Caucasopsis letsurtsume Grego & Mumladze, 2020

Grego, Jozef, Mumladze, Levan, Falniowski, Andrzej, Osikowski, Artur, Rysiewska, Aleksandra, Palatov, Dimitry M. & Hofman, Sebastian, 2020, Revealing the stygobiotic and crenobiotic molluscan biodiversity hotspot in Caucasus: Part I. The phylogeny of stygobiotic Sadlerianinae Szarowska, 2006 (Mollusca, Gastropoda, Hydrobiidae) from Georgia with descriptions of five new genera and twenty-one new species, ZooKeys 955, pp. 1-77 : 1

Caucasopsis letsurtsume Grego & Mumladze sp. nov. Plates 9 (2, 3, 10); 10(1, 2, 4); 11(1-4); Figs 11A, B , 12A, B

Type locality.

Georgia • Samegrelo, Chkhorotsku, Letsurtsume, Letsurtsume Cave (ლეწურწუმეს მღვიმე); 42°32'21"N, 42°06'48"E; 180 m a.s.l.; sandy sediment in cave stream.

Material.

Holotype: Georgia • 1 adult, dry; type locality; 10 May 2018; J. Grego, L. Mumladze and M. Olšavský leg.; ISU FM-T010-H Paratypes: same as for holotype; ISU FM-T010-P1/80 dry, SBMNH 633077/5 dry, NHMW 113368/2 dry, HNHM 104679/2 dry, NHMUK 0191335/2 dry, NHMB 563966/2 dry, SMF 358926/2 dry, ZMH 140631/2 dry, MNHN-IM-2016-7896, ZIN 1/510-2020/2 dry, coll. JG F1045/80 dry, coll. Glöer /1 dry. Other material: Georgia • Samegrelo, Chkhorotsku, Kachara Cave (ქაჩარას მღვიმე); 42°31'47"N, 42°10'39"E; 205 m a.s.l.; sandy sediment at cave stream; 10 May 2018; J. Grego, L. Mumladze and M. Olšavský leg.; ISU FM/6 dry and 7 wet, SBMNH 633080, coll. JG F1051/6 dry and 8 wet. Georgia • Samegrelo, Chkhorotsku, Garakha, Savekuo Cavern; 42°30'23"N, 42°08'46"E; 240 m a.s.l.; mud sediments in the spring pond; 12 June 2019; H. Reip leg.; coll. F. Walther/58, coll. J. Grego/3 dry.

Diagnosis.

Caucasopsis letsurtsume sp. nov. differs from its closest relatives by its elongate-oval shell with inflated whorls and open umbilicus with aperture situated more right of the columellar axis (to viewer; shell in apertural pose, apex up). Caucasopsis letsurtsume sp. nov. has a more robust shell with proportionally larger body whorl, smaller umbilicus and with different protoconch surface. Caucasopsis olsavskyi sp. nov. can be differentiated by its different shell shape, closed umbilicus and proportionally smaller aperture situated adjacent to the columellar axis. The shell of C. egrisi sp. nov. is more slender with less inflated whorls and more closed umbilicus. Its shell morphology also resembles Imeretiopsis nakeralaensis sp. nov., which has a more elongate shell, more open umbilicus, less inflated whorls and a proportionally smaller rounded aperture situated more left of the columella (to viewer; shell in apertural pose, apex up).

Description.

Shell: elongate-oval, 1.64 mm high with blunt apex, inflated, 4½ whorls and deep suture. Shell surface smooth, glossy with very faint growth lines. Umbilicus narrow, slit-like. Aperture ovoid in shape, attached to the body whorl only shortly by an indistinct groove. Lateral and columellar profiles of the aperture straight. Lateral profile of the body whorl slightly expanding. Protoconch densely pitted.

Operculum: paucispiral yellowish, horny elongate ellipsoid with excentric nucleus.

Animal body: not known.

Holotype measurements: H-1.64 mm; W-0.94 mm; BH-0.89 mm; BW-0.72 mm; AH-0.60 mm; AW-0.47 mm; CA: 34°.

