Belknapchiton belknapi ( Dall, 1878 )

Sirenko, Boris, 2024, The chitons of the family Leptochitonidae (Mollusca: Polyplacophora) from the Emperor Seamounts, Pacific Ocean, Zootaxa 5474 (5), pp. 522-532 : 528-529

Belknapchiton belknapi ( Dall, 1878)

( Figures 6 , 7 )

Leptochiton belknapi ; Dall 1878: 1.

Leptochiton macleani ; Sirenko 2019b: 71, not Leptochiton macleani Sirenko 2015b .

Belknapchiton belknapi ; Sirenko et al. 2022: 104 , figs 1–15 (synonymy).

Type material. Holotype (USNM 30972).

Type locality. Off western Aleutian Islands, 53°08’N, 171°19’W, 1840 m depth .

Material examined. Pacific Ocean, Emperor Seamounts, Nintoku Seamount, 40°54’7’’N, 170°33’7’’E, 1150 m, R/ V Odyssey, geological dredge, 1 spm, BL 5.0 mm, leg. Sirenko B. 15.08.1984 ; Ojin Seamount, 37°55’6’’N, 170°28’0’’E, 1060 m, R/ V Odyssey, geological dredge, 2 spms, BL 4.0– 9.5 mm, leg. Sirenko B. 17.08.1984 ;

Distribution. The species, inhabits the Pacific Ocean from off the Pacific side of Hokkaido (38°40.1’N, 143°29.3’E), the Sea of Okhotsk and Bering Sea and of the Pacific coasts of North and South America southwards to 36.22523°S, 73.43115°W, at depths of 100 to 3724 m. This is the first report from the southern part of the Emperor Seamounts.

Remarks. The specimen from Nintoku Seamount with BL 5.0 mm was studied under a scanning electron microscope. It has rather low valves, dorsal elevation of valve V 0.28, each granule with one megalaesthete and two micraesthete in front. Dorsal scales with 2–3 longitudinal ribs. Radula of 2 mm long with 20 transverse row of mature teeth, head of major lateral tooth unidentate, strong, with small denticle-like appendage at inner edge. The specimen has 7 gills on each side, extending from valve VI to anus.

Compared to other studied specimens of this species, the specimen from Nintoku Seamount differs only in the low elevation of the valves. The other two specimens from the Ojin Seamount are similar to the specimen from Nintoku but are more elevated.

Figures

FIGURE 6. Belknapchiton belknapi, Pacific Ocean, Emperor Seamounts, Nintoku Seamount, 1150 m, BL 5.0 mm. A. Valve I, dorsal view. B. Valve V, dorsal view. C. Valve VIII, dorsal view. D. Valve IV, ventral view. E. Valve V, detail of tegmentum in central area. F. Valve VIII, lateral view. G. Valve V, rostral view.

FIGURE 7. Belknapchiton belknapi, Pacific Ocean, Emperor Seamounts, Nintoku Seamount, 1150 m, BL 5.0 mm. A. Dorsal scales, marginal needle and ventral scales. B. Radula.