Carinartemis exacutus (Gould, 1856)

Sian Man, Nem, Siriboon, Thanit, Lin, Aung, Sutcharit, Chirasak & Panha, Somsak, 2022, Revision of the carnivorous land snail family Streptaxidae (Stylommatophora, Achatinina) in Myanmar, with description of four new species, ZooKeys 1110, pp. 39-102 : 39

Carinartemis exacutus (Gould, 1856)

Figs 1 , 2D , 17C, D , 18 , 21A, B , 22 , 24D

Streptaxis exacutus Gould, 1856: 13. Type locality: Burma [Myanmar].

Streptaxis exacuta [sic] - Pfeiffer 1859: 331.

Streptaxis exacutus - Pfeiffer 1871: 30, 31, pl. 115, figs 13, 14. Hanley and Theobald 1870: 40, pl. 98, figs 8-10. Nevill 1878: 3. Tryon 1885: 72, pl. 14, figs 11, 12. Blandford and Godwin-Austin 1908: 8.

Haploptychius exacutus - Kobelt 1906: 142, 143, pl. 57, figs 16-18. Richardson 1988: 215. Siriboon et al. 2014b: 169, 171.

Material examined.

Moulmein: NHMUK 1874.9.3.15 (3 shells) ex. Godwin-Austen. NHMUK 1888.12.4.771-773 (3 shells; Fig. 17C ). NHMUK 1906.2.2.198 (3 shells + 2 juveniles; Fig. 18A ) ex. Blanford collection. NHMUK 1903.7.1.3999 (3 shells) ex. Godwin-Austen collection. Burma: NHMUK1950.12.9.170 (1 shell) ex. Laidlaw collection. Mergui : NHMUK ex. Cuming collection (2 shells). Sadhdan Cave , Hpa-an Township , Hpa-an District , Kayin State, Myanmar (16°44'23.4"N, 97°43'04.2"E): CUMZ 13020 (3 shells). Bayin Nyi Cave , Hpa-an Township , Hpa-an District , Kayin State, Myanmar (16°58'10.1"N, 97°29'30.6"E): CUMZ 13021 (8 shells; Fig. 18B ), CUMZ 13022 (15 specimens in ethanol). Lun Nga Mountain , Hpa-an Township , Hpa-an District , Kayin State, Myanmar (16°44'53.2"N, 97°47'09.5"E): CUMZ 13023 (14 shells; Fig. 18C ), CUMZ 13024 (50 specimens in ethanol). Taung Wine Cave , near Thiri Hpa-an Hotel, Hpa-an Township , Hpa-an District , Kayin State, Myanmar (16°50'31.1"N, 97°37'18.4"E): CUMZ 13025 (3 shells; Fig. 17D ), CUMZ13026 (6 specimens in ethanol). Kaw Ka Taung Cave ( Golden valley ), Hpa-an Township, Hpa-an District, Kayin State, Myanmar (16°50'32.4"N, 97°37'10.9"E): CUMZ 13027 (1 shell) .

Diagnosis.

Carinartemis exacutus is superficially similar to C. sankeyi , C. vesperus Siriboon & Panha, 2014, and C. striatus Siriboon & Panha, 2014 from western Thailand, but it has a larger shell, convex spire, immediately expanded penultimate whorl, semi-ovate aperture, two parietal lamellae, very thickened penial sheath, vas deferens passes through penial sheath, curved portion of vas deferens with very thin connective tissue, and hooks located on irregular trapezoidal penial papillae separated by longitudinal folds. In comparison, C. sankeyi , C. vesperus , and C. striatus have an elevated spire, regularly expanded penultimate whorl, but C. sankeyi has fine transverse ridges on the entire shell, subquadrangular aperture, one parietal lamella, slender atrium, thin penial sheath, vas deferens does not pass through a penial sheath, curved portion of vas deferens is without connective tissue, proximal penial hook located on laterally-flattened penial papillae, and distal penial hooks located on laterally compressed penial papillae separated by reticulated folds. In contrast, C. vesperus has a subcircular aperture, lacks parietal lamellae, has a less axially deflected last whorl, vas deferens passes through the penial sheath, curved portion of vas deferens is without connective tissue, and penial papillae absent. Meanwhile, C. striatus has strong transverse ridges over the entire shell, a semi-ovate aperture, one parietal lamella, vas deferens is attached to the distal end of the penial sheath with very thin connective tissue, and hooks are located on papillae without connected longitudinal folds.

Description.

Shell oblique-heliciform, white, and translucent; whorls 6- 6½; spire convex with distinct suture. Shell surface glossy with fine transverse ridges, nearly smooth with few transverse ridges near peristome; varices present. Embryonic shell ~ 2½ whorls with smooth surface; following whorls intermediately coiled. Shell periphery wide and sharply keeled along nearly the entire penultimate whorl; last whorl axially deflected. Aperture semi-ovate; peristome discontinuous, thickened, expanded, and slightly reflected. Apertural dentition with one strong parietal lamella and sometimes with a second parietal lamella adjoined at a right angle. Umbilicus open and deep (Figs 17C, D , 18 ).

