Porrhomma ozrenense, Komnenov, 2025

Komnenov, Marjan, 2025, A new troglobitic species of the genus Porrhomma (Araneae: Linyphiidae) from Bosnia and Herzegovina with taxonomic remarks on its relative Porrhomma egeria Simon, 1884, Zootaxa 5642 (2), pp. 178-190 : 179-181

Porrhomma ozrenense sp. nov.

Figs 2–16

Type material. Holotype ♂ ( NHMW-ZOO-AR-30349 ), BOSNIA AND HERZEGOVINA, Maglaj, Ozren Mt , 438 m a.s.l., Mokra Megara cave , 18.08.2022, leg. M. Komnenov. Paratypes: 1 ♂ ( NHMW-ZOO-AR-30350 ) and 3 ♀♀ (♀ NHMW-ZOO-AR-30351 ; ♀ NHMW-ZOO-AR-30352 ; ♀ NHMW-ZOO-AR-30353 ), same data as holotype .

Diagnosis. The main big difference that immediately distinguishes P. ozrenense sp. nov. from all other European species (except P. frasassianum Weiss & Sarbu, 2021 , P. matevskii Komnenov, 2025 , P. profundum M. Dahl, 1939 and P. rosenhaueri (L. Koch, 1872)) is that it is a troglobite species with eyes extremely reduced in size ( Fig. 10 ). From P. frasassianum , P. matevskii , P. profundum and P. rosenhaueri , the only troglobitic species in Europe characterized so far (Komnenov in press; Růžička 2018), it differs by very distinct morphological differences in male and female genitalia. It can be easily separated from P. frasassianum and P. matevskii , the only eyeless representatives in the genus, by the presence of eyes ( Fig. 9 ) and by the different shapes of the velum and the spermathecae in males and females respectively. From P. profundum males differs by the unmodified apical part of the embolus (swollen in P. profundum , see fig. 27B in Růžička 2018) and the females by the different shape of the spermathecae. From P. rosenhaueri males differ by the velum being wider and massive (extremely narrow and minute in P. rosenhaueri , see fig. 53B in Růžička 2018) and the females by the different shape of the appendices and the spermathecae.

The new species is closely related to P. egeria from which it can be distinguished by the triangular and pointed anterior process of the embolic plate (more rectangular in P. egeria cf. Fig. 8 vs fig. 21B in Růžička 2018) and by the semi-circular shape of the velum in males (more or less S-shaped in P. egeria , cf. Figs. 7–8 vs fig. 21B in Růžička 2018). Females of Porrhomma ozrenense sp. nov. can be distinguished from those of P. egeria by the circular atrium of the epigyne (considerably broader than long in P. egeria , cf. Fig. 12 vs fig. 21C in Růžička 2018) and by the shape and direction of the appendices being relatively straight and directed towards cuticle in dorsal view (distinctly curved and directed to sides in dorsal view in P. egeria , cf. Figs 13, 15 vs fig. 21D-F in Růžička 2018).

Etymology. The specific name refers to the type locality—the Ozren Mountain; adjective.

Description. Male holotype. Habitus as in Figs 2 , 17 . Total length 2.16, prosoma length 1.04, width 0.76, chelicerae length 0.36, abdomen length 1.12 width 0.68. Clypeus and frontal part of carapace with relatively long and thin hairs. Eyes extremely reduced in size, without black rings around.

Color: chelicerae and prosoma dark yellow, legs and opisthosoma grey-white.

Legs long (see Table 1 ), ventral side of legs with long setae ( Fig. 2 ). Femur I with a dorsal spine located at 0.61 and one prolateral spine; femur II only with one dorsal spine, located at 0.46; femur III and IV with no spines. Patella I–IV with a long spine. All tibiae with two dorsal spines, additionally tibia I with one prolateral one retrolateral spine, tibia II with one retrolateral spine. Metatarsi with no spines, metatarsi I–III with trichobothrium, position: I = 0.54, II = 0.40, III = 0.46.

Pedipalp as in Figs 4–9 . Palpal tibia with two retrolateral and one prolateral trichobothria ( Fig. 4 ). Retrobasal region of cymbium with a short, dome-shaped apophysis (CA) ( Fig. 5 ). Paracymbium hook-like, proximal section covered with relatively short bristles ( Fig. 4 ). Embolus (E) long and curved with broad velum (V), ending above anterior process of embolic plate (AP). Apical edge of velum semi-circular in shape, lower anterior edge of velum forming a long and massive bifurcated tooth (BT), more clearly visible in prolateral view through the transparent anterior extension of embolic plate ( Figs 6, 8 , 9 ). Distal part of embolus surrounded by an embolic membrane (EM), apical edge covered with fine papillae ( Figs 6­ −9 ), anterior process of the embolic plate (AP) barely visible on normal/undissected palp due to its transparency ( Fig. 6 ), clearly visible with higher magnification ( Fig. 9 ) or in dissected embolic division ( Figs 7, 8 ). AP triangular, pointed, ~ longer than wide at its base, directed in same direction as embolus, longitudinal dark mark on upper half ( Figs 8 , 9 ). Distal suprategular apophysis (DSA) fingerlike, projecting distally, visible in retrolateral and prolateral view in undissected palp ( Figs 4, 6 ­), posterior apex of the embolic plate (PA) triangular with a blunt tip.

