Hirudicryptus abchasicus, Golovatch, Sergei, Evsyukov, Aleksandr & Reip, Hans S., 2015

Golovatch, Sergei, Evsyukov, Aleksandr & Reip, Hans S., 2015, Colobognatha millipedes in the Caucasus (Diplopoda: Polyzoniida, Platydesmida, Siphonocryptida), Zootaxa 3972 (2), pp. 250-266 : 260-262

Hirudicryptus abchasicus sp. nov.

Figs 6–10

Material examined. Holotype male ( ZMUM ρ2583), ABKHAZIA, Gumista Nature Reserve, forest litter, 4.VI.1982, leg. J. Boháč. Paratype female ( ZMUM ρ2584), same data, together with holotype.

Name: To emphasize Abkhazia, the terra typica; adjective.

Diagnosis: Distinguished from all congeners but H. canariensis (Loksa, 1967) by the much shorter antennae which are only about as long as collum width, as well as by the smaller and much shorter collum which only forms a quite inconspicuous casque-like shield to cover the head. Differs from H. canariensis by the concave last tergum and less numerous, 9–11 + 9–11 vs 14–15 + 14–15, tubercles at the caudal margin of midbody terga. See also Key below.

Description: Length about 8.5 (holotype) or 7 mm (paratype), width ca 0.9 and 1.0 (holotype) or 0.8 and 0.9 mm (paratype) on midbody pro- and metazonae, respectively. Holotype with 48 podous + 1 apodous segment + telson, paratype with 43p + 1a + telson. Length to width ratio> 10:1.

Coloration in alcohol rather uniformly red- or grey-brown to yellowish with a narrow light axial line (alcohol material), anterior part of body in paratype darker, marbled grey; metatergal bosses/tubercles at caudal margin and antennae mostly dark grey-brown while a very wide mid-dorsal stripe lighter both in holo- and paratype ( Fig. 6 A, C). Ocelli inside a black ocular field. Body very clearly flattened dorsoventrally, hirudiform, regularly, but strongly broadened until segment 6 or 7, similarly regularly and clearly narrowing towards telson on last 4 or 5 segments. Head very small and rather narrow, coniform, about 1/3 as broad as collum and about twice as long as broad; rostrum narrowly rounded ( Figs 6 A, 7A). Ocelli large, convex, 2+2 on each side of head arranged in a nearly longitudinal line, each ocellus with a long seta at base. Antennae short, stout, erect, rod-shaped, not clavate, about as long as collum width; antennomere 6 largest ( Figs 6 A, B, 7A).

Collum biconvex, short and broad ( Fig. 7 A), like head characteristically strongly inclined forward to form a small casque-like shield, also distinctly separated from next tergum ( Fig. 6 B, D); paraterga on collum small, strongly declined, subvertical, each delimited by an oblique sharp bend; dorsal surface rather flat, only slightly impressed medially; caudal margin with a transverse row of several small grains/tubercles ( Fig. 7 A) and a considerable lighter gap between paramedian pair ( Fig. 6 ). Axial suture inconspicuous, but visible starting with collum. Following paraterga nearly acute at caudal corner, especially clearly drawn behind tergal margin only in 2nd and a few caudalmost segments, paraterga of penultimate segment fused medially into a broad, terminally slightly concave plate with two caudolateral denticles and a vestigial axial suture ( Figs 6 C, 7C). Lateral peritremes on paraterga evident, delimited by a sulcus both dorsally and, to lesser degree, ventrally. Metaterga slightly, but clearly elevated caudally, each with 9–11 + 9–11 small bosses/tubercles at caudal margin, like collum with a considerable lighter gap between paramedian pair. Surface of collum and following metaterga faintly rugulose and microtuberculate, dull all over. Ozopores lateral, starting with segment 5, small, inconspicuous, each lying at bottom of a small oblong groove in front of caudolateral corner of a clearly thickened, nearly porostele-shaped peritreme ( Fig. 7 B). Telson small, completely concealed in dorsal view by caudal plate of penultimate segment’s fused paraterga ( Figs 6 A, C, D, 7C).

Sterna about 2/3 as wide as coxae, the latter almost in touch medially ( Fig. 6 A, C, E). Legs 6-segmented. Male coxa 2 with a short, tube-shaped, simple, basal gonapophysis directed caudomesad. Claws simple ( Fig. 8 A). Coxal sacks starting with leg 3.

