Axenyllodes chinki, Babenko & Shveenkova & Arbea, 2025

Babenko, Anatoly, Shveenkova, Yulia & Arbea, Javier I., 2025, Two new and two little-known species of the genus Axenyllodes Stach, 1949 from Russia and Kazakhstan, Zootaxa 5583 (1), pp. 154-170 : 161-163

Axenyllodes chinki sp. nov.

Figs 24–31

Type material. Holotype: female, Kazakhstan, Turkistan Region , Kyzylkum sandy desert, basin of Syr Darya River, 85 km W of Arys, 42.2325 oN 67.8128 oE, 230 m alt., bottom of SE slope of “Small Chink”, pit-traps, 14–16 October 2023. L. Kim leg. Paratypes: 6 females and 4 juveniles, same data as holotype .

Diagnosis. A species of the genus, characterized by the presence of (6)7 clearly differentiated dorsal sensilla and a rather large microsensillum on Ant. IV; 2+2 ocelli with traces of dark pigment under each of them; a distinct pattern of cuticular granulation on the terga; a specific form of PAO, almost completely hidden under the cuticular fold; the absence of lateral microsensilla and the presence of setae m1 on Th. II –III; the basic type of VT, tenaculum and furca; the tibiotarsi with 7–7–7 setae, two of which are distinctly clavate; and the absence of AS.

Description. Length (without antennae) 0.69–0.83 mm. Habitus typical of the genus: body slim and oblong, appendices short ( Fig. 24 ). Colour white with few granules of dark pigment under ocelli. Tegument granulation rather coarse, secondary granules usually spinous at tip. Head with fields of fine granulations in central and posterolateral areas, forming a characteristic pattern of longitudinal stripes; similar granulations present each side of thoracic segments. Abd. I–V with two oval fields of fine granulations located symmetrically with respect to medial line ( Fig. 25 ).

Antennae about as long as head. Ant. IV with a large simple vesicle apically, with 7 clearly differentiated sensilla with pointed apices (four dorso-internal [S1–S4] and three dorso-external [S7–S9]; S9 often absent from immature specimens), ms large, clearly broadened at apex, only slightly shorter in length than sensilla, subapical organite present ( Fig. 27 ), ventral side with few ordinary setae. Antennal organ of Ant. III typical, inner sensilla small, sgv & sgd only slightly larger, ms and about 16–18 ordinary setae present on Ant. III. Ant. I–II with 7 and 10 setae, respectively.

Head with 2+2 subequal ocelli, their diameter equal to 0.24–0.36 of PAO length. PAO sunken in a deep cavity and hardly visible from above, broadly oval in shape, edges pointed ( Fig. 26, 26a ). Buccal cone short, typical of the genus ( Fig. 28 ). Maxillary palp simple. Labrum with 8 usual setae, medial pair of setae in anterior row much stronger, with tips curved laterally; four prelabral setae also present. Labium with five small apical spinules, two tiny organites and three common setae. Basomedial and basolateral fields of labium with 4+4 setae each. Maxilla typical of the family, with a strong and triangular head, mandibles invisible. Ventral side of head with 3+3 postlabial setae along ventral line.

Ordinary setae on dorsal side of body short, smooth and acuminate, distinctly longer on last abdominal terga, sensilla undifferentiated ( Fig. 25 ). Main characteristics of dorsal chaetotaxy: setae m1 present on Th. II–III and absent from Abd. IV; Th. II–III with four setae present in a-row (a1, a3, a4 and a5), m-row with two ordinary setae (m1 and m4) and lateral sensillum in m6 position, lateral microsensilla invisible; Abd. I–III with five setae in a-row (a1, a2, a3, a4 and a5).

