Perrottetia aquilonaris Siriboon & Panha

Siriboon, Thanit, Sutcharit, Chirasak, Naggs, Fred & Panha, Somsak, 2013, Three new species of the carnivorous snail genus Perrottetia Kobelt, 1905 from Thailand (Pulmonata, Streptaxidae), ZooKeys 287, pp. 41-57 : 47-49

Perrottetia aquilonaris Siriboon & Panha sp. n. Figs 2B3 D–H4D–F5H–M 6BTable 1

Type material.

Holotype CUMZ 5003 (Fig. 3D). Measurement: height 3.9 mm, shell width 6.6 mm, and with 6 whorls. Paratypes NHMUK 20130064 (2 shells), SMF 341487 (1 shell), CUMZ 5004 (1 shell).

Other material examined.

Tam Phra Bumpenboon, Phan, Chiangrai: CUMZ 5005. Wat Tam Pha Jaruey, Pa-daet, Chiangrai: CUMZ 5006. Tam Maesuai, Maesuai, Chiangrai: CUMZ 5007. Tam Chiangdao, Chiangmai: CUMZ 5008. Pha Chu, Nanoi, Nan: CUMZ 5009. Tam Pha Nangkoi, Rongkwang, Phrae: CUMZ 5010.

Type locality:

Wat Tam Pha Plong, Chiangdao, Chiangmai, Thailand, 19°24'7.3"N, 98°55'5.6"E.

Diagnosis.

Perrottetia aquilonaris sp. n. can be distinguished from the similar south Indian species Perrottetia watsoni (Blanford, 1860) and Perrottetia beddomii (Blanford, 1899) by its smooth shell surface and the presence of a sinulus and a bifid columellar lamella. In comparison, Perrottetia beddomii possesses a supracolumellar lamella, while Perrottetia watsoni hasa second parietal lamella adjacent to the first parietal lamella (Blanford 1860, 1899, Kobelt 1906). Perrottetia gudei from North Vietnam differs from the new species in its larger, oblique-heliciform shell, which is less deviated from the vertical axis. A fine transverse ridge is present at the suture. A sinulus is absent, the peristome is much thicker, and bifid columellar lamella is absent ( Fulton 1915). The genital system of Perrottetia gudei differs from that of this new species by possession of a long and slender penis, an entirely free long oviduct, a gametolytic duct and sac extending as far as the albumin gland, the absence of seminal vesicles and a more scattered arrangement of penial hooks ( Schileyko 2000).

Description.

Shell suboblique-heliciform, white and translucent; teleoconch with 6 whorls, spire convex, suture indistinct; shell surface glossy, with transverse ridges diminishing below the periphery; embryonic shell large, about 2½ whorls, with smooth surface; following whorls regularly expanding; shell periphery shouldered, in apertural view left periphery of the penultimate whorl extending beyond the diameter of the last whorl; last whorl axially deflected; two deep and short longitudinal furrows present; umbilicus narrow (Fig. 3D); aperture subcircular, peristome discontinuous, thickened and expanded, short sinulus present, sometimes with a longer and tapering sinulus (Fig. 3H); apertural dentition consisting of one strong first parietal lamella, a small second parietal lamella separated at right angles, one small upper palatal lamella, one large palatal lamella, one basal lamella and a bifid columellar lamella (Fig. 3E).

Radula: Teeth arranged in anteriorly V-shaped rows, each row containing 21-23 teeth with the formula (10-11)-1-(10-11); central tooth small, sharp, triangular with pointed cusp; lateral and marginal teeth undifferentiated, unicuspid and lanceolate; lateral teeth gradually reduced in length and size, outer teeth much smaller and shorter than inner teeth (Fig. 6B).

Genital organs: Atrium (at) short; penis tripartite, proximal part long and narrow, central section globular with a thick muscular wall, distal section again long and narrow; penial sheath (ps) thin, extends about half of total penis length; penial sheath retractor muscle (psr) very thin, originating at the atrium, inserting distally on penial sheath (Fig. 4D); vas deferens (vd) passes through about one-fifth of penial sheath length before entering into penis distally (Fig. 4E); penial retractor muscle (pr) thin and very long, inserting at penis and vas deferens junction; internal wall of atrium generally smooth with numerous pores (Fig. 5H); penial wall with scattered and pale brown penial hooks about 24 hooks/200 µm 2; hooks located on papillae (pl), papillae separated by low reticulated folds; penial hooks of small size (<0.02 mm in length), expanding at base, tip sharp and curved towards genital orifice (Figs 5 J–L); vagina (v) short, stout, about a seventh of total penis length; gametolytic duct (gd) long but not extending as far as albumin gland; gametolytic sac ovate (gs); proximal free oviduct (fo) stout and distally enlarged; oviduct (ov) enlarged and folded; prostate gland inconspicuous and bound to oviduct (Fig. 4D); talon (ta) small, very short and club shaped; hermaphroditic duct (hd) bearing long seminal vesicle (sv) about one and half times longer than the length from talon to branching point of seminal vesicle (Fig. 4F); vaginal wall with parallel vaginal folds; vaginal hooks absent (Fig. 5M).

Animal: Live specimens exhibit yellowish reticulated skin, and pale yellowish tentacular retractor muscles are visible through the semi-transparent body (Fig. 2B).

Etymology.

The specific epithet is from the Latin “aquilonaris” meaning "north or northern". It refers to the distribution range of this new species in northern Thailand.

Distribution.

This species is known from severallimestone areas in northern Thailand. The animals can be found in altitudes up to 200 meters above mean sea level.

Remarks.

Some variation has been observed in the sinulus and the bifid columellar lamella. Populations from Chiangmai and Chiangrai Provinces possess a longer and tapered sinulus (Figs 3G, H). Specimens collected between those two provinces have a shorter sinulus, and specimens from Chiangmai possess a large bifid columellar lamella (Fig. 3H).