Acanthophorella didi, Antić & Margalitadze & Šević, 2025

Acanthophorella didi View in CoL sp. nov.

Figs 1– 3 View FIGURE 1 View FIGURE 2 View FIGURE 3 , 16E View FIGURE 16 , 17 View FIGURE 17

Acanthophorella barjadzei View in CoL in part.— Antić et al. (2023: 40 View Cited Treatment , 64–70, 74, figs 1A–D, 17–20)

Diagnosis. Troglobiotic species, which differs from the epigean, pigmented A. aurita , A. chegemi and A. irystoni by the depigmented body. The new species differs from the troglobiotic A. gaumarjos sp. nov., A. valerii and A. spinicoxa sp. nov. by the presence of pale brownish or transparent ommatidia (vs. black ommatidia in A. gaumarjos sp. nov., A. valerii and A. spinicoxa sp. nov.). A. didi sp. nov. differs from the other troglobiotic species by the presence of small mesal lobes on coxae 7 (vs. presence of small, acuminate, mesal teeth in A. barjadzei or the complete absence of mesal lobes in A. eto sp. nov. and A. devi ).

The new species is most similar to A. barjadzei , but besides the structures of coxae 7, it differs in the presence of strongly developed, rounded lobes on coxae 10 (vs. coxae 10 with subtriangular protrusions in A. barjadzei ) or medial parts of anterior gonopod angiocoxites distally rounded (vs. medial parts of anterior gonopod angiocoxites distally subquadrangular in A. barjadzei ).

Name. In Georgian, didi (დიდი) means large, big, which indicates that it is the largest Acanthophorella species to date, measuring up to 26 mm, and one of the largest troglobiotic arthropod species in the caves where it occurs. Noun in apposition.

Material examined

Holotype: GEORGIA ● ♂; Ambrolauri Municipality , Racha karst massif, Nikortsminda village, Nikortsminda Sakinule Cave; 42°27’48”N 43°04’02”E; 1195 m a.s.l.; 24 July 2022; D. Antić, E. Kiria, L. Shavadze and Sh. Barjadze leg.; IZB. GoogleMaps

Paratypes: GEORGIA ● 1 ♀, 1 juvenile; same collection data as for holotype; IZB GoogleMaps ● 1 ♂, 1 ♀; same collection data as for holotype; NHMW-MY10367 GoogleMaps ● 1 ♂; same collection data as for holotype; IZISU GoogleMaps ● 2 ♂♂, 6 ♀♀, 1 juvenile; same cave as for preceding; 14 June 2019; H. Reip, J. Hentschel, L. Binz and E. Göbel leg.; SMNG ● 1 ♂, 1 ♀, 1 juvenile; same cave as for preceding; 21 June 2023; D. Antić, A. Faille, A. Margalitadze, L. Shavadze, E. Maghradze and Sh. Barjadze leg.; SMNS ● 5 ♂♂, 5 ♀♀, 1 juvenile; same collection data as for preceding; IZISU ● 1 juvenile; same collection data as for preceding; IZB .

Additional material: GEORGIA ● 2 ♂♂, 1 ♀, 3 juveniles; Ambrolauri Municipality , Racha karst massif, Muradi Cave; 42°23’45”N 42°58’43”E; 1500 m a.s.l.; 24 July 2022; D.Antić, E. Kiria, L. Shavadze and Sh. Barjadze leg.; IZB GoogleMaps ● 2 ♀♀, 2 juveniles; same cave as for preceding; 18 October 2021; J. Grego and R. Straub leg.; IZISU ● 2 ♂♂, 1 juvenile; Ambrolauri Municipality , Racha karst massif, Tskhrajvari Cave; 42°23’17”N 42°59’04”E; 1496 m a.s.l.; 22 June 2023; D. Antić, A. Margalitadze, L. Shavadze and A. Faille leg.; IZB GoogleMaps ● 1 ♂, 1 ♀, 4 juveniles; same collection data as for preceding; SMNS GoogleMaps ● 1 ♀, 1 juvenile; same collection data as for preceding; IZISU GoogleMaps .

