Camaena saturnia ( Gould, 1846 )

Sutcharit, Chirasak & Panha, Somsak, 2021, Overlooked for a century: Taxonomic status of Camaena saturnia (Gould, 1846) (Eupulmonata: Camaenidae), Raffles Bulletin of Zoology 69, pp. 253-261 : 254-258

Camaena saturnia ( Gould, 1846)

( Figs. 1–3 )

Helix saturnia Gould, 1846: 98 , 99, type locality: Tavoy [Dawei, Tanintharyi Region, Myanmar]; 1862: 198; Pfeiffer, 1853: 250; 1859: 199, 300; Hanley & Theobald, 1870: 13, pl. 25 fig. 3; Johnson, 1964: 145.

Helix (Phania) saturnia – Martens in Albers, 1860: 157.

Helix (Camaena) saturnia – Pilsbry, 1891: 203, 204, pl. 60 fig. 5.

Camaena saturnia – Pilsbry, 1894: 104, pl. 60 fig. 5; Gude, 1914: 151, 152; Richardson, 1985: 77, 78.

Hemiplecta ? saturnia – Godwin-Austen, 1898: 73.

Camaena ngocthachi Huber in Thach, 2020: 86, figs. 932–934, type locality: suburb of Phang Nga city, Phang Nga Province, South Thailand. New synonym.

Material examined. Possible syntype NHMUK 20210010 ex. Cuming collection (1 shell; Fig. 2A ) from Tavoy. NHMUK 1888.12 .4.2004 ex. Theobald collection (1 shell; Fig. 2B ) from Tenasserim. Holotype of C. ngocthachi , MNHN-IM-2000-35587 ( Fig. 2C ) from Suburb of Phang Nga City , Phang Nga Province, Thailand. Limestone outcrop at Phra (Buddha) Cave , Lenya National Park , Tanintharyi Township, Tanintharyi Region, Myanmar (11°13′46″N, 99°10′34″E): CUMZ 7434 (1 broken shell). Klong Laan , Suratthani Province , Thailand: CUMZ 2562 (1 shell; height 31.8 mm, width 53.5 mm). Pala-u waterfall, Phetchaburi Province, Thailand: CUMZ 2561 (2 intact + 1 broken shells; height 29.4 mm, width 52.0 mm, height 26.9 mm, width 51.4 mm), CUMZ 4152 (1 broken shell). Samet Chun Waterfall , Khanom District, Nakhon Sri Thammarat Province, Thailand (9°08′09.2″N, 99°50′53.2″E): CUMZ 7433 (1 ethanol preserved + 1 juvenile shell, height 25.3 mm, width 47.7 mm; Figs. 2D , 3A, B, D, E ).

Shell. Shell dextral, relatively thin, and thick-lens-shaped ( Fig. 2 ). Apex obtuse; embryonic shell rather large, about 2½ whorls, sculptured with regular parallel growth lines; following whorls nearly smooth-surfaced with fine and regular growth lines, and tiny nodules spread on last whorl. Shell reddish-brown to dark brown in colour; periostracum thin and transparent. Whorls 5 to 6 increasing regularly. Spire dome-shaped to little elevated; suture very wide and shallow to little impressed. Last whorl large and angular with strong peripheral keel. Aperture wide, rhomboid-shaped, whitish inside, and connected by thin whitish to transparent parietal callus. Peristome white to brownish, little thickened, and widely expanded. Columella dilated, whitish, and slightly curved. Umbilicus perforated and widely opened.

Genitalia. Atrium (at) short. Penis (p) somewhat slender and long. Epiphallus (e) relatively short and folded. Penial retractor muscle (pr) long and attached near penis. Flagellum (fl) very long, nearly equivalent to length of penis and epiphallus, and coiled terminally. Vas deferens (vd) narrow tube passing forward from free oviduct and joining at junction of epiphallus and flagellum ( Fig. 3A ). Internal wall of penis corrugated and exhibiting series of thin longitudinal penial pilasters (pp), which form fringe around penial verge. Penial verge (pv) long-conical-shaped, and with nearly smooth surface ( Fig. 3B ).

Vagina (v) cylindrical, shorter than penis, and held in position by a series of muscle filaments arising from foot floor ( Fig. 3A ). Gametolytic duct (gd) very long, similar diameter as vagina, then tapering to a narrow and long tube, and connected to swollen and elliptical gametolytic sac (gs). Free oviduct (fo) very short. Oviduct (ov) not enlarged. Albumen gland (ag) slightly enlarged and tongue shaped. Hermaphroditic duct (hd) twisted, curved, and connected to alveoli hermaphroditic gland (hg). Internally, vagina possesses irregular longitudinal vaginal pilasters (vp) that exhibit a series of swollen and smooth ridges. Vaginal pilasters are apparently uniform throughout entire vaginal chamber ( Fig. 3B ).

Radula. Radula arranged in a nearly straight row with about 137 teeth with the formula 68-(21-22)-1-(21-22)-68. Central tooth unicuspid with obtuse cusp ( Fig. 3D ). Lateral teeth unicuspid, oblique-shaped, and with obtuse cusp ( Fig. 3D, E ). Marginal teeth starting around teeth no. 21 to 22. Inner marginal teeth bicuspid; ectocone large with dull cusp; endocone very small, located near the tip and with pointed cusp ( Fig. 3E ). Outer marginal teeth small and tricuspid; endocone and mesocone with rather large and pointed cusps; ectocone very small and located at base of the teeth ( Fig. 3E ).

