Gastropteron japonicum Tokioka & Baba, 1964

Description

A small gastropterid 5-10 mm in length. The parapodia are well developed; when expanded their width exceeds the dorsal hump. Holotype 5.3 mm × 3.6 mm; paratypes show 13 ctenidial leaflets each. The embryonic shell lies postero-ventral to the anus, horn-shaped, strongly curved and about 430 μm long; it is calcified but hyaline and very fragile, as is typical of gastropod veliger shells. Living colour: the body is whitish throughout; the parapodia are dotted with minute purplish-brown pigment spots on both surfaces, but the periphery, especially on the under surface, is dotted with orange spots, and the sole is also densely dotted with orange. The cephalic shield is dotted with purplish-brown spots except for the anterior margin, which is sprinkled with orange spots.

Distribution

Type locality: Kurosaki in Sagami Bay, Japan (110-120 m). Additional material from Zyogasima in Sagami Bay (300 m) and Kannontuka-dasi of Amadaiba (70-90 m).

Etymology

The specific epithet japonicum is an adjective derived from Japan (Latin Japonia), reflecting that the species was described from Japanese material.

Remarks

The embryonic shell, undetected in the original specimens, was confirmed on additional material described in the Postscript of the original paper.

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References

• Gastropteron japonicum n.sp., Tokioka T. & Baba K. (1964). FOUR NEW SPECIES AND A NEW GENUS OF THE FAMILY GASTROPTERIDAE FROM JAPAN (GASTROPODA : OPISTHOBRANCHIA). Publications of the Seto Marine Biological Laboratory. 12(3): 201-229. https://doi.org/10.5134/175366