Theodoxus wilkei Sands & Gloeer ., 2020

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 wilkei Sands & Gloeer. sp. nov. Figures 26A, B , 27A-J , 28A-F

Type locality.

Çifteler spring, Çifteler, Eskişehir, Turkey; 39.34931°N, 31.05527°E (Figs 3D , 26A, B ).

Holotype.

RMNH. MOL.342208 ( Çifteler spring, Çifteler, Eskişehir, Turkey; 39.34931°N, 31.05527°E) stored in NMNL: Shell height 6.9 mm, width 7.5 mm (Fig. 28A-D ) .

Paratypes.

Nineteen specimens from Çifteler spring, Çifteler, Eskişehir, Turkey; 39.34931°N, 31.05527°E (Fig. 26A, B ): 10 in NMNL ( RMNH. MOL.342209-342211; Fig. 27E-J ) and 9 in UGSB ( UGSB 20687, UGSB 20741, UGSB 20742; Fig. 28A-F ) .

Etymology.

The species is named after the molluscan phylogeneticist and evolutionary biologist Thomas Wilke (Justus Liebig University Giessen, Germany).

Description.

Shell (Fig. 27A-C, E-J ): Hemispherical, transversely slightly elongate, consisting of typically three whorls that rapidly grow. Spire low, apex often corroded. Shell height ranges from 4.5-7.8 mm, width from 5.2-8.6 mm. Periostracum colour and patterning uniformly ivory or black, intermediate forms black with white-ivory speckles or stripes also exist; surface glossy or dull but always finely striated with growth lines. Aperture semicircular with no serrations on inner lip. Columellar plate is smooth, flat to slightly concave, inclined towards aperture; blue-grey in colour, some yellowing around edges.

Operculum (Fig. 27D ): Operculum plate made of two parts, calcareous base and conchioline lamella; operculum base bright yellow to deep orange, darkened orange-brown lamella. Left adductor on operculum base blunt and rounded. Strongly defined callus at top right edge of operculum base. Apophysis light to bright yellow. Apophysis broader at top, narrower at bottom (attenuated). Narrow rib-shield and small rib-pouch present on operculum; pseudo-apophysis lacking.

Radula (Fig. 28A-F ): R-central tooth flanked by A-central, B-central, C-central, E-lateral of each side. Additionally, two interconnected layers of marginal teeth encase central and lateral teeth. R-central varies in face shape; can be square face with slightly concave anterior edge or more triangular. A-central large and flat with strong attenuated ridge, broader at cusp. B-central diminished, forms irregular “S” shape. C-central equally diminished, partly hidden below lower edge of E-lateral. E-lateral is simple, semi-smooth to serrate on upper edge. First layer of marginal teeth comprises 37-40 teeth, which decrease in size away from E-lateral but increase in size and bear serrations on edges of small faces; semidetached from second layer, which is fused and forms outer wall.

Differentiating features.

The hemispherical, glossy black, black with white speckles or pure ivory, and finely striated shells of T. wilkei sp. nov. are easily differentiable from T. altenai , which displays light ivory checks on a dark brown-black background (Figs 4A-G , 27A-J ), and T. gloeri , which lacks shell pigmentation and bears strong axial ribs on the shell (Figs 11A-C , 27A-J ). However, using only conchological features of periostracum colouration and patterning and shell shape, it is still challenging to differentiate T. wilkei sp. nov. from some morphotypes of T. anatolicus , T. baeticus , T. fluviatilis , T. gurur sp. nov., T. jordani , T. macri , T. major , T. pallidus , T. syriacus , T. velox , and T. wesselinghi sp. nov., which can share similar shell shapes and colouration patterning (Figs 5A-M , 6A-G, M , 7M-P , 8A-D , 10E-H , 13A-G , 15P-R , 16C-P , 17A-E , 18A-G , 19O, P , 20A-D, I, J , 21A-D, I-R , 22I, J , 24E-J , 27A-D ). Theodoxus wilkei sp. nov. can be distinguished from Anatolian morphotypes of T. baeticus , which typically displays ivory blotches on brown background (Fig. 7A-D ); T. jordani , which typically displays brown diagonal zig-zag line patterning on an ivory background (Fig. 15E-L ); and T. velox , which has white-ivory stripes on a dark background (Fig. 22K-M ). Finally, the bright yellow to deep orange calcareous base of the operculum in T. wilkei sp. nov. can help to distinguish it from T. altenai , T. anatolicus , T. baeticus , T. jordani , T. macri , T. major , T. pallidus , T. syriacus , and T. wesselinghi sp. nov., which typically have lighter calcareous bases ranging from ivory to cream (Figs 4 - 8 , 13 , 15 - 21 , 24 ); Theodoxus gurur sp. nov., differs in having a light to dark brown operculum (Fig. 13 , 27 ).

