Grossuana thasia, Georgiev & Glöer, 2020

Georgiev, Dilian & Glöer, Peter, 2020, Three new hydrobiid species from Thassos Island (Greece) with a re-description of Amnicola charpentieri Roth, 1855, Ecologica Montenegrina 35, pp. 129-137 : 133

Grossuana thasia n. sp. ( Figs. 2 , 4 , 9-10 )

https://zoobank.org/ urn:lsid:zoobank.org:act:019E5D1D-E033-4913-896D-4C779ACA9198

Material studied:

Holotype: shell height 1.7 mm, width 1.1 mm, from type locality ( ZMH 140793 ).

Paratypes: 5 specimens in ethanol ( ZMH 140794 ) , 5 specimens in coll. Glöer, 11 specimens in coll. Georgiev.

Type locality: Greece, Thassos Island, North Aegean, a spring (water source) south of Kinira near the round road of the island, N40 38 07.5 E24 45 52.2, 144 m a.s.l. ( Fig. 3 ) .

Etymology: Named after Thassos Island on which the species lives.

Description: Shell: The corneous shell is elongate ovate with a prolonged body whorl ( Fig. 2 ). The apex is rounded and often eroded. The 4-4.5 whorls are slightly convex with a weak suture, with rough irregular growth lines. The aperture is ovate slightly angled at the top with a sharp periostome thickened at the columella. The umbilicus is closed. The operculum is dark red. Animal: The animal is mostly black colored. The mantle is black with a thin white border. The snout and tentacles are black with white or grayish tips. Penis: The penis is nearly regularly broad with a long tapered penis-tip. There is a dark spot at the near the penis-tip.

Differentiating features: The new species is most similar to Grossuana angeltsekovi Glöer & Georgiev, 2009 which is known to be widely distributed in Bulgaria and North Greece ( Georgiev 2013, Georgiev et al., 2015, Falniowski et al. 2015, Glöer et al., 2018). From this species Grossuana thasia n. sp. differs by its more elongated and slender shell with flatter whorls, which have rough surface with irregular growth lines, and by its more rounded, often eroded apex. The whorls of the shell of the new species are 4-4.5 while in G. angeltsekovi they are 5-5.5 and the later is larger (height of the holotype = 2.1 mm). In addition G. thasia has a well visible bifurcated penis lobe, while in G. angeltsekovi it is very small and hardly visible ( Glöer & Georgiev, 2009).

Grossuana thasia n. sp. is similar by its shell morphology to Grossuana stenaensis Glöer, Reuselaars & Papavasileiou, 2018 described from the nearby mainland of Greece ( Glöer et al., 2018) but this species has a penis with broader base and shorter and thicker tip.

Previously all Grossuana of Thassos were assigned to G. hohenackeri (Küster, 1853) ( Reischütz, 1983) . It was later re-described and split into two species: Radomaniola tritonum (Bourguignat, 1852) and Grossuana tembii Boeters, Glöer & Falniowski (2018) ( Boeters et al., 2018). G. thasia n. sp. differs from G. tembii by its higher whorl number (3.25-3.5 in G. tembii ) and longer penis tip.

Distribution: Known only from the type locality.

Habitat: Karst spring in a mixed broad leaf forest (mainly Platanus orientalis and Quercus spp. ). Found on moss, dry leaves, sand and stones.

Figures

Figure 2. The sampling sites of the species under discussion on Thassos. 1: Rachoni village: type locality of Bythinella rachonica n. sp., localiy of Grossuana beroni n. sp.; 2: Drakotrype cave, Panagia village: localiy of Grossuana beroni n. sp.; 3: type localiy of Grossuana beroni; 4: type locality of Grossuana thasia n. sp., 5: Pernes Mountain, type locality of Bythinella reischuetzi n. sp., 6: Hymettos, type locality of Bythinella charpentieri (Roth, 1855).

Figures 3-5. 3: Type locality of Grossuana beroni n. sp., water source south of Skala Potamia near the round road of the island. 4: Type locality of Grossuana thasia n. sp., a spring south of Kinira near the round road of the island. 5: Type locality of Bythinella rachonica n. sp.

Figures 6-10. The Grossuana spp. 6-7: G. beroni n. sp. (paratypes), 8: penis of G. beroni n. sp. 9: G. thasia n. sp (holotype), 10: penis of G. thasia n. sp.