Annulobalcis albus, DGEBUADzE & FEDOSOv & Kantor, 2012

DGEBUADzE, Polina Y., FEDOSOv, Alexander E. & Kantor, Yuri I., 2012, Host specificity of parasitic gastropods of the genus Annulobalcis Habe, 1965 (Mollusca, Gastropoda, Eulimidae) from crinoids in Vietnam, with descriptions of four new species, Zoosystema 34 (1), pp. 139-155 : 142-146

Annulobalcis albus n. sp.

( Figs 2 ; 6A, B )

Annulobalcis sp. 1 – Dgebuadze & Kantor 2010 (partim): figs 2a, v; 4a.

TYPE MATERIAL. — Vietnam. South China Sea, Nha Trang Bay, Mun Island (Rock Rom), 12°10’12.51”N, 109°18’46.06”E, 5-7 m, holotype ( MNHN 24190).

Same data as holotype, 5 paratypes ( ZIN 61118-61120, MNHN 24191).

OTHER MATERIAL EXAMINED. — 450 specimens from crinoids Oxycomanthus benetti (Müller, 1841) (Comasteridae) , 3 specimens sequenced ( JF717844 - JF717846 ), stored in the Laboratory of Marine Invertebrates of A. N. Severtzov Institute of Ecology and Evolution.

DISTRIBUTION. — South China Sea, Nha Trang Bay.

ETYMOLOGY. — From the Latin “albus”, white reflecting colouration of soft parts.

DESCRIPTION (HOLOTYPE)

Shell narrow, elongated-conical, glossy, translucent porcellaneous, smooth except numerous frequently irregularly spaced axial lines. Shell of nine whorls.

Larval shell pointed, with small nucleus, smooth, border with teleoconch not pronounced.Four upper shell whorls with lower expansion rate than other whorls of teleoconch. Axis slightly curved. Suture shallow, false suture (for definition see Bouchet & Warén 1986) seen by transparency. Teleoconch whorls slightly convex, last whorl high, comprising 0.6 of shell height.

Aperture broadly ovate, with angulated junction of columellar and parietal margins, 0.38 of shell height. Columellar margin short, weakly convex, about half aperture height. Parietal margin evenly rounded without callus. Outer lip in ventral view evenly rounded, in lateral view forms deep anal sinus near suture, lip most protruded in its middle part.

Soft parts hardly visible through the shell.

Measurements

See Table 3.

Host

Molluscs were found on cirri of crinoids Oxycomanthus benetti (Comasteridae) .

Colouration

In live specimens body translucent ( Fig. 6A, B ). Foot translucent with longitudinal stripe of lemon-yellow colour. Tentacles transparent with longitudinal lemon yellow stripes, extending for entire tentacles’ length. Eyes well developed, black, situated at tentacles base. Proboscis present. Pseudopallium absent. Operculum present, oval, spiral, nucleus close to columellar margin ( Fig. 3N ).

Intraspecific variability

Paratypes are very similar to holotype in shell shape and morphology. Shell tending to become more slender (decreasing of SW/SH ratio) with increasing of its height. There is also a weak tendency of decreasing of relative height of the last whorl with increasing of the shell height.

Due to their small size and fragile shell the sequenced specimens were destroyed. The remaining specimens collected from the same host specimen ( Fig. 2K, L ; Table 3, specimens 1-3) are very similar to the type series and no doubt of their conspecifity remains.

REMARKS

Most species of the genus Annulobalcis are characterized by more or less pronounced shell sculpture ( A. yamamotoi Habe, 1974 , A. shimazui Habe, 1965 , A. aurisflamma Simone & Martins, 1995 , A. procera Simone, 2002 ), usually visible under light microscope or even by naked eye. The presence of the spiral sculpture was considered as characteristic of the genus. Thus our new species is markedly different from typical representatives of Annulobalcis . Nevertheless Warén (1981) described Annulobalcis marshalli Warén, 1981 from deep waters of New Zealand (on the crinoid Crotalometra rustica Clark, 1909 ) also lacking spiral sculpture. Warén also transferred another species, Apicalia cicatricosa Warén, 1981 (from unknown host) with very indistinct and scattered spiral sculpture to Annulobalcis . Thus the absence of the sculpture does not preclude including Annulobalcis albus n. sp. in the genus.

The present species resembles Annulobalcis marshalli in smooth shell, but differs by relatively broader shell with taller last whorl and aperture. Also the new species is significantly, more than twice smaller.

In shells proportions the new species is similar to Annulobalcis cicatricosa ( Warén, 1981) (Eagle Island, Queensland, Australia), which has a 0.43 SW/SH ratio in holotype, but has slower increasing and more numerous as well as less convex teleoconch whorls. For comparison with A. wareni n. sp. see the corresponding species.

Figures

FIG. 2.— Annulobalcis albus n. sp.:A, B, holotype (MNHN 24190);C, paratype 1 (ZIN 61118);D, paratype 2 (ZIN 61119);E, F, paratype 3 (ZIN 61120); G, I, paratype 4 (MNHN 24191); H, specimen 3 (Table 3) collected from the same host as the sequenced ones, SEM of the shell; J, paratype 5 (MNHN 24191); K, L, specimens 1 and 2 (Table 3) collected from the same host as the sequenced ones; M, specimen 3 apex, SEM; N, same, operculum, SEM. Scale bars: A-L, 1 mm; M, 200 μm; N, 500 μm.

FIG. 6. — A, live specimen of Annulobalcis albus n. sp.; B, Annulobalcis albus n. sp. specimens on their host Oxycomanthus benetti (Müller, 1841); C, Annulobalcis vinarius n. sp. on arm of crinoid Himerometra robustipinna Carpenter, 1881; D, live specimen of Annulobalcis vinarius n. sp.; E, eggs capsules of Annulobalcis vinarius n. sp. on crinoid Himerometra robustipinna; F, live specimen of Annulobalcis wareni n. sp. Scale bars: A, C-F, 1 mm; B, 10 mm.

FIG. 3. — Annulobalcis wareni n. sp.: A, B, holotype (MNHN 24192); C, D, paratype 1 (ZIN 61121); E, paratype 2 (MNHN 24193); F, specimen 1 (Table 5) collected from the same host as the sequenced ones; G-J, specimen 2 (Table 5) collected from the same host as the sequenced ones; G, operculum, SEM; H, SEM of the shell; I, J, apex in different views, SEM. Scale bars: A-F, H, 1 mm; G, 500 μm; I, 200 μm; J, 100 μm.