There are a number of structural differences on the operculum. The attenuated apophysis in T. wilkei sp. nov. allows a distinction from T. altenai and T. jordani (Figs 4 , 15 , 17 , 27 ). The presence of a rib-shield and rib-pouch further discriminate T. wilkei sp. nov. from T. altenai , T. anatolicus , T. jordani , and T. macri , where these features are either absent or extremely diminished (Figs 4 , 5 , 15 , 17 , 18 , 27 ). Furthermore, the rib-shield in T. fluviatilis and T. baeticus is typically broader than in T. wilkei sp. nov. (Figs 6 - 8 , 9 , 10 , 27 ). Additionally, the lack of a pseudo-apophysis differentiates the new species from T. altenai , T. anatolicus , T. baeticus , T. gurur sp. nov., T. jordani , and T. macri (Figs 4 - 8 , 13 , 15 - 18 , 27 ). Furthermore, the more rounded left adductor of the operculum base is only shared with T. syriacus and T. wesselinghi sp. nov. (Figs 21 , 24 , 27 ). The strongly defined callus on the top right edge of the operculum base in T. wilkei sp. nov. is only shared with T. anatolicus , T. fluviatilis , T. major , T. pallidus , and T. wilkei sp. nov. and may be used to differentiate this species from all others (Fig. 27D ).

Concerning the radula, T. wilkei sp. nov. can be distinguished from T. gurur sp. nov. by a square to triangulate R-central face (Figs 14B , 28B ). The serrations on the upper edge of the E-lateral distinguish this species from T. wesselinghi sp. nov., T. fluviatilis , and T. gurur sp. nov., which have smooth, blade-like edges (Figs 14B, C , 27C , 28B-D ; also see Zettler 2008).

Remarks.

Theodoxus wilkei sp. nov. forms a part of a larger clade that includes T. syriacus and T. wesselinghi sp. nov., where it shares a closer sister-species relationship with T. wesselinghi sp. nov. ( Sands et al. 2019a; Fig. 2 ). The three species likely diverged from one another within a short time around the Pliocene-Pleistocene transition (Fig. 2 ).

Distribution.

Only known from the type locality (Figs 3D , 26A, B ).

Ecology.

Theodoxus wilkei sp. nov. appears endemic to a freshwater spring environment with clear water (Fig. 26A, B ). This spring environment is characterised by macrophytes in the littoral zone and a floor of small and large stones, rocks and course-grained sand (Fig. 26A, B ). Theodoxus wilkei sp. nov. is particularly numerous on larger stones and rocks and co-occurs with Pseudamnicola and Melanopsis (personal observation M.E.G.).

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 4. Theodoxus altenai Schuett, 1965. A - C. Holotype from Lake Kirkgoez, Doesemealti, Antalya, Turkey (RNL V. 56 / 1, NMNL). D - G. Topotype (UGSB 24167) incorporated into the phylogeny (Fig. 2). Scale bars: 1 mm.

Figure 5. Theodoxus anatolicus (Recluz, 1841). A - D. Specimen collected at Isikli, Denizli, Turkey (UGSB 24168) incorporated into the phylogeny (Fig. 2); E - G. Lectotype of N. anatolica from Izmir, Turkey (MHNG-MOLL- 15028). H, I. Paralectotype of N. anatolica from Izmir, Turkey (MHNG-MOLL- 15028); J, K. Paralectotype of N. anatolica from Chios, Greece (MNHN-IM- 2000 - 32519); L, M. Syntype of N. belladonna from Izmir, Turkey (ZMZ 528908). Scale bars: 1 mm.

