Haliella seisuimaruae, Takano & Kimura & Kano, 2020

Takano, Tsuyoshi, Kimura, Shoichi & Kano, Yasunori, 2020, Host identification for the deep-sea snail genus Haliella with description of a new species (Caenogastropoda, Eulimidae), ZooKeys 908, pp. 19-30 : 19

Haliella seisuimaruae sp. nov. Figs 1 , 3 , 4-5

Type material.

Holotype (NSMT-Mo 79088) from the type locality, found attached to the test of Brissopsis sp. cf. luzonica (Figs 1 , 2 ), collected on 28 April 2018 by S. Kimura. Paratype 1 (MPM Coll. No. 21596) and paratype 2 (AORI YK1520) from Tosa Basin, off Kochi, Shikoku Island, Japan without host information, both collected on 24 June 2011 by T. Takano, Y. Kano and H. Fukumori (Tables 1 , 2 ).

Type locality.

Off Tanabe, Wakayama, Honshu Island, Japan; 33°32.2'N, 135°08.1'E; 641-727 m deep.

Etymology.

The name refers to the T/V “Seisui-maru” of Mie University, which captured the holotype of the new species.

Distribution.

Known only from the localities of the type specimens.

Diagnosis.

A typical Haliella species with high, narrow aperture. Columellar lip tilted at 20° angle from coiling axis, twisted, extended outward near base; junction of parietal wall and columella at ca. 38% of aperture height from suture.

Description.

Shell slender, conical with blunt apex, up to 9.8 mm high, 2.2 mm wide and 9 slightly convex whorls (7.8 mm high, 2.0 mm wide, 7.8 whorls in holotype), smooth, thin but not fragile, translucent white. Protoconch large, smooth, paucispiral with 1.5 whorls, indistinctly demarcated from teleoconch. Teleoconch whorls bear straight, irregularly spaced incremental lines or growth pause scars, which are situated at 0.5, 1.6, 2.2, 2.9, 3.4, 3.7, 4.4, 4.7, 5.3 and 5.8 whorls in holotype. Body whorl occupies 45% of total shell height. Aperture high, narrow and oblique; outer lip simple, only slightly curved or almost straight in lateral view, with its most protruding part at 3/4 of aperture height from suture; parietal callus absent; columellar lip tilted at angle of 20° from coiling axis in holotype, thick, twisted, extended outward near round base; junction of parietal wall and columellar lip placed at ca. 38% of aperture height from suture. Umbilicus absent. Operculum teardrop shaped, thin, yellowish. Pigmented eyes absent.

Remarks.

The generic position of the present species is determined most readily by its shell with (1) a slender and cylindrical outline, (2) a blunt apex, (3) slightly convex whorls, and (4) a high, narrow aperture with (5) a twisted columella (Figs 3 - 5 ). In addition, (6) the absence of pigmented eyes agrees with the condition reported for the type species H. stenostoma from the North Atlantic and Barents Sea ( Bouchet and Warén 1986). Actually, the present new species shows the closest resemblance to H. stenostoma in having a tall shell with an almost straight outer lip with its most protruding part at 3/4 of the aperture height from the suture. However, H. seisuimaruae sp. nov. has a junction of the parietal wall and columellar lip at 38% of the aperture height (33% in H. stenostoma ), a slightly wider aperture and a more curved and extended columellar lip (Fig. 3 ; see Warén 1984; Nekhaev 2013 for comparison).

Haliella seisuimaruae sp. nov. is more easily distinguished from the five other described species of the genus. Haliella ventricosa from the South China Sea is characterized by a larger body whorl relative to the total shell height (> 60%) and an accordingly higher aperture ( Feng 1996). Haliella abyssicola from off California differs in having a columellar lip that almost parallels to the coiling axis ( Bartsch 1917). The other three congeners, H. chilensis from Chile, H. canarica from the northeastern Atlantic and H. tyrrhena from the Mediterranean, have a much wider, more ovate shell aperture ( Bartsch 1917; Bouchet and Warén 1986; Di Geronimo and La Perna 1999).

