Microcystina muscorum Van Benthem Jutting, 1959

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 : 40-43

Taxon classification Animalia Stylommatophora Ariophantidae

Microcystina muscorum Van Benthem Jutting, 1959 Figure 35, 38

Microcystina muscorum Van Benthem Jutting, 1959: 146; Clements et al. 2008: 2761-2762; Schilthuizen et al. 2013: online supplementary data. Wilhelminaia muscorum (Van Benthem Jutting) Maassen, 2001: 97. Type from Indonesia, Sumatra, Berastagi.

Microcystina sp. “BO-05”, Schilthuizen and Vermeulen 2003: 96; Schilthuizen 2004: 94.

Examined material from Sabah.

Interior Province. Upper Padas valley, Matang River South of Long Pasia, ridge on West bank (leg. J.J. Vermeulen, V 9823). Kudat Province. Balambangan Island, South end, Batu Sireh (leg. J.J. Vermeulen & M. Schilthuizen, V 9551). Banggi Island, South end, Karakit Hill (leg. J.J. Vermeulen & M. Schilthuizen, V 9465). Sandakan Province. Kinabatangan valley, Batu Batangan (leg. M. Schilthuizen, BOR/MOL 1338); Batu Keruak 2 near Sukau (leg. J.J. Vermeulen & M. Schilthuizen, V 12727; leg. M. Salverda & H. van Oosten, BOR/MOL 1336, BOR/MOL 3614, BOR/MOL 3616; leg. T.S. Liew & B. Elahan, BOR/MOL 1859); Batu Mawas (leg. M. Schilthuizen, BOR/MOL 1341); Batu Materis (leg. T.S. Liew & B. Elahan, BOR/MOL 3615, BOR/MOL 2128; leg. T.S. Liew & M. Schilthuizen, BOR/MOL 1972, BOR/MOL 2007); Batu Pangi (leg. J.J. Vermeulen & M. Schilthuizen, V 12731); Bod Tai (leg. M. Schilthuizen, BOR/MOL 1342); Batu Tai (not Bod Tai) near Gomantong (leg. J.J. Vermeulen & M. Schilthuizen, V 12730) (leg. T.S. Liew & B. Elahan, BOR/MOL 2643, BOR/MOL 1944); Batu Tomanggong Besar (leg. M. Schilthuizen, BOR/MOL 1350, BOR/MOL 3613); Batu Tomanggong Kecil (leg. J.J. Vermeulen & M. Schilthuizen, V 12729); Batu Tulug (Batu Putih) along road Lahad Datu-Sandakan, North of bridge over Kinabatangan River (leg. J.J. Vermeulen & H. Duistermaat, V 1498); Gomantong Hill 30 km South of Sandakan (leg. J.J. Vermeulen & H. Duistermaat, V 1633; leg. T.S. Liew & J.P. King, BOR/MOL 3650); Tandu Batu (leg. J.J. Vermeulen & M. Schilthuizen, V 9616). Segama valley, North end of limestone ridge on East bank Tabin River (leg. J.J. Vermeulen & M. Schilthuizen, V 7782); Unnamed hill near Sukau Police Station (leg. T.S. Liew & B. Elahan, BOR/MOL 2234, BOR/MOL 2199; leg. T.S. Liew, BOR/MOL 2167; leg. M. Schilthuizen, BOR/MOL 1337). Tawau Province. Batu Baturong c. 50 km W.S.W. Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1857). Gua Madai c. 40 km S.S.W. of Lahad Datu (leg. J.J. Vermeulen & H. Duistermaat, V 1727). Segama valley, hill N.W. of crossing road Sandakan-Lahad Datu with the Segama River (leg. J.J. Vermeulen & H. Duistermaat, V 1696); ‘Kirk’s Cave’ 8 km North of Lahad Datu (leg. J.J. Vermeulen, V 14346); Sabahmas Cave (leg. J.J. Vermeulen, V 7459, V 12728, BOR/MOL 1126). Semporna, Bohey Dulang Island (leg. T.S. Liew, BOR/MOL 4607, BOR/MOL 4620, BOR /MOL 4655; leg. T.S. Liew & M. Ruf, BOR/MOL 4697, BOR/MOL 4709); Bod Gaya Island (leg. T.S. Liew, Abdul & Ladja, BOR/MOL 4749, BOR/MOL 4760, BOR/MOL 4801, BOR/MOL 4831, BOR/MOL 4856, BOR/MOL 4864, BOR/MOL 4875, BOR/MOL 4885, BOR/MOL 4896, BOR/MOL 4917); Sibuan Island (leg. T.S. Liew & Abdul, BOR/MOL 5058). West Coast Province. Kinabalu N.P., Poring Hot Springs, along path to waterfall (leg. J.J. Vermeulen, V 13004); Serinsim (leg. M. Schilthuizen, BOR/MOL 3078).

Description.

Shell very small, thin, translucent, straw yellow to brown, approx. lenticular; spire moderately elevated, conical with a rounded apex. Surface shiny. Whorls moderately convex. Protoconch with a fine, moderately spaced spiral striation consisting of rows of minute, rather sharply outlined pits which are arranged in a reticulate pattern towards the teleoconch; with or without patches of fine, densely placed riblets. Teleoconch: above the periphery with a very fine (just visible at 40 times magnification), dense and regularly spaced spiral striation, the striae consisting of rows of disconnected or partially connected, minute, rather deep, sharply outlined pits (best visible in tangential light); below the periphery the pits are sometimes more or less connected to continuous grooves. Spiral sculpture sometimes absent on the teleoconch. Radial sculpture teleoconch: inconspicuous growth lines, next to these with inconspicuous to distinct, well-spaced to densely placed, very shallow grooves, often at irregular intervals. Umbilicus open, narrow, columellar side of the peristome somewhat thickened but not covering the umbilicus. Dimensions: Height up to 1.9 mm; width up to 3.1 mm; diameters of the first three whorls 0.3-0.5 mm, 0.6-0.9 mm, 1.1-1.5 mm respectively; number of whorls up to 5 1/4; height aperture up to 1.2 mm; width aperture up to 1.5 mm.

Habitat in Sabah and distribution.

Primary and secondary forest, coastal woodland on limestone and sandstone soil, up to 2100 m alt. Sabah: rather common in East Sabah, only few localities in West Sabah. Distribution: Laos; Peninsular Malaysia; Sumatra; Java; Bali.

Cross diagnosis.

Usually well-characterized by the spiral striation consisting of minute pits. Rare populations (one in Sabah) lack this striation on the teleoconch. On the protoconch, however, the pits are always present, which serves to distinguish Microcystina muscorum from Microcystina gratilla .

Microcystina sinica has a similarly pitted protoconch, see under that species.