Amphidromus (Amphidromus) atricallosus temasek, Tan & Chan & Panha, 2011

Tan, Siong Kiat, Chan, Sow Yan & Panha, Somsak, 2011, A New Subspecies Of Amphidromus (Amphidromus) Atricallosus From Singapore (Mollusca: Gastropoda: Camaenidae), Raffles Bulletin of Zoology 59 (1), pp. 39-46 : 40-42

Amphidromus (Amphidromus) atricallosus temasek , new subspecies

( Figs. 1A , 2A , 3A )

Amphidromus atricallosus perakensis – Ng & Lim, 1992: 262; Chou et al., 1994: 73; Sutcharit & Panha, 2006: 21–22, Fig. 4. F–G, Fig. 11. A–C, Fig. 12. C; Prasankok et al., 2007; Sutcharit et al, 2007; Chou & Tan, 2008: 57; Lok & Tan, 2008.

Amphidromus atricallosus – Ho, 1995: 108–109.

Material examined. – SINGAPORE: Holotype: 1 S SH 44 x SD 25.6 ( ZRC.MOL.3058), Nee Soon Swamp Forest , Singapore, coll. S. K. Tan & S. Y. Chan, 03 Oct.2010 . Paratypes: 2 D SH 42.7 x SD 26–SH 46.4 x SD 27.7, 2 S SH 40.1x SD 25–SH 40.8 x SD 25.1 ( ZRC.MOL.2992), Nee Soon, coll. E. Alfred ; 1 D SH 46.9 x SD 28.3 ( ZRC.1992.3163), Nee Soon Swamp Forest , coll. National Park Survey, 30 Apr.1992 ; 1 D SH 45.0 x SD 26.4 ( ZRC 1994.4118 ), outside Nee Soon range, Seletar Reservoir Park ( NS 43 ), coll. H. K. Lua , 1994; 1 D ( CUMZ 2133 ), Nee Soon Nature Reserve , coll. S. Panha, 26 Jun.1998 ; 2 D ( CUMZ 2067 ), Nee Soon Nature Reserve , coll. S. Panha & Ms Loua, 19 Feb.2000 ; 10 D ( CUMZ 2198 ), Nee Soon Nature Reserve , coll. S. Panha & C. Sutcharit, 19 Feb.2001 ; 11 D ( CUMZ 2633 ), Nee Soon Nature Reserve , coll. S. Panha & P. Prasarnkok, 04 Mar.2004 ; 2 S (1 juv.) SH 43.4 x SD 26.8 ( ZRC.MOL.2843), Nee Soon Swamp Forest , coll. H. H. Tan & A. F. S. L. Lok, 13 Oct.2008 ; 1 D (juv.) ( ZRC. MOL.3059), Nee Soon Swamp Forest , coll. Y. C. Ng, Sep.2010 ; 1 D SH 43.5 x SD 27.1 ( ZRC.MOL.3057), Nee Soon Swamp Forest , coll. S. K. Tan & S. Y. Chan, 03 Oct.2010 ; 1 S SH 38.9 x SD 25.1 ( ZRC.MOL.3060), Nee Soon Swamp Forest , edge of swamp forest, behind Nee Soon Range, coll. P. X. Ng, B. Y. Q. Ng & C. K. Yeo, 03 Nov.2010 .

Non-type material. – 3 D SH 42.1 x SD 24.9–SH 42.9 x SD 26.4 ( ZRC 1989.1109 – 1111 ), no data; 10 D (9 juv.), SH 42.7 x SD 26.5 ( ZRC 1989.1135 – 1144 ), no data. SINGAPORE: 1 D (juv.) ( ZRC 1990.1528 ), Nee Soon, on tree along road, coll. CLM, Sep.1969 ; 3 S (juv.) ( ZRC 1998.3373 - 3377 ), Nee Soon Swamp Forest , coll. C. M. Yang et al., 9 Sep.1988 ; 1 D SH 44.3 x SD 25.4 ( ZRC 1990.10741 ), Nee Soon Swamp Forest , NW sector, in leaf litter on open scrubland, coll. K. Lim, 9 May 1990 ; 3 S (juv.), 2 D (broken, not measured) ( ZRC.MOL.3061) Nee Soon Swamp Forest , dead on ground, coll. S. K. Tan, 2009 ; 2 D (juv.) ( CSY 409.3.4.30), Pulau Tekong , dead on ground among low shrubs, coll. S. Y. Chan, 25 Dec. 1993 ; 1 S SH 43.7 x SD 26.2 ( CSY 409.3.4.31), Dairy Farm , dead on road path beside forest, coll. S. Y. Chan, 25 Oct. 1994 ; 1 S SH 39.5 x SD 24.8, Central Catchment area , on artifact, coll, R. Koh, Apr. 1995 ; 1 D SH 37.4 x SD 25.1 ( TSK 11017), Mandai Road Track 7, on fishtail palm, coll. S. K. Tan, 04 Apr.1999 ; 2 D (juv.), ( ZRC.MOL.3065), Lower Peirce Reservoir , arboreal on leaves, forest edge, coll. A. F. S. L. Lok, 23 Jul.2010 . MALAYSIA: 1 D (broken, not measured) ( CSY 409.3.4.14), Gunung Ledang ( Mount Ophir ), Johor, dead, among leaf litter in forest, coll. S. Y. Chan et al, 13 Oct.1996 .

