Pseudachorutella circassiana, Babenko & Kuznetsova, 2024

Babenko, Anatoly & Kuznetsova, Natalia, 2024, Three new species of the genus Pseudachorutella Stach, 1949 (Collembola, Neanuridae) from Russia, Zootaxa 5447 (2), pp. 188-198 : 189-192

Pseudachorutella circassiana sp. nov.

Figs 1–2 , 5–10

Type material. Holotype: female, Russia, NW Caucasus, Karachay-Cherkess Republic , vicinity of Rozhkao, 43.8133 oN 40.9215 oE, 1140 m alt., hornbeam forest, litter, 29.06.2017. N. Kuznetsova & A. Geras’kina leg. Paratypes: 5 male (pread.) and 3 female (same sample); one male, 3 female and 2 juveniles, NW Caucasus, Republic of Adygea, vicinity of Guzeripl, Caucasian State Nature Reserve , mixed forest (fir and beech), litter near tree trunk, 26.06.2017. N. Kuznetsova & A. Geras’kina leg.

Diagnosis. A small-sized species of the genus. Ant. IV with usual eight dorsal sensilla, ventral «file» with rather long sensilliform setae covering about half of ventral side. Ventral guard sensillum in antennal organ on Ant. III significantly longer than dorsal one. Buccal cone long, labrum with pointed edge and 2/2334 setae, i.e. medial pair of prelabral setae absent, labium with 12 ordinary setae and a subapical spine L, organites small, hardly visible. Maxillae styliform with a tiny hook at apex. Mandibles delicate with two apical teeth. Generally, dorsal chaetotaxy of a basic type (as in P. asigillata , see Fjellberg 1985, p. 351, fig. 3), but two setae d1 usually present on head instead of unpaired d0.

Description. Length (without antennae) 0.72–1.24 mm, holotype –– 1.24 mm. Colour of dorsal side quite dark, grayish-blue, with numerous light spots; ventral side noticeably paler. Tegument granulation coarse and uniform.

Antennae about as long as head, Ant. III–IV fused dorsally, ventral separation well marked. Ant. IV with a trilobed apical vesicle, external ms, subapical or and seta i present; eight sensilla (S1–S8) on dorsal side of Ant. IV clearly differentiated ( Fig. 6 ), ventral «file» with rather long sensilliform setae covering about half of ventral side ( Fig. 5 ). Antennal organ of Ant. III typical, inner sensilla small, sgv clearly longer than sgd (cf. Fig. 5 and Fig. 6 ), ventral ms and about 20 common setae present on Ant. III. Ant. I–II with 7 and 13 setae, respectively.

Head with 8+8 subequal ocelli. PAO absent. Buccal cone long and pointed. Maxilla styliform with an apical hook and a pointed lamella ( Fig. 8 ). Mandibles thin and delicate, with two apical teeth as a rule ( Fig. 7 ); rarely 1–2 tiny denticles visible between them. Distal edge of labrum pointed (ogival), number of prelabral and labral setae as follows 2/2334; medial pair of prelabral setae always absent. Labium with usual 12 setae and a subapical spine L ( Fig. 9 ), organites invisible or present in a form of tiny remains. Total length of labium is 3.9–4.6 of distance between postlabial setae a1 and m1. Perilabial area with 4+4 setae.

Ordinary setae on dorsal side of body short, smooth and acuminate, sensilla 1.8–2.2 times longer than ordinary setae ( Figs 1–2 ), their number as usual: 22/11111. Main characteristics of dorsal chaetotaxy: head with neither a0 nor d0, position of setae d1 unstable; Th. I with 3+3 setae; Th. II with a2-setae and ms present, number of setae in dorso-external group on Th. II–III slightly variable ( Fig. 1 ). Abd. I–IV without additional setae; setae p2 on Abd. V absent ( Fig. 2 ).

Thoracic sterna without setae. Ventral tube with 4+4 distal setae, no seta on sternum of Abd. I, Abd. II with 4–5 ventral setae on each side. Tenaculum with 3+3 teeth as usual. Furca strong, dorsal side of dens with six setae and coarse granulation, hyaline field on its ventral side shorter than mucro length. Mucro with lateral lamella not reaching tip. Each anal valve with two small hr-setae.

Legs I–III with an almost stable set setae: 1, 2, 2 setae on upper subcoxae, 0, 2(3), 2(3) setae on lower subcoxae, 3, 8, 8 setae on coxae, 6, 6, 6 on trochanters, 13, 12, 11 setae on femora and 19, 19, 18 setae on tibiotarsi. Unguis with clear tooth in mid part of inner edge, two lateral teeth usually present but poorly visible ( Fig. 10 ).

Etymology. The new species is named after the Circassians, an indigenous ethnic group of the northwestern Caucasus who currently live in various North Caucasian republics, as well as in Turkey, Iran and other countries of the Middle East.

Affinities. The dorsal chaetotaxy of P. circassiana sp. nov. is almost identical to that of both P. asigillata and P. ellisi , except for the usual presence of a pair of setae d1 on the head instead of the unpaired do. According to Jordana et al. (1977), Fjellberg (1998) and Smolis et al. (2023), the latter character is typical for both of these species. Considering some variability in position of setae on area frontalis detected in Caucasian specimens, it can hardly be considered significant. However, the three species can be distinguished by the length of their buccal cone. Thus, the ratio of the length of the labium to the distance between the a1 and m1 setae on the ventral side of the head, according to Smolis et al. (2023), is only 2.5 in P. asigillata and 4.5–5.0 in P. ellisi , while in P. circassiana sp. nov. this ratio is 3.9–4.6. In addition, these three species differ in the degree of development of the labial organites (large and clearly visible in P. asigillata , absent from P. ellisi and tiny, hardly visible in P. circassiana sp. nov.) and the ventral «file» on Ant. IV (several slightly modified sensilla in P. asigillata and P. circassiana sp. nov., vs numerous small sensilla in P. ellisi ), as well as the presence/absence of p2 setae on Abd. V (absent from P. asigillata and P. circassiana sp. nov., but present in P. ellisi ).

It is noteworthy that, at most of the localities listed in the Type material part of P. circassiana sp. nov., that species was collected together with larger sized specimens of P. plurichaetosa sp. nov. At first, we believed they all represented the same species differing in sizes. However, a closer examination of the available material showed their significant differences (see Table 1 ), detailed below under the description of P. plurichaetosa sp. nov.

Figures

FIGURES 1–4. Dorsal chaetotaxy of Pseudachorutella circassiana sp. nov. (1–2) and P. plurichaetosa sp. nov. (3–4): 1, 3, head and thorax; 2, 4, Abd. III–VI. Scales: 0.1 mm.

FIGURES 5–19. Pseudachorutella circassiana sp. nov. (5–10) and P. plurichaetosa sp. nov. (11–19): 5, antenna (ventral side); 6,Ant. III–IV (dorsal side); 7, mandible; 8, maxillary apex; 9, labium; 10, unguis and tibiotarsus of leg.2; 11, Ant. III–IV (ventral side); 12, antenna (dorsal side); 13, mandible; 14, maxillary apex; 15, labrum; 16, labium; 17, unguis and tibiotarsus of leg 2; 18, dens and mucro (dorso-lateral view); 19, ibid. (inner side); Scales: 5–6, 11–12, 17–19, 0.1 mm, 7–10, 13–16, 0.01 mm.