, 540– 490 m, BL 7.5 mm (figs. 36–38A, B, 39), and additionally on three specimens from: South Island, Pegasus Canyon, NE of Banks Peninsula, 505 m, BL 7.0 mm (NMNZ M 319763) (figs. 42C, D); South Island, shelf NE of Tiaroa Head, 50 m, BL 5.5 mm (NMNZ M 319795) (figs. 40–42A, B, 43); Head of Pegasus Canyon, Pegasus Bay, 446 m, mud, BL 6.0 mm, (NMNZ M 152576) (figs. 38C, D). These specimens and two more were disarticulated and studied by means of SEM and light microscopes.
Emended description. Small size, length usually 6–8 mm, sometimes up to 9 mm. Valves rather thick, from subcarinated to arched, low or strongly elevated (elevation ratio varies from 0.33 up to 0.78 in valve V) not beaked. Color of tegmentum white.
Head valve semicircular, posterior margin widely V-shaped. Intermediate valves rhomboidal, broadly rectangular or roughly triangular, anterior margin concave in the jugal part, convex to obliquely truncated in the pleural parts, posterior margin rather convex or straight, lateral area not raised, lateral margins rounded. Tail valve narrower than head valve, bluntly triangular; mucro anterior or subcentral, not prominent, antemucronal slope straight, postmucronal slope little convex or concave. Head valve, lateral areas and postmucronal area with distinct growth line.
Tegmentum sculptured with flattened, oval granules, arranged in longitudinal rows on central area of intermediate valves (50–60 rows) and antemucronal area of tail valve, in vague radial rows on head valve, and in a random manner on lateral areas of intermediate valves and on postmucronal area of tail valve. Granules in lateral areas are flattened and obscure. Each granule with one megalaesthete and four or rare six micraesthetes.
Articulamentum thick, well developed, apophyses small, widely separated, narrower than jugal sinus in old specimens.
Girdle narrow (about 0.3 mm near valve V), dorsally covered with bluntly pointed scales (75 x 27–40 μm) with four to eight distinct narrow ribs. Sutural and dorsal needles long and smooth (120 x 11 µm). Margin with two kinds of spicules: elongate pointed needles (80 x 11 µm) and sharply pointed spicules with eight riblets. Ventrally girdle covered with elongate, smooth, pointed scales (55 x 20–25 µm), next to margin with two short riblets in their distal ventral part.
Radula of specimen with BL 7.5 mm 2.9 mm long with 32 transverse rows of mature teeth. Central tooth narrow, elongate with distinct blade, major lateral teeth with bidentate cusps, inner denticle rather shorter than outer one. Radula of specimen with BL 7.0 mm 3.0 mm long with 38 transverse rows of mature teeth.
Specimen with BL 7.5 mm has 6 gills and specimen with BL 7.0 mm – 7 gills per side arranged from valve VI to anus.
Remarks. Despite the fact that the intermediate valve (length 2.4 mm, width 3.4 mm) of the holotype of L. subantarcticus is strongly damaged, the majority of the studied larger specimens are very similar in shape and sculpture to the holotype. The examination of more than 40 available specimens show a very strong variability in the shape of valves, especially in the range of elevation from low to high (figs. 36C, G, 38C, D, 40B, F, 42C, D). Smaller specimens often have a lower elevation and more distinct radial rows of granules on the head valve and on the lateral areas of intermediate valves than older specimens. The features of the girdle and radula are very similar in all studied specimens. It is noteworthy that Leptochiton kerguelensis ( Haddon, 1886) from Antarctic and Subantarctic waters shows a similar variability of the valve profile from subcarinated to roundly arched ( Sirenko 2015).
In their re-description of L. subantarcticus, Kaas & Van Belle (1994) used a specimen from the same sample as the present author (off Otago Heads, South Island, 45°50’S, 171°1’E, stn. Mu 70–45, 540– 490 m), but their description and drawings of the central and major lateral teeth of the radula differ considerable from the present observations. While the examined radula in this study shows the central tooth narrow and the cusp of the major lateral tooth bidentated, Kaas & Van Belle (1994) detected an unidentate cusp of the major lateral tooth and a wider shaft in the central tooth. All other features of shell and girdle of both specimens from off Otago Heads are similar.
Leptochiton subantarcticus is most similar to L. columnarius from South Australia and Tasmania but differs from the latter by having an anterior or subcentral mucro (vs. posterior mucro in L. columnarius ), bluntly pointed dorsal scales (vs. sharply pointed scales in L. columnarius ), subcarinated or arched valves (vs. carinated valves in L. columnarius ). The differences are not strong. It is possible that both taxa are synonymous but it is necessary to study L. columnarius from Australia to substantiate this.
Leptochiton subantarcticus is also very similar to L. deecresswellae . There are only two small differences between these two species: L. subantarcticus has strongly elevated valves (vs. weak elevated in L. deecresswellae ) and granules are arranged in vague radial rows on the head valve and on the lateral areas of the intermediate valves in L. subantarcticus (vs. in a random manner in L. deecresswellae ). The first character obviously depends on the age variability, whereas the second difference is probably a result of intraspecific variability. Moreover, L. deecresswellae was described from Papanui Canyon, off Otago Heads ( Anseeuw & Terryn 2002), where specimens very similar to the holotype of L. subantarcticus were collected (see present study, figs. 34–37 and Kaas & Van Belle 1994, page 24). Consequently, L. deecresswellae regarded to represent a synonym of L. subantarcticus .
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.
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Genus |
Leptochiton subantarcticus (Iredale & Hull, 1930)
Sirenko, Boris 2020 |
Leptochiton subantarcticus
Kaas, P. & Van Belle, R. A. 1994: 24 |
Leptochiton (Leptochiton) subantarcticus
Kaas, P. & Van Belle, R. A. 1985: 160 |
Parachiton subantarcticus
Powell, A. W. B. 1979: 22 |
Kaas, P. 1977: 85 |
Lepidopleurus subantarcticus
Beu, A. G. 1977: 39 |
Lepidopleurus columnarius
Ashby, E. 1929: 372 |