Radomaniola curta, 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 : 413-414

RADOMANIOLA CURTA SUBSP. MAXIMA SUBSP. NOV.

( FIGS 10 , 11 )

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: D86C5BA4-235B-410B-93B7-531D97B30A4D

Etymology: From Latin maximus, very large, referring to its large body size.

Type material: Holotype ( MNCN 15.05 /200153), 20 paratypes ( MNCN 15.05 /200154) in the MNCN collection and> 500 paratypes ( UGSB 19540 ) in the UGSB collection. Type locality: Crnojevića River , Montenegro.

Material studied: Crnojevića River , near the bridge, Montenegro, 42.3550°N, 19.0284°E, T.H., C.W. and D.E., September 2009, MNCN 15.05 /200154 and UGSB 19540 (80% ethanol) .

Diagnosis: Protoconch microsculpture pitted; central radular tooth formula 5-C-5/1-1; bursa copulatrix ovoid, with a long duct; SR1 elongate, duct short; SR2 small, pyriform, duct short; penis unpigmented, gradually tapering, shorter than head length, sometimes with one medial outgrowth on its left side; nervous system unpigmented, elongate (mean RPG ratio = 0.52).

Description: Shell ovate-conic, 4.0–4.5 whorls, height 2.5–3.5 mm ( Fig. 10A–D ; Supporting Information, Table S6). Periostracum yellowish. Protoconch ~400 µm wide, 1.5 whorls; nucleus ~150 µm wide; protoconch microsculpture pitted ( Fig. 10G ). Teleoconch whorls slightly convex, with deep sutures; body whorl large, occupying about three-quarters of total shell length. Aperture oval; inner lip thicker than outer lip; peristome margin simple, straight ( Fig. 10B ). Umbilicus narrow, not covered by the inner lip. Operculum oval, brownish, about two whorls; muscle attachment area oval and located near the nucleus ( Fig. 10E, F ). Radular length intermediate, ~700 µm (~25% of total shell length), with ~50 rows of teeth ( Fig. 10H ). Central tooth formula 5-C- 5/1-1 ( Fig. 10I ); basal tongue V-shaped, length about equal to lateral margin. Lateral tooth formula (4)3-C- 3(4). Inner marginal teeth bearing 18–21 tapered cusps, shortening toward the base. Outer marginal teeth with 22–23 sharp cusps ( Fig. 10J ).

Animal darkly pigmented except for neck and tentacles ( Fig. 11F ). Ctenidium with 13–16 welldeveloped gill filaments, occupying ~50% of pallial cavity length and positioned posteriorly. Osphradium of intermediate width and opposite middle of ctenidium ( Fig. 11A ). Stomach approximately as long as wide, with two chambers almost equal in size; style sac longer than wide, surrounded by an unpigmented intestine ( Fig. 11B ; Supporting Information, Table S7). Nervous system unpigmented, elongate (mean RPG ratio = 0.52); cerebral ganglia approximately equal in size ( Fig. 11C ).

Female glandular oviduct approximately three times longer than wide. Albumen gland shorter than capsule gland. Bursa copulatrix ovoid, about as long as wide. Bursal duct longer than bursal length. Renal oviduct unpigmented, coiled. SR1 elongate, with a short duct, joining renal oviduct slightly above the insertion point with bursal duct. SR2 shorter than SR1, pyriform, with a short duct, located on renal oviduct near loop ( Fig. 11D, 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. 11H ). Penis unpigmented, gradually tapering, shorter than head length, weakly folded along inner edge and with one medial outgrowth (sometimes absent) on its left side ( Fig. 11F, G ; Supporting Information, Table S9); penis attached to the area close to the right eye; penial duct narrow, near outer edge, almost straight.

Habitat: This is a riverine subspecies collected from the margins of the Crnojevića River when the water level was low. Snails were found in high abundance on stones and small rocks. Co-occurring species are Ancylus sp. , Theodoxus sp. , Bithynia sp. and Anagastina matjasici (Bole, 1961) .

Remarks: Although specimens of R. c. maxima are larger than those of other conspecific populations and present a more ovate shell shape, they are included in R. curta by the presence of a long SR1, an ovoid bursa copulatrix with a long duct, a gradually tapering penis with a medial outgrowth on the left edge and an RPG ratio from moderately concentrated to elongate. All these features have been described for R. c. curta by Radoman (1983). In this monograph, Radoman (1983) stated that Orientalina (= Radomaniola ) curta subspecies differ from each other mainly in shell rather than in anatomical features, which applies to R. c. maxima. Other than by shell shape and size, this subspecies is diagnosable by its small number of cusps on the radular teeth, a high RPG ratio and a wide base of the penis. Our phylogenetic inferences also place the studied specimens of R. c. maxima unambiguously within the R. curta clade ( Fig. 2 ).

Figures

Figure 2. Majority-rule consensus tree from a Bayesian analysis based on the multilocus dataset (COI, 16S and 28S) of Radomaniola. Branch support values (BPP, Bayesian posterior probability; BS, bootstrap support) are provided on nodes. Tip labels correspond to the sequence codes given in the Supporting Information (Table S1). Vertical bars on the right represent entities identified by the molecular species delimitation methods automatic barcode gap discovery (ABGD), Bayesian generalized mixed Yule-coalescent method (bGMYC) and Poisson tree processes species delimitation method in a Bayesian framework (bPTP) and the multi-rate version (mPTP) with Bayesian support values. Scale bar below topology: substitutions per site.

Figure 10. Shells, operculum and radulae of Radomaniola curta maxima subsp. nov.A, B, holotype (MNCN 15.05/200153). C–J, paratypes (UGSB 19540). C, D, shells. E, F, operculum (E, inner side; F, outer side). G, protoconch. H, portion of radula ribbon. I, central radular teeth. J, outer marginal teeth.

Figure 11. Anatomy of Radomaniola curta maxima subsp. nov. A–H, paratypes (UGSB 19540). A, ctenidium and osphradium. B, stomach. C, partial nervous system. D, pallial oviduct. E, bursa copulatrix and seminal receptacles. F, head of male and penis. G, penis. H, prostate gland.