Theodoxus fluviatilis (Linnaeus, 1758)

Sands, Arthur F, Gloeer, Peter, Guerlek, Mustafa E, Albrecht, Christian & Neubauer, Thomas A, 2020, A revision of the extant species of Theodoxus (Gastropoda, Neritidae) in Asia, with the description of three new species, Zoosystematics and Evolution 96 (1), pp. 25-66 : 25

Theodoxus fluviatilis (Linnaeus, 1758) Figures 9A-S , 10A-L

Nerita fluviatilis Linnaeus 1758: 777.

Theodoxus lutetianus Montfort 1810: 351-352.

Neritina Saulcyi Bourguignat 1852: 25-26.

Theodoxus fluviatilis var. subthermalis Issel 1865: 22-23; Issel 1866: 406-407.

Neritina fluviatilis : Martens 1879: 204-221, pl. 21, figs 1-6; Kobelt 1899: 16-18, pl. 215, figs 1359-1365.

Neritina Heldreichi Martens 1879: 225, pl. 22, figs 9, 10; Kobelt 1899: 9, pl. 213, fig. 1337.

Neritina euxina Clessin 1886: 55.

Neritina (Theodoxus) heldreichi var. graeca Westerlund 1886: 152.

Neritina brauneri Lindholm 1908: 217.

Neritina danubialis var. Danasteri Lindholm 1908: 215-217.

Neritina fluviatilis var. abrauensis Milaschewitsch 1914: 429-430.

Theodoxia Ghigii Gambetta 1929: 107, fig. 23.

Theodoxus dniestroviensis Put’ 1972: 80-82, text fig. 5.

Theodoxus (Theodoxus) heldreichi fluvicola Schütt and Şeşen 1992: 64-66.

Theodoxus fluviatilis euxinus : Yıldırım 1999: 885.

Theodoxus fluviatilis fluviatilis : Yıldırım 1999: 884.

Theodoxus heldreichi fluvicola : Yıldırım 1999: 885 (as " fluviocola "); Kebapçı and Yıldırım 2010: 77; Gürlek et al. 2019: 2993.

Theodoxus (Theodoxus) heldreichi : Yıldırım 1999: 885.

Theodoxus subthermalis : Yıldırım 1999: 885-886; Sitnikova et al. 2012: 88-89, fig. 1A-F.

Theodoxus (Theodoxus) heldreichi heldreichi : Yıldırım 2004: 99, pl. 1, fig. 1.

Theodoxus fluviatilis : Anistratenko 2005: 7-8, figs 3, 4; Gürlek et al. 2019: 2993; Glöer 2019: 41-43, figs 26, 27.

Theodoxus heldreichi heldreichi : Kebapçı and Yıldırım 2010: 77; Gürlek et al. 2019: 2993.

Theodoxus brauneri : Welter-Schultes 2012: 27.

Theodoxus euxinus : Welter-Schultes 2012: 27, unnumbered text figures.

Theodoxus heldreichi : Welter-Schultes 2012: 28, unnumbered text figures.

Theodoxus saulcyi : Welter-Schultes 2012: 29, unnumbered text figures.

Theodoxus (Theodoxus) euxinus : Vinarski and Kantor 2016: 155.

Theodoxus (Theodoxus) fluviatilis : Vinarski and Kantor 2016: 154-155.

Theodoxus (Theodoxus) subthermalis : Vinarski and Kantor 2016: 157-158; Gürlek et al. 2019: 2993.

Type locality.

Near Uppsala, Sweden.

Type material.

Lectotype of T. fluviatilis are stored in LSL (coll. no. LSL.566; lectotype designated by Anistratenko et al. 1999; also see Anistratenko 2005) . Syntypes of N. saulcyi are stored in MHNG (coll. no. MHNG-MOLL-111736) . Seven syntypes of T. fluviatilis var. subthermalis are stored in MHNG (coll. no. MHNG-MOLL-11737) . The type material of T. heldreichi fluvicola is stored in NSMF (coll. no. 309.439 and 309.440) . Most taxa described by Lindholm are deposited in ZIN, including five syntypes of N. fluviatilis var. cereoflava (coll. no. 6055/1) , three syntypes of N. brauneri (coll. no. 6046/1) , one syntype of N. brauneri f. alboguttata (coll. no. 6051/1) , two syntypes of N. brauneri f. lacrymans (coll. no. 6052/1) , one syntypes of N. brauneri f. pulcherrima (coll. no. 6053/1) , and three syntypes of N. danubialis var. danasteri (coll. no. 5910/3) .

Remarks.

Theodoxus fluviatilis exhibits considerable variation in periostracum colouration ( Neumann 1959; Glöer and Pešić 2015). It is not surprising that molecular studies already support the synonymy of a number taxa such as T. euxinus (Clessin, 1886), T. fluviatilis abrauensis (Milaschewitsch, 1914) T. danasteri (Lindholm, 1908), and T. subthermalis Issel, 1865, and further suggest the inclusion of T. saulcyi (Bourguignat, 1852) (including N. graeca Westerlund, 1886, T. ghigii Gambetta, 1929; both listed as synonyms of T. saulcyi by Bank (2006)) and T. heldreichi (Martens, 1879) ( Bunje and Lindberg 2007; Sands et al. 2019a). The above species share near identical operculum structures, with a strong rib-shield, rib-pouch and the absence of a pseudo-apophysis (Figs 9 , 10 ), which were often disregarded in early Theodoxus species descriptions. Moreover, a number of taxa including T. brauneri (Lindholm, 1908) (along with subspecies T. b. alboguttatus (Lindholm, 1908), T. b. lacrymans (Lindholm, 1908) and T. b. pulcherrimus (Lindholm, 1908 )), T. fluviatilis cereoflava (Lindholm, 1913), and T. dniestroviensis Put’, 1972 are well within the variability of T. fluviatilis and are considered junior synonyms herein as well.

