Geophilus hadesi Stoev, Akkari, Komericki , Edgecombe & Bonato

Stoev, Pavel, Akkari, Nesrine, Komericki, Ana, Edgecombe, Gregory D. & Bonato, Lucio, 2015, At the end of the rope: Geophilushadesi sp. n. - the world's deepest cave-dwelling centipede (Chilopoda, Geophilomorpha, Geophilidae), ZooKeys 510, pp. 95-114 : 97-102

Taxon classification Animalia Geophilomorpha Geophilidae

Geophilus hadesi Stoev, Akkari, Komericki, Edgecombe & Bonato sp. n. Figs 2, 3-6, 7-10, 11-14, 15-19

Material examined.

Holotype: female, 28 mm long, with 33 pairs of legs; Croatia, Zadarska županija (Zadar County), Southern Velebit Mountain, Crnopac massif, city Gračac, Munižaba cave, N44°15'57.4", E 15°52'09"; circa -250 m below the surface (cave entrance at 915 m a.s.l.); hand collected, 19 February 2011, leg. B. Jalžić (CBSS, collection code: CHP 532).

Paratype: female (damaged), approx. 22 mm long, with 33 pairs of legs; same area as the holotype, Muda labudova cave, N44°15'38.5", E15°51'18.2"; -500 m below the surface (cave entrance at 1020 m a.s.l.); hand collected, 2-3 July 2011, leg. J. Bedek (NHMW, collection code: NHMW8363, 3 SEM stubs)

Other specimen examined: male, approx. 27 mm long, with 33 pairs of legs; Croatia, Ličko-senjska županija (Lika-Senj County), Northern Velebit Mountains, Hajdučki i Rožanski kukovi Strict Reserve, Lukina jama - Trojama cave system, N44°46'01.6", E15°01'52.7"; -980 m below the surface (cave entrace at 1475 m a.s.l.); hand collected on boulder, 1-3 August 2011, leg. J. Bedek (CBSS: CHP515).

Origin of name.

The specific epithet derives from Hades, god of the underworld in Greek mythology and husband of Persephone, in analogy with the name of the only other known troglobite in the genus.

Diagnosis.

A species of Geophilus with a slender body, adult circa 2.2-2.8 cm in length; antennae circa 4.5-5 times as long as the head; second maxillary pretarsus very small, tubercle-like with a short tip; exposed part of the forcipular coxosternite more than 1.8 times as wide as long, coxopleural sutures strongly diverging forwards all along their length, chitin-lines incomplete; trunk metasternites elongate, with carpophagus pit; sternal pore-fields on both anterior and posterior parts of trunk; legs elongate, 33 pairs, with long claws; metasternite of the ultimate leg-bearing segment wider than long; coxal pores only on the ventral side, most of them close to the margin of the metasternite, also a single one isolated posteriorly; legs of the ultimate pair with claws.

From the other European species of Geophilus with a similarly low number of legs, it can be readily distinguished by a number of traits (see Table 1 and Discussion below).

Description of the holotype.

Length 28 mm (damaged paratype: circa 22 mm).

Cephalic plate. Cephalic plate as long as wide (also in paratype: Fig. 3), anterior margin slightly angulated, lateral margins evidently convex and convergent forward for their anterior two thirds, posterior margin almost straight; transverse suture absent. Most setae 100-120 µm long.

Antennae. Circa 4.6 times as long as the maximum width of the head (also in paratype: Figs 5, 6); all but first article longer than broad, proportions between articles: V=VI>VII=IV>VIII>IX>III>II=X>XI>I>XIV>XIII>XII. Ultimate article twice as long as penultimate (also in paratype: Fig. 6a). Antennae densely covered with setae, which are nearly as long as antennal breadth on the basal articles, gradually shorter and more dense from basal towards the distal articles. Apical sensilla slender, spear-like, circa 14 μm long, slightly narrowing towards the tip. Club-like sensilla (sensilla basiconica) in two groups, one on the internal side and the other on the external side on article XIV (also in paratype: Fig. 6b).

