Domitius Culsu sp. nov. (Araneae, Nestici-dae), a new troglobiont spider from Italy with notes on Italian nesticids of the genus Domitius Ribera, 2018 Author Ballarin, Francesco Systematic Zoology Laboratory, Department of Biological Sciences, Tokyo Metropolitan University 1 - 1 Minami-Osawa, Hachioji-shi, Tokyo, 192 - 0397, Japan ballarin.francesco@gmail.com text Journal of Cave and Karst Studies 2020 2020-06-30 82 2 82 94 http://dx.doi.org/10.4311/2019lsc0103 journal article 10.4311/2019lsc0103 7fbb4285-59e7-49e6-a890-df9610e94455 3925078 Domitius culsu Ballarin sp. nov. Figures 1 A‒G, 2A‒E, 3A‒D. Nesticus speluncarum Brignoli, 1979: 214 (misidentification) Type material. Holotype ♂ . ITALY , Toscana : Garfagnana area, Lucca Province , Coreglia Antelminelli Municipality , Tana delle Fate di Coreglia Antelminelli cave, 141/T/LU , 260m a.s.l., 44.046336°N 10.523525°E , 21.VIII.2018 , leg. F. Ballarin and D. Avesani ( MSNV ). Paratypes . Same locality as the holotype, 1♀ , 04.IX.1967 , leg. A. Vigna Taglianti ( MSNV ) ( Brignoli 1979 , sub Nesticus speluncarum ); 1♀ , 15.VIII.2015 , leg. F. Ballarin and M. Gaiga ( MSNV ) ; 4♀♀ , 24.VI.2017 , ( 3♀♀ collected as juveniles and raised in captivity, adults : 20.VIII.2017 , 15.IX.2017 and 28.VI.2018 respec- tively), leg. F. Ballarin and R. Ballarin ( MSNV ); 4♀♀ , 21.VIII.2018 , leg. F. Ballarin and D. Avesani ( MSNV , MSNB ) . Table 1. Species, GenBank accession numbers, and locality of the specimens used in the phylogenetic analysis.

Species	Code	COI	16S	H3	Locality
Domitius baeticus	Dbae	MF693114	MF693118	MF693106	Cueva del Castillo. Siles, Jaén. Spain
Domitius luquei	Dluq	MF693112	EU746439	MF693104	Cueva de la Picona, San Pedro de Carmona, Cabuérniga, Cantabria, Spain
Domitius lusitanicus	Dlus	MF693113	EU746429	MF693105	Algar de Marradinhas II, Concelho de Alcanena, Portugal
Domitius menozzii	D213	MK860151a	MK860133a	MK860142a	Tanna da Suja, Prati di Bavari, Liguria, Italy
Domitius culsu sp. nov.	D555	MK860152a	MK860134 a	MK860143a	Tana delle Fate di Coreglia Antelminelli, Coreglia Antelminelli, Toscana, Italy
Domitius sbordonii	Dsbo	MF693110	MF693116	MF693102	Tana degli orchetti, Supino, Lazio, Italy
Domitius speluncarum	D557	MK860153a	MK860135a	MK860144a	Tana di Magnano, Canigiano, Lucca, Toscana, Italy
Nesticus cellulanus	N214	MK860154a	MK860136a	MK860145a	Cave of Koufovouno, Didimoticho, Thrace, Greece
Kryptonesticus dimensis	K566	MK860155a	MK860137a	MK860146a	Dim cave, Antalya, Turkey
Kryptonesticus eremita	K211	MK860156a	MK860138a	MK860147a	Grotta di Ponte Subiolo, Mori, Veneto, Italy
Carpathonesticus fodinarum	C162	MK860157a	MK860139a	MK860148a	Small cave along the river, Sighistel, Bihor, Romania
Carpathonesitcus lotriensis	C166	MK860158a	MK860140a	MK860149a	Humid and shadowed cliff near Lazaret village, Sibiu, Romania
Typhlonesticus obcaecatus	Tobc	KF939309	EU746437	MF693109	Cueva del Molino de Aso, Boltana, Huesca, Spain
Typhlonesticus idriacus	T167	MG201050	MG200521	MG201227	Grotta Pre Oreak, Nimis, Udine, Friuli Venezia Giulia, Italy
Typhlonesticus morisii	Tmor	KF939311	KF939308	∙∙∙	Sotterranei del Forte di Vernante, Vernante, Cuneo, Italy
Gaucelmus augustinus	G601	MK860159a	MK860141a	MK860150a	Climax cave, Bainbridge, Georgia, USA

a New Sequences. Examined comparative material. Domitius speluncarum (Pavesi, 1873) : ITALY: Liguria : 1♂, 1♀, (topotypes), La Spezia Province, Grotta Bocca Lupara cave, 74/Li/SP, 120m a.s.l., 05.III.1969, leg. P.M. Brignoli (MSNV) ( Brignoli, 1971 ); Toscana : 1♀, Lucca Province, Garfagnana area, Villa Collemandina Municipality, Canigiano village, Tana di Magnano cave, 162/T/LU, 653m a.s.l., 44.177285°N, 10.38803°E, 03.XI.1967, leg. A. Vigna Taglianti (MSNV) ( Brignoli, 1971 ), 1♀, 01.VIII.1975, leg. P. Magrini (MSNV), 4♀♀, 14.VIII.2015, leg. F. Ballarin and M. Gaiga (MSNV); 1♀, Forno- volasco (not reported in the label but very likely from Grotta