Landouria strobiloides, Tumpeesuwan & Tumpeesuwan, 2019

Tumpeesuwan, Chanidaporn & Tumpeesuwan, Sakboworn, 2019, First verified record of the genus Landouria Godwin-Austen, 1918 from Thailand (Gastropoda: Stylommatophora: Camaenidae) with description of a new species, Raffles Bulletin of Zoology 67, pp. 298-305 : 301-304

Landouria strobiloides , new species

( Figs. 2–5 ; Table 2)

Aegista sp. : Naewla, 2002: 11, 13–16, 28–31.

Landouria sp. 1 : Lakkhamphan, 2014: 29–32, 62, 68, 73, 78, 105–112.

Landouria sp. : Ounchareon, 2015: 42–44, 71, 74, 76, 78–80.

Landouria sp. : Yingkhamhang, 2016: 18–20, 39–41, 43–45, 47–48, 57–59.

Landouria sp. : Tanmuangpak et al., 2017: 1195, 1197–1199, 1201–1202.

Type material. Holotype: NHMSU-0017 ( Fig. 3 ). Suan Hin Pha Ngam Limestone at an elevation of about 350 m above mean sea level ( Fig. 1 ) in Nong Hin District, Loei Province, northeastern Thailand, 17°3′7″N, 101°44′9″E; 28 June 2014.

Paratypes: NHMSU-00018 (27 shells): collected with holotype at type locality (genital structure in ethanol). ZRC. MOL.14241 (one shell), THNHM-Iv-18175 (one shell), same data as holotype .

Etymology. The specific epithet strobiloides derived from the strobilus, referring to the flagellum of the new species, which looks similar to the strobilus of non-flowering plants because it possesses many tubercles on its surface.

Diagnosis. Body whorl of shell with very sharp keeled, aperture slightly thickened and with a reflexed rim. Flagellum slightly long, club-shaped, with variably-sized tubercles. Base of gametolytic sac enlarged and swollen.

Description. Shell ( Fig. 3 , Table 3): Shell small, 13.4–16.7 mm in width, 7.1–9.6 mm in height, conical-lenticular, color pale brown at early whorls and gradually changing to dark brown on body whorl, with 5.25–5.50 slowly increasing whorls; protoconch consisting of about two whorls, sculpture irregular, very fine; suture rather shallow, last whorl with very sharp peripheral keel, keel with paler color than other parts of shell. Umbilicus very deep and moderately wide (about ¼ of the shell width), showing all whorls. Aperture irregularly ovate, moderately oblique, with little reflected thin margin; columellar margin more reflected.

Body ( Fig. 2 ): Animal without shell lobes. Dark brown to black body and tentacles. Posterior part of foot very short, caudal foss and caudal horn absent.

Radula ( Fig. 4 ): Elongated lanceolate, comprising 100 transverse rows of teeth, with 3–53 teeth in each row. Central teeth unicuspid, lanceolate, and smaller than flanking first lateral teeth. Latero-marginal teeth gradually changing from unicuspid, lanceolate shape to bicuspid, and oblique tricuspid. Genital system ( Fig. 5 ): Prostate gland very long. Uterus long and swollen. Vas deferens long and slender tube, entering the epiphallus apicaly. Epiphallus as long as penis, but shorter than flagellum. Flagellum resembling strobilus of non-flowering plant, with many variously sized tubercles. Penis divided into two portions, both are short and slightly stout. Gametolytic sac connected to free oviduct, comprising three parts, including, small ovate gland at distal end, very long slender tube at middle, and large swollen tube at base. Vagina is longer than penis and epiphallus taken together, of a long-cylindrical in shape. Free oviduct very short, cylindrical. Amatorial organ absent.

Remarks. The genitalia of the new species agree in general detail with the genital anatomy of congeneric species, but it has the longest tubercles on the flagellum within the genus. The anatomy of Landouria differs from Aegista by the absence of a well-developed dart sac, lateral accessory sacs, and mucous glands ( Schileyko, 2004). In Thailand, the snails that have the last whorl slightly descending in front and large umbilicus were assigned to Aegista , but this needs to be confirmed by a study of their anatomical characters.

Biodiversity Heritage Library (www.biodiversitylibrary.org) for old literature made available for us. We are indebed to Cholawit Thongcharoenchaikit, Cyler Conrad, and Barna Páll-Gergely for their kindness to seek and send the rare literature for us. Special thanks to Dr. Jolyon Dodgson for kindly checking the manuscript. We are deeply thankful to the two reviewers Menno Schilthuizen and John Stanisic, and Tan Siong Kiat and Fred Wells for their valuable comments and suggestions. This research project was financially supported by Mahasarakham University (Fast Track 2019- 6207018). The Animal Care and Use Protocal Review No. IACUC-MSU-014/2019.

Figures

Fig. 2. Living specimen of Landouria strobiloides, new species. Photograph by: Benchawan Nahok.

Fig. 3. Empty shell of Landouria strobiloides, new species, holotype (NHMSU-00017). Photograph by: Benchawan Nahok.

Fig. 4. Radula morphology of Landouria strobiloides new species, paratype (NHMSU-00018). A, whole radula; B, close up view of widest part of radula; C, close up view of central part of radula; D, close up view of central and first lateral teeth; E, close up view of left side of radula; F, close up view of right side of radula.

Fig. 5. Genital anatomy of Landouria strobiloides, new species, paratype (NHMSU-00018). pro = prostate gland, ut = uterus, vd = vas deferens, ep = epiphallus, ef = flagellum, p = penis, gs = gametolytic sac, v = vagina, fo = free oviduct.

Fig. 1. Approximate location of type localities of Landouria spp. and type localities of Landouria strobiloides, new species, from Suan Hin Pha Ngam, Loei Province (star in circle).