Bythinella istanbulensis Yildirim , Kebapci & Yuece

Yildirim, Mehmet Zeki, Kebapci, Uemit, Koca, Seval Bahadir & Yuece, Arzu, 2015, New Bythinella (Gastropoda, Bythinellidae) species from western Turkey, ZooKeys 481, pp. 1-13 : 3-6

Taxon classification Animalia Littorinimorpha Bythinellidae

Bythinella istanbulensis Yildirim, Kebapci & Yuece sp. n. Figs 3, 6b

Bythinella opaca , Schütt, H., 1965 Zur Systematik und Ökologie Türkischer Süsswasserprosobranchier. Zoologische Mededelingen, 41: 43-71. (misidentification).

Bythinella " opaca " , Schütt, H., 1980 Zur Kenntnis griechischer Hydrobiiden, Arch.Moll.110 (4/6):115.

Bythinella sp. A, Yıldırım et al. 2006 Supplement to the Prosobranchia ( Mollusca: Gastropoda) Fauna of Fresh and Brackish Waters of Turkey, Tr. J. Zool. 30: 197-204.

Holotype

(Coll. Yıldırım): Shell height: 2.74 mm, width 1.43 mm (Coll. M.Z. Yıldırım); TURKEY, Istanbul, Bahçeköy, a small spring at the entrance of Bahçeköy in Belgrad Forest, N41°11.09', E28°59.5', 23.02.2013, leg. A. Yüce. Paratypes: 27 ex., same data and locality as holotype; 5 ex. Zoologisches Museum Hamburg (ZMH 79661), 5 ex. Naturhistorisches Museum in Wien (NHMW 109174), rest in the Coll. Yıldırım. Additional material: 5 ex. in the University of Giessen (Coll. Prof. Wilke), rest in the Coll. Yıldırım (5 dissected).

Type locality.

A small spring at the entrance of Bahçeköy in Belgrad Forest, Bahçeköy, Istanbul.

Etymology.

Named after the type locality.

Description.

Shell broad cylindrical oval, yellowish horn-colored, surface smooth and glossy covered by a thick, solid and rough encrustation due to chemical conditions of the spring water; apex blunt; 3½– 4 convex whorls, rapidly and regularly increasing to form a cylindrical shape, last whorl about 2/3 of the shell height, sutures relatively deep; aperture pear-shaped, height nearly the same as or slightly less than the penultimate whorl, columellar margin with an distinct inner lip reaching basal and apical corners of the aperture; operculum orange, umbilicus narrow and slit-shaped (Figs 2a, 6a).

Tubular gland relatively short and thick. Pallial roof unpigmented, head having little pigmentation (Fig. 2b), rs1 small and attached to oviduct (Fig. 2c), thus not easily discernible.

Measurements (n=28): SH: 2.67 mm (min 2.18/max 2.87), SW: 1.66 mm (min 1.37/max 1.94), SH/SW: 1.61 (min 1.39/max 1.84), SW/SH: 0.62 (min 0.54/max 0.72), ah/SH: 0.41 (min 0.37/max 0.50).

Differential diagnosis.

This new species is distinguished from other Turkish Bythinella species by its nearly cylindrical shell with broad and blunt apex. Small and attached rs1, unpigmented and light coloured pallial roof are the other key characters.

Habitat.

Specimens were collected from the stones in a small spring and its pond.

Remarks.

Based on shell characters only, Schütt (1965) misidentified Bythinella specimens from Belgrad Forest as Bythinella opaca (Frauenfeld, 1857), a species originally described from Carniola (Slovenia) and Italy. Bythinella angelitae was introduced as a replacement name for the preoccupied name Paludinella opaca Frauenfeld, 1857, a homonym of Paludinella opaca M. von Gallenstein, 1848, by Haase et al. (2007). The two closely related species Bythinella angelitae and Bythinella opaca can be morphologically separated only by radular dentition, and the geographic range of Bythinella angelitae is restricted to the border areas of Austria and Slovenia ( Haase et al. 2007). Although they have been recorded in previous studies ( Wagner 1941; Grossu 1956; Angelov 1960, 2000), Bythinella austriaca (Frauenfeld, 1857) and Bythinella opaca (M. von Gallenstein, 1848) have not been confirmed from the eastern Balkan countries in recent studies ( Falniowski et al. 2009a, b). Therefore, there is a large distribution gap between the ranges of Central European taxa and that of Bythinella istanbulensis sp. n.

Despite the conchological similarities, the new species is anatomically distinct from the Central European species Bythinella austriaca and Bythinella opaca . While the lighter pallial roof colouration is also observed in Bythinella opaca ( Glöer & Pešic, 2006), Bythinella austriaca has a dark pallial roof colouration. The new species differs from both of these taxa in having a very short and broad penial appendix (cf. long trumpet-shaped penial appendix in these species).