Hemiplecta esculenta Maassen, 2006

Sutcharit, Chirasak & Panha, Somsak, 2021, Systematic review of the dextral Hemiplecta Albers, 1850 (Eupulmonata, Ariophantidae) from Thailand with description of a new species and list of all the Indochinese species, ZooKeys 1047, pp. 101-154 : 101

Hemiplecta esculenta Maassen, 2006

Figures 1F , 5C , 7 , 10H, I

Hemiplecta esculenta Maassen, 2006: 17, 18, figs 10-12. Type locality: limestone area near village Hang, Pu Luong National Park, Thanh Hoa, Vietnam. Inkhavilay et al. 2019: 76, fig. 35d, e. Páll-Gergely 2019: figs 11-13.

Type specimen.

See the species list of Indochinese species.

Material examined.

Thailand: Tam Chiang Dao , Chiang Mai: CUMZ 4553 (5 specimens in ethanol; Fig. 1F ), CUMZ 4564 (10 specimens in ethanol), CUMZ 4565 (9 specimens in ethanol), CUMZ 4574 (8 specimens in ethanol; Fig. 5C ); Tam Tab-Tao, Chaiprakarn, Chiang Mai: CUMZ 4580 (10 specimens in ethanol) .

Shell. Shell relatively small (height up to 25 mm, width up to 35 mm), elevated to slightly depressed, upper surface with distinct nodules arranged on growth line, and lower shell surface nearly smooth. Last whorl keeled; aperture large and ovate; lip simple to slightly expanded and dark brown. Umbilicus widely opened and deep (Fig. 5C ).

Genitalia. Genital tracts similar to those of H. humphreysiana (Fig. 7A ). Internal wall of penis with sculpture encircling penial verge. Penial sculpture (ps) consists of small to large papillary knobs arranged in oblique lines on penial wall; relatively smaller knobs surrounding penial verge. Penial verge (pv) small, short, conic, and with smooth surface (Fig. 7B ). Gametolytic sac (gs) bulbous with undifferentiated duct. Internal wall of vagina with series of thin longitudinal vaginal pilasters (vp). Dart apparatus (da) relatively short; internal wall of chamber with smooth wall, and papilla of dart apparatus (dp) slightly elongate, conic, and with smooth surface (Fig. 7B ).

Radula. Each row possesses about 161 teeth (80-(18-21)-1-(19-21)-80). Central tooth triangular, tricuspid; ectocones small; mesocone large (Fig. 10H ). Lateral teeth tricuspid; endocone small; mesocone large with pointed tip; ectocone large, basal, and with pointed tip. Outer lateral teeth arranged slightly obliquely, bicuspid; endocone very small to absent; mesocone large trapezoid; ectocone basal, relatively small, and pointed tip. Latero-marginal transition starts from tooth no. 18 to 21. Marginal teeth with curved teeth, bicuspid; endocone usually larger than ectocone (Fig. 10I ).

External features. Living snail exhibits similar soft body morphology, pulmonary cavity and caudal structure (Fig. 7D ) to that of H. humphreysiana . The distinct characters are the brownish to greyish body and mantle edge; right and left shell lobes absent (Fig. 1F ).

Distribution.

Previously known only from the type locality in northern Vietnam ( Maassen 2006) and Xieng Khaung, northeastern Laos ( Inkhavilay et al. 2019). Recently, we have located populations from northern Thailand in Chiang Mai Province.

Remarks.

The shell features were carefully described in Maassen (2006). The original description of H. esculenta was based on seven shells and placement within Hemiplecta was provisional ( Maassen 2006), and none of the topotypic specimens have subsequently been examined. The samples from Thailand show only minor variations from the type series, in the presence of a narrow brownish spiral band and slightly elevated spire, which we attribute to intraspecific variation. It is important to examine the genitalia of the topotypic material.

Figures

Figure 1. Living snail. A Hemiplecta humphreysiana from Singapore (width about 45 mm) B, C Hemiplecta distincta B from Saraburi, Thailand (width about 65 mm) and C mating pairs D, E Hemiplecta funerea from Nan, Thailand (width about 50 mm) D yellow shell form and E dark shell form (width about 50 mm) F Hemiplecta esculenta from Chiang Mai, Thailand (width about 30 mm).

Figure 5. A, B Hemiplecta funerea, specimens CUMZ 4575 from Nan, Thailand A yellow shell form and B dark shell form C Hemiplecta esculenta, specimen CUMZ 4553 from Chiang Mai, Thailand.

Figure 7. Genitalia, mantle edge structure, and caudal region of Hemiplecta esculenta, specimen CUMZ 4553 from Chiang Mai, Thailand A whole genital organ B internal wall sculpture of penis, vagina and dart chamber C ventral view of mantle edge and D right view of caudal region.

Figure 10. Representative SEM images of radula A-C Hemiplecta humphreysiana, specimen CUMZ 4573 from Singapore A central and lateral teeth B transition from lateral teeth to marginal teeth and C outermost marginal teeth D, E Hemiplecta distincta, specimen CUMZ 4560 from Chanthaburi, Thailand D central and lateral teeth and E outermost marginal teeth F, G Hemiplecta funerea, specimen CUMZ 4575 from Nan, Thailand F central and lateral teeth and G outermost marginal teeth H, I Hemiplecta esculenta, specimen CUMZ 4553 from Chiang Mai, Thailand H central and lateral teeth I transition from lateral teeth to marginal teeth J Hemiplecta nemorosa sp. nov., paratype CUMZ 5253 from Maehongsorn, Thailand. Central tooth indicated by ' C'. Numbers indicate the tooth order from lateral to marginal end.