Bunje and Lindberg (2007) also suggested T. velox V. Anistratenko in O. Anistratenko et al., 1999 as conspecific with T. fluviatilis . However, Sands et al. (2019a) found substantial differentiation on the molecular level, indicating a sister relation between T. fluviatilis and T. velox (also see Fig. 2 ). Although it may be challenging to differentiate these species morphologically in some instances, there appears to be a stronger callus on the operculum in T. fluviatilis and greater phenotypic plasticity in shell shape and periostracum colouration as compared to T. velox (Figs 9 , 10 , 22 ).

Distribution.

Theodoxus fluviatilis is widely distributed across Europe, northern Africa, and western Asia. Records of this species and its synonyms are noted as far as Ireland to the West ( Anderson 2005), Morocco in the South ( Taybi et al. 2017), Sweden and Finland in the North ( Kangas and Skoog 1978), and European Russia in the East ( Vinarski and Kantor 2016). In addition, there are numerous records from across Anatolia ( Schütt and Şeşen 1989b, 1992; Yıldırım et al. 2006; Gürlek et al. 2019) and Georgia ( Vinarski and Kantor 2016) within the study region. The wide distribution range has been substantiated through molecular studies ( Bunje 2005; Bunje and Lindberg 2007; Sands et al. 2019a; Fig. 3C ). Some authors suggested that this species also occurs in Iran ( Roth 1987; Glöer and Pešić 2012), but molecular analyses of material from these parts do not support this hypothesis ( Sands et al. 2019a, 2019b; personal observation A.F.S.).

Figures

Figure 2. Dated phylogeny of the genus Theodoxus constructed with BEAST, based on existing GenBank and newly incorporated data for COI, 16 S and ATPα (Suppl. material 1: Table S 1). Morphospecies where associations are queried are highlighted by a question mark after the species name (see the " Systematic checklist " for more information). Small green (PP ≥ 0.95) and red (PP <0.95) dots on nodes indicate the relative posterior probability support of divergence events. Node labels (1 - 32) correspond to divergence dates and HPD intervals in millions of years ago (Mya) for selected nodes (see Suppl. material 1: Table S 3). Dashed dark blue and light blue lines represent the minimum interspecific and maximum intraspecific variation determined by Sands et al. (2019 a) to aid Theodoxus spp. delimitation (see see Methods, Phylogenetics and species delimitation and that study for more information on the delimitation methods).

Figure 3. Occurrence map for Theodoxus spp. in Asia. All points conform to specimens used in the phylogenetic analyses (Suppl. material 1: Table S 1), except for T. gloeri for which no molecular data are available and only the type and paratype localities are indicated. Species are partitioned across four identical maps (A - D) to limit overlap of points as far as possible. Barring T. gloeri, closer related species are grouped together (Fig. 2).

Figure 9. Theodoxus fluviatilis (Linnaeus, 1758). A - D. Specimen collected close to Oued Laabid, Morocco (UGSB 18106) (Fig. 2); E - H. Specimen from the Danube River, Woerth an der Donau, Germany (UGSB 24173); I - L. Specimen (T. euxinus - morphotype) collected in the Papuc Creek, Kiyikoey, Turkey (UGSB 24172) (Fig. 2); M - P. Specimen (T. euxinus - morphotype) from Ovidiopol, Ukraine (UGSB 18124); Q - S. Specimen (T. heldreichi - morphotype) collected in Lake Egirdir, Turkey (UGSB 20361); T, U. Specimen (T. danasteri - morphotype) collected in Krasna Kosa, Ukraine (UGSB 18417) (Fig. 2); V. Opercula of a T. danasteri - morphotype from Lake Skadar, Montenegro (UGSB 24171). Specimens A-D, I-L and T-U were used in the phylogeny (Fig. 2). Scale bars: 1 mm.

Figure 10. Theodoxus fluviatilis (Linnaeus, 1758). A - D. Specimen (conforming to T. sarmaticus) from the Dnieper-Bug estuary, Ukraine (UGSB 18328); E - H. Specimen (T. subthermalis - morphotype) from Novy Afon, Abkhazia, Georgia (UGSB 18402); I - K. Syntype of N. saulcyi from near the Penteli Monastery, Greece (MHNG-MOLL- 111736); L. Specimen (T. saulcyi - morphotype) from Stilos, Crete, Greece (UGSB 20519) incorporated into the phylogeny (Fig. 2). Scale bars: 1 mm.

Figure 22. Theodoxus velox V. Anistratenko in O. Anistratenko et al., 1999. A - D. Specimen from the Dnieper River, Kiev, Ukraine (UGSB 24186); E - H. Specimen collected in the Danube delta, Vylkove, Ukraine (UGSB 24184) used in the phylogeny (Fig. 2); I, J. Holotype from Dnieper Delta, Zbur'ivka Liman, Ukraine (IZAN); K - M. Specimen from Lake Sapanca, Yeni Esme, Turkey (UGSB 20691). Theodoxus sarmaticus (Lindholm, 1901). N - P; Q - S; T - U. Three syntypes from the Oskol River, near Golubino, Russia stored in ZIN (coll. no. 6099 / 24). Scale bars: 1 mm.