Distribution. The historical record of this species is known only from the type locality “Tavoy” and the broad geographical area of “Tenasserim” ( Hanley & Theobald, 1870; Pilsbry, 1891; Gude, 1914). Both records are currently located in the Tanintharyi Region, southern Myanmar

( Fig. 1 ). A recent study collected records from several localities along the east coast of the Tenasserim Range in Petchaburi , Suratthani, Phang Nga and Nakhon Sri Thammarat Provinces, Thailand. The southern limit of the distribution of the species is possibly in Phang Nga Province .

Remarks. Although C. saturnia has a wide distribution, ranging from Myanmar to Thailand, its populations are low in density and quite rare. In this study, only four heavily worn shells and one live specimen were collected from the non-limestone areas examined. The live snail was found among leaf litter with decaying leaves and rotten logs in primary forest. Gradually increasing deforestation is probably the main reason for the restricted habitats and population decline of this species.

The nominal species Camaena ngocthachi was recently described from southern Thailand based on one holotype now deposited in the MNHN collection and two paratypes housed in the author’s personal collection. The holotype MNHN-IM-2000-35587 ( Fig. 2C ) is a worn specimen showing no informative character differences from the syntype of C. saturnia ( Fig. 2A ) and other specimens from nearby areas ( Fig. 2B, D ). Therefore, we do not hesitate to synonymise Camaena ngocthachi as a junior subjective synonym of C. saturnia .

Pilsbry (1891) stated that C. saturnia has a similar shell to C. ochthoplax ( Benson, 1860) . For comparison, C. saturnia has a smaller shell size (width about 51 mm) with a strong peripheral keel on the last whorl, widely opened umbilicus, nearly smooth shell surface, and a very shallow suture. In contrast, C. ochthoplax ( Fig. 4A ) has a larger shell (width about 68 mm), a rounded last whorl, rimate umbilicus, shell surface with strong growth lines and rough with malleations, and impressed suture. Gude (1914) also noted that C. saturnia is similar to C. vanbuensis Smith, 1896 . However, the recently examined type specimen clearly shows no similarity between them. Camaena saturnia has a thinner and smaller shell, a widely opened umbilicus, and nearly smooth or thin growth lines of the shell surface. On the other hand, C. vanbuensis ( Fig. 4C ) has a relatively larger and thicker shell, nearly closed umbilicus, and shell surface with strong malleated surface.

The other two umbilicate species, C. pachychila ( Smith, 1893) and C. suprafusca Möllendorff, 1898 , also closely resemble C. saturnia . However, C. pachychila ( Fig. 4B ) from Vietnam is distinct in having narrow brownish spiral bands on the periphery and below the periphery surrounding the umbilicus and more convex whorls. In contrast, C. suprafusca ( Fig. 4D ) from Laos has a wide-angled peripheral keel, dome-shaped spire, last whorl inflated below the periphery, and reddishbrown spiral bands on the periphery and below the periphery surrounding the umbilicus (for further comparison, see Inkhavilay et al., 2019: fig. 47e). However, C. suprafusca has been treated as a junior synonym of C. pachychilus without clear evidence ( Páll-Gergely et al., 2020). The molecular phylogenies of the umbilicate group ( Wang et al., 2020) and sinistral group ( Ai et al., 2016; Ding et al., 2016) clearly indicate that the traditional morphological-based classification using shell and genitalia characters is effective and able to differentiate species. In addition, field observation and a genetic study both revealed that Camaena species tend to be locally endemic and are restricted to primary forest, which may play an important role in their isolation ( Ding et al., 2016; Wang et al., 2020). Therefore, the opinion of Páll-Gergely et al. (2020) is still provisional; we treat C. suprafusca as a distinct species and await further data from genitalia anatomy and molecular studies.

Figures

Fig. 1. Distribution range of Camaena saturnia. Open dot indicates the approximate type locality of the species, “Tavoy” [Dawei, Tanintharyi Region, Myanmar].

Fig. 2. Shell characteristics of Camaena saturnia. A, possible syntype NHMUK 20210010 ex. Cuming collection from Tavoy; B, specimen NHMUK 1888.12.4.2004 ex. Theobald collection from Tenasserim; C, holotype of Camaena ngocthachi, MNHN-IM-2000-35587; D, specimen CUMZ 7433 from Nakhon Sri Thammarat, Thailand.

Fig. 3. Camaena saturnia. A, B, genitalia of specimen CUMZ 7433. A, whole genitalia; B, internal sculpture of penis and vagina. C, protoconch sculpture, specimen CUMZ 7433. D, E, radular morphology of specimen CUMZ 7433. D, central teeth with the first to fifth lateral teeth; E, lateral teeth with the tricuspid marginal teeth transition and outer marginal teeth. Central tooth indicated by ‘C’; numbers indicate the order of lateral and marginal teeth.

Fig. 4. Shell characteristics for further comparison. A, Camaena ochthoplax (Benson, 1860), specimen SMF 26478/1 from Naga Burge; B, Camaena pachychila (Smith, 1893), syntype NHMUK 1893.2.26.2.3 from Annam; C, Camaena vanbuensis Smith, 1896, syntype NHMUK 1896.1.25.1 from Vanbu, Tonkin; D, Camaena suprafusca Möllendorff, 1898, lectotype SMF 8105/1 from Boloven, Annam.