Ligidium cuspidatum Li & Jiang, 2025

Zong, Zili, Wang, Jin, Jiang, Chao & Li, Weichun, 2025, Integrative taxonomy reveals two new species of Ligidium (Crustacea, Isopoda, Oniscidea) from China, Zoosystematics and Evolution 101 (3), pp. 1187-1195 : 1187-1195

Ligidium cuspidatum Li & Jiang sp. nov.

Figs 1 , 3 B , 4

Type material.

Holotype. China • male, Sichuan Province, Leshan City, Mabian Dafengding National Nature Reserve (28°51'N, 103°31'E), alt. 1100 m, 12 August 2012, Weichun Li and Li Huang leg., prep. slide nos. L 15054 - L 15067.

Paratypes. Two females, same collection data as holotype, DNA nos. DFD 2004 , DFD 2005 .

Diagnosis.

Male pleopod 2 endopod bears a beak-shaped tooth at approximately distal one-sixth on outer margin and has two small spines near distal apex on inner margin, slender distal part bent outwards and ending with a pointed apex.

Description.

Maximum length: males 5.0 mm and females 6.0 mm.

Body elliptic, ochre mixed with dark grey, and bears pale green muscle spots on dorsal surface; pereonite 1 without setae on posterior margin (Fig. 1 ).

Antennula with one aesthetasc at apex of third article (Fig. 4 A ).

Antenna with flagellum composed of eleven articles (Fig. 4 B ).

Mandible with three-toothed incisor in left mandible, lacinia mobilis three-toothed, six penicils between lacinia mobilis and molar process (Fig. 4 C ); right mandible with three-toothed incisor, lacinia mobilis four-toothed, three penicils between lacinia mobilis and molar process (Fig. 4 D ).

Maxillule with three stout penicils and one small seta near distal margin of inner lobe; outer lobe with twelve apical teeth of various sizes (Fig. 4 E ).

Maxilla distally divided into two parts with blunted rounded apices, large lappet with six elongated setose penicils at subapical part, small lappet with four elongated setose penicils near distal margin (Fig. 4 F ).

Maxilliped endite rectangular, distal margin with two teeth at inner distal angle; palp with six setae (Fig. 4 G ).

Pereopod 1 basis with two setae on sternal face and single seta at distal angle on ternal face; ischium concave on ternal face; merus with four setae on sternal face and single seta at distal angle on ternal face; carpus with six setae on sternal face and single seta at distal angle on ternal face; propodus bears four small setae on sternal face and single small seta at distal tip on ternal face (Fig. 4 H ). Pereopod 7 basis bears single distal seta at distal angle on sternal face; ischium narrow and concave basally, broadened towards subtip, then narrowed towards distal tip, bears two setae on sternal face and ternal face, respectively; merus with three long setae on sternal face and two setae at distal angle on ternal face; carpus bears three long setae on sternal face and two setae at distal angle on ternal face; propodus bears three small setae on sternal face (Fig. 4 I ).

Male pleopod 1 exopod with blunted distal apex, and bears three long setae; endopod with triangular projection, distal apex with three long setae (Fig. 4 J, K ). Male pleopod 2 exopod subrectangular; endopod long and thin, second segment with outcurve distal part and pointed apex, bears a beak-shaped tooth at approximately distal one-sixth on outer margin, and has two small spines near distal apex on inner margin (Fig. 4 L, M ).

Etymology.

Latin: cuspidatus = pointed. The new species name refers to the male pleopod 2 endopod with a pointed distal apex.

Distribution.

This species is only known from Mabian Dafengding National Nature Reserve, Sichuan Province, China.

Natural history.

The habitat in which this species has been collected is under the fallen leaves near a waterfall. The vegetation of the collection site is composed of shrubs and evergreen broadleaf trees (Fig. 3 B ).

Remarks.

This species is similar to L. denticulatum , L. deltodontum , L. gracilentum , and L. sichuanense by having a tooth at the distal part of the male pleopod 2 endopod on outer margin. It can be distinguished by the slender and outcurved distal part of the male pleopod 2 endopod with two small spines on the inner margin. In the latter four species, the distal part of the male pleopod 2 endopods without spines on the inner margin ( Shen 1949: fig. 26; Li 2017: figs 3, 7; Nunomura 2002: fig. 3). We provided additional molecular evidence to distinguish them. Every species was represented by a well-supported clade (Fig. 1 ).

Figures

Figure 1. Bayesian consensus tree based on COI and 12 S rRNA sequences. Asterisks and circles represent high node support with Bayesian posterior probabilities > 0.95 and maximum bootstrap values > 95. The tree scale represents the number of nucleotide substitutions per site.

Figure 3. Natural environment of the collecting locality of Ligidium species. A. Collecting locality of L. alpinum sp. nov.; B. Collecting locality of L. cuspidatum sp. nov.

Figure 4. Ligidium cuspidatum sp. nov., holotype. A. Antennula; B. Antenna; C. Left mandible; D. Right mandible; E. Maxillule; F. Maxilla; G. Maxilliped; H. Pereopod 1; I. Pereopod 7; J. Pleopod 1 exopod; K. Pleopod 1 endopod; L. Pleopod 2 exopod; M. Pleopod 2 endopod. Scale bars: 0.1 mm.