Research Article |
Corresponding author: Jozef Grego ( jozef.grego@gmail.com ) Academic editor: Vincent Prié
© 2021 Jozef Grego, Vladimir Pešić.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Grego J, Pešić V (2021) First record of stygobiotic gastropod genus Travunijana Grego & Glöer, 2019 (Mollusca, Hydrobiidae) from Montenegro. Subterranean Biology 38: 65-76. https://doi.org/10.3897/subtbiol.38.64762
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The stygobiotic genus Travunijana Grego & Glöer, 2019 is one of the typical elements of the subterranean freshwater fauna of the Trebišnjica River Basin in Bosnia and Hercegovina. The previous records of the genus suggested that its distribution was limited to the basin of the Trebišnjica River and adjacent parts of the southwestern Neretva Basin. In this paper we describe a new species, Travunijana djokovici sp. nov. from “Vriješko Vrelo” spring in Montenegro. The recent finding of a new species in the Skadar Lake basin (The Drin River system) suggests the possibility of a subterranean route between the Trebišnjica and the Drin drainages, indicating that likely the endemic subterranean fauna in both basins has a lower level of historical isolation than has been considered so far.
Bosnia, cave, karst-water, Plagigeyeria, spring
The genus Travunijana Grego & Glöer, 2019 was only recently recognised based on its characteristic anatomy and shell morphology (
Distribution of the Genus Travunijana Grego & Glöer, 2019 (Green dots 1–17) and type locality of Travunijana djokovici sp. nov. (Red dot 18). Grey: Permeable karstified carbonates; White: impermeable unkarstified bedrocks; Yellow: Permeable alluvial deposits; Orange: sand deposits with limited permeability for subterranean gastropod dispersal. Light blue ring: karst springs; Blue ring with green centre and black X: estavelles; Dark green diamond: submarine or brackish karst spring.
The distribution pattern of the genus Travunijana appears to reflect well the relative isolation within the hydrogeological conditions with possible faunal dispersal pathways to adjacent basins. The genus is a typical element of the stygobiotic and crenobiotic fauna of the Trebišnjica River Basin, as a part of a remarkable and unique diversity that characterises the central part of the Dinaric Karst. The latter region is home to a number of typical stygobiotic species such as the olm Proteus anguinus (Laurenti, 1768), the bivalve Mytilopsis kusceri (Bole, 1962) and a polychaete, Marifugia cavatica (Absolon & Hrabě, 1930), whose southernmost distribution range is bounded by the Trebišnjica River Basin (see
Recently,
The subterranean drainage boundaries between the Trebišnjica River Basin and Drin Basin together with the Kotor Bay drainage area is hydrogeologically well defined (
Several freshwater genera can be found on both sides of the drainage boundaries, but are represented in them by different species (
Nevertheless, there is evidence for the existence of an underground hydrological connection between the Trebišnjica Basin and the neighbouring Skadar Lake Basin. A remarkable example is the existence of an intermittent karst-water connection which seasonally drains the water from the Skadar Lake Basin through the Gornjepoljski Vir Estavelle (628 m alt.) towards the “Nikšićko Vrelo” spring (468 m alt.) near Bileća in the Trebišnjica Basin. This unique subterranean route represents a distance of 38 km of aerial distance and 189 m elevational difference. The latter route is an aquatic migratory corridor for some of the stygobiotic species such as Plagigeyeria zetatridyma Schütt, 1960 (confirmed by empty shells; see Schütt 1970) and Montenegrospeum bogici (confirmed by molecular data,
The studied material was collected during a field trip in April 2019 to both Montenegro and Bosnia and Hercegovina. The samples were collected by wet sieving (
JG Collection Jozef Grego;
H Shell height;
W Shell width;
WB Width of the body whorl;
HA Aperture height;
WA Aperture width.
Family Hydrobiidae Stimpson, 1865
Holotype: Type locality: J. Grego, G. Jakab. M. Olšavský, M. Kováčiková leg. 20.04.2019, NHMW1132628.
Paratypes: same data: NHMW113629/ 2 dry specimens, HNHM105300/ 2 dry specimens and 37 dry specimens T 1293 in coll. Grego.
Holotype H 3.23 mm; W 1.77 mm; WB 1.46 mm; HA 1.44; WA 1.14.
Paratype H 3.33 mm; W 1.86 mm; WB 1.46 mm; HA 1.49; WA 1.26.
