Microcystina arabii, Marzuki & Liew & Mohd-Azlan, 2021

Marzuki, Mohammad Effendi bin, Liew, Thor-Seng & Mohd-Azlan, Jayasilan, 2021, Land snails and slugs of Bau limestone hills, Sarawak (Malaysia, Borneo), with the descriptions of 13 new species, ZooKeys 1035, pp. 1-113 : 1

Microcystina arabii sp. nov. Figures 23A , 24A-F

Material examined.

Holotype (SH 1.38 mm, SW 1.75 mm) (MZU.MOL.20.06), Malaysia, Sarawak, Kuching Division , Bukit Sokwang (Site 2), northern site of Gunung Doya, limestone hill along Skio road, 2.05 miles E Bau, 1°23'45.69"N, 110°10'35.04"E, coll. M. E. Marzuki, 22.IV.2017 . Paratypes: 1 ex. (ME0009154), same data as the holotype ; 9 ex. (ME0009165), Bukit Sokwang ( Site 1), northern site of Gunung Doya, limestone hill along Skio road, 2.05 miles E Bau, 1°23'52.11"N, 110°10'27.93"E, coll. M. E. Marzuki, 22.IV.2017 ; 6 ex. (ME0009168), Bukit Sokwang ( Site 3), northern site of Gunung Doya, limestone hill along Skio road, 2.05 miles E Bau, 1°23'49.87"N, 110°10'32.14"E, coll. M. E. Marzuki, 22.IV.2017 ; 2 ex. (ME0002899), Gunung Batu , limestone outcrop along Skio road, Jambusan, 2.4 miles E Bau, 1°23'50.65"N, 110°11'19.99"E, coll. M. E. Marzuki, 23.VI.2010 ; 4 ex. (ME0001757), the same locality, coll. M. E. Marzuki, 11.III.2011 ; 1 ex. (ME0008889), the same locality, coll. M. E. Marzuki, 10.II.2017 ; 2 ex (ME0002899), Fairy Caves (Site 1), south part of Gunung Kapor, 4 miles SW Bau, 1°22'53.76"N, 110°7'4.34"E, coll. M. E. Marzuki, 23.VI.2010 ; 2 ex. (ME0001762), 2 ex. (MZU.MOL.20.07), South Flank of Bukit Akud , near Kampung Beratok, Serian-Kuching road, 14 miles NW Serian, 1°18'23.26"N, 110°24'15.07"E, coll. M. E. Marzuki, 21.VI.2010 ; 7 ex. (ME0007020), small limestone outcrop at Kampung Beratok , Serian-Kuching road, 14.3 miles NW Serian, 1°18'41.05"N, 110°24'37.13"E, coll. M. E. Marzuki, 27.XII.2015 ; 1 ex. (ME0011489), Lobang Angin ( Site 1), limestone outcrop near Sungai Sarawak Kanan, 1.75 miles W of Bau, 1°24'48.14"N, 110°8'12.21"E, coll. M. E. Marzuki, 15.IV.2017 ; 6 ex. (ME0008138), Limestone escarpment near Kampung Benuk, 8.2 miles SW Kota Padawan, coll. M. E. Marzuki, 13.IX.2017 .

Differential diagnosis.

It differs from Microcystina sinica Möllendorff, 1885, Microcystina oswaldbrakeni sp. nov., and Microcystis bunguranensis Smith, 1894 by having cancellated sculpture on the shell surface.

Description.

Shell very small, thin, translucent, white, straw yellow to brown; spire distinctly elevated, conical with convex sides or depressed-ovoid; apex rounded. Surface with a silky to glossy lustre. Whorls convex, periphery rounded. Last whorl with a thin, inconspicuous peripheral thread coinciding with the suture of the penultimate whorl. Number of whorls < 4¼. Protoconch: with a fine, moderately spaced spiral striation consisting of rows of minute spiral grooves crossed by equally strong radial riblets which are arranged in a cancellated pattern towards the teleoconch. Teleoconch moderately spaced spiral striation consisting of rows of minute spiral grooves crossed by equally strong radial riblets which are arranged in a cancellated pattern. Radial sculpture teleoconch of very fine, densely spaced radial riblets, oblique, predominant at the peripheral region and inconspicuous at the umbilical region. Aperture: lunulate. Peristome simple; somewhat thickened and reflected on the columellar side, not thickened nor reflected on the basal and palatal side. Umbilicus open, narrow, partly covered; umbilical region moderately concave. Dimensions: shell height <1.38 mm; shell width <1.75 mm; diameters of the first three whorls 0.38-0.42 mm, 0.75-0.83 mm, and 1.17-1.29 mm, respectively; aperture height <0.67 mm; aperture width <0.92 mm.

Remarks.

The shells of this species display high variability in terms of colour and height/width ratio.

Geographic distribution and habitat.

It is known from the Bau and Padawan-Serian limestone hill clusters. Only dry shells specimens were found during the surveys.

Etymology.

The specific epithet honours Mr. Abang Arabi Abang Aimran, Chief Wildlife Warden of Sarawak Forestry Corporation, who has contributed significantly to the conservation of wildlife in Sarawak.

Figures

Figure 23. A Microcystina arabii, sp. nov., MZU. MOL. 20.06 Holotype Gunung Batu B Microcystina atoni, sp. nov., MZU. MOL. 20.11 Paratype Gunung Batu C Microcystina kilat, sp. nov., MZU. MOL. 20.19 Paratype Gunung Batu D Microcystina lirata, sp. nov., MZU. MOL. 20.15 paratype Gunung Kapor.

Figure 24. Microcystina arabii sp. nov. A-F MZU. MOL. 20.07 Paratype A Apertural view B Apical view, C Basal view D Enlargement of the apical side showing the apex E Enlargement of the body whorl showing the shell sculpture F Enlargement of the basal side of the shell.