Genital organs. Atrium (at) short. Penis (p) a very thin, and long tube. Penial sheath (ps) muscularly enlarged, very thickened and extending entire length of penis; penial sheath retractor muscle (psr) thin, originating near genital orifice, attached to atrium with short and thin connective tissue, and inserting distally on penial sheath (Fig. 21A ). Vas deferens (vd) passes through a short portion of penial sheath, then extends to curved portion at ~ 1/11 of the penial sheath length before entering penis distally. Curved portion of vas deferens with very thin connective tissue originating at penial sheath (Fig. 21B ). Penial retractor muscle (pr) thin, very long, inserting at penis and vas deferens junction.

Internal wall of atrium generally smooth with sparse atrial pores (Fig. 22A ). Penial wall with scattered pale brownish penial hooks, ~ 20 hooks/200 μm 2; hooks located on laterally flattened penial papillae and separated by longitudinal folds (Fig. 22B-D ). Penial hooks small (<0.02 mm in length), expanded at base, tips pointed and curved towards genital orifice (Fig. 22E, F ).

Vagina (v) very short and ~ 1/12 of penis length. Gametolytic duct (gd) a long tube extending as far as albumin gland; gametolytic sac (gs) ovate. Proximal free oviduct (fo) enlarged then tapering to smaller diameter distally. Oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct. Talon (ta) small, short and club shaped. Hermaphroditic duct (hd) bearing long seminal vesicle (sv) ~ 1/2 the length from talon to branching point of seminal vesicle (Fig. 21A ).

Vaginal wall with longitudinal oblique vaginal folds, folds with nearly smooth surface and vaginal hook absent (Fig. 22G ).

Radula . Each row consists of 41-45 teeth with formula (22-20)-1-(20-22). Central tooth is very small with pointed cusp. Lateral and marginal teeth undifferentiated, lanceolate, unicuspid, and lanceolate. Latero-marginal teeth gradually reduced in size, with outermost teeth much smaller and shorter than inner teeth (Fig. 24D ).

Distribution.

This species was collected from five limestone hills in Kayin State, southern Myanmar, in this survey.

Remarks.

This species appears at a high abundance among the limestone karsts in Hpa-an, Kayin State. All the specimens examined from the populations from Lun Nga Mountain and Bayin Nyi Cave have a very small to indistinct upper parietal lamella, and some specimens from Bayin Nyi Cave have strong transverse ridges on almost the entire whorl. Moreover, the Lun Nga Mountain population have a last whorl that is more extended anteriorly and an elongated semi-ovate aperture (Fig. 18C ). However, the genitalia in all localities show no difference from this locality; thus, we consider them as intraspecific variations within C. exacutus . Some specimens from Bayin Nyi Cave have strong transverse ridges on almost the entire whorl.

Although the type locality was listed as ‘Burma’ [Myanmar], all the known records and specimens examined in this study were collected from Kayin State. Therefore, the precise type locality of this species is probably southwestern Myanmar in Mon State and Kayin State.

Figures

Figure 1. Approximate sampling locations used in this study. The location name and coordinates are listed in Table 1. Historical type localities of a broad scale, such as Tavoy, Burma, Moulmein, Mergui, and Tenasserim, are not indicated on this map.

Figure 2. Living snails A Discartemon tonywhitteni from near Phra (Buddha) Cave, Tanintharyi Region (shell width ~ 10 mm) B Discartemon paurodeviatus sp. nov. from the type locality (shell width ~ 11 mm) C Haploptychius heliakosus sp. nov. from the type locality (shell height ~ 9 mm) D Carinartemis exacutus from Lun Nga Mountain, Kayin State (shell height ~ 14 mm) E, F Carinartemis sankeyi (E) from Kayon Cave, Mon State (shell height ~ 10 mm) and (F) from Saddan Cave, Mawlamyine, Mon State (shell height ~ 10 mm).

Figure 17. A, B Carinartemis petitii A syntype MCZ 169290 from Tavoy, British Burmah and B specimen NHMUK 1909.3.15.67 from Moulmein C, D Carinartemis exacutus C specimen NHMUK 1888.12.4.771 - 773 from Moulmein with apertural dentition and D specimen CUMZ 13025 from Taung Wine Cave, Hpa-an, Kayin State with apertural dentition.

Figure 18. Carinartemis exacutus A specimen NHMUK 1906.2.2.198 from Moulmein B specimen CUMZ 13021 from Bayin Nyi Cave, Hpa-an, Kayin State C specimen CUMZ 13023 from Lun Nga Mountain, Hpa-an, Kayin State with apertural dentition.

Figure 21. Genital anatomy of A, B Carinartemis exacutus, specimen CUMZ 13021 A reproductive system and B insertion of vas deferens into penial sheath C, D Carinartemis sankeyi, specimen CUMZ 13029 C reproductive system and D insertion of vas deferens into penial sheath.

Figure 22. Internal sculpture of genitalia of Carinartemis exacutus, specimen CUMZ 13021 A atrium surface B overview of internal penial wall C arrangement of penial hooks on proximal part of penis D lateral view of penial hooks E arrangement of penial hooks on middle part of penis F lateral view penial hooks G arrangement of longitudinal oblique vaginal folds.

Figure 24. Radula of specimens A Discartemon tonywhitteni, paratype CUMZ 13001 B Discartemon paurodeviatus sp. nov., paratype CUMZ 13003 C Haploptychius heliakosus sp. nov., paratype CUMZ 13014 D Carinartemis exacutus, specimen CUMZ 13021 E, F Carinartemis sankeyi, specimen CUMZ 13029 E overview of radula and F high magnification of central teeth.