del Vento cave), 700m a.s.l., 16.VI.1970, leg. O. Osella (MSNV) ( Brignoli, 1971 ); 1♀, Grotta del Buggine cave, 166/T/Lu, 315m a.s.l., 07.X.1967, leg. G. Castellini (MSNV) ( Brignoli, 1971 ); 1♀, Massa-Carrara, Buca della Freddana cave, 230/T/Ms, 550m a.s.l., 05.VI.1977, leg. C. Bonzano (MSNV) ( Brignoli, 1985 ); 1♀, Buca del Bacile cave, 226/T/Ms, 10.III.1975, leg. unknown (MSNV) ( Brignoli, 1985 ). Domitius menozzii (di Caporiacco, 1934) : ITALY, Liguria , 1♂, 4♀♀, north-east of Genova town, Tanna da Vulpe cave, 264/Li/GE, 23.XI.1969, leg. A. Vigna Taglianti (MSNV) ( Brignoli, 1971 ); 2♂♂, 2♀♀, Creto, Tanna de Fate cave, 17/ Li/GE, 30.X.1971, leg. G. Gardini (MSNV); 2♀♀ (topotypes), Prati di Bavari locality, Tanna da Suja cave, 5/Li/GE, 582m a.s.l., 44.422894°N, 09.035239°E, 30.V.2013, leg. F. Ballarin, A. Trotta, G. Gardini, and S. Zoia. Domitius sbordonii ( Brignoli, 1979 ) : ITALY, Lazio , 1♂ (holotype), Frosinone Province, Supino, Valle Serena, Grot- ta della Croce cave, 01.IX.1977 leg. V. Sbordoni (MSNV) ( Brignoli, 1979 ); 1♀ (paratype), 08.II.1976, leg. V. Sbordoni (MSNV) ( Brignoli, 1979 ). Kryptonesticus eremita (Simon, 1880) : ITALY, Liguria : 2♂♂ (sub. Nesticus menozzii ), Creto, Tanna de Fate cave, 17/Li/GE, 30.X.1971, leg. G. Gardini (MSNV); Emilia-Romagna: 2♀♀ Ravenna Province, Riolo Terme, Borgo Rivola, Grotta del Re Tiberio cave, 36/Er/RE. 19.II.1951, Leg. Denis (MSNV) ( Zangheri, 1966 , sub. Nesticus speluncarum ); Toscana : 1♀ Garfagnana area, Lucca Province, Coreglia Antelminelli Municipality, Tana delle Fate di Coreglia Antel- minelli cave, 141/T/LU, 260m a.s.l., 44.046336°N, 10.523525°E, 15.VIII.2015, leg. F. Ballarin and M. Gaiga (MSNV); 3♀♀, 24.VI.2017, Leg. F. Ballarin and R. Ballarin (MSNV-MSNVRAr/m 0007); 1♀, 21.VIII.2018, leg. F. Ballarin and D. Avesani (MSNV); Campania: 1♀, Avellino Province, Bagnoli Irpino, Mt. Piacentini, Grotta Giovannino cave, 16.VI.1956, leg. S.Ruffo (MSNV) ( Kritscher, 1958 , sub. Nesticus speluncarum ). Etymology The name of the new species is derived from the Etruscan goddess Culsu who, according to the Etruscan mytholo- gy, ruled the cave-like entrance of the underworld. Noun in apposition. Diagnosis Species closely re- lated to D. speluncarum and D. menozzii. Males of D. culsu sp. nov. can be separated from males of all other Italian species of the genus Domitius by the different shape of the apophyses of the para- cymbium (Figs. 1A‒C, 2B,C vs. Fig. 4A‒I). D. culsu sp. nov shows a robust, S-shaped dorsal apophysis 1 in contrast with a large, flat and axe- like Da 1 in D. speluncar- um (Figs. 1A‒C, 2B, C vs. Fig. 4A‒C); a short and stumpy Da 1 in D. me- nozzii (Figs. 1A‒C, 2B, C vs. Fig. 4D‒F) or a long and thread-like Da 1 in D. sbordonii (Figs. 1A‒C, 2B, C vs. Fig. 4G‒I). Addi- tionally, males of D. culsu sp. nov. have a well-de- veloped, triangular medi- an apophysis, absent in males of the other three species (Figs. 1A, 2A vs. Fig. 4A, D, G). Female D. culsu sp. nov. can be easily distin- guished from female D. speluncarum by the nar- rower, trapezoid-shaped median septum with slant- ing edges, in contrast with the larger, lobate Ms with rounded edges in D. spe- luncarum (Figs. 1E, 2D vs. Fig. 5A). Female D. culsu sp. nov. are separated from female D. morisii by the absence of a bulge on the Ms (clearly visible in D. morisii , Figs. 1E, 2D vs. Fig. 5C). Additionally, they can be distinguished by the different shape of copulatory ducts when the vulva is observed dorsally: with a rather uniform diameter in D. culsu sp. nov. and bearing a large, flattened middle trait in D. morisii (Figs. 1G, 2E vs. Fig. 5D). Female D. culsu sp. nov. are easily sepa- rated from those of D. sbordonii by the trapezoid-shaped Ms with slanting edges, in contrast with the squared Ms with vertical edges in D. sbordonii (Figs. 1E, 2D vs. Fig. 5E). They can further be distinguished by the different position