Hasegawa (2001, 2005, 2009) and Hasegawa and Okutani (2011) reported four eulimid species from Japanese bathyal waters as undescribed members of Haliella . The shell outline and apertural features also distinguish H. seisuimaruae sp. nov. from these unnamed taxa. A species from off Miyako, Iwate, northern Honshu shares a near-straight outer lip with the present new species but differs in having a more tapering apex ( Hasegawa 2009: figs 142, 143). The second species from Tosa Bay, Shikoku Island and the third from the East China Sea have the parietal wall and columellar lip joining in a straight line ( Hasegawa 2001: pl. 2, fig. L; Hasegawa 2005: fig. 7H). The fourth species from Sagami Bay shows a strongly curved outer lip with its protruding part at half of the total aperture height ( Hasegawa and Okutani 2011: fig. 20).

As a side note, Adams (1861: 126) described Eulima stenostoma A. Adams, 1861 from "26 fathoms, Tsu-Sima" (Tsushima, Japan), unaware of the primary homonym Eulima stenostoma Jeffreys, 1858 (now the type species of Haliella ). Identical species-group names established for different nominal taxa when originally combined with the same generic name are primary homonyms and the junior name is permanently invalid (International Code of Zoological Nomenclature, Article 57.2). The holotype of the Adams’s species (BMNH 1878.1.28.127 in the Natural History Museum, London; see Higo et al. 2001: 57, fig. G2044) most closely resembles the aforementioned, alleged Haliella from Sagami Bay ( Hasegawa and Okutani 2011) in the apertural morphology of the shell. This latter species from Sagami Bay, however, is actually a member of the ophiuroid-parasite genus Eulima (T. Takano, unpublished data), as probably is the case with Adams’s stenostoma . In order to prevent further confusion between species and genera, we propose a new substitute name, Eulima tsushimensis Takano, Kimura & Kano nom. nov., for E. stenostoma A. Adams, 1861 with Adams’s original specimen as the holotype.

This study presents the first direct observation of parasitic ecology and echinoderm host for the genus Haliella . The holotype of H. seisuimaruae sp. nov. was found attached to the dorsal (aboral) side of an irregular sea urchin, Brissopsis sp. cf. cf. luzonica (Fig. 1 ). Eulimid species in a single genus generally exploit hosts of the same echinoderm class ( Warén 1984), suggesting that the other congeners may also parasitize (irregular) sea urchins. Previously known parasites of irregular sea urchins include the species of three other eulimid genera, Clypeastericola Warén, 1994, Hypermastus Pilsbry, 1899 and Turveria Berry, 1956 ( Warén and Crossland 1991; Warén et al. 1994; Matsuda et al. 2010, 2013a, b). Those eulimids, however, appear to be distantly related to Haliella with rather different shell morphology (see Warén 1984). They inhabit much shallower waters ranging from intertidal to shallow subtidal zones, with Hypermastus bulbulus (Murdoch & Suter, 1906) from 200 m deep as a single known exception ( Warén and Crossland 1991; Warén et al. 1994). The host specialization to irregular sea urchins might thus have occurred more than once in the evolutionary history of the Eulimidae .

Figures

Figures 1 - 3. Holotype of Haliella seisuimaruae sp. nov. and its host sea urchin Brissopsis sp. cf. luzonica (both NSMT-Mo 79088). 1 Photograph of living holotype, attaching to latero-dorsal surface of sea urchin test 2 dorsal or aboral view of same host specimen 3 holotype, apertural and lateral views. Scale bars: 10 mm (2); 2 mm (3).

Figures 4, 5. Paratypes of Haliella seisuimaruae sp. nov., apertural and lateral views. 4 Paratype 1 (MPM Coll. No. 21596) 5 paratype 2 (AORI YK 1520). Scale bar: 2 mm.