Figure 6. Theodoxus baeticus (Lamarck, 1822). A - C. Paralectotype of N. baetica from Andalusia, Spain (MHNG-MOLL- 51319). D) Operculum of a paralectotype of N. baetica from Andalusia (MHNG-MOLL- 51319); E - G. Lectotype of N. baetica from Andalusia (MHNG-MOLL- 51319); H-J; K; L; M; N. Five syntypes of N. meridionalis from Sicily (ZMB, without coll. no.); O - R. Topotype of N. guadianensis collected in the Guadiana River near Mertola, Portugal incorporated into the phylogeny (UGSB 22084); S - V. Specimen from Soller, Balearic Islands used in the phylogeny (UGSB 19162). Scale bars: 1 mm.

Figure 7. Theodoxus baeticus (Lamarck, 1822). A - D. Specimen (T. callosus - morphoype) collected in Akyaka, Turkey (UGSB 19118); E - H. Specimen (T. callosus - morphotype) collected in Kato Tragana, Greece (UGSB 2488); I - L. Specimen (T. varius - morphotype) collected at the Blue Eye Nature Monument, Albania (UGSB 24170); M - P. Specimen (T. meridionalis - morphotype) collected at the Ketana Oasis, Gabes, Tunisia (UGSB 18111). All specimens, except A-H, were used in the phylogeny (Fig. 2). Scale bars: 1 mm.

Figure 8. Theodoxus baeticus (Lamarck, 1822). A - D. Specimen from Cuquillo, Granada, Andalusia, Spain (UGSB 22089); E - H. Specimen (T. meridionalis - morphotype) collected in the Palancia River, Navajas, Spain (UGSB 22090); I - L. Specimen (T. elongatulus - morphotype) from Arrancada, Pombal, Portugal (UGSB 22080); M - P. Specimen (T. velascoi - morphotype) from Montanejos, Castellon, Spain (UGSB 22082). Theodoxus cf. valentinus (Graells, 1846). Q - S. Specimen conforming to T. valentinus from the Verd River, Masalaves, Spain (UGSB 21787); T. Operculum of a specimen conforming to T. valentinus from the same locality as Q-S (UGSB 22087). All specimens, except Q-S, were used in the phylogeny (Fig. 2). Scale bars: 1 mm.

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 11. Theodoxus gloeri Odabasi & Arslan, 2015. A - C. Paratype from Balikdami Wetland-Sakarya River, Eskisehir, Turkey (coll. Gloeer). Scale bar: 1 mm.

Figure 13. Theodoxus gurur Sands & Gloeer sp. nov. A - D. Holotype from the Suyunbasi spring complex, Ayrancilar, Izmir, Turkey stored in NMNL (RMNH. MOL. 342197); E - G. Paratype from same locality and storage facility (RMNH. MOL. 342199). Scale bars: 1 mm.

Figure 14. Radula of Theodoxus gurur Sands & Gloeer sp. nov. paratypes (UGSB 20689). A. Portion of the radula showing full sets of teeth; B. Magnified view of the central and lateral teeth; C. Magnified view of the lateral and marginal teeth; D. Magnified view of the first row of marginal teeth; E. Merging point between the first and second rows of marginal teeth; F. Magnified view of the faces of inner marginal teeth belonging to the first row. Scale bars: 100 μm (A-D), 20 μm (E-F).

Figure 15. Theodoxus jordani (G. B. Sowerby I, 1836). A - D. Specimen from the Avakas Gorge, Peyia, Cyprus (UGSB 18321) incorporated into the phylogeny (Fig. 2); E - H. Specimen collected in the Ceyhan River, Eski Misis, Adana, Turkey (UGSB 20777); I - L. Specimen from the Orontes River, Antakya, Hatay, Turkey (UGSB 24175) used in the phylogeny (Fig. 2); M - O. Specimen (T. euphraticus - morphotype) from the Seyed Hosein Park spring, near the Bishapur, Fars, Iran (UGSB 22233); P - R. Topotype of N. jordani from the River Jordan, Israel (UGSB 24177) incorporated into the phylogeny (Fig. 2); S, T. Specimen (T. euphraticus - morphotype) from the Karun River, Ahvaz, Iran (UGSB 21681); U. Specimen (T. niloticus - morphotype) collected in the Nile River, Egypt (UGSB 24178) used in the phylogeny (Fig. 2); V. Specimen (T. euphraticus - morphotype) from the Karun River, Ahvaz, Iran (UGSB 21682). Scale bars: 1 mm.