of spermathecae, located in the lower half of the vulva and below the vulval pockets in D. culsu sp. nov., in contrast with S located in the upper half of vulva and above Vp in D. sbordonii (Figs. 1G, 2E vs. Fig. 5F). Description. Male (holotype). Total length 4.19. Carapace: 1.81 long, 1.56 wide. Figure 1. Nesticus culs u sp. nov. Male palp: A. ventral view; B. dorsal view; C. retrolateral view; D. female, cephalic region showing the eye pattern; E. epigyne, ventral view; F. epigyne after clearing, ventral view, the schematic course of internal ducts is outlined with a white line; G. vulva after clearing, dorsal view. Figure 2. Genitalia of Nesticus culsu sp. nov. Male palp: A. ventral view; B. dorsal view of the paracymbium; C. retrolateral view; D. female epigyne, ventral view; E vulva, dorsal view. Habitus as in Fig. 3A . Carapace uniformly pale yellow with some sparse setae (more reddish while alive, see Fig. 3A ). Cephalic region not clearly differentiated from the rest of carapace. Eyes reduced, AM missing, reduced to black maculae. Eye diameters: AM -, AL 0.079, PM 0.080, and PL 0.078. Thoracic grooves and fovea distinct. Mouthparts and sternum uniformly colored as the carapace. Promargin of chelicera with three teeth approximately of the same size, retromargin with several small denticles. Legs uniformly light yellowish. Legs measurements as follows: I 17.40 (4.89, 0.90, 4.78, 4.90, 1.93), II 14.03 (3.92, 0.80, 3.67, 3.76, 1.88), III 10.35 (3.19, 0.69, 2.53, 2.79, 1.15), IV 13.47 (4.34, 0.84, 3.53, 3.49, 1.27). Leg formula: I, II, IV, III. Opisthosoma gray-yellowish colored (lighter than carapace while alive, see Fig. 3A ), covered with long hairs. Palp as in Figs. 1 A‒C, 2A-C. Cymbium oval, covered with short, sparse setae, with a tuft of longer hairs in the pro- lateral distal area near the tip. Embolus filamentous, slender in the terminal part. Conductor complex with three distinct processes: Cp 1-3. Cp 1 stocky and roughly triangularly shaped, Cp 2 and Cp 3 located at the distal part of the bulb and diagonally protruding (approx. 2 o’clock seeing the left palp ventrally), their tips curved towards each other ( Figs. 1A, C , 2A, C). Median apophysis well-developed, shaped as a long, sharp triangle, heading prolaterally ( Figs. 1A , 2A). Para- cymbium large with well-developed, sclerotized dorsal, distal and ventral processes. Two dorsal apophyses, Da 1-2: Da 1 robust and long, ending sharply, S-shaped when the palp is observed dorsally, Da 2 stocky, triangularly-shaped. Distal apophysis triangularly shaped. Ventral apophysis lobate, dorso-ventrally flattened and heading toward the cym- bium ( Figs. 1 A‒C, 2A-C). Female (based on 4 paratypes) . Total length 3.65–5.27. Carapace: 1.71–1.98 long, 1.54–1.64 wide. Habitus as in Fig. 3B, C . Carapace uniformly yellowish with some sparse setae (often more reddish while alive, see Fig. 3B ). Cephalic region not clearly differentiated from the rest of the prosoma.Eyes reduced, AM strongly reduced and bare- ly visible, reduced to small, dark maculae in some specimens. Eye diameters: AM (when present): 0.032, AL: 0.087, PM: 0.078, and PL: 0.77. Thoracic grooves and fovea distinct. Mouthparts and sternum uniformly colored as in the carapace. Teeth of chelicera as in the male. Legs uniformly light yellowish. Leg measurements as follows: I 17.07 (4.38, 1.01, 4.95, 4.90, 1.83), II 13.69 (4.04, 0.92, 3.57, 3.64, 1.52), III 10.46 (3.43, 0.80, 2.50, 2.56, 1.17), IV 13.89 (4.64, 0.92, 3.59, 3.41, 1.33). Leg formula: I, IV, II, III. Opistho- soma yellowish-gray (often lighter colored than carapace while alive, see Fig. 3B ), covered with long hairs. Figure 3. Habitus and type locality of Domitius culsu sp. nov. A. Habitus of male; B. habitus of female; C. female with prey; D. juvenile in captivity; E. entrance of Tana delle Fate di Coreglia Antelminelli cave; F. map of the cave and detail of