Belgrandiellopsis chorfensis, Khalloufi & Béjaoui & Delicado, 2020

Khalloufi, Noureddine, Béjaoui, Mustapha & Delicado, Diana, 2020, Two new genera and three new subterranean species of Hydrobiidae (Caenogastropoda: Truncatelloidea) from Tunisia, European Journal of Taxonomy 648 (648), pp. 1-27 : 10-14

Belgrandiellopsis chorfensis gen. et sp. nov.

urn:lsid:zoobank.org:act:2C5704A1-BDFC-41BA-86C6-CF17A999BBC8

Figs 3–4

Diagnosis

Shell 1.45 to 1.65 mm high, elongate-conic, brown-yellowish; central radular tooth formula (5)4–C– 4(5)/1–1; bursa copulatrix ovoid, with the same length as the duct; two seminal receptacles, SR1 more developed and pedunculated, SR2 small, globular, located near loop before the pouch; prostate gland bean shaped, ovate in section, folded; penis cylindrical, slender, distal end tapered, unpigmented, with two lobes distantly positioned; basal lobe more developed. Distinguished from other closely related species by> 8.0% for COI.

Etymology

A geographic epithet referring to Chorfa Spring, where the species was found.

Type material

Holotype

TUNISIA • 1 spec. (sex unknown, preserved in ethanol 80%); Béja Province, ca 15 km west of Joumine, Chorfa Spring ; 36.865918º N, 9.363313º E; 430 m a.s.l.; 15 Mar. 2015; N. Khalloufi leg.; MNCN 15.05/200097H

Paratypes

TUNISIA • 5 specs (preserved in ethanol 80%); same collection data as for holotype; MNCN 15.05/200097P • 40 specs (preserved in ethanol 80%, 2 ♀♀, 2 ♂♂ dissected and 2 specs processed for DNA sequencing); same collection data as for holotype; UGSB 17663 • 150 specs (preserved in ethanol 95%, ca 70 individuals dissected); same collection data as for holotype; Khalloufi’s collection .

Type locality

TUNISIA: Béja Province, ca 15 km west of Joumine, Chorfa Spring, 36.865918º N, 9.363313º E, 430 m a.s.l.

Description

MEASUREMENTS. Holotype: SL = 1.61 mm, SW = 0.88 mm, SL/SW = 1.83, AH = 0.66 mm, SL-LBW = 0.49 mm, WBW = 0.84 mm, AL = 0.78 mm, AW = 0.53 mm, WPW = 0.64 mm, WAW = 0.10 mm.

SHELL. Elongate-conic, brown to yellowish, with 4–4.5 whorls ( Fig. 3 A–D; Table 2). Protoconch ( Fig. 3G ) obtuse, near planispiral, about 1.2 whorls, diameter about 350 µm; protoconch microsculpture granulated. Teleoconch whorls weakly convex, separated by deep sutures; body whorl occupying ¾ of total shell length. Aperture about 40% of total shell length, pyriform, strongly angled on the top and narrowly disjunct from parietal wall of body whorl; inner lip thin but thicker than outer lip; peristome margin ( Fig. 3B ) straight. Umbilicus narrow and closed by inner lip.

OPERCULUM. As for genus, thin, flat, whitish (nuclear region slightly yellowish), with ca 2 whorls ( Fig. 3 E–F); attachment scar area, oval and located near nucleus.

RADULA. Length intermediate (20% total maximum shell length), having about 80 rows of teeth. Central tooth ( Fig. 3 H–I) formula (5)4–C–4(5)/1–1, cutting edge concave; basal tooth face M-shaped and relatively narrow wings; basal tongue broadly V-shaped, about equal to lateral margins; a single small pair of basal cusps, triangular. Lateral teeth ( Fig. 3J ) formula (4)3–C–5; central cusp large, narrow, pointed. Inner marginal teeth ( Fig. 3H ) having 25–27 sharp cusps. Outer marginal teeth having 20–22 sharp cusps.

