Radomaniola curta, SUBSP. OMBLENSIS, 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 : 410-413

RADOMANIOLA CURTA SUBSP. OMBLENSIS SUBSP. NOV.

( FIGS 8 , 9 )

Radomaniola curta curta (Küster, 1842) – Hirschfelder, 2017

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: 903123AE-A06C-4F45-8759-5F7E68F93BBF

Etymology: Referring to Ombla Spring, in which this subspecies was originally found.

Type material: Holotype (MNCN 15.05/200155), six paratypes (MNCN 15.05/200156) in the MNCN collection and ~ 70 paratypes (UGSB 18778) in the UGSB collection. Type locality: Ombla Spring, Rozat, Croatia.

Material studied: Ombla Spring, Rozat, Croatia, 42.6749°N, 18.1374°E, T.H. and D.D., June 2016, MNCN 15.05/200156 and UGSB 18778 (80% ethanol). Diagnosis: Protoconch microsculpture wrinkled; central radular tooth formula 7-C-7/1-1; bursa copulatrix ovoid, with a long duct; SR1 elongate, duct short; SR2 small, pyriform to elongate, duct short; penis unpigmented, gradually tapering, smaller than head length and with one medial outgrowth on its left side; nervous system moderately concentrated (mean RPG ratio = 0.49).

Description: Shell ovate-conic, 4.0–4.5 whorls, height 2.5–3.2 mm ( Fig. 8A–D ; Supporting Information, Table S6). Periostracum yellowish. Protoconch ~400 µm wide, 1.5 whorls; nucleus ~150 µm wide; protoconch microsculpture pitted ( Fig. 8G ). 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. 8B ). Umbilicus narrow, not covered by the inner lip. Operculum oval, brownish to yellowish, about two whorls; muscle attachment area oval and located near the nucleus ( Fig. 8E, F ). Radular length intermediate, ~700 µm (~25% of total shell length), with ~50 rows of teeth ( Fig. 8H ). Central tooth formula 7-C-7/1-1 ( Fig. 8I ); basal tongue U-shaped, length about equal to lateral margin. Lateral tooth formula 3-C-3. Inner marginal teeth having 20–25 tapered cusps, shortening toward the base. Outer marginal teeth with 18–26 sharp cusps ( Fig. 8J ).

Animal darkly pigmented except for neck and tentacles ( Fig. 9F ). Ctenidium with 14–16 welldeveloped gill filaments, occupying ~50% of pallial cavity length and positioned posteriorly. Osphradium of intermediate width and opposite middle of ctenidium ( Fig. 9A ). Stomach approximately as long as wide, with two chambers almost equal in size; style sac longer than wide, surrounded by an unpigmented intestine ( Fig. 9B ; Supporting Information, Table S7). Nervous system slightly pigmented, moderately concentrated (mean RPG ratio = 0.49); cerebral ganglia approximately equal in size, presenting small black granules ( Fig. 9C ).

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 slightly 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 to elongate, with a short duct, located on renal oviduct near loop ( Fig. 9D, 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. 9I ). Penis unpigmented, gradually tapering, smaller than head length, base narrow, weakly folded along inner edge and with one medial outgrowth on its left side ( Fig. 9F–H ; Supporting Information, Table S9); penis attached to the area close to the right eye; penial duct narrow, near outer edge, almost straight.

Habitat: Radomaniola curta omblensis is known only from its type locality, a large karstic spring fed by subterranean waters. Snails were deeply submerged (> 1 m) and attached to the walls, the aquatic vegetation and stones. A closely co-occurring species was Bithynia tentaculata (Linnaeus, 1758) .

Remarks: Hirschfelder (2017) found Radomaniola - like snails in Ombla Spring and assigned them to R. c. curta . Our morphological and genetic data from a Radomaniola population living in the same spring indicate that this population differs from R. c. curta and from any other subspecies. Specifically, this new subspecies differs from the conchologically similar R. c. curta and R. c. kicavica according to its more slender shell, slightly larger bursa copulatrix and shorter bursal duct. The COI sequence divergence with other subspecies ranges between 1.2 and 2.6%.

Figures

Figure 8. Shells, operculum and radulae of Radomaniola curta omblensis subsp. nov.A, B, holotype (MNCN 15.05/200155). C–J, paratypes (UGSB 18778). 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 9. Anatomy of Radomaniola curta omblensis subsp. nov. A–H, paratypes (UGSB 18778). 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, H, penis. I, prostate gland.