Female paratype (NHMW-ZOO-AR-30351). Habitus as in Figs 3 , 18 . Total length 2.72, prosoma length 1.12, width 0.76, chelicerae length 0.64, abdomen length 1.64, width 1. Clypeus with no setae. Eyes as in the male, distance between posterior median eyes PME-PME = 0.1 ( Fig. 10 ). Leg measurements are given in Table 2 . Femur I with a dorsal spine located at 0.68 and one prolateral spine; femur II only with one dorsal spine located at 0.61; femur III with one dorsal spine, femur IV with no spine. Patella I–IV with a long spine. All tibiae with two dorsal spines, additionally tibia I with one prolateral and one retrolateral spine, tibia II with one retrolateral spine. Metatarsi with no spines, metatarsi I-III with trichobothrium, position: I = 0.48, II = 0.47, III = 0.40. Color as in male, but abdomen more whitish ( Fig. 3 ).

Epigyne with circular atrium ( Fig. 12 ), open fish mouth-shaped ( Fig. 16 ). Anterior plate with V-shaped socket ( Figs 11 , 12, 14 ). Spermathecae kidney-like, together with appendices visible through the integument ( Figs 11 , 12, 14 ). Appendices relatively straight and in dorsal view directed towards cuticle ( Figs 13, 15 ).

Natural history. Porrhomma ozrenense sp. nov. is extremely rare in the type locality. After eight hours of exploration along the entire length of the cave, only five individuals were observed. They were collected in the deep dark zones of the cave with high humidity, specifically on the floor in waterless areas of the cave and in crevices on the cave walls. This species is a troglobitic spider having extremely reduced eyes and a significant reduction in cuticular pigmentation.

The word “Mokra” in the cave's name, means “wet” in the local language, which further explains the nature of the cave with an underground river flowing through almost its entire length ( Figs. 23, 24 ). During heavy rains, the level of the underground river rises to the point that large part of the cave is washed by the flowing water. This may be one of the reasons why this new species is so rarely encountered in the cave. The partial destruction of the wooden platform at the cave's entrance ( Fig. 21 ) further demonstrates the force of the flowing water.

Distribution. Known only from the type locality—Mokra Megara cave on Ozren Mt. in Bosnia and Herzegovina ( Fig. 1 ).

Endemism. Probably local endemite.

Conservation remarks. Until the end of 2021, not only was the cave not subjected to any protection measures, but it was also impossible to visit or explore because its entrance was mined during the Bosnian War (1992–1995). Thanks to the initiative of the Citizens' Association "Fojničani" from Maglaj, the cave was demined at the end of 2021 and making it accessible to visitors and researchers. Other nearby speleological sites remain inaccessible because they are still mined.

Due to our limited knowledge of its ecology, P. ozrenense sp. nov. is not directly considered endangered. However, because of its exceedingly small population size and relatively restricted range, it should be regarded as potentially vulnerable in the case of frequent and unprofessional human visits to the cave. Together with the endemic troglobitic beetle Duvalius maglajensis (Apfelbeck, 1908) , which was also described from this cave, P. ozrenense sp. nov. should be added to the list of nationally protected species.

Figures

FIGURE 1. Geographical location of Mokra Megara cave in Bosnia and Herzegovina.

FIGURES 2–3. Porrhomma ozrenense sp. nov. male holotype (2) and female paratype (NHMW-ZOO-AR-30351) (3). 2−3 habitus, lateral view. Scale bar: 0.5 mm.

FIGURES 4–8. Porrhomma ozrenense sp. nov. male holotype (4–6) and paratype (7–8). 4 left palp, retrolateral view; 5 same, dorsal view, arrows indicating location of cymbial apophysis, 6 same, prolateral view; 7 embolic division, retrolateral view; 8 same, prolateral view. Abbreviations: AP = anterior apex of the embolic plate, BT = bifurcated tooth on the lower anterior edge of the velum, CA = cymbial apophysis, DSA = distal suprategular apophysis, E = embolus, EM = embolic membrane, PA = posterior apex of the embolic plate, V = velum. Scale bars 0.1 mm.

FIGURES 9–11. Porrhomma ozrenense sp. nov. 9 male holotype, detail of embolus enlarged at magnification of 400x; 10 female paratype (NHMW-ZOO-AR-30351), cephalic area, frontal view; 11 female paratype (NHMW-ZOO-AR-30352), abdomen, ventral view. Scale bars: 0.1 mm.

FIGURES 12–16. Porrhomma ozrenense sp. nov. female paratype (NHMW-ZOO-AR-30352) (12, 13) and female paratype (NHMW-ZOO-AR-30353) (14−16­). 12 epigyne, ventral view; 13 vulva, dorsal view; 14 epigyne, antero-dorsal view; 15 vulva, dorsal view; 16 epigyne, lateral view. Abbreviations: A = atrium, arrow indicates the V-shaped socket; DP = dorsal plate of epigynum; S = spermathecae; SA = spermathecal appendices. Scale bars: 0.1 mm.

FIGURES 17–24. Habitus and type locality of Porrhomma ozrenense sp. nov. (17, 18, 21−24) and other endemic troglobitic arthropods registered in the same cave (19, 20). 17 habitus of male holotype in life; 18 same, female paratype (NHMW- ZOO-AR-30351); 19 Duvalius maglajensis, the only other troglobitic species described from Mokra Megara cave to date; 20 Niphargus sp., possible new species, found in still water; 21−24 entrance and interior of Mokra Megara cave.