Belgrandiellopsis secunda, 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 : 14-16

Belgrandiellopsis secunda gen. et sp. nov.

urn:lsid:zoobank.org:act:D3A45301-6EBE-4086-A740-FEFBE9328FB5

Figs 5–6

Diagnosis

Shell 1.7 to 2.1 mm high, elongate-conic, brown-yellowish; central radular tooth formula (6)5–C– 5(6)/1–1; bursa copulatrix ovoid with short duct; two seminal receptacles, SR1 more developed and pedunculated, SR2 very 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 relatively distant positioned; basal lobe more developed and middle positioned. Distinguished from other closely related species by>8.4% for COI.

Etymology

Referring to the second species of the genus Belgrandiellopsis gen. nov. discovered so far.

Type material

Holotype

TUNISIA • 1 spec. (sex unknown, preserved in ethanol 80%); Bizerte Province, 40 km south of Mateur, Ettoute Spring ; 36.883898º N, 9.505894º E; 415 m a.s.l.; 15 Mar. 2015; N. Khalloufi leg.; MNCN 15.05/200098H.

Paratypes

TUNISIA • 5specs (preserved in ethanol80%);same collection data as for holotype; MNCN15.05/200098P • 26 specs (preserved in ethanol 80%, 2 ♀♀, 2 ♂♂ dissected and 2 specs processed for DNA sequencing); same collection data as for holotype; UGSB 17666 • 250 specs (preserved in ethanol 95%, ca 70 individuals dissected); same collection data as for holotype; Khalloufi’s collection .

Type locality

TUNISIA: Bizerte Province, 40 km south of Mateur, Ettoute Spring; 36.883898º N, 9.505894º E; 415 m a.s.l.

Description

MEASUREMENTS. Holotype: SL = 2.09 mm, SW = 1.16 mm, SL/SW = 1.80, AH = 0.90 mm, SL-LBW = 0.59 mm, WBW = 1.09 mm, AL = 0.99 mm, AW = 0.70 mm, WPW = 0.78 mm, WAW = 0.09 mm.

SHELL. Elongate-conic, brown to yellowish, with 4–4.5 whorls ( Fig. 5 A–D; Table 2). Protoconch ( Fig. 5G ) obtuse, near planispiral, about 1.3 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 50% 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. 5B ) straight. Umbilicus narrow and closed by inner lip.

OPERCULUM. As for genus, thin, flat, whitish (nuclear region slightly yellowish), with ca 2 whorls ( Fig. 5 E–F); attachment scar area oval and located near nucleus.

RADULA. Length intermediate (25% total maximum shell length), having about 80 rows of teeth. Central tooth ( Fig. 5 H–I) formula (6)5–C–5(6)/1–1, cutting edge slightly 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. 5H ) formula 5–C–3(4); central cusp large, narrow, pointed. Inner marginal teeth having 32–35 sharp cusps. Outer marginal teeth having 30–33 sharp cusps ( Fig. 5J ).

PIGMENTATION AND ANATOMY. Visceral coil pale-yellowish, showing by transparency the gonad. Pallial coil with uniform and dense brown pigmentation on roof (left side), anterior edge of mantle, foot and between tentacles ( Fig. 6C ). 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. 6A ). Stomach slightly longer than wide with a small gastric (posterior) caecum ( Fig. 6B ); rectum wide, folded and S-shaped.

MALE GENITALIA. Penis cylindrical ( Fig. 6D ), medium sized, unpigmented, slender, slightly folded; filament short, tapering; basal portion intermediate in width, longer than distal portion, attached centrally to the head well behind the eyes; penis having two developed lobes, both with distal papilla, showing by transparency tubular glands; lobes located relatively distant from one another on opposite sides of penis; basal lobe large, conic, sessile, positioned centrally along penis; distal lobe smaller, pyriform, pedunculated. Prostate gland small, close, bean-shaped, longer than wide (0.2 mm / 0.10 mm). Posterior vas deferens whitish, forming the seminal vesicle and developed in its median portion with several loops (about 3.5 mm in length and 0.05 mm in section). 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 50% of pallial roof; albumen gland less developed than capsule gland ( Fig. 6E ). Bursa copulatrix ovoid to pyriform, having a duct slightly shorter than bursal length. Renal oviduct unpigmented, coiled, having a very small, ovoid to 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. 6 F–G).

Ecology and distribution

This species was found in a spring and its outflow in the rural village Ettoute between the cities of Mateur and Beja, in northern Tunisia. Specimens were attached to the underside of gravel and stones covered by algae. In the small stream flowing out of the spring, the snails were found in the central section featuring clean and oxygenated waters and a silty substrate. The density of this species decreased drastically downstream from the water resurgence. Co-occurring gastropod species were Pseudamnicola sp., Galba truncatula (O.F. Müller, 1774) , Bulinus truncatus (Audouin, 1827) and Physella acuta Draparnaud, 1805 .

Remarks

Despite similarities in mean COI divergence between this species and the closely related species Bullaregia tunisiensis Khalloufi, Béjaoui & Delicado, 2017 , Biserta putealis gen. et sp. nov. and Belgrandiellopsis chorfensis gen. et sp. nov. (9.1%, 8.9% and 8.4%, respectively), B. secunda gen. et sp. nov. was assigned to Belgrandiellopsis gen. nov. based on the combination of two glandular lobes located relatively distant from one another on opposite sides of the penis [one lobe in Bullaregia ( Khalloufi et al. 2017) , two lobes closely positioned to one another in Biserta gen. nov.], small bursa copulatrix with a long duct (larger bursa copulatrix with a shorter duct in Biserta gen. nov.), small gastric caecum (larger in Bullaregia ) and small shell umbilicus (larger in Biserta gen. nov.).

Figures

Fig. 5. Shells, opercula and radulae, Belgrandiellopsis secunda gen. et sp. nov. A–D. Shells. A–B. Holotype, MNCN 15.05/200098H. C–D. Paratypes, MNCN 15.05/200098P. 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. Outer marginal teeth.

Fig. 6. Anatomy of Belgrandiellopsis secunda gen. et sp. nov. (paratypes, UGSB 17666). A. Ctenidium and osphradium. B. Stomach. C. Head of male and penis. D. Detail of penis and penis lobes. E. Pallial oviduct. F. Bursa copulatrix and seminal receptacles. G. Ditto, observed by transmitted light. Anatomical abbreviations explained in the text.