Anterior gonopods ( Fig. 8 B) apparently 5-segmented, C-shaped, strongly incrassate and stout. Tarsus with a strong apical stylet and a gutter for accommodation of posterior gonopod tarsus ( Fig. 8 B, C). Posterior gonopods ( Fig. 8 D) apparently 6-segmented, much slenderer; tarsus longest, flagelliform, very simple.

Remarks. The order Siphonocryptida has hitherto been known to contain only six species in two genera and a single family ( Enghoff and Golovatch 1995; Korsós et al. 2008, 2009; Enghoff 2010). The group’s highly peculiar distribution only emphasizes its relictual status ( Shelley and Golovatch 2011). Thus, the genus Siphonocryptus Pocock, 1894 , comprises three species, one in Sumatra, Indonesia, the other two in continental Western Malaysia ( Enghoff and Golovatch 1995; Enghoff 2010). In contrast, the distribution pattern of Hirudicryptus Enghoff & Golovatch 1995 is trans-Palaearctic ( Fig. 10 ). The type species, H. canariensis (Loksa, 1967) , occurs only on Madeira and the Canaries, where it is largely confined to the relict laurisilva biome. The second species, H. taiwanensis Korsós, Enghoff & Chang, 2008 , is endemic to Taiwan, whereas the third, H. quintumelementum Korsós, Geoffroy & Mauriès, 2009 , is only known from a few females collected at a 2500 m elevation in Nepal, Himalayas ( Enghoff and Golovatch 1995; Korsós et al. 2008, 2009). It may well be that the distribution pattern under consideration dates back at least to the Oligocene times of the so-called “Warm Earth” to have highly probable explanations rooted in palaeobotanical evidence. These imply a gradual shrinkage and disruption ever since of the previously dominating and continuous subtropical biome ( Golovatch 1997; Zherikhin 2003). Being so vastly disjunct, the present-day distribution of Siphonocryptida is best accounted for by extinction events ( Shelley and Golovatch 2011).

The discovery of H. abchasicus sp. nov. in the Caucasus very nicely bridges the huge gap between Macaronesia and the Himalayas (Fig, 10). This species is clearly a highly relictual element in the Caucasian fauna. Luckily, it stems from a nature reserve, thus demanding no other special measures of protection.

The following key can be offered to separate all four presently known species of Hirudicryptus .

1. Caudal margin of last tergum straight, devoid of lateral prongs.................................................. 2

- Caudal margin of last tergum clearly concave, flanked by small lateral prongs ( Figs 6 C, 7C).......................... 3

2. Midbody terga with 14–15 + 14–15 tubercles at caudal margin. Macaronesia........................... H. canariensis

- Midbody terga with 9–11 + 9–11 tubercles at caudal margin. Nepal............................. H. quintumelementum

3. Midbody terga with 6–8 + 6–8 tubercles at caudal margin Adults larger: length 10.5–16.8 mm (males), up to 19.4 mm (females), width 1.2–2.0 or 1.3–2.5 mm, respectively. Taiwan....................................... H. taiwanensis

- Midbody terga with 9–11 + 9–11 tubercles at caudal margin ( Fig. 6 C). Adults smaller, 7–8.5 mm long, 0.9–1.0 mm wide. Cau- casus.............................................................................. H. abchasicus sp. nov.

Figures

FIGURE 6. Hirudicryptus abchasicus sp. nov., male holotype (A – C) and female paratype (D, E). A, D, E: habitus, mainly sublateral, lateral and mainly ventral views, respectively. B: anterior part of body, subventral view. C: anterior and posterior parts of body, dorsal view. Pictures by K. Makarov, taken not to scale.

FIGURE 7. Hirudicryptus abchasicus sp. nov., male holotype. A: head, collum and segment 2, oral view. B: midbody paraterga, lateral view. C: caudal end of body, dorsal view. Scale bar: 0.5 mm.

FIGURE 8. Hirudicryptus abchasicus sp. nov., male holotype. A: leg 11, caudal view. B: anterior gonopods, anterior view; C: tip of right anterior gonopod, anterodorsal view. D: right posterior gonopod, ventrolateral view. Scale bar: 0.1 mm.

FIGURE 9. Distribution of Colobognatha in the Caucasus and adjacent parts of Turkey and Iran. Blue square— Hirudisoma roseum (Victor, 1839); red asterisk— Fioria hyrcana Golovatch, 1980; green triangle— Hirudicryptus abchasicus sp. nov.

FIGURE 10. Distribution of the genus Hirudicryptus.