Radomaniola variabilis, Delicado & Hauffe, 2022

Delicado, Diana & Hauffe, Torsten, 2022, Shell features and anatomy of the springsnail genus Radomaniola (Caenogastropoda: Hydrobiidae) show a different pace and mode of evolution over five million years, Zoological Journal of the Linnean Society 196, pp. 393-441 : 427-430

RADOMANIOLA VARIABILIS SP. NOV.

( FIGS 22 , 23 )

Z o o b a n k r e g i s t r a t i o n: z o o b a n k. org:act: BACA04A4-0420-4FB3-B15B-A3CD6789A303

Etymology: From Latin variabilis , variable, referring to its high intraspecific variation in shell shape.

Type material: Holotype ( MNCN 15.05 /200169), three paratypes ( MNCN 15.05 /200170) in the MNCN collection and ten paratypes in the UGSB collection ( UGSB 23975 ). Type locality: Vellas Spring , Kalpaki, Greece.

Material studied: Vellas Spring, Kalpaki, Greece, 39.8660°N, 20.6243°E, T.W. and C.A., May 2005, MNCN 15.05 /200170 and UGSB 23975 (80% ethanol); unnamed spring, 3 km west of Qafë Murrës , Albania, 41.63°N, 20.2°E, Z.F., June 2003, UGSB 14440 (80% ethanol); unnamed spring, 7 km south of Tepelenë , Albania, 40.27°N, 20.28°E, Z.F., October 2004, UGSB 14441 (80% ethanol); Syri i Kaltër Lake, 7 km west of Muzinë, Albania, 39.92°N, 20.18°E, Z.F., October 2004, UGSB 2294 (80% ethanol) .

Diagnosis: Protoconch microsculpture pitted; central radular tooth formula 7-C-7/1-1; bursa copulatrix ovoid, duct slightly longer than bursal length; SR1 pyriform, duct short; SR2 pyriform, duct short, slightly larger than SR1; penis unpigmented, gradually tapering, base narrow, approximately as long as head length; nervous system weakly pigmented, moderately concentrated (mean RPG ratio = 0.47).

Description: Shell ovate-conic, 4.0–4.5 whorls, height 2.0– 2.6 mm ( Fig. 22A–F ; Supporting Information, Table S6). Periostracum yellowish, sometimes whitish. Protoconch ~425 µm wide, 1.5 whorls; nucleus ~175 µm wide; protoconch microsculpture pitted ( Fig. 22I ). Teleoconch whorls convex, with deep sutures; body whorl large, occupying about two-thirds of total shell length. Aperture slightly oval; inner lip thicker than outer lip; peristome margin simple, straight ( Fig. 22B, F ). Umbilicus narrow, not covered by the inner lip. Operculum oval, brownish, about two whorls; muscle attachment area oval and located near the nucleus ( Fig. 22G, H ). Radular length intermediate, ~600 µm (~25% of total shell length), with ~60 rows of teeth. Central tooth formula 7-C-7/1-1 ( Fig. 22J–L ); basal tongue U-shaped, length about equal to lateral margin. Lateral tooth formula (3)4-C-4(3). Inner marginal teeth having 25–32 tapered cusps, shortening toward the base. Outer marginal teeth with 27–34 sharp cusps ( Fig. 22M, N ).

Animal darkly pigmented except for neck and tentacles ( Fig. 23G, H ). Ctenidium with 12 or 13 welldeveloped gill filaments, occupying ~50% of pallial cavity length and positioned posteriorly. Osphradium of intermediate width and opposite middle of ctenidium ( Fig. 23A ). Stomach as long as wide, with two chambers almost equal in size; style sac longer than wide, surrounded by an unpigmented intestine ( Fig. 23B ; Supporting Information, Table S7). Nervous system slightly pigmented, moderately concentrated (mean RPG ratio= 0.47); cerebral ganglia approximately equal in size, presenting small black granules ( Fig. 23C ).

Female glandular oviduct approximately three times longer than wide. Albumen gland shorter than capsule gland. Bursa copulatrix ovoid, slightly longer than wide. Bursal duct slightly longer than bursal length. Renal oviduct unpigmented, coiled. SR1 pyriform, duct short, joining renal oviduct slightly above the insertion point with bursal duct. SR2 slightly larger than SR1, pyriform, with a short duct, located on renal oviduct near loop ( Fig. 23D, E ; Supporting Information, Table S8).

Male genitalia with a prostate gland approximately two times longer than wide, bean shaped; seminal duct entering the middle-posterior region; pallial vas deferens emerging close to its anterior edge ( Fig. 23F ). Penis unpigmented, gradually tapering, approximately as long as head length, base narrow, weakly folded along inner edge and with one medial outgrowth on its left side ( Fig. 23G–K ; Supporting Information, Table S9); penis attached well behind the right eye; penial duct narrow, near outer edge, almost straight.

Habitat: Radomaniola variabilis lives in cold water springs and lacustrine habitats; it has been found on stones and aquatic vegetation. It co-occurs with Ancylus fluviatilis Müller, 1774 , Radix cf. peregra (Müller, 1774) and Bithynia sp. in the type locality.

Remarks: Populations of R. variabilis are particularly variable in the number of cusps on the lateral radular teeth, intensity of body pigmentation, penis width ( Figs 22 , 23 ) and shell morphology (e.g. shells of the Vella Spring population in Greece are slightly larger, more elongate than those of the Albanian populations and present a smaller aperture with a thin inner lip). Female genitalia could not be examined in detail because most of the dissected females from the type locality were parasitized and had stunted organs. Also, we found no females among the few specimens collected at the localities in Albania. Although the ABGD and GMYC methods subdivided this species into three entities, we consider this taxon as a single species based on the geographical proximity and phylogenetic clustering of the studied populations as a monophyletic group, a small intraspecific divergence <1.6% for COI and similar shape of the shell and penis. Fehér & Erőss (2009) assigned the three populations from Albania studied herein to R. curta based on shell morphology. However, penis features and genetic data suggest that these populations are members of R. variabilis and not of R. curta . The authors also reported the species R. curta and R. albanica co-occurring in the Syri i Kaltër Spring ( Fehér & Erőss, 2009). Based on morphological and molecular results, we conclude that the snails from the same locality examined in the present study are likely to be conspecific with R. variabilis and R. albanica .

Radomaniola variabilis is morphologically distinguishable from the geographically and phylogenetically proximate species R. dolens , R. albanica and R. haesitans according to its wider shell, wider shell umbilicus, longer penis, shorter bursal duct and SR1 and sequence divergence from these three species (5–6% average divergence for COI).

Figures

Figure 22. Shells, operculum and radulae of Radomaniola variabilis sp. nov. A, B, holotype (MNCN 15.05/200169). C, paratype (UGSB 23975). D, shell (UGSB 14440). E, F, shell (UGSB 2294). G–J, N, paratypes (UGSB 23975). G, H, operculum (G, inner side; H, outer side). I, protoconch. J, portion of radula ribbon (UGSB 23975). K, portion of radula ribbon (UGSB 2294). L, central radular teeth (UGSB 14440). M, outer marginal teeth (UGSB 2294). N, outer marginal teeth (UGSB 23975).

Figure 23. Anatomy of Radomaniola variabilis sp. nov.A–G, I, paratypes (UGSB 23975). H, J, UGSB 14440. K, UGSB 2294. A, ctenidium and osphradium. B, stomach. C, partial nervous system. D, pallial oviduct. E, bursa copulatrix and seminal receptacles. F, prostate gland. G, H, head of male and penis. I–K, penis.