Note. Antić et al. (2023) misidentified this new species with the very similar A. barjadzei , which inhabits the same region. Remarks, localities and ecology for A. barjadzei in Antić et al. (2023) refer mostly to the new species we describe here, while all figures labelled as A. barjadzei [except fig. 21B from Antić et al. (2023)] refer exclusively to the new species. Below we give a detailed description of the new species with additional figures, while the others can be seen in Antić et al. (2023: figs 1A–D, 17–20).

Description

Number of body segments and size. Body with 31 segments (including collum and telson). Holotype male 20 mm long, vertical diameter of the largest segment 1.4 mm. Paratype and non-type males 19–23.5 mm long, vertical diameter of the largest segment 1.4–1.5 mm. Paratype and non-type females 17.5–26 mm long, vertical diameter of the largest segment 1.4–1.7.

Coloration ( Fig. 1 View FIGURE 1 ; see also Antić et al. (2023: fig. 1A–D)). Living animals white.

Head ( Fig. 1C, D View FIGURE 1 ; see also Antić et al. (2023: figs 17B, D, 18A–D). Densely setose, roundly convex in females, in males with labral and frontal surfaces flat with a convexity between and with a pair of lateral lobes, each below antennal sockets. Labrum with three medial teeth and 3+3 labral and 2+2 supralabral setae. Promentum subtriangular, without setae. Lamellae linguales with 10+10 setae in two rows. Stipites with ca 35 setae each. Antennae 3.2 mm long in holotype male. Length of antennomeres (in mm): I (0.15), II (0.26), III (0.90), IV (0.45), V (0.85), VI (0.28), VII (0.25) and VIII (0.06). Length/breadth ratios of antennomeres I–VII: I (1.0), II (1.6), III (7.0), IV (3.0), V (5.7), VI (1.4) and VII (1.7). Antennomeres II, IV, V, VI and VII with one, three, one, four and one long sensillum trichoideum, respectively. Antennomere 6 with a distal corolla of longer sensilla basiconica. Antennomere 7 with one rather bacilliform sensillum (sensillum basiconicum?) curved distad, located below sensillum trichodeum. Lateral to antennal sockets, a group of papilliform outgrowths present. Number of ommatidia 5–10, in 2–3 rows, arranged in elongated triangles; ommatidia pale brownish or completely transparent in adults.

Collum. Narrower than head, with six macrochaetae as all body segments. Anterior edge semi-circular, posterior margin gently concave.

Body segments ( Fig. 1 View FIGURE 1 ; see also Antić et al. (2023: figs 17A, C, E, 18E–G). With well-developed lateral keels, anterior margins rounded in dorsal view. Macrochaetae long and trichoid.

Telson. Epiproct with a pair of spinnerets and 3+3 setae (1+1 paramedian, 2+2 marginal). Hypoproct with 1+1 distal setae. Paraprocts with 3+3 marginal setae in distal part.

Leg pairs 1 and 2. In both sexes with tarsal combs; femora, postfemora and tibiae with long and robust setae.

Male sexual characters ( Figs 1 View FIGURE 1 , 2A–H View FIGURE 2 ). Gonopores mesally on coxae 2 ( Fig. 2A View FIGURE 2 ). Leg-pairs 3–7 enlarged, especially leg-pairs 3, 4 and 7 ( Fig. 1 View FIGURE 1 ). Leg-pairs 3 and 4 very thick ( Figs 1 View FIGURE 1 , 2B–D View FIGURE 2 ), each with a proximal lateral protrusion on prefemora; prefemora and femora strong, rectangular; tarsi shorter and thicker compared to other legs; femora, postfemora and tibiae each with a distoventral pad. Leg-pair 5 with a proximal, anterior, triangular, coxal protrusion ( Fig. 2E View FIGURE 2 ). Leg-pair 6 with proximal lateral protrusion on prefemora; without other peculiarities ( Fig. 2F View FIGURE 2 ). Leg-pair 7 robust; coxae with wide, well-developed, flattened and bilobed posterior processes, covered with long setae anteriomesally; lateral lobes strongly developed, mesal ones much smaller ( Fig. 2G View FIGURE 2 ). Leg-pair 10 with coxal glands and strongly developed, rounded coxal lobes ( Fig. 2H View FIGURE 2 ). Leg-pair 11 with coxal glands, no other peculiarities.

