Amimopina subangulatus ( Pfeiffer, 1862 )

Sutcharit, Chirasak, Naggs, Fred & Panha, Somsak, 2010, A First Record Of The Family Cerastidae In Thailand, With A Description Of A New Species (Pulmonata: Orthurethra: Cerastidae), Raffles Bulletin of Zoology 58 (2), pp. 251-258 : 255-256

Amimopina subangulatus ( Pfeiffer, 1862)

( Figs. 1E–G, I ; 2C ; 3E–H )

Bulimus subangulatus Pfeiffer, 1862: 274 , 275 (type locality: Laos Mountains, Cambodia); Martens, 1867: 82; Pfeiffer, 1868: 148; Pfeiffer, 1877: 181.

Amimopina subangulatus — Mordan, 1992: 3, 4. Material examined. – Lectotype BMNH 1986166 ( Fig. 1E ). Pu Kae Botanic Garden, Saraburi: CUMZ 4290 (3 shells). Jed Sao Noi Waterfall, Muaklek , Saraburi: CUMZ 3798 (2 shells; Fig. 1F ), 3799 (2 shells; Fig. 1G ), 4650 (8 shells). Muaklek Waterfall , Muaklek , Saraburi: CUMZ 4651 (2 in ethanol).

Shell. – Shell rather small, dextral, pellucid, very thin and fragile, ovate conical, and narrowly perforate. Spire short conical; apex acute with dark spot on the tip; 5–6 whorls, slightly convex with depressed suture. Last whorl large, and round. Shell surface with very fine growth lines to nearly smooth. Last two whorls corneous to brownish; somewhat dark brown on first 2–3 whorls. Aperture ovate; lip simple; columella dilated and triangular. Parietal callus transparent.

Genitalia. – Atrium (at) rather large, long, with no black pigment on male side ( Fig. 2C ). Penial appendix (pa) relatively short, proximally with constriction and enlarging distally. Penis (p) small, distally forms round knotty shape; penial flagellum (pf) very thin and long. Epiphallus (e) slightly larger than vas deferens. Retractor muscle thin and split into three bundles: penial retractor muscle (pr) inserted on proximal end of penial appendix, and atrial retractor muscle (ar) inserted on globular end of penis and epiphallus. Vas deferens (vd) thin tube connected to head of epiphallus ( Fig. 2C ).

Female reproductive organ is similar to that described for Rhachistia conformalis Sutcharit & Panha , new species, except the spread and cover of prominent black pigments extends to approximately half the vaginal length.

Radula . – Teeth arranged in V-shaped rows, each row contains about 99 (48-1-50) teeth. Central tooth monocuspid with notable narrow extension ( Fig. 3E ). Lateral teeth bicuspid, endocone spatulate, ectocone triangular and located at tooth base ( Fig. 3E, F ). Marginal teeth tricuspid with small entocone; mesocone rather large with blunt cusp; ectocone with two to four cusps located laterally ( Fig. 3G, H ).

Distribution. – Amimopina subangulatus was described from the Laos Mountains, Cambodia ( Pfeiffer, 1862), and so far no one has subsequently reported this species. Including data from the present study, the distribution of this species is confined to the type locality in Cambodia ( Pfeiffer, 1862) and to Saraburi Province, central Thailand.

Remarks. – Originally, “ Bulimus subangulatus Pfeiffer, 1862 ” was described from only two shells ( Pfeiffer, 1862). In this study, we compared the recently collected specimens from Thailand to the lectotype (BMNH 1986166) and found no significant shell morphological differences. No other representatives of this species have been recorded since the types were described almost 150 years ago.

The shell shapes of A. subangulatus and R. conformalis Sutcharit & Panha , new species, are very similar; the principal differences between these two species are the translucent corneous shell, which is slightly darker in the earlier whorls of A. subangulatus , whilst R. conformalis has a creamy shell, decorated with two rows of black spots and spiral bands. Amimopina subangulatus has a short penial appendix, longer caecum and blackish pigments distributed approximately to half of the vaginal length, while it is spread over nearly the entire vaginal length in R. conformalis Sutcharit & Panha new species. The arrangements of excretory, respiratory and circulation systems are similar to the previously mentioned species and to A. macleayi (see Solem, 1964a; Smith & Stanisic, 1998).

Figures

Fig. 1. Shell of Rhachistia sulphurea: A, lectotype NMW 1955.158.01155; B, paralectotype BMNH 1939.6.6.17. Shell of Rhachistia conformalis Sutcharit & Panha, new species: C, holotype CUMZ 3796; D, paratype CUMZ 3797. Shell of Amimopina subangulatus: E, lectotype BMNH 1986166; F, G, specimens from Jed Sao Noi Waterfall, Saraburi (CUMZ 3798, 3799). Rhachistia conformalis Sutcharit & Panha, new species: H, at type locality (shell height about 17 mm) CUMZ 3797. Amimopina subangulatus: I, at Jed Sao Noi Waterfall, Saraburi (shell height about 15 mm) CUMZ 3650.

Fig. 2. Anatomy of Rhachistia conformalis Sutcharit & Panha, new species (Paratype CUMZ 3797): A, reproductive system; B, pallial system; C, genitalia of Amimopina subangulatus from Jed Saw Noi Waterfall, Saraburi (CUMZ 3798).

Fig. 3. Radula morphology. Rhachistia conformalis Sutcharit & Panha, new species (Paratype CUMZ 3797): A, central tooth with first to third lateral teeth; B, C, lateral teeth with bicuspid marginal teeth transition; D, outermost marginal teeth. Amimopina subangulatus (CUMZ 3798): E, central tooth with first to third lateral teeth; F, G, lateral teeth with bicuspid marginal teeth transition; H, outermost marginal teeth. The numbers indicate the order of the teeth and the letter 'C’ in the images indicates the central tooth.