Acmella changphueakensis Seedee, Dumrongrojwattana & Poeaim, 2025

Seedee, Kunya, Dumrongrojwattana, Pongrat & Poeaim, Supattra, 2025, Four new species of genus Acmella W. T. Blanford, 1869 (Gastropoda, Assimineidae) from Southern Thailand, ZooKeys 1256, pp. 275-292 : 275-292

Acmella changphueakensis Seedee, Dumrongrojwattana & Poeaim sp. nov.

Fig. 6

Type material.

Holotype: Thailand • Samnaksong Tham Chang Phueak , Ban Na Subdistrict, Mueang District, Chumphon Province; 10.4463, 99.0349; November 2023; Kunya Seedee; Deposited in the Malacological Collection; catalog no. ZRCBUU 0991 ; GenBank accession number: PV 157993 , SH = 1.37 mm, SW = 0.96 mm, AH = 0.52 mm, AW = 0.53 mm (Fig. 6 A – E , Table 2 ) . Paratype: Thailand • 4 shells; same locality data as holotype; November 2023; Deposited in the same institution as the holotype; catalog no. ZRCBUU 0992 ; GenBank accession number: PV 157994 , SH = 1.33–1.49 mm (1.38 ± 0.08 mm), SW = 0.95–1.09 mm (1.01 ± 0.07 mm), AH = 0.51–0.57 mm (0.54 ± 0.03 mm), AW = 0.48–0.54 mm (0.50 ± 0.03 mm) .

Diagnosis.

Shell conical, white; a visible suture; 5–5 ½ whorls. Aperture oblique and oval. The last whorl sculpture has a prominently spiraled, low convex pattern. Umbilicus open and narrow.

Description.

Shell conical, white, translucent; apex rounded; whorls convex up to deep suture; 5–5 ½ whorls. The aperture is oblique oval, with a wall adjacent to the upper body, a concave portion following the shell shape, and a thin peristome. Umbilicus open, narrow, and nearly closed (Fig. 6 A ). Protoconch sculpture consisting of malleation, scattered throughout the area up to the second whorl (Fig. 6 B, C ). The last whorl sculpture consists of a spiral low convex pattern with 30–32, conspicuous, regularly spaced rows, each with a narrow groove. The radial sculpture is almost absent and irregularly spaced (Fig. 6 D ). Operculum paucispiral, thin, transparent, and composed of chitin (Fig. 6 E ).

Differential diagnosis.

Acmella changphueakensis sp. nov. resembles A. minutissima Maassen, 2000 in having a similar sculpture pattern on the last whorl. However, it can be distinguished by its higher number of spiral rows and greater number of whorls (five), whereas A. minutissima has only four. Among the newly described species, A. changphueakensis sp. nov. differs from A. krueangensis sp. nov. and A. thamsingensis sp. nov. by its faint radial sculpture, which is well developed in the latter two species. It shares a similar spiral sculpture with A. kanchanaditensis sp. nov., but it differs in having more widely spaced spiral rows.

Etymology.

The name changphueakensis is derived from Samnaksong Tham Chang Phueak, where this species was discovered.

Habitat and distribution.

This species is known only from the study site.

Ecology.

The new species inhabits cave environments where no light penetrates, specifically in areas where water seeps through the cave walls.

Figures

Figure 6. Scanning electron micrographs (SEM) of Acmella changphueakensis sp. nov. (A – E) various shell views. A. Overall shell view; B, C. Protoconch and sculpture details; D. Last whorl sculpture; E. Operculum. Scale bars: 0.5 mm (A, B); 0.1 mm (C – E).