Spinonychiurus vandeli ( Cassagnau, 1960 )

Beruete, Enrique, Arbea, Javier I., Baquero, Enrique & Jordana, Rafael, 2021, The family Onychiuridae (Collembola) from karst caves of the Basque biospeleologic district, with description of four new species, Zootaxa 5040 (2), pp. 151-194 : 185

Spinonychiurus vandeli ( Cassagnau, 1960)

Onychiurus vandeli Cassagnau, 1960 . Bull. Soc. Hist. nat. Toulouse, 95: 405.

Spinonychiurus vandeli (Cassagnau) : Sun et al. 2011. ZooKeys, 78: 33.

Figs 40−42 , Table 9

Studied Material. Loc. 22. 2 ex., 1.X.1988.

Troglophilous species known, until now, only from the type locality, in the Central Pyrenees , at 2500 m asl, in cold mosses .

Description of the specimen from the cave of Istaürdi. Whitish body. Body length (without antennas) 1.4 mm. Cylindrical body with fine and uniform granulation. Well-marked antennal bases.

Pso formula: 3,3/2,3,3/3,3,3,4,3 dorsally and 1,0/0,0,0/0,0,0,0 ventrally ( Figs 40–41 ). Each subcoxa 1 of leg I−III with 1 pso. Neither psx nor psp could be distinguished.

Head. Antennae about as long as the head. Ant IV with subapical organite and two slightly differentiated cylindrical sensilla in dorsal-subapical and basal-internal position. Microsensillum of Ant IV in lateral-external position, slightly above the first proximal row of chaetae. AIIIO with 5 papillae, 5 guard chaetae, 2 small internal sensilla, and 2 thick external curved and granulated sensilla; the lateral ms is located just behind the sense organ. Ant I−III with 9, 16 and 17 ordinary chaetae, respectively. Well-defined antennal base, with finer granulation. PAO with 17–18 finely granulated vesicles, arranged in two rows. Dorsal cephalic chaeta d 0 present ( Fig. 40 ). Maxillary palp simple with 1 basal and 2 sublobal chaetae. Labral formula 4/542. Labium type A, with 6 proximal, 4 basomedial (E, F, G, f) and 5 basolateral (b, c, d, e, e ‘) chaetae. 4−5+4−5 postlabial chaetae along the ventral groove .

Dorsal body chaetotaxy according to Table 9 and Fig. 40 , almost symmetrical, with weak differentiation between meso- and microchaetae. Sensory body chaetae cylindrical and well-differentiated, number per semi-tergite: 1/011/221121 dorsally and 2/00/000100 ventrally. Th I tergite with 8−9 +8−9 chaetae. Th II–III tergites with lateral ms. Axial chaetotaxy of Th II to AbdV tergites is 3,3/3,3,3,3,1 pairs of pointed microchaetae ( Fig. 40 ). Abd IV tergite with axial p 0, AbdV with axial a 0 and p 0, and AbdVI with 2 axial and 1 +1 prespinal chaetae. Relatively long AS ( Fig 42 ) (ratio AS /inner edge of claw III =1).

Ventral abdominal body chaetotaxy according to Fig. 41 . Th I–III sternites with 0 +0, 1+ 1, 1+1 chaetae, respectively. VT with 5−6+5−6 apical chaetae. Abd III sternite divided into two subsegments, each with 5+5 and 6−7+ 6−7 chaetae, respectively. Furcal vestige reduced to a finely granulated area, with 4 posterior dental mi- crochaetae and a row of manubrial chaetae: mp row with 2 +2 chaetae, of which the outer ones are macrochaetae ( Fig. 41 ). Anal valves with numerous acuminate chaetae; each lateral valve with chaeta a 0 and 2a 1; posterior valve with chaetae a 0, 2b 1, 2b 2, c 0, 2c 1 and 2c 2.

Legs. Subcoxa 1 of legs I–III with 4,5,5 chaetae, respectively. Tibiotarsi of the legs I–III with 20 (11,8,1), 20 (11,8,1), 19 (11,7,1) chaetae, respectively ( Fig. 42 ). Claw without internal or lateral teeth. Empodium reaching 50 % of the inner edge of the claw, with a narrow basal lamella which reaches 50% of its length ( Fig. 42 ).

Discussion. The specimen found match in all diagnostic characters to the type specimens of S. vandeli (Deharveng, personal communication). Cassagnau (1960) described the species with: a) 2 posterior pso on the head, while in the observation again of the types deposited in the MNHN (Deharveng, personal communication) 3 have been seen; b) 4 papillae in AIIIO, 5 in the new observation of the types; and c) 1 axial chaeta in AbdVI, 2 in the new observation of the types. S. vandeli belongs to the group of species with 11 chaetae on distal whorl of the tibiotarsus, and a labium type A (Pomorski & Kaprus’ 2015). It clearly differs from these species by presenting a lower number of dorsal pso mainly on abdominal tergites I–V.

Figures

FIGURES 40−42. Spinonychiurus vandeli. 40, dorsal view of the specimen of Istaürdi cave; 41, same as 39, ventral view; 42, tibiotarsus and claw of leg III, and anal spine (AS). Scales: 0.2mm (40−41), 0.05 mm (42).