Pseudachorutella plurichaetosa, 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 : 192-194

Pseudachorutella plurichaetosa sp. nov.

Figs 3–4 , 11–19

Type material. Holotype: female (preadult), Russia, NW Caucasus, Republic of Adygea, vicinity of Guzeripl [43 o 59’N 40 o 07’E], Caucasian State Nature Reserve , mixed forest (fir and beech), litter near tree trunk, 26.06.2017. N. Kuznetsova & A. Geras’kina leg. Paratypes: one male (pread.) and one female, same data as holotype ; one female, NW Caucasus, Karachay-Cherkess Republic , Damkhurts River valley, 43.6658 o N, 40.8287 o E, 1235 m alt., mixed birch-fir forest, rotten wood, 02.06.2017. A. Geras’kina leg. ; one female, same republic, vicinity of Rozhkao , 43.8133 o N 40.9215 o E, 1140 m alt., hornbeam forest, litter, 29.06.2017. N. Kuznetsova & A. Geras’kina leg.

Diagnosis. A large-sized species. Sensorial equipment of Ant. IV usual for the genus, with eight blunt dorsal sensilla and many small sensorial elements ventrally. Buccal cone long and pointed, labrum with 4/2334 setae, labium with 12 ordinary setae and subapical spine, labial organites invisible. Maxillae with two apical hooks, mandibles with 5 teeth. Dorsal chaetotaxy of abdomen characterized by the presence of supplementary setae, especially in dorso-external parts of Abd. IV. Abd. V lacking setae p2.

Description. Length (without antennae) 1.5–2.3 mm, holotype − 1.64 mm. Colour of dorsal side dark, grayish-blue, ventral side paler. Tegument granulation coarse and uniform.

Antennae slightly longer than 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. 12 ), ventral «file» with numerous sensilliform setae covering about ¾ of ventral side ( Fig. 11 ). Antennal organ of Ant. III typical, inner sensilla small, sgv about as long as sgd (cf. Fig. 11 and Fig. 12 ), ventral ms and about 20 common setae present on Ant. III. Ant. I–II with 7 and 13–14 setae, respectively.

Head with 8+8 subequal ocelli. PAO absent. Buccal cone long and pointed. Maxilla styliform with two apical hooks and one visible lamella ( Fig. 14 ). Mandible rather delicate, with three thin apical teeth and two basal ones ( Fig. 13 ). Distal edge of labrum pointed (ogival), number of prelabral and labral setae as follows: 4/2334 ( Fig. 15 ). Main part of labium with four proximal ordinary setae and a subapical spine L, labial organites invisible; basomedian (submentum) and basolateral (mentum) parts of labium with a usual set of four setae each, i.e. 4+4 ( Fig. 16 ). Total length of labium is 4.5–4.75 of distance between postlabial setae a1 and m1. Perilabial area with 4+4 setae.

Dorsal side of body, especially on Abd. I–IV, with some additional setae, ordinary setae short, smooth and acuminate, sensilla 1.8–2.2 times longer than ordinary setae ( Figs 3–4 ), their number as usual: 22/11111. Main characteristics: head with neither a0 nor d0; Th. I with 4+4(5) setae; Th. II with a2-setae and ms present, dorso-external group on Th. II with 4 setae (a3–a4, m3–m4) in front of p3–p4; Th. III often with one additional seta (m2?) in this group ( Fig. 3 ). Abd. I–IV always with some additional setae in dorso-external group; setae p2 on Abd. V absent ( Fig. 4 ). Some setae at abdominal tip (Abd. VI) thickened, blunt or even slightly clavate.

Thoracic sterna without setae. Ventral tube with 3+3 long distal setae and usually with 1–3 smaller ones on each side near posterior distal seta, no seta on sternum of Abd. I, Abd. II with 9–10 ventral setae on each side. Tenaculum with 3+3 teeth as usual. Furca strong, dorsal side of dens with six setae and coarse granulation ( Fig. 19 ), hyaline field on its ventral side shorter than mucro length ( Fig. 18 ). Mucro with upturned tip and rather broad lateral lamella not reaching tip ( Fig. 18–19 ). Each anal valve with two small hr-setae.

Legs I–III with most usual number of setae: 1, 2, 2(3) setae on upper subcoxae, 0, 2, 2(3) setae on lower subcoxae, 3, 8, 8 setae on coxae, 6, 6, 6 on trochanters, 11–13, 12, 11–12 setae on femora and 19, 19, 18 setae on tibiotarsi ( Fig. 17 ). Unguis with clear tooth in mid part of inner edge and two lateral teeth basally ( Fig. 17 ), one tooth usually also present in mid part of outer side and several tiny ones in its basal part.

Etymology The name of the new species reflects the presence of supplementary setae on the dorsal side of the body.

Affinities. The most characteristic feature of the new species is a pronounced plurichaetosis on the dorsal side of the body, especially on Abd. I–IV. This character makes P. plurichaetosa sp. nov. distinguished from all other species of the genus (with a known chaetotaxy) except P. bescidica Smolis & Skarżyński, 2007 and P. stebaevae sp. nov. (see Table 1 ). These three species can be fairly easily separated by the number of setae in the dorsolateral parts of Th. II–III: 2 ordinary setae + S in P. plurichaetosa sp. nov., 4(5) setae + S in P. bescidica and 3 setae + S in P. stebaevae sp. nov. Besides this, P. plurichaetosa sp. nov., unlike P. bescidica , has a pointed (ogival) labral edge (vs non-ogival in P. bescidica ), the mandible with 5 teeth (vs 3–4 teeth in P. bescidica ), two apical hooks on the maxilla (vs styliform in P. bescidica ) and lacks p2 setae on Abd. V. The latter setae are also absent from P. asigillata and another Caucasian species, described above, but present in P. bescidica and P. ellisi , as well as in P. stebaevae sp. nov.

Unfortunately, the chaetotaxy of two European species of the genus, P. remyi and P. balcanica , is completely unknown. The former species can be distinguished from P. plurichaetosa sp. nov. by the presence of eight teeth on the mandibles (5 teeth in P. plurichaetosa sp. nov.) and 3–4 teeth at the inner edge of the unguis (only one internal tooth in P. plurichaetosa sp. nov.). Pseudachorutella balcanica , in contrast to P. plurichaetosa sp. nov., is characterized by a rather short buccal cone (the ratio of the length of the labium to the distance between a1 and m1 setae on the ventral side of the head in P. balcanica is 2.5 ( Smolis et al. 2023) and 4.5–4.8 in P. plurichaetosa sp. nov., as well as the non-ogival shape of the labral edge.

Two coexisting Caucasian species, P. circassiana sp. nov. and P. plurichaetosa sp. nov., are morphologically rather different. Apart from the size and the peculiarities of the dorsal chaetotaxy, there are a number of small, but stable and essential characters that make them easy to distinguish (see Table 1 ). To the characteristics given in the table, one can add, for example, a significantly large difference in the relative sizes of sgv and sgd on Ant. III. In P. circassiana sp. nov. the sgv/sgd ratio is larger, and the tip of sgv significantly surpasses the boundary between Ant. III and Ant. IV ( Fig. 5 ), whereas in P. plurichaetosa sp. nov. sgv does not even reach it ( Fig. 11 ). Quite interesting is also the noticeable difference in the position of seta M in relation to the A and B whorls on the tibiotarsi––in P. plurichaetosa sp. nov. this seta is located almost in the middle between these whorls, and in P. circassiana sp. nov. clearly closer to whorl B (cf. Fig. 10 and Fig. 17 ).

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.