Fenouilia undata Chen & He, 2024

Chen, Hui, He, Yue Ming, Wang, Chong Rui & Pan, Da, 2024, A new species of freshwater snail of Fenouilia (Gastropoda, Pomatiopsidae) from northern Guangxi, China, based on morphological and DNA evidence, ZooKeys 1196, pp. 271-283 : 271

Fenouilia undata Chen & He sp. nov.

Materials examined.

Holotype: China • Guangxi Province, Hechi City, Yizhou District, Longjiang River ; 24.4927°N, 108.6851°E; August 2022; Xu Cheng Wei & Yue Ming He leg.; NNU230701 (Fig. 2A-D ), shell height 3.39 mm . Paratypes: China • 2 specimens; same locality data as holotype; August 2022; NNU230702-03 • _2_ specimens; same locality data as holotype; March 2023; NNU230704-05. Shell height of all paratypes: 3.04-3.44 mm (Fig. 2E-P , Table 2 ) .

Diagnosis.

Shell small, thin but solid, with rounded, rather flattened shape, and width greater than height; sculptured with low, rounded axial ribs and fine spiral striae; whorls 4-5; body whorl swollen and large. Suture shallow; umbilicus narrow, crescent-shaped or closed. Aperture large, its length greater than shell height. Operculum ovate, corneous, slightly transparent, yellowish.

Description.

Shell small, 3.04-3.44 mm high, thin but solid, with a rounded, rather flattened shape; whorls 4-5; body whorl swollen and large, taking up most (about 84-94%) of shell; whorls of spire rapidly expanding. Shell width longer than shell height (Fig. 2 ). Apex obtuse, usually eroded. Suture low. Shell amber-yellow, with low, prosocline, rounded axial ribs and fine spiral striae. Aperture round, large, broader than shell height. Lip slightly thickened; inner lip smooth, white; outer lip white or yellowish and slightly rolled outward. Umbilicus narrowly crescent-shaped or closed; base white (Fig. 2A-N ).

Operculum ovate, smaller than aperture, corneous, thin, slightly transparent, yellowish, length 1.86-2.12 mm, width 1.53-1.72 mm; surface, including nucleus, of operculum smooth; nucleus located at bottom left third (Fig. 2O, P ).

Radula small; ribbon approximately 0.88 mm long. Central tooth with one large, triangular, pointed major cusp without serrations, with two small, sharp cusps on either side at base. Inner side of lateral teeth with two or three faint, wavy ridges; outer side smooth. Inner marginal teeth with five or six small cusps. Outer marginal teeth with 6-8 small cusps (Fig. 3 ).

Tentacles short, white; snout stubby, white, black pigmented. Mantle smooth, light gray, with small black spots. Intestine wider than base of tentacle; digestive gland milky white. Penis translucent white, thin, coiled, located behind right tentacle in neck area (Fig. 4 ).

Habitat and distribution.

The new species was discovered in the Longjiang River, where the depth of the water was less than 5 m, water flow is variable, and the substrate is composed of large stones (Fig. 5 ).

Biology.

In the laboratory aquarium, the new species fed on algae present on the surface of stones or watergrass. Snails reproduced many times during their year in captivity. Each brownish egg was laid 1.5 mm from the next. Eggs were affixed to the surfaces of rocks with a secretion. In some months, some individuals were observed to occasionally perform a “dance” in which they repeatedly twisted their shells clockwise or counterclockwise. They were more active at night.

Remarks.

The genus Fenouilia was established by Heude (1889) for Fenouilia bicingulata (Heude, 1889) from Dali, Yunnan, China; this species has a trochoidal shell, with rough, raised prosocline growth lines and no umbilicus. Subsequently, Davis et al. (1983) considered F. bicingulata to be a synonym of F. kreitneri (Neumayr, 1880); thus, the genus was thought to contain only a single species, until now. With prosocline axial ribs, triangular central tooth, and narrowly crescent-shaped or absent umbilicus, the new species is similar to F. kreitneri . However, the new species can be distinguished by its broader shell. In addition, F. undata sp. nov. has shorter tentacles (vs longer tentacles in F. kreitneri ), and there are three ridges only on the inner side (vs. lateral teeth with obvious ridges on both sides). The adult shell of F. undata sp. nov. is similar to that of Lacunopsis munensis (Brandt, 1968) and Lithoglyphopsis modesta (Gredler, 1886). These species differ in the relative length of the aperture to shell height (the aperture is longer than shell height in F. undata , but shorter in L. munensis ) and in relative shell width (the shell is broader than height in F. undata , but narrower in L. modesta ).

Molecular results.

The concatenation of COI and 16S rDNA yielded 1229 sites. The GTR+F+R5 model was selected as the best-fit of nucleotide substitution by BIC. Phylogenetic analyses revealed BI and ML trees with largely consistent topologies (Figs 6 , 7 ). The average 16S genetic distance (uncorrected p -distance) between the F. undata sp. nov. and F. kreitneri is 1.04%; the COI p -distance is 6.96%.

Etymology.

From the Latin adjective undata (wavy or wave-like form). We suggest the Chinese common name 波浪龙骨螺.

Figures

Figure 2. Fenouilia undata sp. nov. shells and operculum A-D holotype, NNU 230701 E-H paratype, NNU 230702 I-L paratype, NNU 230703 M paratype, NNU 230704 N paratype, NNU 230705 O, P operculum, holotype, NNU 230701. Scale bars: 2 mm (A-N); 1 mm (O-P).

Figure 3. Radula of Fenouilia undata sp. nov. A frontal view of radula B, C magnified view of radula.

Figure 4. Fenouilia undata sp. nov. A dissection with labelled structures of female B head of male. Abbreviations: e, eye; t, tentacle; sn, snout; f, foot; op, operculum; dg, digestive gland; int, intestine; pe, penis. Scale bars: 1 mm (A); 0,5 mm (B).

Figure 5. Fenouilia undata sp. nov. A color in life B natural habitat. Photographs by Xu Cheng Wei and Yue Ming He.

Figure 6. Bayesian-inference (BI) tree inferred from concatenated 16 S and COI gene sequences. Posterior probabilities are shown on the left of nodes on the tree.

Figure 7. Maximum-likelihood (ML) tree inferred from concatenated 16 S and COI gene sequences. Bootstrap supports are shown on the left of nodes on the tree.