the entrance, showing the spatial distribution of the two co-existing nesticid species living inside: green = D. culsu sp. nov. , orange = Kryptonesticus eremita , arrow = en- trance of the cave. Epigyne as in Figs. 1E, F , 2D, E. Medi- an septum short, not protruding, shaped as an inverted trape- zoid with a narrower base. Vulval pockets and copulatory ducts externally visible by transparence trough the tegument. Copu- latory openings at the lower, lateral side of median septum. Vul- va as in Figs. 1G , 2E. Spermathecae small and round, located in the lower-half of the vulva, below vulval pockets and being partially covered by them. Vulval pockets wide and rounded, sac-shaped, located above spermathecae. Copulatory ducts with a wider diameter in the ventral trait and narrower in the dor- sal trait, rolling up around the lower part of vulval pockets and reaching spermathe- cae with some turns ( Figs. 1F , 2E). Insem- ination ducts begin- ning from the lower part of spermathe- cae and following the same course of copu- latory ducts. Figure 4. Male palps of the Italian Domitius species for comparison. D. speluncarum male palp: A. ventral view; B. dorsal view; C. retrolateral view; D. menozzii male palp: D. ventral view; E. dorsal view; F. retrolateral view; D. sbordonii male palp: G. ventral view; H. dorsal view; I. retrolateral view. Distribution Italy, endemic to the northern Apennines. Known only from the type locality; Tana delle Fate di Coreglia Antelminelli cave ( Fig. 6 ). Biospeleological and ecological notes Figure 5. Female epigyne of the Italian Domitius species for comparison. D. speluncarum : A. epigyne, ventral view; B. vulva, dorsal view; D. menozzii : C. epigyne, ventral view; D. vulva, dorsal view; D. sbordonii : E. epigyne, ventral view; F. vulva. The entrance of Tana delle Fate di Coreglia Antelminelli cave (Italian National Caves Registry number: 141/T/LU; Fig. 3E ) opens in the left bank of the narrow valley of Segone Creek in the Province of Lucca (Toscana region) at an elevation of 260 m a.s.l. The cave occurs in the limestone of the Maiolica formation (lower Tithonian‒lower Aptian, ~150–120 Ma), which is particularly rich in flint nodules. After an initial steep slope (approximately 10 m deep), the cave continues with a long and sub-horizontal spatial development and a general NW‒SE orientation ( Fig. 3F ). It branches with several, sub-circular tunnels as a result of ancient groundwater flows. The cave has an estimated total extension of 1100 m, although the deeper segments are still unexplored, as they are either filled with water or ending with sumps. The inner section is generally humid, with mud often covering the bottoms of the tunnels. The cave hosts a rich sub- terranean fauna including some endemic or locally protected species, e.g. the carnivorous land snail Oxychilus sp. ( Gastropoda , Oxychilidae ), the cave cricket Dolichopoda laetitiae Minozzi, 1920 ( Orthoptera , Rhaphidophoridae ), the blind subterranean beetle Duvalius apuanus lanzai Straneo, 1943 ( Coleoptera , Trechinae), the Italian cave salamander Speleomantes italicus (Dunn, 1923) ( Amphibia , Plethodontidae ), and three species of bats: the greater horseshoe bat Rhinolophus ferrumequinum (Schreber, 1774) , the lesser horseshoe bat Rhinolophus hipposideros (Bechstein, 1800) ( Chiroptera , Rhinolophidae ), and the common bent-wing bat Miniopterus schreibersii (Kuhl, 1817) ( Chiroptera , Miniop- teridae). Other animals known from the cave from the literature ( Lanza, 1961 ) or directly observed by the author include: Octodrilus complanatus (Dugès, 1828) , O. hemiandrus ( Cognetti, 1901) , O. transpadanus (Rosa, 1884) , and Aporrectodea rosea (Savigny, 1826) (Anellida, Lumbricidae ); Chaetophiloscia cellaria (Dollfus, 1884) ( Isopoda , Philosciidae ), Androniscus dentiger Verhoeff, 1908 , and Spelaeonethes mancinii (Brian, 1913) ( Isopoda , Trichoniscidae ); Euscorpius carpathicus (Linnaeus, 1767) ( Scorpiones , Euscorpiidae ); Trogulus sp. ( Opiliones , Trogulidae ), Ischyropsalis a damii Canestrini, 1873 ( Opiliones , Ischyropsalididae ); Lithobius tylopus Latzel, 1882 ( Chilopoda , Lithobiidae ), Gryllomorpha dalmatina (Ocskay, 1832) ( Orthoptera , Gryllidae ), Hypaena sp. ( Lepidoptera , Noctuidae ), Stenophylax permistus Mc- Lachlan, 1895 (Tricoptera, Limnephilidae ), and a large population of limoniid crane flies ( Diptera , Limoniidae ). Near the entrance and in the early section of the cave, numerous spiders were also observed: Amaurobius ferox (Walckenaer, 1830) , A. pesarinii Ballarin and Pantini, 2017 ( Amaurobiidae ), Kryptonesticus eremita (Simon, 1880) ( Nesticidae ), Meta menardi (Latreille, 1804) , Metellina merianae (Scopoli, 1763) ( Tetragnathidae ), Pholcus phalangioides (Fuesslin, 1775) ( Pholcidae ), and Tegenaria sp. ( Agelenidae ). The new species was found in the initial segments of the cave, but at some distance from the entrance ( Fig. 3F ). During summer, when the cave was visited, adults, subadults, and juveniles of D. culsu sp. nov. were observed together, with a substantially higher number of adults and subadults during the month of August. Most of the juveniles collected in the cave and bred in captivity became adults after 2‒3 months of captivity, while it took approximately one year for the youngest specimens to reach sexual maturity. Figure 6. Distribution of the genus Domitius in Italy. Yellow dots  D. menozzii , blue dots  D. speluncarum ; red dot  D. culsu sp. nov. ; green dot  D. sbordonii . Figure 7. Phylogenetic tree of the main European nesticid genera inferred using ML in RAxML. Different colored branches reflect different genera: violet = Typhlonesticus , green = Carpathonesticus , yellow = Nesticus , blue = Kryptonesticus , red = Domitius . The newly-described species is highlighted in bold. Species distributed in Italy are underlined. Code before each species refers to the origin of the data, see Table 1. Branch lengths are scaled in relation to the number of substitutions per site; numbers at nodes denote bootstrap support according to ML. Two different species of nesticid spiders, K. eremita and D. culsu sp. nov. , were collected together in the Tana delle Fate di Coreglia Antelminelli cave. These species cover a different spatial distribution within the cave ( Fig. 3F ), coexisting without overlapping despite occupying approximately the same ecological niche. Cohabitant nesticids, in particular involving D. menozzii or D. speluncarum together with K. eremita , have been previously observed in several occasions in Italian caves, and sometimes collected at short distances from each other ( Brignoli, 1971 ). However, no clear species overlap are reported within the same cave. Such distinct spatial partition can be explained by the different grade of adaptation to the hypogean environment showed by these arachnids. In fact, K. eremita appears to be a less specialized cave-dweller, lacking extreme morphological adaptations to subterranean life. Therefore, it mostly occurs near the entrance of caves or inside artificial tunnels, including, occasionally, shadowed epigean habitats with constant temperature and high relative humidity ( Brignoli, 1971 and personal observations by the author). On the other hand, all Domitius species show a greater degree of adaptation to the subterranean habitat, as suggested by reduction of the eyes and body depigmentation. Such strong adaptation allows Domitius to occupy deeper segments of the caves, thus avoiding direct competition with K. eremita . Conservation Notes Since caves are a unique and delicate ecosystem, they are highly susceptible to external disturbance ( Culver and Pipan, 2009 ). Its visible entrance and sub-horizontal extension makes Tana delle Fate di Coreglia Antelminelli cave easily accessible