Thoracic sterna without setae. Ventral tube with 3+3 distal setae, one seta also present each side of VT on sternum of Abd. I, Abd. II–III with 4–5 ventral setae each side ( Fig. 29 ). Tenaculum with 2+2 teeth, as usual. Furca small ( Fig. 31 ), manubrium with 4+4 setae on main part, 1+1 basal and 3+3 basolateral setae (8+ 8 in total); dorsal side of dens with two setae and rather fine granulations. Mucro about as long as dens, strongly hooked and with clear lateral lamella. Anal opening located terminally; anal spines completely absent.

Legs I–III with a stable set of setae: 1, 2, 2 setae on upper subcoxae, 0, 3, 3 setae on lower subcoxae, 3–4, 3–4, 3–4 setae on coxae, 5, 5, 4(5) on trochanters, 7, 7, 7 setae on femora, inner one thinner and longer. Seven setae also present on each tibiotarsi including two longer and clearly clavate at apex ( Fig. 30 ). Unguis toothless, unguiculus rather long, needle-shaped ( Fig. 30a ).

Etymology. Named after “chink”, a regional term used, according to Wikipedia <https://en.m.wikipedia.org/ wiki/Chink_(geology)>, “ in Central Asia for steep chalk and limestone escarpments and cliffs heights up to 350 m, often around flat-top elevation ” ( Fig. 32 ).

Affinities. Currently, there are only five known species in the genus characterized by such a small number of chaetae (7 or 6) on the tibiotarsi as in A. chinki sp. nov.: A. echinatus , A. nematodes Fjellberg, 1995 , A. japonicus Tamura in Tamura & Yue, 1999, A. sinensis and A. comoriensis Thibaud, 2011 . Most of them have a reduced number of ocelli (0–1). The only exception is A. sinensis , described from the mountainous regions of southwestern China, which, like A. chinki sp. nov. has 2+2 ocelli, almost identical dorsal and ventral chaetotaxies, as well as similar pattern of the integument granulation. These two species can easily be distinguished by the shape of the PAO (a single triangular lobe in A. sinensis , vs broadly oval PAO with pointed edges, sunken in a deep cavity and hardly visible from above in A. chinki sp. nov.), as well as the presence of anal spines and the absence of clavate tenent setae in A. sinensis .

One more species, A. potapovi sp. nov., also characterized by a strong reduction of the tibiotarsal setae, is described below. It can easily be distinguished from A. chinki sp. nov. by the complete absence of eyes (for other differences, see Table 1 ).

Unfortunately, the number of tibiotarsal setae was not specified in two known species of the genus, i.e. A. caecus and A. monoculatus ( Jordana & Ardanaz, 1981) , in the original descriptions or subsequently, although the Canarian specimen identified by A. Fjellberg as A. cf. monoculatus was noted to have 10–10–9 setae on the tibiotarsi and 7 femoral setae ( Fjellberg, 1995, p. 156). Both of them have a reduced number of ocelli (less than 2+2): A. caecus is blind, whereas A. monoculatus has only 1+1 ocelli.

Using the most recent key to species of the genus ( Thibaud 2006), the new species can be identified as A. marci , described from a sandy beach in Albania, which, like A. chinki sp. nov., has 2+2 ocelli and lacks anal spines. These two species clearly differ in the chaetotaxy of the thoracic terga ( A. marci is characterized by the absence of setae m1 and the presence of lateral ms on Th. II–III) and the number of tibiotarsal setae (10 in A. marci , vs 7 in A. chinki sp. nov.).

Figures

FIGURES 32. The type locality of Axenyllodes chinki sp. nov.

FIGURES 24–31. Axenyllodes chinki sp. nov.: 24, general habitus; 25, cuticular granulation and dorsal chaetotaxy; 26 and 26a, PAO and ocelli; 27, chaetotaxy of antenna, dorsal view; 28, ventral chaetotaxy of head; 29, ventral chaetotaxy of abdomen; 30, tibiotarsi III; 30a, tip of leg III; 31, furca, lateral view. Scales: 24–25, 28–29, 0.1 mm, 26–27, 30–31, 0.01 mm.