Micranurida sectilis, Babenko & Shveenkova & Potapov, 2022

Babenko, Anatoly, Shveenkova, Yulia & Potapov, Mikhail, 2022, The genus Micranurida Börner, 1901 sensu Deharveng 1982 (Collembola Neanuridae, Pseudachorutinae) in the fauna of the Russian Far East, Zootaxa 5188 (5), pp. 489-500 : 490

Micranurida sectilis sp. nov.

Figs 1–11 ; Table 1

Type material. Holotype: female, Southern Primorye , Partisan District, Mount Olkhovaya, mixed forest in valley, 43°18.35'N 133°40.07'E, aprox. 500 m alt., rotten wood, 20 August 2018. M. Potapov, Yu. Shveenkova & A. Kuprin leg. Paratypes: 1 immature male, same data as holotype ; 1 male, same region, Shkotov District , Ussuri State Nature Reserve, valley of Anikin River, broadleaf forest, litter, 43°40.10'N 132°29.91'E, 25 August 2017. N. Kuznetsova, A. Kuprin & A. Geraskina leg.

Diagnosis. A white, unpigmented species characterized by the presence of 2+2 relatively large ocelli; five spherical antennal sensilla with S7 being slightly larger; PAO with subdivided vesicles; the presence of only two prelabral setae; almost complete dorsal chaetotaxy with p2 present on all terga from Th. II to Abd. IV; thickened lateral sensilla on Th. II and dorsal ones on Abd. IV, and only 12–12–11 setae on the tibiotarsi I–III, respectively.

Description. Length (without antennae) 0.38–0.42 mm, holotype – 0.42 mm. Habitus typical of the genus, slender and elongated. Body white in ethanol, sometimes with few dark pigment granules in ocular fields. Tegument granulation uniform.

Antennae slightly shorter than head, Ant. III–IV fused dorsally. Ant. IV with simple apical vesicle; external ms, subapical or, seta i and five spherical sensilla (S2 absent, S7 larger than S8) present as usual ( Fig. 6 ). Antennal organ of Ant. III typical, inner sensilla small, both sgv and sgd curved, sgv longer, ventral ms present. Ant. I–II with 7 and 11 setae, respectively.

Head with 2+2 relatively large ocelli, clearly visible on ocular fields among surrounding secondary granules ( Figs 2 , 4–5 ). PAO rounded or slightly elliptic, morula-like, consisting of 7–10 subdivided vesicles ( Figs 4–5 ); ratio of its longer axis to nearby ocellus as 2.5–2.8: 1. Buccal cone not especially long ( Fig. 8 ). Maxilla styliform, lamellae not seen. Mandible delicate, with at least three apical teeth. Labrum with 8–9 (?) labral and only two prelabral setae ( Fig. 8 ). Main part of labium with four ordinary setae A–D, sensorial elements absent; submentum and mentum with usual set of four setae each ( Fig. 7 ). Head ventrally with 2+2 postlabial setae as usual.

Dorsal chaetotaxy almost complete and symmetrical ( Fig. 1 ). Ordinary setae thin and acuminate, lateral sensilla on Th. II and dorsal one on Abd. IV clearly thickened, candle-like or even ovoid; other dorsal sensilla slender, thin and longer than ordinary setae, total number of tergal sensilla as usual: 22/11111; lateral ms present only on Th. II. Head with unpaired seta d0 and 3 setae on ocular field ( Fig. 2 ). Th. I with 2+2 setae. All terga from Th. II to Abd. IV with setae p2 present. Abd. V with 2+2 axial setae (a1 and p1) and without setae p2.

Thoracic sterna without setae. Ventral tube with 4+4 setae. Unpaired axial seta usually present on sternum of Abd. III ( Fig. 3 ). Furcal remnant without distinct cuticular swelling with few tiny setae in mid sternal position of Abd. IV ( Figs 3 , 9 ). Anal valves with two hr setae each.

Legs I–III with 1, 2, 2 setae on upper subcoxae, 0, 1–2, 1–2 setae on lower subcoxae, 3, 5–6, 6–7 setae on coxae, 5, 5, 3–5 on trochanters, and 12, 10–11, 10–11 setae on femora. Tibiotarsi with 12–12–11 setae: all setae T, A4, A5 and M absent , as well as seta B7 on leg III ( Figs 10–11 ). Unguis toothless, unguiculus absent as usual.

Etymology. The species is named after its most characteristic feature, which appears to be unique to the genus, namely, the compound lobes in PAO; from Latin sectilis ––divided.

Affinities. Micranurida sectilis sp. nov. shows a number of unusual features ( Table 1 ), therefore being hardly comparable to any known species of the genus. For instance, the complex lobes in PAO is not known in any of the described congeners. The absence of a medial pair of prelabral setae has been noted only in M. rostrata Babenko, 2007 (Central Siberia). The strong reduction of tibiotarsal setae is also quite unusual: the presence of 12–12–11 setae is known only in three congeners, i.e., M. sensillata ( Gisin, 1953) , M. balta Fjellberg, 1998 (both from Europe), and M. potapovi (Russian Far East). A complete dorsal chaetotaxy with the presence of p2 setae on all terga from Th. II to Abd. IV is not common either. It is not typical of most European species, but, besides M. sectilis sp. nov., it is also known in a number of Eastern Palaearctic congeners, for example, M. rostrata , M. russica , M. potapovi and M. distincta sp. nov. (see description below). All these species are easily distinguished from M. sectilis sp. nov. by other features, for example the absence ( M. rostrata , M. potapovi and M. distincta sp. nov.) or fewer ocelli ( M. russica ).

Figures

FIGURES 1–3. Micranurida sectilis sp. nov.: 1, Th II–Abd. VI, dorsolateral view; 2, head and Th. I, dorsolateral view; 3, Abd. I–Abd. VI, ventrolateral view. Scales: 0.1 mm.

FIGURES 4–11. Micranurida sectilis sp. nov.: 4, PAO and ocelli (holotype); 5, ibid. (paratype); 6, Ant. III–IV (outer side); 7, labium; 8, buccal cone, lateral view (pr – prelabral seta); 9, tibiotarsus of leg II (outer side); 10, ibid. (inner side); 11, furcal remnant. Scales: 0.01 mm.