Theodoxus major Issel, 1865

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 major Issel, 1865 Figure 19A -Zb

Neritina liturata Eichwald 1838: 156-157; Martens 1879: 223-224, pl. 21, figs 24-26; Kobelt 1899: 8, pl. 212, fig. 1336 (non Neritina liturata Schultze, 1826).

Theodoxus schirazensis var. major Issel 1865: 24; Issel 1866: 408.

Neritina Schultzii Grimm 1877: 77-78, pl. 7, fig. 5, pl. 8, fig. 16.

Neritina Schulzii [sic]: Martens 1879: 239-240, pl. 23, figs 13-16.

Theodoxus pallasi Lindholm 1924: 33, 34 (nom. nov. pro Neritina liturata Eichwald, 1838, non Schultze, 1826); Starobogatov 1974: 255-256, text fig. 224; Akramovskiy 1976: 88, text fig. 23, pl. 1, figs 1, 2; Anistratenko et al. 2017: 221, figs 4, 7, 10, 11; Neubauer et al. 2018: 48-51, figs 4A-F; Wesselingh et al. 2019: 64-65; Glöer 2019: 48-49, fig. 36.

Theodoxus (Theodoxus) pallasi var. nalivkini Kolesnikov 1947: 106, 110.

Theodoxus (Ninnia) schultzi [sic] var. jukovi Kolesnikov 1947: 106, 110.

Theodoxus zhukovi [sic]: Starobogatov 1974: 255, text fig. 223.

Theodoxus astrachanicus Starobogatov in Starobogatov et al. 1994: 8-9, fig. 1(1-2); Degtyarenko and Anistratenko 2013: 22-23, pl. 1, fig. 2a-c.

Theodoxus (Theodoxus) schultzii : Zettler 2007: 249-250, figs 4a-h, 5a-h; Vinarski and Kantor 2016: 157.

? Theodoxus doriae : Mansoorian and Samaee 2012: 44-45 (partim, only material from Gilan and Mazandaran provinces; non Theodoxus doriae Issel, 1865 [= T. pallidus ])

? Theodoxus euphraticus : Mansoorian and Samaee 2012: 61 (partim, only material from the Khorasan provinces; non Neritina euphratica Mousson, 1874 [= T. jordani ])

Theodoxus fluviatilis : Glöer and Pešić 2012: 16-17 (partim, only Khorrasan material; non Nerita fluviatilis Linnaeus, 1758).

Theodoxus (Theodoxus) astrachanicus : Vinarski and Kantor 2016: 155-156.

Theodoxus (Theodoxus) pallasi : Vinarski and Kantor 2016: 156-157 (and synonyms therein).

Theodoxus schultzii : Wesselingh et al. 2019: 66; Glöer 2019: 52, fig. 40.

Theodoxus major : Sands et al. 2019b: 3, fig. 1.

Type locality.

Lake Sevan, Armenia. However, Akramovskiy (1976) suggested the type locality given by Issel (1865) was erroneous and should be Yerevan in Armenia.

Type material.

The syntypes of T. schirazensis var. major are supposed to be stored in MRSN, but the collection is inaccessible at the moment due to renovation and restoration of the museum (E. Gavetti pers. comm. 09/2019) . The lectotype of N. liturata and T. pallasi (designated by Starobogatov et al. 1994) is stored in ZIN (coll. no. 54547/63) . Twenty syntypes of N. schultzii are stored in ZIN (coll. no. 6214/5) and a single in ZMD (coll. no. ZB-M W. Dyb. 71; see Anistratenko et al. 2018) .

Remarks.

Wesselingh et al. (2019) reviewed the taxonomy of the Pontocaspian Theodoxus spp. They showed that N. liturata Eichwald, 1838 (described from Derbent, Dagestan, Russia, north-western Caspian Sea) was invalid as a junior primary homonym of N. liturata Schultze, 1826 (described from the Americas) and was replaced by Lindholm (1924) with T. pallasi Lindholm, 1924. Moreover, they supported the synonymy of T. astrachanicus Starobogatov in Starobogatov et al. 1994 with T. pallasi ( Anistratenko et al. 2017). Wesselingh et al. (2019) additionally suggested T. schultzii (Grimm, 1877) and T. major (the latter originally described as a variety of the unavailable name T. schirazensis ) may additionally be conspecific with T. pallasi given morphological similarities. However, Wesselingh et al. (2019) refrained from synonymising T. major , T. pallasi , and T. schultzii , pending molecular support. This was provided recently by Sands et al. (2019b), who corroborated the synonymy of T. astrachanicus , T. major , T. schultzii , and T. pallasi (also see Fig. 2 ). As already argued by Wesselingh et al. (2019), the name T. major has priority.

