Acmella striata Vermeulen, Liew & Schilthuizen

Vermeulen, Jaap J., Liew, Thor-Seng & Schilthuizen, Menno, 2015, Additions to the knowledge of the land snails of Sabah (Malaysia, Borneo), including 48 new species, ZooKeys 531, pp. 1-139 : 8-10

Taxon classification Animalia Littorinimorpha Assimineidae

Acmella striata Vermeulen, Liew & Schilthuizen sp. n. Figure 7

Acmella striata nomen nudum: Clements et al. 2008: 2761-2762; Schilthuizen et al. 2013: online supplementary data.

Holotype. Malaysia, Sabah, Kudat Province , Balambangan Island , South end , Batu Sireh (leg. J.J. Vermeulen & M. Schilthuizen, RMNH.5003947 ).

Examined material from Sabah.

Interior Province. Pinangah valley, Batu Urun (= Bukit Sinobang) (leg. J.J. Vermeulen, V 8017, BOR/MOL 608; leg. R. Haegens, V 5630). Pun Batu c. 30 km West of Sepulut (leg. J.J. Vermeulen, V 1272). Sepulut valley, Batu Temurung (leg. J.J. Vermeulen, V 12682); Gua Sanaron (leg. J.J. Vermeulen & M. Schilthuizen, V 8062). Kudat Province. Balambangan Island, Kok Simpul (leg. J.J. Vermeulen & M. Schilthuizen, V 9518); South end, Batu Sireh (leg. J.J. Vermeulen & M. Schilthuizen, V 9563). Sandakan Province. Kinabatangan valley, Batu Tomanggong Kecil (leg. J.J. Vermeulen & M. Schilthuizen, V 9695); Tandu Batu (leg. J.J. Vermeulen & M. Schilthuizen, V 9621). Tawau Province. Batu Baturong c. 50 km W.S.W. of Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1845). Tawau Hills N.P., waterfalls near Headquarters area (leg. J.J. Vermeulen, V 13199). West Coast Province. Mantanani Group, Pulau Mantanani Besar (leg. M. Schilthuizen, V 9846; leg. T.H. Liew, BOR/MOL 3726).

Description: Shell minute, rather thin, slightly translucent, corneous to white. Surface shiny. Spire conical with approx. flat sides, apex somewhat narrowly obtuse, whorls convex, often somewhat shouldered. Sculpture. Spiral sculpture predominant. Radial sculpture: growth lines, grading into irregularly and widely spaced riblets locally. Spiral sculpture: densely placed to moderately spaced, thin, narrow, very fine, distinctly wavy spiral threads which are occasionally interrupted or bifurcated, which have shallow and wide furrows in between and which run either approx. parallel to the suture or run slightly obliquely downwards. Aperture approx. elliptic in outline, with a slightly convex parietal side, transition from parietal to basal side rounded. Umbilicus open, narrow. Dimensions. Height 1.40-1.80 mm; width 1.05-1.25 mm; h/w 1.33-1.44; number of whorls 4 1/8-5 1/4; height aperture 0.50-0.70 mm; width aperture 0.55-0.65 mm.

Habitat in Sabah and distribution.

Primary forest, primary coastal woodland and secondary vegetation on limestone bedrock, also found in soil over sandstone and volcanic bedrock, at 0-1400 m alt. Sabah: scattered localities, including islands on the North and West coast. Also in Sarawak and Kalimantan. Distribution: Ambon, Ceram, Tanimbar Islands (see note below).

Cross diagnosis.

Characterized among Sabah Acmella by the comparatively high spire with distinctly convex whorls, and the teleoconch with fine, inconspicuous to rather distinct, but always very wavy spiral sculpture.

Also similar to Acmella sutteri Van Benthem Jutting, 1958, from Sumba. Acmella striata differs by the parietal side of the aperture, which is attached to the previous whorl over slightly more than half the distance between the periphery and the umbilicus of the latter. In Acmella sutteri it is only attached to the previous whorl over a very short distance near the angular corner.

Remarks.

Most Sabah samples have a slightly oblique spiral striation. In Sarawak shells with a spiral striation parallel to the suture predominate in most localities.

Samples from Mantanani and Balambangan Islands contain relatively large shells of dark colour. Similar shells are found locally in the Kinabatangan River valley; but towards the West populations grade into a smaller form with white shells, as is found in Gunung Mulu N.P., Sarawak. A sample from Kalimantan contains medium-sized and white shells.

The samples V 4721 (Indonesia, Tanimbar Islands, Yamdena, near Kampong Makatian), V 5052 (Indonesia, Ambon, 1 km from Poka), and V 5248 (Indonesia, Ceram, Moso) contain shells identical to the Borneo material. We regard these as the same species, and conclude that Acmella striata is a rather widespread species. It may well occur in Philippines, but we cannot find any described species identical to it.

Etymology.

The name refers to the shell surface [striata (L.) = striate].