Same locality data: 12 fragmented shells in coll. JG T 1294.
The faintly pitted protoconch clearly distinguishes the new species from the members of the genus Plagigeyeria and indicates its position within the genus Travunijana. Moreover, the weakly sinuated columellar margin also supports its generic assignment.
Compared to the most closely related Travunijana gloeri Grego, 2020, T. vruljakensis Grego & Glöer, 2019 and T. ovalis (Kuščer, 1937), all from Trebišnjica Basin (Fig.
Shell: elongate-conical, milky whitish colour, periostracum yellowish, consisted of five moderately convex whorls with a semi-deep suture. The surface covered by dense, regular weak axial ribs. Aperture elongate, lens-like, its axis declined from the columella; the labral peristome straight in its lateral profile and slightly outward curved and callous. The columella peristome weakly sinuated at its middle part. The siphon and anal groves clearly indicated at the tips of elongated aperture. The umbilicus is tiny, almost closed and hidden behind the reflected columellar margin.
Protoconch very faintly and densely pitted, at the penultimate whorls smoothly transferring through weak malleated structures, faint regular growth lines into a regular weak ribbing covering the rest of the teleoconch.
The new species is named after Novak Djokovic a famous Serbian tennis player to acknowledge his inspiring enthusiasm and energy.
Montenegro; only known from the type locality.
The type locality is a medium sized karst spring with stable water outflow, situated at the border of a limestone massif and alluvium of the Matica River. The status of empty shells washed out of the spring-head suggests its stygobiont habitat inside the karst conduit. The new species was syntopic with Plagigeyeria cf. montenegrina Bole, 1961, Bracenica cf. spiridoni Radoman, 1973, Zeteana sp. and Montenegrospeum cf. bogici (Pešić & Glöer, 2012) at its type locality thanatocoenosis.
Number of known locations (1) fewer than 5 and AOO (area of occupancy) smaller than 20 km2. There is no reason to suppose that AOO, EOO (extent of occurrence), number of locations, number of subpopulations or the number or mature individuals are declining or extremely fluctuating. However, due to small AOO it is assessed as Vulnerable (VU) D2 species.
The find-site of the stygobiotic Travunijana djokovici sp. nov. in the Skadar lake Basin belonging to the Southeastern Adriatic Ecoregion, is located 60 km southward from the main distribution range of the genus in Hercegovina and south Dalmatia. This represents not only a significant range extension of the genus (
However it is known that the drainage boundaries do not represent absolute barriers for the dispersal of subterranean animals, and as we mentioned in the Introduction, there is at least one such karst conduit intermittently cross-connecting both basins and draining water from Gornjpoljski Vir Estavelle (the Drin River Basin) to “Nikšićko Vrelo” spring in the Trebišnjica Basin (
On the other hand, the recent finding of the live specimens of Montenegrospeum bogici, a species that was supposed to be limited to the Skadar Lake basin (the Drin River system), in springs located far downstream and upstream of Bileća (
All the above mentioned observations indicate occurrence of only one dispersal mode from the Skadar Lake Basin to the Trebišnjica Basin through the above explained connection route. On the other hand, for Travunijana, we can speculate a similar dispersal mode though the same route but in an opposite direction, from Trebišnjica to Zeta River Basin, which probably occurred under different historical hydrological conditions. Despite the intensive sampling of the stygobiont malacofauna of the Skadar lake basin, which began in the middle of the last century (
The permanent submersion of the Trebišnjica spring group at Bileća by Lake Bilećko in the 1970s (when the Trebinje 1 Hydroelectric Power Plant was completed) has made it impossible to find living specimens of stygobiont species for molecular analysis and, consequently, no molecular evidence of the gene flow between two basins which would confirm the functionality of this migration route. Therefore, the origin and dispersal route of T. djokovici sp. nov. still remains a mystery. We cannot exclude the existence of similar divergent channels between the basins during the geological history of the area, especially knowing that the present hydrological situation does not necessarily have to reflect the paleohydrology. Last, but not least, anthropogenic changes in the directions of karst-water flows as a result of several large dams and diversion of river flows, with the aim of diverting water to power plants (on the rivers Zeta and Trebišnjica) make the understanding of possible migration routes of stygobionts even more difficult.
We would like to express our thanks to Daniel Geiger and Vanessa Delnavaz for their support with SEM imaging; to Anita Eschner and Sara Schnedl (