Austrobela rufa, Criscione & Hallan & Puillandre & Fedosov, 2021

Criscione, Francesco, Hallan, Anders, Puillandre, Nicolas & Fedosov, Alexander, 2021, Where the snails have no name: a molecular phylogeny of Raphitomidae (Neogastropoda: Conoidea) uncovers vast unexplored diversity in the deep seas of temperate southern and eastern Australia, Zoological Journal of the Linnean Society 191, pp. 961-1000 : 983-984

AUSTROBELA RUFA SP. NOV.

( FIGS 3F, 5E, 6D)

Z o o B a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: 9212F7D7-D734-49A7-94AB-B24011C9BFF9.

Holotype: Australia, GAB, 965 m, IN2015_C02_131, (–35.153, 134.109), AMS C.571709.

Paratypes: Australia, GAB, 978 m, IN2015_C02_382, (–33.516, 130.265), one wet ( AMS C.571680); 1029 m, IN2015_C01_110, (–34.629, 132.356), one wet ( AMS C.483817); 1016 m, IN2015_C01_117, (–34.674, 132.479), one wet ( AMS C.571681); 994 m, IN2015_ C01_114, (–34.705, 132.531), one wet ( AMS C.571679); 1350 m, IN2015_C01_108, (–34.738, 131.841), two wet ( SAMA D44253) ; two wet ( AMS C.483801); one wet ( AMS C.483802); two wet ( AMS C.571668); 1015 m, IN2015_C02_167, (–34.823, 132.692), one wet ( AMS C.532677); 1509 m, IN2015_C02_134, (–35.345, 134.045), one wet ( AMS C.532691); one wet ( AMS C.571699) . Australia, Tasmania, St Helens flat, 1127 m, IN2018_ V06 _184, (–41.209, 148.797), one wet ( AMS C.574588); one wet ( AMS C.271201) .

Distribution: Known from the Great Australian Bight, northern Tasmania and the southern coast of New South Wales.

Etymology: The epithet is derived from the Latin adjective rufus, red, in reference to the coloration of its shell.

Description

Shell ( Fig. 3F) (SL = 35.4, SW = 14.6) thin-walled, fusiform, semitranslucent to opaque. Protoconch ( Fig. 5E) (based on paratype AMS C.571681) orange, cyrthoconoid, multispiral, with 4.5 whorls, first whorl with punctate sculpture ( Fig. 5E), remaining whorls with fine, evenly distanced arcuate riblets (about 35 on last whorl). Protoconch–teleoconch transition sharply delineated, broadly sinuate. Teleoconch of about six whorls with broad, slightly concave subsutural ramp. Whorl lower portion with axial sculpture of strong, sharp opisthocline ribs, well-pronounced at shoulder of two earliest and last teleoconch whorls; whorls subcylindrical below shoulder. Third and penultimate whorls without pronounced axials. Microsculpture of dense growth lines on subsutural ramp and fine spiral cords on whorl lower portion. Last adult whorl with about 16 axials, vanishing shortly below shoulder. Shell base evenly convex, clearly demarcated from long, slender tapering siphonal canal. Aperture elongate, about half of length of shell, rounded below shoulder and narrowing toward siphonal canal. Outer lip thin, inner lip smooth, with narrow callus on long, straight columella bearing vertical orange stain. Sinus wide, moderately deep, L-shaped. Shell surface glossy, early teleoconch whorls pale orange or cream, subsequent whorls of orange colour.

Anatomy based on AMS C.27120, female, except penial characters based on AMS C.571679, male. Animal uniform whitish/cream. Cephalic tentacles large, muscular, long, subcylindrical; large eyes on outer lower base of tentacles. Rhynchostome subcircular, lined with numerous epithelial cells; large, thin-walled introvert with numerous longitudinal folds. Oviduct large; intestine lightly curved along length of oviduct, posterior to it. Penis large, coiling clockwise, simple. Rectal gland greenish, filamentous/bristly in appearance, parallel to anterior of intestine. Rhynchocoel with dark red content. Venom apparatus extremely large, occupying most of rhynchoocoel; proboscis large, elongate; radular sac extremely large; venom gland large, thick, whitish, long and convoluted; muscular bulb lustrous, yellow, extremely large, elongate, with indentation posteriorly where pressed against oesophagus.

Radula ( Fig. 6D) (based on: AMS C.571679; AMS C.571709; AMS C.574588) of straight to gently curved, somewhat loosely rolled hypodermic teeth of up to 350 µm in length; lower half of shaft cylindrical, somewhat inflated, distal half weakly tapering toward prominent dorsal and ventral distal barbs, of which ventral barb more distal from tip; dorsal barb sharper than ventral barb. Adapical opening elongate, narrow, boundaries not clearly defined due to loosely overlapping tooth margins, up to one-fifth of shaft length. Basal third of shaft with weakly rugose texture. Base broad, with medium coarse texture on exterior. Basal opening large. Ligament about half width of base, solid, thick.

Remarks

This species can be differentiated from other raphitomids by the following combination of characters: a glossy shell with weakly developed sculpture, clearly pronounced but rounded shoulder and yellowish orange to reddish brown coloration; a hypodermic radula with two large, sharply hooked barbs; an extremely large venom apparatus occupying almost the entire rhynchocoel; a thin-walled, strongly folded introvert and the presence of well-developed, large eyes. Although DNA sequence data for the holotype were not included in the analysis of Figure 2, a COI sequence was generated and is available on Genbank (AN MN983272 ). This is a variable taxon based on shell morphology, with some specimens examined exhibiting shells with little to no distinct sculpture.

Based on its shell morphology, this new taxon bears considerable similarity to the north-east Atlantic Gymnobela fulvotincta (Dautzenberg & Fischer, 1996) . However, when compared to the holotype of the latter, the following characters observed in Gym. fulvocincta distinguishes this species from A. rufa : more prominent axial ribs, producing a more angulate whorl profile; a shoulder situated lower on adult whorls; a less cylindrical whorl periphery and a columella that is distinctly curved when observed in apertural view as opposed to the straight columella in A. rufa . In terms of radular morphology, the hypodermic tooth figured in Bouchet & Warén (1980: fig. 24) shows barbs that appear distinctly less prominent in Gym. fulvotincta , and a shaft that tapers gradually as opposed to the somewhat inflated lower half of the shaft in A. rufa ( Fig. 6D). When compared to the superficially similar Gymnobela yoshidai (Kuroda & Habe, 1961) , A. rufa possesses a significantly broader shell and a more sharply inclined subsutural ramp ( Sysoev & Bouchet, 2001: figs 134–144).