Clypeus. Uniformly areolate, without finely areolate clypeal areas; three pairs of setae including a paramedian pair close to the anterior margin and two pairs of larger setae in the middle of clypeus (also in paratype: Fig. 4).

Labrum. About eight triangular denticles on the intermediate part of the margin, and some longer and thinner bristles on the lateral parts (also in paratype: Fig. 7).

Maxillary complex. First maxillae: coxosternite entire; coxal projections subtriangular, bearing four large setae and one subapical spine-like seta; telopodites almost the size of the coxal projections, with the intermediate articulation weakly distinct; lappets apparently absent or very short (also in paratype: Fig. 8). Second maxillae: coxosternite entire, uniformly areolate, the anterior margin widely concave, with setae close to the anterior margin; telopodite composed of three articles, gradually narrowing towards the tip; basal article with three long setae close to the inner margin, article 2 with one seta, article 3 with 13-15 setae; pretarsus small, tubercle-like with a small apical tip (also in paratype: Fig. 8).

Forcipular segment. Forcipules, when closed, not exceeding the anterior margin of the head. Tergite wider than long, lateral margins evidently convex. Ventrally exposed part of the coxosternite 1.8-1.9 times as wide as long, anterior margin without denticles (also in paratype: Figs 9, 10); coxosternal denticles replaced by a prominent coxosternal ridge, with a pair of long setae exceeding the coxosternal margin (Fig. 10); coxopleural sutures strongly diverging forwards all along their length; chitin-lines incomplete and pointing lateral from the condyles. Trochanteroprefemur with external side almost twice as long as the internal side. Tarsungulum with a small denticle at the base, abruptly narrowing and bent basad, then gradually tapering. No denticles on the other forcipular articles.

Leg-bearing segments. A total of 33 leg-bearing segments (also in paratype). Tergites wider than long (Fig. 11), tergite 1 slightly wider than metatergite 2. Metasternites longer than wide, both in the anterior and the posterior part of trunk. Those in the anterior part of the trunk, with the exception of the first segment, with anterior carpophagus pits taking up one third of the length of the metasternite (also in paratype: Figs 12, 13); pits decreasing in size towards the body end to almost vanishing in the last five segments (Fig. 14). Pore-fields present on most part of the metasternites (also in paratype: Figs 12-15): a single transverse band along the posterior margin of each metasternite, appearing as two paramedian groups on the metasternites of the posterior half of the trunk, and poorly visible posterior to leg-bearing segment 26. Legs distinctly longer than the breadth of the body; their length increases towards leg pairs 25-26, then gradually decreasing until pair 32; leg 1 shortest. Leg claws very slender (Figs 16, 17, 19), more than 6 times as long as broad at the basis, with two long and pointed accessory spines.

Ultimate leg-bearing segment. Metasternite sub-trapezoidal, circa 1.3 times as wide as long, lateral margins converging posteriorly; posterior margin narrower than anterior; setae uniformly scattered. Coxopleura moderately swollen, reaching backward approximately two thirds of first genital pleurosternite. Coxal organs opening through distinct pores, all on the ventral side, mostly close to the lateral margins of the metasternite, 5+6 (5+5 in paratype). Coxal pores generally large, one lying in the middle of the ventral side of the posterior part of the coxopleuron, somewhat apart from the rest (also in paratype: Figs 18, 20). Telopodites of the ultimate pair almost as long as legs 25-26. Proportions between the lengths of the leg articles: trochanter<prefemur<coxa=tarsus2<femur=tibia=tarsus1; claws shorter than those of preceding legs, accessory spines distinctly shorter.

Postpedal segments. First genital pleurosternite entire. Gonopodal lamina distinctly bilobed. Anal pores present (also in paratype: Fig. 18).