There is large intraspecific morphological variability within this species, especially regarding the radula, shell shape and periostracum colouration ( Zettler 2007; Anistratenko et al. 2017; Fig. 19 ). For example, specimens from deeper parts of the Caspian Sea ( T. schultzii -morphotype) may lack colouration and have a broadened columellar plate making the shell look somewhat flattened ( Zettler 2007; Fig. 19 ), while shoreline samples ( T. pallasi -morphotype) lack this broadened columellar plate and display clear, black diagonal banding patterning (Fig. 19 ). Inland specimens ( T. major -morphotype) from Iran and Armenia tend to be dark and with a less distinct banding pattern (Fig. 19 ). The operculum of this species is somewhat similar to those of T. pallidus , T. fluviatilis , and T. velox with a strong rib-shield and no pseudo-apophysis (Figs 9 , 10 , 19 , 20 , 22 ). It is not surprising that molecular data of material from locations in Khorrasan province studied by Glöer and Pešić (2012) and identified as T. fluviatilis conforms to T. major ( Sands et al. 2019b; Fig. 2 ). Akramovskiy (1971) already suggested that specimens considered T. subthermalis [= T. fluviatilis ] from Armenia represented black-coloured morphotypes of T. pallasi [= T. major ]. However, T. major only shares a close phylogenetic relationship with T. pallidus and likely diverged from their common ancestor during the Pleistocene ( Sands et al. 2019b; Fig. 2 ).

Distribution.

Theodoxus major is found in the Caspian Sea and parts of the Azov Sea ( Roth 1987, Karpinsky 2002; Anistratenko et al. 2017; Sands et al. 2019a) and is also present in the Volga and Don river systems ( Sands et al. 2019b). It has likely become regionally extinct in the Aral Sea ( Andreev et al. 1992; Aladin et al. 1998; Plotnikov et al. 2016), although it may still persist in some of its associated drainages ( Zettler 2007). In Western Asia it can be found in the Aras River system ( Aliyev and Ahmadi 2010), Lake Yerevan and its catchment systems in Armenia ( Sands et al. 2019b), and Masalli in Azerbaijan. Records of T. doriae Issel, 1865 [= T. pallidus ], T. euphraticus [= T. jordani ], or T. fluviatilis by Glöer and Pešić (2012) and Mansoorian and Samaee (2012) from several mineral springs and streams in Gilan, Mazandaran, and the Khorasan provinces of northern Iran are likely misidentifications of T. major ( Sands et al. 2019b; Fig. 3B ). Its presence in Lake Sevan (the supposed type locality) or the adjacent area around the lake was questioned by Akramovskiy (1976) (see above).

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 19. Theodoxus major Issel, 1865. A, B. Specimen (T. pallasi - morphotype) collected in the Caspian Sea, offshore from Aktau, Kazakhstan (UGSB 20712); C, D. Specimen (T. pallasi - morphotype) collected in the Aral Sea, Kazakhstan in 1979 (UGSB 19129); E - H. Specimen (T. pallasi - morphotype) from the Shahpol River, Aliabad Askar Khan, Iran (UGSB 18091); I - K. Specimen of T. major collected at the outflow of Lake Akna, Aknalich, Armenia (UGSB 20482); L - N. Specimen (T. astrachanicus - morphotype) collected in Utlyukskij Liman, Ukraine (UGSB 18130); O, P. Specimen of T. major collected in the Hrazdan River at the inflow of the Yerevan Reservoir, Armenia (UGSB 20496); Q - T. Specimen of T. major from Zoeram, North Khorasan, Iran (UGSB 21661); U, V. Specimen of T. schultzii collected in the Caspian Sea, offshore from Aktau, Kazakhstan (UGSB 20714); W - Y. Lectotype of T. pallasi from Caspian Sea, Dagestan, Russia (ZIN 54547 / 63); Za, Zb. Syntype of N. schultzii from the Caspian Sea (ZIN, no. 5 in systematic catalogue). Specimens E-K and O-T used in the phylogeny (Fig. 2). Scale bars: 1 mm.

Figure 20. Theodoxus pallidus (Dunker, 1861). A - D. Specimen from Haji Abad, Fars, Iran (UGSB 22227); E - H. Syntype of N. pallida from southern Iran (ZMB 108.792); I, J; K, L. Two syntypes of N. pallida from southern Iran (ZMB 108.793); M - P. Specimen (T. doriae - morphotype) from a spring near Harat, Yazd, Iran (UGSB 21706); Q, R; S, T; U, V; W - Y. Four syntypes of N. doriae from the thermal springs of Kerman, Iran (MSNG, without coll. no.). Specimens A-D and M-P were used in the phylogeny. 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.