Axenyllodes potapovi, Babenko & Shveenkova & Arbea, 2025

Axenyllodes potapovi sp. nov.

Figs 33–39 View FIGURES 33–39

Type material. Holotype, juvenile, Russia, Eastern Caucasus, Dagestan, north of Izberbash, 42.6090 o N 47.7898 o E, coast of Caspian Sea , ~ 30 m alt., sand, zone of weak vegetation (flotation), 23 April 2018. N. Kuznetsova, M. Potapov & A. Kremenitsa leg. GoogleMaps

Diagnosis. A blind species of the genus with the complete absence of dark pigment, characterized by: a more or less distinct pattern of cuticular granulation on thorax and in the anterior part of the abdomen; the presence of 7 clearly differentiated dorsal sensilla and a rather large microsensillum on Ant. IV; star-shaped PAO with three lobes, not sunken into the cuticle; 2+2 postlabial setae; Th. II–III with setae m1 present and lateral microsensilla absent, lateral sensilla on the thorax slightly thickened; the basic type of VT, tenaculum and furca; manubrial field with 8+8 setae; the tibiotarsi with 7–7–7 subequal setae and 7 setae on each femur; and the absence of AS.

Description. Length (without antennae) of the only known specimen, 0.54 mm. Habitus typical of the genus: body oblong, appendices short. Colour white without any traces of dark pigment. Tegument granulation rather coarse, secondary granules usually spinous at tip. Th. II–Abd. II with rather long and narrow longitudinal fields of finer granulations located symmetrically with respect to medial line, only traces of such fields developed on Abd. III–IV ( Fig. 36 View FIGURES 33–39 ).

Antennae about as long as head. Ant. IV with a large simple vesicle apically, with 7 clearly differentiated sensilla (four dorso-internal [S1–S4] and three dorso-external [S7–S9, S8 longer and thinner, S9 located higher than usual], ms about 0.4 times as long as nearest sensillum, subapical organite present, ventral side with few ordinary setae ( Figs 33–34 View FIGURES 33–39 ). Antennal organ of Ant. III typical, inner sensilla small, sgv & sgd larger and subequal to ms. Ant. I–III with 7, 10 and 17 ordinary setae, respectively.

Ocelli absent. PAO star-shaped, with three lobes, located superficially in a small depression ( Fig. 35 View FIGURES 33–39 ). Buccal cone short, typical of the genus ( Fig. 37 View FIGURES 33–39 ). Labrum with 8 labral setae, medial pair of which in anterior row much stronger and with their tips curved laterally, as usual; prelabral setae invisible. Maxillary palp simple. Labium with several small apical spinules and three common setae; basomedial and basolateral fields of labium with 4+3 setae, respectively. Maxilla typical of the family with a strong and triangular head, mandibles invisible. Ventral side of head in holotype with 2+2 postlabial setae along ventral line ( Fig. 37 View FIGURES 33–39 ).

Ordinary setae on dorsal side of body short, smooth and acuminate, those on last abdominal terga only slightly longer, dorsal sensilla undifferentiated, but lateral ones on Th. II–III clearly thickened ( Fig. 36 View FIGURES 33–39 ). Main characteristics of dorsal chaetotaxy: setae m1 present on Th. II–III and absent from Abd. IV; Th. II–III with only three setae in a-row (a1, a3 and a5), three m-setae (including S=m6), and five setae in p-row as usual, lateral microsensilla absent; Abd. I–III with four setae in a-row (a1, a2, a3 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 3 and 5 ventral setae each side, respectively ( Fig. 38 View FIGURES 33–39 ). Tenaculum with 2+2 teeth, as usual. Furca small ( Fig 38 View FIGURES 33–39 ), manubrial field with 4+4 setae on main part, 1+1 basal and 3+3 basolateral setae (8+8 setae totally); dorsal side of dens with two setae and rather fine granulation. Mucro about as long as or slightly longer than dens, strongly hooked, lateral lamella present. Anal opening located terminally; anal spines completely absent.

Chaetotaxy of Legs I–III as following: 1, 2, 2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 3, 4, 4 setae on coxae, 5, 5, 4–5 on trochanters, 7, 7, 7 setae on femora, and seven subequal setae also present on each tibiotarsi. Unguis toothless, unguiculus invisible ( Fig. 39 View FIGURES 33–39 ).

Etymology. The new species is to honour our friend and colleague, Mikhail B. Potapov, whose contribution to springtail taxonomy is outstanding.

Affinities. Currently, only four completely blind species of the genus which lack anal spines are known: A. clevai Thibaud, 1995 ( France), A. nematodes Fjellberg, 1995 (Canary Islands), A. japonicus ( Japan) and A. comoriensis ( Comoro Islands). In addition, A. americanus Vázquez & Palacios-Vargas, 1989 , the only South American species of the genus, sometimes also has no anal spines, but it also lacks a mucro (a unique feature for the genus) and is hardly comparable to A. potapovi sp. nov.

Three of the four species listed above are fairly easily distinguished from A. potapovi sp. nov. because all of them have lateral microsensilla on Th. II–III (for other differences, see Table 1 View TABLE 1 ). The only exception is A. nematodes , which, however, unlike A. potapovi sp. nov., is characterized by the presence 6 and 6 setae on each femur and tibiotarsus, respectively (vs 7 and 7 setae in A. potapovi sp. nov.) and 7+7 setae on the manubrial field, i.e. basal pair of setae absent ( Fig. 14 View FIGURES 10–15 ) (vs 8+8 setae including a basal pair in A. potapovi sp. nov., Fig. 38 View FIGURES 33–39 ). In other words, the holotype of the new species is clearly characterized by a larger number of setae on the legs and in the manubrial region than A. nematodes , not fewer, as could be expected based on its juvenile state. In our opinion, this supports its status as a new species.

There is one more character that could probably be used to distinguish the two species (3+3 postlabial setae ventrally on the head in A. nematodes , vs 2+2 such setae in A. potapovi sp. nov.), but unfortunately this may be related to the immature status of the only known specimen of the latter species.