to visitors even with limited experience in speleology, and the cave is often used for training purpos- es by local speleological clubs. Although not threatened, D. culsu sp. nov. should be considered potentially at risk in case of frequent and long-lasting human disturbance due to its strict habitat requirements, its reduced population, and its extremely limited distribution, which appears to be confined to a single cave. Therefore, the new species is a good candidate for species conservation, deserving a place in the list of locally protected species. Phylogenetic Analysis A total of 16 nesticid species were used in this study, including representatives of the main nesticid genera present in Europe and all the species distributed in the Italian peninsula. Taxon sampling comprised the wide majority of Domitius species. Only D. murgis (Ribera and De Mas, 2003) from Spain was excluded from the analysis due to the absence of available sequences and fresh samples. The final dataset was formed by 1975 pair bases (bp) distributed as; COI = 1197 bp, 16S = 469 bp, and H3 = 309 bp. The resulting phylogenetic tree is illustrated in Figure 7 , and the uncorrected pairwise distance between the species is reported in Table 2 . The European nesticids cluster into five different clades corresponding to the main genera Carpathonesticus , Domitius , Kryptonesticus , Nesticus , and Typhlonesticus , each of them highly supported (bootstrap support value = 100%). Each lineage represents a different and well-defined evolu- tionary line. These results concur with the outcomes of recent morphological and phylogenetic studies on the family Nesticidae ( Pavlek and Ribera, 2017 ; Ribera, 2018 ; Ballarin and Li, in prep.), supporting the validity of the newly-es- tablished genera. According to these results, Domitius represents the sister lineage of the monophyletic clade formed by the genera Carpathonesticus , Kryptonesticus , and Nesticus , with which it shares a common ancestor. The analysis supports Typhlonesticus as a basal clade within the European Nesticidae , as also suggested by recent molecular stud- ies ( Ballarin and Li, 2018 ; Ribera, 2018 ). Within Domitius , D. culsu sp. nov. shows a closer affinity with the species from the same geographic area; particularly D. speluncarum , but also D. menozzi . Its position at the far end of the phyloge- netic tree of the genus suggests a more recent origin in comparison with the other congeneric species. All the Domitius species distributed in the Northern Apennines share a close affinity with species from the Iberian Peninsula. Such close relations also reflected in genital morphology. For instance, all these species share a similar position of spermathecae, located in the lower-half of the vulva, and below the vulval pockets (see Figs. 1G , 5B, D and Figs. 4 A‒E in Ribera, 2018 ). On the other hand, D. sbordonii from the Central Apennines appears to be morphologically and genetically separated from all the other species of the genus, including those from Northern Apennines. The differ- ence is highlighted in the peculiar shape of the vulva, being the only Domitius species showing simple-coiled internal ducts and spermathecae located in the upper-half of the vulva, over the vulval pockets (see Fig. 5F vs. Figs. 1G , 5B, D and Figs. 4 A‒E in Ribera, 2018 ). Upper-positioned spermathechae are also present in several other European nesticid genera such as Carpathonesticus ( sensu stricto ), Krypthonesticus , and Nesticus ( sensu stricto ). Based on these results it is possible to speculate that D. sbordonii represents a basal element within the genus Domitius , possibly still carrying the ancestral characters of the older forebear of the European nesticids. Table 2. Uncorrected genetic p-distance of the COI partial sequence of the nesticid species discussed in the text. The newly described species is in bold.