Diagnosis. – Shell relatively large, ovate, chirally dimorphic coiling. Whorls 5½–6¾, slightly convex, surface generally smooth with indistinct axial striations or growth lines. Colour uniformly yellow with a thin white subsutural line (shells of living animals yellowish-green due to the dark colouration of soft body showing through), varix always absent. Columella simple, straight. Periostracum thin, transparent. Peristome in mature animals white, thickened and expanded except for parietal side, outer lip reflected but not adnate. Parietal callus usually inconspicuous, very rarely thickened to being whitish or translucent.

Animal body very pale greyish white in colour, reticulated, the recessed parts being darker, light brown around the head to greyish on the body. Mantle edge dark cream coloured to brown around the peristome. Upper and lower tentacles dark yellow, central part of the head between the upper tentacles occasionally pigmented with yellow, foot with longitudinal yellow stripe on either side.

Distribution. – The distribution of A. atricallosus temasek , new subspecies, is largely confined to Singapore, and tentatively, Johor, southern Peninsular Malaysia (Sutcharit & Panha, 2006 [part]; Prasankok et al., 2007 [part]; this study). Known Singapore localities include: Seletar ( Hanitsch, 1908), Nee Soon Swamp Forest, Bukit Timah Nature Reserve, Mandai, and Pulau Tekong (Ng & Lim, 1992; Chou & Tan, 2008; Lok & Tan, 2008). Although a specimen from Johor (CSY 409.3.4.14) is provisionally determined to be this subspecies in the material examined, identification was based on a weathered and broken specimen with only the body whorl intact. Verification with better preserved material would be required. Available evidence suggests A. atricallosus temasek to be endemic, but this has to be verified with greater sampling effort, particularly around the southern part of Peninsular Malaysia and the Riau islands of Indonesia. In Singapore, these arboreal snails are apparently restricted to the remnant forests. Preference for particular tree species has not been observed or reported, and the animals can be found on a wide variety of plants and on man-made structures.

Etymology. – The subspecies epithet is derived from Temasek, the historical name of the type locality Singapore. It is used as a noun in apposition.

Remarks. – The thin white subsutural line and simple and straight columella that is never twisted is diagnostic. Shells of juvenile s can also be separated from A. atricallosus perakensis Fulton, 1901 , by lack of a white zone around the columella (see Fig. 2 ). Although the convexity of the whorls of A. atricallosus perakensis is evidently variable throughout West Malaysia populations, shell whorls of A. atricallosus temasek , new subspecies, seem to be generally more convex in profile and resulting in the suture appearing more sunken in comparison. Living A. atricallosus temasek individuals are easily distinguished by the soft body colouration, and a pale yellowish-green shell with a thin white subsutural line ( Fig. 3. A ). The SEM images of the radula and genital system of A. atricallosus temasek , new subspecies, are described in detail and figured in Sutcharit & Panha (2006, as A. (A.) atricallosus perakensis [CUMZ 2198; herein designated paratypes]; radula, pg. 16: Fig. 11A–C; genital system, pg. 17: Fig. 12C).

Figures

Fig. 1. A, Amphidromus atricallosus temasek, new subspecies: Holotype, SH 44 x SD 25.6 (ZRC.MOL.3058), Nee Soon Swamp Forest, Singapore; B–E Amphidromus atricallosus perakensis (Fulton, 1901): B, SH 45 x SD 26.4 (TSK 11041), Bukit Serdam, Pahang, West Malaysia; C, SH 47.1 x SD 25.3 (CBB), Tapah Hill, Perak, West Malaysia; D, SH 47.2 x SD 27.6 (ZRC.MOL.3064), Pulau Tulai, near Pulau Tioman, West Malaysia; E, SH 46.4 x SD 24.2 (ZRC.MOL.3062), Gunung Genting, Perak, West Malaysia; F, Amphidromus atricallosus atricallosus (Gould, 1843): SH 45 x SD 25.7 (CSY 409.4.4.16), Ranong, Thailand; G, Amphidromus atricallosus leucoxanthus (von Martens, 1864): SH 51 x SD 28.5 (CSY 409.3.49.1), Chantaburi, East Thailand.

Fig. 2. A–C, Shells of juveniles: A, SH 31 x SD 19.7, juvenile shell of Amphidromus atricallosus temasek, new subspecies, showing the white columella; B–C, Amphidromus atricallosus perakensis (Fulton, 1901), juveniles, has a white zone bordering the columella: B, SH 33.9 x SD 22.4, Tapah Hill, Perak, West Malaysia; C, SH 34.7 x SD 25, Pulau Tulai, West Malaysia.

Fig. 3. A–B, Live animal colouration: A, Amphidromus atricallosus temasek, new subspecies, holotype (ZRC.MOL.3058); B, Amphidromus atricallosus perakensis (Fulton, 1901), Pulau Tulai, West Malaysia. (Photographs by Tan Heok Hui)