PIGMENTATION AND ANATOMY. Visceral coil brown-yellowish, showing by transparency the gonad; pallial coil nearly pale with traces of pigment on the roof, anteriorly to edge of mantle; foot and area between tentacles slightly pigmented ( Fig. 4C ). Black small eyes surrounded by brownish pigment. Snout with medium distal lobation. Tentacles parallel-side, distal end nonexpanded. Ctenidium filaments about 12, small, taller than wide. Osphradium whitish, ellipsoidal, positioned centrally along ctenidium ( Fig. 4A ). Stomach slightly longer than wide with a small gastric (posterior) caecum ( Fig. 4B ); rectum wide, folded and S-shaped.

MALE GENITALIA. Penis cylindrical ( Fig. 4 D–E), medium sized, unpigmented, slender, slightly folded; filament short, tapering; basal portion intermediate in width, shorter than distal portion, attached centrally to the head well behind the eyes; penis having two developed lobes located relatively far from one another on opposite sides of penis; both lobes with distal papilla, showing by transparency tubular glands distal; basal lobe larger, thumb-like, not pedunculated; distal lobe smaller, pyriform, pedunculated. Prostate gland small, close, bean-shaped, longer than wide (0.2 mm / 0.10 mm). Posterior vas deferens developed in its median portion with several loops (about 4 mm in length and 0.01 mm in section); seminal vesicle yellowish. Pallial vas deferens straight, narrow, whitish, unciliated, entering the posteroventral portion of gland and exiting from its anterior end.

FEMALE GENITALIA. Ovary simple, with stalked lobes, occupying near 40% of visceral coil. Distal female genitalia occupying near 70% of pallial roof; albumen gland approximately as long as capsule gland ( Fig. 4F ). Bursa copulatrix ovoid to pyriform, having a duct as long as bursal length. Renal oviduct unpigmented, coiled, having a spherical pouch at the end of the coiled section. Two seminal receptacles; SR1 medium sized, elongate, pedunculate, joining renal oviduct just above the insertion point with bursal duct; SR2 small, globular, sessile, located on renal oviduct near loop before pouch ( Fig. 4 G–H).

Ecology and distribution

Belgrandiellopsis chorfensis gen. et sp. nov. was found in a small spring near a rural settlement called Chorfa between the cities of Mateur and Beja, in northern Tunisia. It is known only from the type locality and some springs in this region (e.g., Ain Elgaid Spring). The specimens were found on the bottom and attached to the underside (algae-side) of gravel and stones. Density decreased drastically downstream from the water resurgence. Pseudamnicola sp. was the only co-occurring gastropod species.

Remarks

Differentiated from its congener according to its smaller shell size ( Table 2), smaller number of lateral cusps on the central radular teeth, larger penis and slightly smaller bursa copulatrix. Belgrandiellopsis chorfensis gen. et sp. nov. also differs in its mean COI divergence by 8.4% from B. secunda gen. et sp. nov.

Figures

Fig. 3. Shells, opercula and radulae, Belgrandiellopsis chorfensis gen. et sp. nov. A–D. Shells. A–B. Holotype, MNCN 15.05/200097H. C–D. Paratypes, MNCN 15.05/200097P. E–F. Operculum (E = inner side; F = outer side). G. Detailed microsculpture of protoconch. H–J. Radulae. H. Portion of radula ribbon. I. Central radular teeth. J. Lateral teeth.

Fig. 4.Anatomy of Belgrandiellopsis chorfensis gen. et sp. nov. (paratypes, UGSB 17663). A. Ctenidium and osphradium. B. Stomach. C. Head of male and penis. D. Detail of penis and penis lobes (observed by transmitted light in E). F. Pallial oviduct. G. Bursa copulatrix and seminal receptacles. H. Ditto, observed by transmitted light. Anatomical abbreviations explained in the text.