Anatomy: the penis (Fig. 11A, B ) simple, straight, proximally and medially broad, distally with a moderately long, narrow filament; below the filament a delicately marked outgrowth on the left side.

Etymology.

Name derived from the name of Letsurtsume Cave, the type locality of the species.

Habitat.

Stygobiotic species. Empty shells of the new species were found in the sandy sediments of a cave stream penetrating through Miocene conglomerate deposits. Live individuals were found on a blackish microbial slime covered surface of rocks and gravel at the bottom of cave stream.

Distribution.

Only known from the type locality.

Conservation status.

The number of known locations (3) is no more than 5 and EOO is smaller than 20 km2. There is no reason to suppose that AOO, EOO, number of locations, number of subpopulations or the number or mature individuals are declining however due to its extremely small EOO we assessed as Vulnerable (VU) D2.

Remarks.

The shell shape of the species varies considerably in the only known locality. A second morphotype occurs in the type locality and differs significantly in shell morphology from the typical form. It is characterised by a more inflated-conical shell with 4½ whorls, by proportionally larger body whorl and open umbilicus (Morphotype B, Plates 9 (10); 10(2), Fig. 12A ). Shell morphology is similar to the genus Motsametia Vinarski, Palatov & Glöer, 2014. However, the DNA sequences (COI and H3) of both morphotypes are almost identical (see 1Z82 and 1Z80 on molecular trees in Figs 5 - 7 ); we consider them for the time being as one species with extraordinary morphological variability. The occurrence of the robust morphotype in much lower ratio, and the few available anatomical data do not suggest a sexual dimorphism. No parasites explaining the malformation found.

The population of C. letsurtsume sp. nov. from Kachara Cave differs from the type series by less inflated whorls and more closed umbilicus. The molecular distance within Clade B (Fig. 7 ) is 0.007 for COI, which indicates, that very closely situated hypogean habitats could host typical populations as a result of early allopatric evolution without any recent communication among the two populations.

Figures

Figure 5. Maximum Likelihood tree inferred from mitochondrial COI. Bootstrap supports and Bayesian probabilities are given. Newly obtained sequences in bold.

Figure 7. Maximum Likelihood tree inferred from COI + H 3. Bootstrap supports and Bayesian probabilities are given. Red and green bars indicate results from the ABGD and PTP methods, respectively. Newly obtained sequences in bold.

Plate 9. 1 Caucasopsis olsavskyi sp. nov., Samegrelo, Chkhorotsku, Nazodelavo Cave, holotype 2 C. letsurtsume sp. nov., Samegrelo, Chkhorotsku, Letsurtsume, Letsurtsume Cave, holotype 3 C. letsurtsume sp. nov., Samegrelo, Chkhorotsku, Kachara Cave 4 C. egrisi sp. nov., Samegrelo, Pirveli Balda, Motena Cave form 5, 6 C. egrisi sp. nov., Samegrelo, Pirveli Balda, spring in village: 5 holotype 6 paratype 7 Imeretiopsis prometheus sp. nov., Imereti, Kumistavi, Prometheus Cave, holotype 8 I. cameroni sp. nov., Imereti, Kutaisi, Iazoni (Tskhal-Tsiteli) Cave Spring, holotype 9 I. nakeralaensis sp. nov., Imereti, Tikibuli, spring above Tikibuli-Nikortsminda road to Nakerala pass, holotype 10 C. letsurtsume sp. nov., Samegrelo, Chkhorotsku, Letsurtsume, Letsurtsume Cave, robust morphotype. The numbers correspond to individuals, and the letters represent the different views of the same individual. Photograph J. Grego.

Figure 11. Morphology of the penis A, B Caucasopsis letsurtsume sp. nov., Samegrelo: A ventrally B dorsally C Imeretiopsis gorgoleti sp. nov. Photograph A. Falniowski and A. Rysiewska.

Figure 12. A, B Caucasopsis letsurtsume sp. nov., Samegrelo, Chkhorotsku, Letsurtsume, Letsurtsume Cave, specimens used for molecular studies. Photograph A. Falniowski.