Kryptonesticus georgescuae spec. nov., a blind troglobitic spider species from the mesothermal sulfidic Movile Cave (Romania), is described and illustrated based on two female specimens. The male is unknown. The relationship between this new species and other European species of Nesticidae is discussed.
Movile Cave is located near the town of Mangalia in southeastern Romania, at a distance of two kilometers from the Black Sea shore. It was discovered in 1986 when a 20 m deep artificial shaft intercepted a natural cave passage developed in Sarmatian limestones (12.5 MY). The lower sections of Movile Cave are flooded by thermomineral water (21 °C) rich in reduced chemical compounds such as H2S, CH4 and NH4+. The redox interface created at the water surface between these reduced substances and the oxygen in the cave's atmosphere enables chemoautrophic microorganisms to thrive here creating organic molecules in situ (Sarbu et al. 1996). These represent the food base for a rich and abundant community of aquatic and terrestrial troglobitic invertebrate species, the majority of which are endemic to this ecosystem (Sarbu 2000).
To date, 30 new species of aquatic and terrestrial arthropods have been described from Movile Cave (Sarbu 2000, Nitzu et al. 2016). Three endemic spiders have so far been described from this ecosystem: Agraecina cristiani (Georgescu, 1989), Hahnia caeca (Georgescu & Sarbu, 1992) and Lepthyphantes constantinescui Georgescu, 1989. Movile Cave also hosts a very interesting population of Carniella brignolii Thaler & Steinberger, 1988, which has adaptations for the subterranean environment (Nae 2012), unlike the populations found outside caves in Central and Western Europe (Thaler-Knoflach et al. 2014).
The presence of a troglobitic Nesticidae living in Movile Cave was already reported in 1994 but, unfortunately, the new species could not be described then as two out of the three specimens were juveniles and the third was a female without an opisthosoma (Georgescu 1994). Since the cave was discovered in 1986, only two additional females have been found (Giurginca et al. 2009). So far our attempts to find males were unsuccessful. The genus Kryptonesticus is new for the Romanian fauna; the family Nesticidae is represented by 22 species, belonging to Carpathonesticus and Nesticus. Except Nesticus cellulanus (Clerck, 1757), all species are endemic (Nae 2013).
Material and methods
This study is based on two females from the Movile Cave, deposited in the following institutions:
SMF:
Senckenberg Research Institute, Frankfurt am Main, Germany
ISER:
Institute of Speleology „Emil Racovitza“, Bucarest, Romania.
The specimens were conserved in 70 % ethanol. The dissection was made in glycerol under a Zeiss Stemi 2000 stereo-microscope and mounted for observation in a mixture of gelatin Merk and anhydrous glycerol. An Olympus CH2 with a drawing attachment was used for microscopic examination and drawings. The photos were made on Zeiss Discovery V8 with Canon A 640 camera. Nomenclature follows the WSC (2017). Terminology for the copulatory organs follows López-Pancorbo et al. (2013) and Pavlek & Ribera (2017). Measurements are given in millimeters (mm).
Taxonomy
Family Nesticidae Simon, 1894
Genus Kryptonesticus Pavlek & Ribera, 2017 (type species: K. deelemanae Pavlek & Ribera, 2017)
Kryptonesticus georgescuae spec. nov. (Figs 1–6)
Type data. Holotype: 1 female (SMF), Movile Cave, Mangalia, ROMANIA (geographical coordinates: 43.825N/28.560E), 24 July 1997, leg. Serban M. Sarbu. Paratype: 1 female (ISER, Nr. 5/2017), same locality as holotype, 14–17 March 2008, leg. Augustin Nae.
Etymology. The specific name is a patronym in honor of the Romanian arachnologist Maria Georgescu. She described only the pro soma (female) of this species as Nesticus sp. (Georgescu 1994).
Diagnosis. Completely eyeless, depigmented, troglobiont spider with long legs; can be recognized by genital characters: epigyne and vulva. The spermatheca form and the position of the medial vulval pockets of this new species resembles that of K. henderickxi (Bosselaers, 1998) and K. beshkovi (Deltshev, 1979), but can be distinguished by the position and orientation of insemination ducts (ID in Figs 1 & 4), anteriorly divergent through most of their course, roughly heart-shaped (approximately parallel with a longitudinal axis of symmetry in K. henderickxi and K. beshkovi) and by the shape of the median septum, which is narrower than that of K. henderickxi.
Description of female. Measurements: prosoma length 1.2, width 1.17; opisthosoma length 2.05; sternum length 0.75, width 0.65; total length 2.37. Leg measurements in Table 1. The opisthosoma is oval, the legs long, the first pair is notably longer than the other three. The ratio between the length of the prosoma and leg I is approximately 1:10. Prosoma, legs and opisthosoma pale white (holotype) and pale yellowish-orange respectively (paratype: Fig. 6). Eyes absent. Darker stains discernible on lateral prosoma in paratype female.
Chelicerae: 0.6 mm long, same colour as prosoma, with 3 pro-marginal teeth, median longest (see Georgescu 1994). Frontal part of chelicerae with 4 rigid and serrated setae, brush shaped, flanked by 2 longer setae, delicately feathered. Retromargin of chelicerae with 4 small teeth, decreasing in size from proximal to distal, and with several feathered setae.
Trichobothrium on metatarsus I in position 0.64.
Epigyne and vulva (Figs 1–5): Epigyne is wider than long, in lateral view not prominent and without depressions. The median septum has no prominences or hollows as in K. beshkovi and is narrower in the area where it meets the epigastric furrow than in K henderickxi. The holotype has well-developed vulval pockets and well defined median parts. The spermathecae are lemon-shaped, their longitudinal axes being oblique to the body's longitudinal axis of symmetry. The insemination ducts converge posteriorly. The result is a characteristic heart-shaped overall impression of the epigyne with a small central median septum.
Male. Unknown.
Distribution. Only known from the type locality.
Habitat. The specimens were collected close to the sulfidic lake and in the second bell shaped zone at the end of the cave's main gallery.
Tab. 1:
Leg measurements (mm)
Discussion
The recently defined genus Kryptonesticus currently includes eight species. With the exception of the widespread K. eremita (Simon, 1880), all other species are endemic in Croatia, Montenegro, Bosnia and Herzegovina, Bulgaria, Greece (Crete) and Turkey (Pavlek & Ribera 2017). The species described here from Movile Cave is the ninth belonging to this group. In terms of size, in being totally eyeless, in the length of the legs and in the absence of pigment, K. georgescuae resembles especially K. henderickxi (Bosselaers, 1998) and K. beshkovi (Deltshev, 1979), both from caves in Crete. However, all these features are not necessarily a hint of close relationship, but could be merely a consequence of extreme adaptation to subterranean life. In contrast, the structure of the epigyne may better show the true affinities or differences between species. But also in this respect, K. georgescuae seems to be closer related to these two troglobitic spiders from Crete. The females of K. beroni (Deltshev, 1977) from a cave in Bulgaria (only 370 km air-line distance from Movile Cave) appear rather closely related to the western Balkan species K. deelemanae Pavlek & Ribera, 2017 and K. arenstorffi (Kulczyński, 1914), and show no resemblance to K. georgescuae.
Acknowledgements
The authors would like to thank the members of the GESS team for their efforts towards the protection of Movile Cave and for their help with field work, fauna survey and specimen collection. Movile Cave is a strictly protected site, part of the Natura 2000 sites (Code ROSCI0114 — Mlastina Hergheliei — Obanul Mare and Pestera Movile). We thank also Theo Blick, Peter Jäger, Carles Ribera and Yuri Marusik for helpful comments on the manuscript.