Anterior gonopods ( Figs 2I View FIGURE 2 , 3A–C View FIGURE 3 , 16E View FIGURE 16 ; see also Antić et al. (2023: fig. 19A–F). Gonopodal sternum (s) wide, medially with a poorly developed and fimbriate lamella (sl) on anterior side. Angiocoxites (a) consisting of a medial part (mp), lateral lamellae (ll) and a synangiocoxal base (sa) with anterior processes (ap). Medial parts well developed, high, divided, but appressed to each other, shieldlike, distally rounded, distomesal margins expressed and denticulate posteriorly; angiocoxites posteroproximally with a pair of tufts (tf) including lobes with long and short hairlike outgrowths and spiculiform outgrowths, distally with an opening. Lateral lamellae very low, denticulate distally. Synangiocoxal base with a pair of anterior, mesal lobes (lo); anterior processes somewhat sigmoid, tapering distad, acuminate, slightly shorter than and partially covered by medial parts. Coxal vesicles (cv) present posteriorly.

Posterior gonopods ( Figs 2J View FIGURE 2 , 3D View FIGURE 3 ). Gonopodal sternum (s) wide, well developed. Angiocoxites (a) positioned posteriorly, well developed, wide, curved anterolaterad, distally with small tubercles; of the same height as colpocoxites (c). Colpocoxites subtriangular, fused with basal halves of angiocoxites. Telopodites (t) small, rounded, placed posteriolaterally.

Leg pair 2 in females. With well-developed distomesal protrusions on coxae covered with small tubercles and setae.

Vulvae (see Antić et al. (2023: figs 19G–I, 20)). Anterior part as wide as vulval length. Operculum well developed, bilobed, with 6+6 setae (5+5 lateral shorter setae and 1+1 mesal longer setae). Bursa with strongly thickened anteroproximal lips on which the operculum rests. Lateral valve with eight setae, mesal valve with nine setae. Posteriorly, bursa with wrinkled lateral lobe.

Locality and ecology. Antić et al. (2023) already gave some information about the Muradi and Nikortsminda Sakinule caves. The Tskhrajvari cave is also located in Ambrolauri Municipality, in the Racha karst massif, on the Racha ridge, near the Nakerala Pass. The total length of the cave is 470 metres. At the beginning of the cave there is a giant mixture of limestone boulders. The cave consists of two intersecting sections. The first section—the “Entrance hall” (length 100 metres)—is connected by a narrow and low hole to a relatively wide and high hall, which is 15–25 metres wide and 15–20 metres high. The air temperature at the entrance is 17°C, at the end of the first half, 12°C at the connecting hole and 6.5–7°C in some parts of the cave and at the end of the “Big hall” ( Tatashidze et al. 2009). The cave is also known as the site where the cave bear was found ( Chichinadze 2022). It is interesting to note that the cave is characterised by the presence of cave hygropetric habitats. The specimens were found in dark and humid parts of the “Entrance hall” and in the main hall, where they mainly crawled on the rocks. In addition to the new species, another troglobiotic millipede was found in the cave, the hygropetricolous Leucogeorgia longipes Verhoeff, 1930 ( Fig. 1E View FIGURE 1 ). Besides these two troglobites, one more cave-dwelling species was recently described from this cave, the leech Dina kobakhidzei Grosser, Maghradze & Barjadze, 2025 ( Grosser et al. 2025).

Distribution. A Georgian endemic, known so far from three caves in the Racha karst massif ( Fig. 17 View FIGURE 17 ).