Lacunopsis yuxiensis, Shi & Shu & Qiang & Xu & Tian & Chang, 2020

Shi, Ling, Shu, Yu, Qiang, Chen, Xu, Ping, Tian, Ying & Chang, Yaqing, 2020, A new freshwater snail (Gastropoda, Pomatiopsidae) endemic to Fuxian Lake (Yunnan, China) identified, based on morphological and DNA evidence, Biodiversity Data Journal 8, pp. 57218-57218 : 57218

Lacunopsis yuxiensis sp. n.

Materials

Type status: Holotype. Occurrence: catalogNumber: DLSM0001 ; Taxon: scientificNameID: urn:lsid:zoobank.org:pub:C1FF9D49-158C-4D86-A3D4-8E8818CC2DD8; phylum: Mollusca; class: Gastropoda; order: Littorinimorpha; family: Pomatiopsidae; genus: Lacunopsis; infraspecificEpithet: yuxiensis; taxonRank: species; Location: country: China; stateProvince: Yunnan Province; municipality: Yuxi; locality: Fuxian Lake ; verbatimDepth: 10 m; locationRemarks: alive on stones hiding under the grass, at depth of 1-6 m; verbatimLatitude: 24°18'14.53''N; verbatimLongitude: 102°46'42.76''E; Event: eventDate: 04-2019; Record Level: institutionCode: DLSM; basisOfRecord: PreservedSpecimen

Description

Shell: Shell (Fig. 2 ) small, thick, solid, with low conical spire. Apex obtuse. Four to five whorls, body whorl large, taking up most of the shell. Shell usually dark red (occasionally brown) with four yellow spiral ribs; ribs not obvious in the early whorls. First spiral rib below the suture, wide and usually yellow; second spiral rib granulated; third spiral rib strong; fourth spiral rib on base of the shell, gracile and not obvious. Umbilicus absent, base white, aperture round, slightly concave at sides, operculum smaller than aperture, corneous, thin and ovate, yellow and translucent, length 6 mm, width 4 mm (Fig. 2 P-R). Lip thickened, inner lip thick and smooth, without columellar folds. Protoconch yellowish-orange or orange red (Fig. 3 ), originally smooth (Fig. 3 A), but usually appears rough owing to corrosion and abrasion (Fig. 3 B).

Radula: Radula (Fig. 4 ) length 4 mm, comprising at least 60 rows. Formula 0+3+1+3+0. Rachidian tooth wide, cusp triangular, obtuse and smooth, there are wing-like protrusions on both sides of the shafts and 5-6 rib decorations on the edges of the protrusions. Three lateral teeth (including l1, l2, l3), l1 is closest to the rachidian tooth, cusp triangular, large and wide, more obtuse than the rachidian tooth; l2 and l3 cusp obtuse, more thin and slender. No marginal teeth.

Anatomy: The Lacunopsis species has not been anatomically studied previously. In this study, a male specimen (Fig. 5 A, B) was dissected.

Diagnosis

Shell (Table 1 , Fig. 2 ) small, solid, dark red, comprising four to five whorls, with four yellow spiral ribs and the second one granulated. Lip distinctly thickened, inner lip thick and smooth, without any columellar folds, umbilicus absent, operculum corneous and ovate, radula formula 0+3+1+3+0.

Etymology

This species takes the name of its type locality, the city of Yuxi, Yunnan Province.

Taxon discussion

The morphology of L. yuxiensis sp. nov. is significantly different from that of L. auris (Fig. 6 A, B) and L. yunnanensis (Fig. 6 C, D), which are also from Yunnan, China ( Liu et al. 1980). Firstly, the shells of L. auris and L. yunnanensis are very small around 2-3 mm, while the shell of L. yuxiensis sp. nov. is around 10 mm. Secondly, L. yuxiensis sp. nov. is characterised by its four yellow spiral ribs, while L. auris and L. yunnanensis is not. The four ribs have different appearances, the first spiral rib is below the suture between the body whorl and penultimate whorl, it is wide and usually yellow; the second spiral rib is granulated; the third spiral rib is strong; and the fourth spiral rib is on the base of the shell, gracile and not obvious (Fig. 2 A-M).

DNA analysis

For the phylogenetic analysis of 18S rDNA sequence fragments, we included eight specimens representing eight species (18S gene sequences downloaded from GenBank), with seven species belonging to the family Pomatiopsidae , one species from Lymnaeidae being used as the outgroup. The partial 18S sequence length of L. yuxiensis sp. nov. is 987 bp. Accession numbers of the sequences downloaded from GenBank are shown in Table 2 . All seqeunces were aligned by clustalW in MEGA X ( Sudhir et al. 2018). The phylogenetic tree was constructed using MEGA X ( Sudhir et al. 2018) by the neighbour-joining method (Fig. 7 ), with a Kimura 2-parameter substitution model, the numbers at the nodes indicating the bootstrap proportions and 1000 replicates were calculated to obtain bootstrap supports. L. yuxiensis sp. nov. and Lacunopsis MG98.09 together formed a well-supported clade in the phylogenetic tree and they could be distinguished from the other five freshwater gastropod taxa in the family (Fig. 7 ). The DNA analysis provides support for the taxonomic placement of the new species.

Figures

Figure 2. Lacunopsis yuxiensis sp. nov. shells. A-D. holotype; E-G. paratype 1; H, L. paratype 2; I. paratype 3; J. paratype 4; K. paratype 5; M. paratype 6; N-O. subfossil; P-Q. operculum; R. SEM of the operculum. Scale bar = 5 mm (A-O); operculum size is 6 mm x 4 mm (P-R).

Figure 3. Lacunopsis yuxiensis sp. nov. protoconch. A, B. yellowish-orange protoconch; C. Orange red protoconch; D. SEM of the protoconch. Scale bar = 500 µm.

Figure 4. Lacunopsis yuxiensis sp. nov. radula. A. Front view of radula, r: rachidian tooth, l: lateral teeth; B. Magnified view of panel A showing the rachidian tooth; C. The separated lateral teeth; D. The separated rachidian tooth; E. Magnified view of l 1; F. Magnified view of l 2 and l 3.

Figure 5. Lacunopsis yuxiensis sp. nov. photographs. A. dissection with labelled structures; B. radula; C. photo of live specimen. Scale bar A, B = 2 mm. Abbreviations: fo = foot, gi = gill, he = hepatopancreas, mo = mouth, pa = pallium, ph = phallus.

Figure 6. Original figures of two known Lacunopsis species (Lacunopsis auris and Lacunopsis yunnanensis) in Yunnan, China (Liu et al. 1980). A-B. Lacunopsis auris Y. - Y. Liu, Y. - X. Wang & W. - Z. Zhang, 1980; C-D. Lacunopsis yunnanensis Y. - Y. Liu, Y. - X. Wang & W. - Z. Zhang, 1980. Scale bar = 1 mm.

Figure 7. Neighbour-joining phylogenetic tree of Lacunopsis yuxiensis sp. nov. within the Pomatiopsidae, using partial 18 S rDNA sequences. Lacunopsis MG 98.09 is the name of this species recorded on the National Center for Biotechnology Information database.