Dalipaludina oxytropoides (Heude, 1889) Zhang & Du & von Rintelen, 2023

Zhang, Le-Jia, Du, Li-Na & von Rintelen, Thomas, 2023, A new genus of river snails, Dalipaludina (Gastropoda, Viviparidae), endemic to the Yunnan Plateau of SW China, Zoosystematics and Evolution 99 (2), pp. 285-297 : 285

Dalipaludina oxytropoides (Heude, 1889) comb. nov.

Paludina oxytropoides Heude, 1889: 176 ('lacu prope Tchao-tong’ = lake near Zhaotong City,Yunnan Province, China).

Vivipara oxytropoides - Kobelt 1909: 128.

Margarya sp. - Du et al. 2012: 45.

Margarya oxytropoides - Zhang et al. 2015: 777; Wiese et al. 2022.

Material examined.

2 syntypes, IZCAS-FG-492586, IZCAS-FG-492587; 1 paratype, MCZ-Mala-167343; 91 specimens in ZMB, collected by Frank Riedel from around 1 to 6 metres depth in all over the Lake Lugu in September and October 2014 ; 5 specimens in ZMB, collected by Le-Jia Zhang from 1 metre depth in the east shore of Lake Lugu in April 2022 .

Description.

Shell (Fig. 4A-H ) large, conical, thin, greenish yellow to dark brown in colour; up to six whorls at adulthood, including one relatively smooth protoconch whorl, apex acute; each teleoconch whorls with one strong keel at suture, above suture with many rather weak spiral threads, sometimes with additional two to three strong cords, base of shell with many thin weak spiral threads, weak spiral cords and threads with short periostracum setae; aperture ovate, less than half of shell in height, lip thin and simple, umbilicus narrow, sometimes bordered by a keel.

Operculum (Fig. 4I ) corneous, ovate, thin to relatively thick, yellow to reddish brown, with darker coloured nuclear region, exterior surface of operculum rather smooth, inner opercular region relatively small, nuclear region smooth or with small grains.

Radular (Fig. 7C, D ) central tooth with one broad central denticle and three to four small sharp cusps on either side; lateral tooth with one broad central denticle and three to four small sharp cusps on either side; inner marginal tooth with one broad central denticle and four small sharp cusps on either side; each outer marginal tooth with 10 to 11 small sharp cusps.

Remarks.

This species has the most variable shell within Dalipaludina . The form with strong cords of this species can be easily distinguished from the other Dalipaludina species. It used to be considered as a species of Margarya with a distribution in Lake Dianchi as well ( Zhang et al. 2015). However, the COI-based phylogeny showed that " Margarya oxytropides " from Dianchi is not a species of Dalipaludina , but indeed a member of the Cipangopaludina / Margarya complex. The syntypes of Paludina oxytropoides Heude, 1889 from Zhaotong in Northeast Yunnan show a strong keel at the suture, two strong keels above the suture, a relatively smooth shell base with many weak spiral keels, and a narrow umbilicus with a keel around it. It is distinct from the " Margarya oxytropides " from Lake Dianchi but quite similar to the strongly keeled form of D. oxytropoides from Lake Lugu. Meanwhile, the shell morphology of " Margarya oxytropides " from Lake Dianchi matches the description and figure of Cipangopaludina dianchiensis Zhang, 1990 endemic to Lake Dianchi ( Zhang 1990). Therefore, instead of D. oxytropoides , " Margarya oxytropides " from Lake Dianchi is here recognised as Margarya dianchiensis (Zhang, 1990) comb. nov. Paludina oxytropoides Heude, 1889 is reclassified as a member of Dalipaludina . The recommended Chinese name of this species is “尖龙骨理田螺”.

Habitat and distribution.

shallow to medium-depth water area with sandy bottoms in Lake Lugu, Yunnan/Sichuan, China; lakes in Zhaotong, Yunnan, China.

Figures

Figure 4. Shell and operculum of Dalipaludina oxytropoides. A-C. Specimen collected from Lake Lugu, ZMB. Moll. 250844; D-F. Varieties collected from Lake Lugu, ZLJ; G. Syntype IZCAS-FG- 492587 from a lake in Zhaotong, Yunann, photo taken by Kaibaryer Meng, Institute of Zoology, Chinese Academy of Sciences; H. Paratype MCZ-Mala- 167343 from a lake in Zhaotong, Yunann, photo taken by Alana Rivera, Museum of Comparative Zoology, Harvard University, President and Fellows of Harvard College; I. Exterior (left) and interior (right) surface of operculum. Scale bar: 1 cm, B-F, H-I with the same scale bar of A.

Figure 7. SEM photo of the radula and the protoconch of Dalipaludina species. A, B. Radula of Dalipaludina delavayana, A- ZMB. Moll. 181719, B- ZMB. Moll. 122707; C, D. Radula of Dalipaludina oxytropoides, ZMB. Moll. 250844; E, F. Radula of Dalipaludina occidentalis, ZMB. Moll. 122713. Abbreviations: ct-central teeth; lt-lateral teeth; imt-inner marginal teeth; omt-outer marginal teeth. Scale bars: 100 µm.