Figure 16. Theodoxus jordani (G. B. Sowerby I, 1836). A, B. Syntype of N. euphratica from the Euphrates River at Samawah, Iraq (ZMZ 528916); C - E. Syntype of N. michonii from Syria (MHNG-MOLL- 111706); F - H. Syntype of N. karasuna collected from the Karasu River, south-eastern Turkey (ZMZ 528937); I, J; K, L. Two syntypes of N. ponsoti from Lake Muzayrīb, Syria (MNHN-IM- 2000 - 32754); M. Syntype (labelled as paratype) of N. ponsoti from Lake Muzayrīb (MT 820, RBINS); N. Syntype of N. jordani var. turris collected in the Sea of Galilee (ZMZ 528930); O, P. Syntype of N. bellardii from the Litani River, Beqaa valley, Lebanon (ZMZ 528918). Scale bars: 1 mm.

Figure 17. Theodoxus jordani (G. B. Sowerby I, 1836). A - C. Syntype of N. meridionalis var. mesopotamica from near Diyarbakir, Turkey (ZMZ 528914); D, E. Specimen (T. mesopotamicus - morphotype) collected in Sanliurfa, Turkey (UGSB 23426) and used in the phylogeny (Fig. 2); F - H; K - M. Two syntypes of N. cinctella collected at the source of River Chabur near Ras al-Ayn, Syria (ZMB / Moll 21732); I, J. Topotype of N. cinctella from the same locality (UGSB 18762). Scale bars: 1 mm.

Figure 18. Theodoxus macri (G. B. Sowerby II, 1849). A - D. Specimen collected close to Harbiye Falls, Harbiye, Antakya, Turkey (UGSB 24179); E - H. Specimen from Lake Yenisehir, Reyhanli, Turkey (UGSB 24180); I, J. Specimen from Lake Balik, Adalar, Turkey (UGSB 24181). All specimens (A-J) were used in 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 21. Theodoxus syriacus (Bourguignat, 1852). A - D. Specimen collected at Sultankoeyue, Mardin, Turkey (UGSB 24182); E - H. Specimen from the Yanarsu Stream, Alicli, Turkey (UGSB 20518). I - L. Specimen collected near Basdegirmen, Diyarbakir, Turkey (UGSB 24183); M - O; P - R. Two specimens collected by Bourguignat from Iskenderun, Turkey (MHNG-MOLL- 111712). All UGSB specimens 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.

Figure 24. Theodoxus wesselinghi Sands & Gloeer sp. nov. A - D. Holotype collected in the Sakarya River, Caykoey, Bilecik, Turkey (RMNH. MOL. 342200); E - G. Paratype from the same location as the holotype (RMNH. MOL. 342202); H - J. Paratype from Fele, Isparta province, Turkey (RMNH. MOL. 342204); K - M. Paratype from Eflatun Pinari, Konya province, Turkey (RMNH. MOL. 342206). All photographed material (A-M) is stored in NMNL. Scale bars: 1 mm.

Figure 26. Type locality of Theodoxus wilkei Sands & Gloeer sp. nov. A, B. Cifteler spring, Cifteler, Eskisehir, Turkey, 39.34931 ° N, 31.05527 ° E.

Figure 27. Theodoxus wilkei Sands & Gloeer sp. nov. A - D. Holotype (RMNH. MOL. 342208); E - G. Paratype (RMNH. MOL. 342210); H - J. Paratype (RMNH. MOL. 342211). All photographed material is from the Cifteler Spring, Cifteler, Eskisehir, Turkey and stored in NMNL. Scale bars: 1 mm.

Figure 28. Radula of Theodoxus wilkei Sands & Gloeer sp. nov. paratypes (UGSB 20687). A. Portion of the radula showing full sets of teeth; B. Magnified view of the central and lateral teeth; C. Magnified view of the lateral and first and second rows of marginal teeth; D. Magnified view of the lateral teeth; E. The first row of marginal teeth; F. Magnified view of the faces of inner marginal teeth belonging to the first row. Scale bars: 100 μm (A-D), 20 μm (E-F).