Laoennea renouardi Jochum & Wackenheim, 2020

Jochum 1,2,3, Adrienne, Bochud 1,2, Estee, Favre 3, Adrien, Ferrand 4, Marina & Wackenheim 5,6, Quentin, 2020, A new species of Laoennea microsnail (Stylommatophora, Diapheridae) from a cave in Laos, Subterranean Biology 36, pp. 1-9 : 1

Laoennea renouardi Jochum & Wackenheim sp. nov. Fig. 1A-J

Type locality.

Laos, Vientiane Province, Tham Houey Yè, 2.7 km W of Vang Vieng, 245 m a.s.l., 18°56'11"N, 102°25'28"E, collected 150 m from cave entrance in a horizontal gallery usually flooded during the rainy season (18°56'15"N, 102°25'25"E) (Fig. 3 ), 9 March 2019, M. Ferrand leg.

Type material.

Holotype: 1 shell, SH: 1.80 mm, SW: 1.00 mm, PH: 0.54 mm, PW: 0.54 mm; Fig. 1A-J ( NMBE 565863).

Diagnosis.

Shell tiny, compact and less elongate than the type species, Laoennea carychioides , conical-ovate with fewer whorls. Penultimate whorl inflated above the narrower last whorl. Parietal lamella protrudes slightly beyond peristome margin, long, continuing deep into shell. Sinulus in line (on the same plane) with entire peristome and not shifted laterally.

Description.

Shell tiny, apical part of the shell dome-shaped, shell white and transparent when fresh, compact with inflated penultimate whorl bulging above the narrower last whorl, shell bears 5 convex whorls separated by a deep suture and a thin white band directly below at the transition of each new whorl; protoconch not clearly discernable. Entire shell glossy, finely pitted, teleoconch streaked by occasional, uneven growth lines. Thin, widely spaced ribs behind peristome extend 1/6 the surface of the last whorl and overlap radial striations of varying thickness embedded within the shell matrix of the last whorl. Aperture heart-shaped, reinforced by thick callus; parietal shield extends to over half the height of the preceding whorl. Apertural dentition three-fold with the parietal lamella and the upper palatal tooth well-formed but not swollen, together forming a round sinulus. Upper columellar side of the aperture shows slight angularity and a low, weak columellar denticle close to peristome. Sinulus opening not shifted laterally but on the same plane as the rest of the aperture. Parietal lamella slender, twisting slightly to the right at the front of the aperture, directed towards the opposing palatal denticle. The parietal lamella forms a smooth ridge which narrows as it continues deep into the shell. Peristome expanded and slightly reflected; umbilicus slit-like, straight columella visible through transparent shell.

Etymology.

This species is dedicated to the French speleologist, Louis Renouard, who is a cave and karst specialist of central and northern Laos and who significantly contributed in the discovery, exploration and mapping of the two caves from which both Laoennea species derive.

Distribution.

Known only from the type locality, Tham Houey Yè cave.

Ecology.

Laoennea renouardi sp. nov. was collected 150 m from the cave entrance in a horizontal gallery usually flooded during the rainy season (18°56'15"N, 102°25'25"E). The ambient temperature outside the cave on 9 March 2019 at time of collection was 34 °C. Inside the cave, the temperature measured 26 °C. Tham Houey Yè is located within the Vang Vieng karst region comprising numerous cavities formed in Upper Permian limestone ( Dussault 1919; Saurin 1962; Hédouin and Renouard 2000) and harbours 11.2 km of galleries ( EEGC et al. 2003; EEGC et al. 2005) (Fig. 3 ).

Until fresh individuals can be found, it is not yet clear if Laoennea is cavernicolous/cave-dwelling or not. The lack of pigment in the transparent fresh shells of L. renouardi and the paratype of L. carychioides suggests a subterranean ecology. Other taxa encountered March 2019 in Tham Houey Yè during the Phouhin Namno expedition ( EEGC 2019) and which are mostly still unidentified include: 1 juvenile cameanid snail, singular members of Rhaphidophoridae , Zarcosia sp., Collembola, and different unidentified harvestmen ( Arachnida, Opiliones) as well as members of the spider genera, Sinopoda and Heteropoda ( Arachnida, Araneae). The geoecological context of Tham Houey Yè is indicated also in its name: “Houey” means stream or river in the Kra-Dai language of the Lao people and “Yè” is the name of the river.

Conservation.

Subterranean snails have a low tolerance to pollution and habitat disturbance. Tham Houey Yè is situated very close to a long-time popular tourist cave, Tham Pha Leusi (18°56'06"N, 102°25'27"E, 250 m a.s.l.) (Fig. 3A ). The year after its discovery in 2000, Tham Houey Yè was opened for tourism. Direct tourist activity fortunately ceased a few years later due to the inconvenient necessity of having to crawl into the narrow opening of the cave (Fig. 3D ). The proximity of these two caves, and the sharing of the wear and tear impact associated with tourism in addition to potentially polluted allogenic runoff draining into their karst cavities, would very probably threaten Laoennea renouardi sp. nov. as well as other subterranean fauna. It is paramount that conscientious regulation of tourism and water management schemes guard against this potential threat.

Figures

Figure 1. Comparison between species. Laoennea renouardi sp. nov. A-J holotype (NMBE 565863) K, L holotype and paratype shells of Laoennea carychioides Pa ́ ll-Gergely, A. Reischu ̈ tz & Maassen, 2020 (NHMW 113107). Scale bar: 1 mm.

Figure 3. Speleological map and ecology of Tham Houey Ye (18 ° 56 ' 11 " N, 102 ° 25 ' 28 " E) including 11.2 km of caverns A shell of L. renouardi sp. nov. on moist substrate (image: M. Ferrand) and map of the cave showing the entrance to the cave, the collection site of L. renouardi sp. nov. marked by a red star and the entrance to the nearby touristic cave of Tham Pha Leusi. Tiny question marks on the map indicate uncertainties regarding the continuation of unexplored tiny galleries (EEGC et al. 2003, 2005) B landscape view from the entrance of Tham Houey Ye (image: M. Ferrand) C west gallery (image: M. Ferrand) D natural upper entrance of the cavern system Tham Houey Ye - Tham Pha Leusi (image: M. Ferrand) E active section of Ye River during the dry season in Tham Houey Ye (image: J- F. Fabriol).