Diaphana hiemalis ( Couthouy, 1839 )

Ohnheiser, Lena Tina & Malaquias, Manuel António E., 2014, The family Diaphanidae (Gastropoda: Heterobranchia: Cephalaspidea) in Europe, with a redescription of the enigmatic species C olobocephalus costellatus M. Sars, 1870, Zootaxa 3774 (6), pp. 501-522 : 505-507

Diaphana hiemalis ( Couthouy, 1839)

( Figs 3 A–F, 4 A–C)

Bulla hiemalis Couthouy 1839: 180 , 181, pl. 4 fig. 5.

Diaphana hiemalis — G. O. Sars 1878: 291, tab. 18, fig. 3. Schiøtte 1998: 118, figs 16 D, 19 C–D, 23. Høisaeter et al. 2001: 250. Sneli et al. 2005: 96. Kantor & Sysoev 2006: 250, pl. 124 fig. F. Høisaeter 2009: 78. Chaban & Chernyshev 2013: 159, figs 3 A–J, 5 A.

Diaphana globosa - G. O. Sars 1878: 290, pl. 18 figs 3 c, 4, pl. XI, fig. 12. Pilsbry 1893: 286, pl. 26 fig. 75. Thompson 1988: 29.

Diaphana minuta — Lemche 1948, in part.

Diaphana tibai Habe 1976: 152 , pl. 1 fig. 11 (based on Schiøtte 1998).

Diagnosis. Shell external, whitish transparent, smooth, apex involute. Body white. Foot posteriorly bifurcated, cephalic shield with tentacular lobes. Rachidian tooth denticulate, not asymmetrical, lateral teeth with minute denticulation, teeth on left side smaller than on the right.

Type locality. Massachusetts Bay, inside cod stomachs from off Provincetown, Cape Cod, USA.

Material examined. Vadsø, Norway, 1 spc (dissected), ZMBN 82156, H = 6.4 mm. Ålesund, Norway, 1 spc (dissected), ZMBN 82160, H =?. Fensfjorden, 60°48’03’’ N, 0 5°05’48’’ E, Norway, 1 spc (dissected), ZMBN 82171, H = 2.0 mm. Fensfjorden, 60°40’45’’ N, 0 5°26’45’’ E, Norway, ZMBN 82167, H = 2.7 mm. Fensfjorden, 60°49’54’’ N, 0 5°03’15’’ E, Norway, 1 spc (dissected), ZMBN 82175, H = 2.1 mm. Raunefjorden, Norway, 1 spc (dissected), ZMBN 62056, H = 3.5 mm. Bergen, Norway, 1 sh, ZMBN 28711, H = 2.5 mm. Lofoten, Norway, 1 sh, ZMBN 68048, H = 2.4 mm. 60°08'27.6’’ N 06°16'22.8’’ E, Mauranger Nordrepollen, Norway, 1 spc (dissected), ZMBN 90609, H = 3.8 mm. 67°39'30’’ N, 11°36'42’’ W, NE off Iceland, 1 spc, ZMBN 85951, H = 4.11 mm.

Shell ( Fig. 3 C–F): Maximum H = 6.4 mm. External, thin; transparent; globose in shape, aperture wide with thin parietal callus, apex involute, umbilicated; shell surface smooth, faint spiral lines visible.

Animal ( Fig. 3 A, B): Body white. Foot posteriorly bifurcated, anteriorly widened into two lobes. Cephalic shield with tentacular lobes posteriorly.

Radula ( Fig. 4 A–C): Radular formula 12–15 x 1.1.1. Rachidian tooth with two large denticulated lobes separated by gap, lobes not asymmetrical. Lateral teeth long, inner edge denticulate. Radula asymmetrical with left laterals slightly smaller than the right laterals, one large denticle on tip of left laterals only.

Male reproductive system ( Fig. 4 D): Prostate with a thin and thick lobe emerging from penial sheath in a right angle.

Ecology. Occurs between 5–2725 m depth on mud, clay, sandy clay with stones, gravel, shells, foraminiferans, sand, muddy sand, silty sand, shell sand and mire ( Schiøtte 1998; Høisaeter, 2009; Chaban & Chernyshev 2013; present study). It is a characteristic species on clay bottoms below 400 m, most abundant between 750–2000 m ( Høisaeter 2009; 2010).

Distribution. Schiøtte (1998) refers its distribution as circumpolar, as far as Japan and Massachusetts and maybe in the Mediterranean Sea. Along the entire Norwegian coast, the continental slope, Faroes-Shetland Channel ( Høisaeter 2009) and the Faroes ( Sneli et al. 2005).

Remarks. Schiøtte (1998) redescribed this species, which, in spite of its involute spire and shell shape and reproductive system with shorter prostate branches, was formerly an accepted synonym of Diaphana minuta . Apparently, the radula of this species can depict some variation; typically the inner edges of the lateral teeth are denticulate but Chaban and Chernyshev (2013) reported specimens from NW Japan with smooth lateral teeth. Schiøtte (1998) lists Philine laevissima and Utriculopsis vitrea as synonyms but the confusion surrounding these two names have been recently discussed by Ohnheiser and Malaquias (2013) who considered these species names to be senior synonyms of the new name P. confusa Ohnheiser and Malaquias, 2013 .

Figures

FIGURE 3. Diaphana hiemalis. A. dorsal view of complete animal. B. ventral view of complete animal. C. dorsal view of shell (SEM). D. ventral view of shell (SEM). E. apex of shell (automontage picture). F. dorsal surface of shell (SEM). Scale bars: A, B = 1 mm; C, D = 0.5 mm; E = 100 Μm; F = 50 Μm.

FIGURE 4. Diaphana hiemalis. A. radula (LM). B. rachidian tooth (SEM). C. detail of lateral tooth (SEM). D. male reproductive system (drawing). Abbreviations: ga, genital aperture; pr, prostate; ps, penial sheath. Scale bars: A = 25 Μm; B = 3 Μm; C = 2 Μm; D = 250 Μm.