No.	Species	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
1	Dbae_ Domitius _baeticus
2	Dluq_ Domitius _luquei	0.142
3	Dlus_ Domitius _lusitanicus	0.135	0.135
4	D213_ Domitius _menozzii	0.140	0.146	0.119
5	D555_ Domitius _culsu sp. nov.	0.167	0.144	0.133	0.121
6	Dsbo_ Domitius _sbordonii	0.181	0.176	0.167	0.181	0.185
7	D557_ Domitius _ speluncarum	0.162	0.144	0.121	0.121	0.071	0.190
8	N214_ Nesticus _cellulanus	0.172	0.174	0.151	0.190	0.181	0.176	0.172
9	K566_ Kryptonesticus _ dimensis	0.156	0.151	0.135	0.144	0.165	0.172	0.146	0.121
10	K211_ Kryptonesticus _ eremita	0.149	0.156	0.142	0.156	0.169	0.169	0.162	0.117	0.078
11	C162_ Carpathonesticus _ fodinarum	0.169	0.153	0.153	0.176	0.178	0.172	0.167	0.085	0.089	0.108
12	C166_Carpathonesitcus_ lotriensis	0.144	0.160	0.146	0.162	0.190	0.176	0.190	0.112	0.094	0.101	0.069
13	Tobc_ Typhlonesticus _ obcaecatus	0.197	0.178	0.167	0.165	0.178	0.176	0.181	0.149	0.156	0.158	0.140	0.142
14	T167_ Typhlonesticus _ idriacus	0.181	0.174	0.167	0.183	0.192	0.197	0.185	0.142	0.156	0.165	0.149	0.156	0.096
15	Tmor_ Typhlonesticus _ morisii	0.174	0.174	0.174	0.181	0.199	0.208	0.181	0.183	0.160	0.183	0.176	0.174	0.117	0.124
16	G601_ Gaucelmus _ augustinus	0.229	0.229	0.227	0.222	0.245	0.243	0.236	0.252	0.211	0.238	0.240	0.233	0.249	0.254	0.247

Conclusions All Italian species of the genus Domitius appear to be highly adapted to a permanent life in the subterranean environ- ment, showing eye reduction and lack of body pigmentation. They further present a localized distribution, with distinct genetic and morphological differences between the species living in the Northern and Central areas of the Apennines. At the same time a close affinity with the species distributed in the Iberian Peninsula is observed. Such features, to- gether with a high genetic p-distance among the species ( Table 2 ), suggests a potentially complex evolutionary history of the genus Domitius that still needs to be properly explored (see also Ribera, 2018 ). Because of their apparent similarities in habitus and female genitalia, D. culsu sp. nov has previously been mistaken for D. speluncarum and ignored as a distinct species by previous arachnologists. A detailed molecular and morpho- logical analysis of both sexes of D. culsu sp. nov carried out in this work supports the validity of the new species and its close relationship with the other Domitius species from the same geographical area. Its potential susceptibility to external disturbance, and extremely limited distribution, makes D. culsu sp. nov of interest for conservation. Finding a new nesticid species in Italy further suggests that our knowledge on the diversity of the family Nesticidae in Southern Europe is still far from complete. Further collections along the Italian peninsula will probably lead to the discovery of other highly-specialized nesticid species allowing a deeper and more precise understanding of the spider cave fauna in Italy and in the Mediterranean area.