Appendisotoma monomorpha Potapov, 2024

Potapov, Mikhail, Babenko, Anatoly, Bu, Yun, Bayartogtokh, Badamdorj, Gulgenova, Ayuna & Luan, Yun-Xia, 2024, Taxonomy of the Cryptopygus complex. IV. Cyclomorphosis in three species of Appendisotoma and description of a new species from Kazakhstan (Collembola, Isotomidae), Zootaxa 5453 (4), pp. 487-510 : 499

Appendisotoma monomorpha Potapov sp. nov.

Figs 35–42 , 63

Type material. Holotype and 11 paratypes deposited on 3 slides at MSPU. Kazakhstan, Alma-Ata area , Jambul district , Jasurken , floodplain of Talas River, winter pasture, under snow, January: 28.01.1988, leg. Tischenko.

Other material: The same location, spring pasture, March, 23.03.1988, leg. Tischenko.

Description. Body size 0.9–1.2 mm, habitus slender, as in A. bisetosa . Body with pigmentation. Abd.V separated from Abd.IV and fused with Abd.VI ( Fig. 41 ). Cuticle “smooth”, with hardly visible fine hexagonal primary granulation. Ocelli 8+8 ( Fig. 37 ), PAO about 2.5 as long as ocellus, half as long as width of Ant.I and shorter than inner unguis length (~0.8). Maxillary head with unmodified lamellae. Maxillary outer lobe with 4 sublobal hairs, maxillary palp simple. Labral formula as 4/5,5,4. Labium with 5 usual papillae (А–Е) and labial formula A1B4C0D4E5–6 (14–15), guard chaetae e7 always absent, 3 proximal, 4 basomedian and 5 basolateral chaetae. Ventral side of head with 4+4 chaetae. Ant.I with 12 common chaetae, 2 ventral s-chaetae (s) and 2 bms-chaetae, 1 dorsal and 1 ventral. Ant.II with 1 latero-distal s and at least with 4 bms (2 dorsal set together and 2 ventral), with 1 additional ventral chaeta in basal position (the firth bms?). Ant.III with 1 bms and with 6 distal s (including 2 lateral), without additional s-chaetae ( Fig. 40 ). Lateral s in more proximal position subequal to outer s of AO. All bms-chaetae of middle size, some of them can be confused with common chaetae. S-chaetae on Ant.IV weakly differentiated. Organite small, set very close to micro s-chaeta.

Common chaetae smooth. S-formula as 3,3/2,2,2,3,4 (s), 1,0/0,0,0 (ms) ( Fig. 42 ). Tergal s-chaetae shorter than common chaetae and well distinguishable ( Fig. 41 ). All s-chaetae on Abd.I and IV and medial s-chaetae on Abd. II and Abd.III situated in p-row, lateral s-chaetae on Abd.II and Abd.III in more anterior position. All s-chaetae on Abd. V set in one posterior transversal row. Macrochaetae 1,1/3,3,3 in number, medial ones on Abd.V 1.1–1.4 times longer than dens and 2.4–3.5 times longer than mucro. Foil chaetae at the tip of abdomen absent. Axial chaetotaxy as 7(6),6(5)/3–4,3–4,4–5,5–6. Thoracic segments without ventral chaetae.

Unguis with lateral and weak inner teeth ( Fig. 39 ). Empodial appendage 0.6–0.7 as long as unguis. Tibiotarsi without additional chaetae on Leg I and II (at whole, with 21 chaetae), and with few additional chaetae on tibiotarsi III (with the whole number>22), T-chaetae absent. Adult males without differentiated spurs on Leg III. Tibiotarsal tenent hairs pointed, 0.6–0.9 as long as length of inner edge of unguis. Ventral tube with 4+4 laterodistal and 5–6 posterior chaetae, anteriorly without chaetae. Tenaculum with 4+4 teeth and 2 chaetae. Anterior furcal subcoxa with 9–11, posterior one normally with 8 chaetae. Anterior side of manubrium with 1+1 chaetae ( Fig. 36 ), posterior side with 3+3 laterobasal, many chaetae on main part, and with 2+2 lateral chaetae ( Fig. 35 ). Dens stout, without clear crenulation, with 2 rigid and short anterior and 5 posterior chaetae ( Figs 35, 36, 38 ). External lobe near apex of dens absent. Mucro with 4 teeth ( Fig. 38 ). Ratio manubrium: dens: mucro = 3.7–4.6: 1.4–2.3: 1.

Males present, without any specific morphological modifications.

Cyclomorphosis. Specimens collected in January and April did not show any morphological differences in shape of dens, length of tenent hairs on tibiotarsi and size of ocelli. Manubrium and basal rods of furcal apparatus are not chitinized.

Etymology. The name is derived from the presumable similarity between the summer and the winter forms of the new species. At least, the external lobe near apex of dens in winter form absent.

Remarks. Short dens and only one pair of chaetae on anterior part of manubrium are shared only with A. bisetosa . The new species differs from the latter one by 7 (vs. 11) chaetae in apical whorl of tibiotarsi, 2 (vs. 3) anterior chaetae on dens, and 3 (vs. 4) s-chaetae on Abd.IV. Ant.I has fewer common chaetae (12 in A. monomorpha sp. nov. vs. 13–15 in A. bisetosa ), and Ant.III with lateral s-chaetae subequal (vs. shorter) to outer s-chaetae of AO. 7 chaetae in apical whorl of tibiotarsi is shared only with A. stebayevae , which differs from the new species by more chaetae on anterior side of furca. Unlike A. stebayevae and A. bisetosa , cyclomorphosis in the new species was not observed.

Distribution and ecology. Know only from the type locality ( Fig. 63 ). The species was collected under snow and is presumably active in winter.

Figures

FIGURES 35–40. Appendisotoma monomorpha sp. nov.: 35, 36, furca, posterior (35) and anterior (36) views; 37, ocelli and PAO; 38, furca, lateral view; 39, tibiotarsus III, lateral view; 40, Ant.I–III, dorsal view of right antenna. Abbreviations: bms— basal ms-chaetae, os—outer s-chaetae of AO, ls, ls’—lateral s-chaetae of AO.

FIGURES 41–42. Appendisotoma monomorpha sp. nov.: 41, chaetotaxy of Abd.II–VI, s-chaetae encircled; 42, macrochaetae and s-chaetae on body tergites. Abbreviations: s—s-chaetae, ms—ms-chaetae.

FIGURES 62–64. Records of A. stebayevae (62), A. bisetosa (63), A. monomorpha sp. nov. (63), and A. sibirica (64). The records blocking previous ones are not shown and not referred (especially in Tuva). Open circles—literature records (Dunger 1982; Grinbergs 1962; Hao & Huang 1995; Haybach 1961; Martynova 1971; Martynova & Sklyar 1973; Potapov et al. 2020; Sławska 2000; Smolis & Skarżyński 2003; Stebaeva 1974; Traser et al. 1993). The records in Siberia are given in more detail by Stebaeva (1976). Abbreviations: type—type locality, A.a., A.f., A.j., A.m., A.x.—type localities of A. asiatica, A. franzi, A. juliannae, A. montana, A. xinjiangica, respectively.