Anurida hirsuta, Babenko & Nakamori, 2021

Babenko, Anatoly & Nakamori, Taizo, 2021, A new Anurida species of the hammerae-group from the Russian Far East (Collembola, Neanuridae), Zootaxa 4995 (2), pp. 367-374 : 368-372

Anurida hirsuta sp. nov.

Figs 1–10

Type material. Holotype, female, Russia, Khabarovsk Territory, Vaninsk District, ~ 5 km N of Vysokogorny, Mulinka River valley [~ 50.145°N 139.151°E], ~ 600 m alt., larch forest with Rhododendron sp. , litter, 29.09.2011. M. Potapov leg.; paratypes, 2 males, same data as holotype; 2 females, same area but ~ 5 km S of Vysokogorny, ~ 400 m alt., litter under old poplar-trees, 30.09.2011. M. Potapov leg. The types are kept in the collection of MSPU.

Diagnosis. A large and whitish species of the hammerae -group characterized by the presence of 5+5 uncoloured ocelli, six blunt sensilla on Ant.4, one of which (S2) being much thinner than others, an oval PAO with about 30 finely granulated lobes, mandibles with three apical teeth set in an oblique line and two strong basal teeth, maxillae with three serrate lamellae, one of which (L2) passing tip of capitulum, and by the presence of 3+3 p-setae between sensilla p4 on all abdominal terga apart from Abd.6.

Description. Length of holotype without antennae 2.8 mm. Colour of live specimens unknown, all available specimens mounted on slides without any traces of dark pigment even on ocular area. Body shape typical of hammerae -group: Abd.6 wide, slightly constricted at base and with straight posterior edge ( Figs 8, 10 ). Integument granulation fine and uniform, cuticle with distinct inner reticulation ( Fig. 7 ) especially clear on head and last abdominal terga.

Ocelli present, 5+5, anterior group with three ocelli. PAO elongate, consisting of 28–35 finely granulated lobes, its long axis 3.4–4.3 time as long as diameter of nearest ocellus ( Fig. 2 ). Antennae about as long as head diagonal, shape typical of genus. Ant.4 with large 3-lobed apical bulb and 6 curved sensilla, S2 clearly thinner, subapical ms, organite and seta i present ( Fig. 1 ). Ant.3 with 18(19) ordinary setae and AO of typical shape, sgd about as long as sgv, small ms present ventrally.Ant.1–2 with 7 and 14(15) setae, setae on basal segments of antenna (Ant.1–3) much longer than those on Ant.4, longest ones on Ant.2 reaching third of antenna length and more than 1.5 of segment width. Labrum with usual setal set, distributed as 4/2-3-5-2, proximal pair longest. Apical part of labium with three setae and two small sensillar papillae; its basal parts with eight setae. Perilabial area with five setae: b1: b2: b3: b4: b5 ratio as 2.7: 1.6: 2.5: 1: 1.6, 2+2 postlabial setae present on head along ventral line. Mandibles ( Fig. 4 ) with three small apical teeth set in oblique line and two larger basal ones. Maxillary capitulum with three apical teeth on main part followed by serrated cutting edge and three serrate lamellae, L.2 very long, reaching much beyond tip of capitulum ( Fig. 3 ).

Common dorsal setae long, erect, rather coarse and sparsely ciliate ( Fig. 5 ), clearly differentiated into macro- and microsetae; sensilla thin, whip-like, more or less subequal on all terga, their number as usual 22/11111; lateral microsensilla (ms) present on Th.2. Dorsal chaetotaxy as in Fig. 8 . Main characteristics: tergum of Th.1 usually with 3+3 setae. Th.2–3 with both p2 macrosetae and sensilla (p3) in anterior position in front of p1–p4 line, four setae (a1, a3, a4 and a5) of a-row and seta m4 present ( Fig. 8 ). Abd.1–4 with 3+3 p-setae between sensilla (p4): i.e. microsetae p1 present on all abdominal terga, macrosetae p2 and sensilla p4 slightly moved anteriorly. Chaetotaxy of Abd.5 almost identical ( Fig. 8 ) but setae p1 sometimes absent ( Fig. 10 ). Lateral parts of abdominal terga clearly plurichaetotic. Thoracic sterna without setae. Ventral tube with up to 9 distal setae on each side. Chaetotaxy of abdominal sterna as in Fig. 9 , each segment with some macrosetae in addition to microsetae. Furca reduced to two small tubercles near anterior border of Abd.4 sternum, each with 3–4(5) tiny setulae with hardly visible alveoli and one longer seta. Each anal valve with three small hr-setae.

Chaetotaxy of legs 1–3 as following: upper subcoxae—1, 3–4, 3–4; lower subcoxae—0, 3, 3; coxae—3, 8, 8; trochanters—6, 6, 5; femora—13, 12, 11; tibiotarsi—19, 19, 18 setae, respectively. Tibiotarsal setae rather long and slightly thickened, longest inner setae of B -whorl about two times longer than inner unguis edge (1.9–2.3: 1). Unguis with clear inner tooth ( Fig. 6 ), lateral ones invisible.

Etymology. The name derives from the Latin « hirsutus », reflecting its shaggy appearance due to the presence of numerous long setae on the lateral sides of the body.

Affinities. The most characteristic feature of the new species, which possesses all main characteristics of the hammerae -group (weak colouration even in species with eyes, serrate maxillary lamellae, the anterior position of both p2 and p3 setae on Th.2–3, the peculiar shape of the abdomen with Abd.6 truncated and slightly constricted at base, as well as pronounced integument reticulation), is its peculiar chaetotaxy with 3+3 axial chaetae (a1, p1 and p2) on all terga from Th.2 to Abd.5. In most of the known species of the group, progressive reduction of the axial setae with the loss of p1 on some or all of the segments is observed (Fjellberg 1985). A chaetotaxy pattern, similar to that of A. hirsuta sp. nov., is only known in two species: A. hammerae which has a more boreal, amphi-Beringian distribution, and the Japanese A. trioculata . The former species shows the same number of ocelli as A. hirsuta sp. nov., but it differs clearly by the presence of a large number (up to nine) of additional sensilla on Ant.4 (vs none in A. hirsuta sp. nov.), the mandibles with six teeth arranged in a row (vs five teeth in A. hirsuta sp. nov., of which three apical ones arranged in an oblique line), the noticeable polychaetosis on Th.1 (vs only 3+3 setae in A. hirsuta sp. nov.), lateral m5 setae on Th.2–3 (absent from A. hirsuta sp. nov., as well as in all other known congeners except A. cf. trioculata [see below]) and Abd.5 with 3+3 setae between sensilla p3 (4+4 setae present in this position in A. hirsuta sp. nov., as a rule).

The species A. trioculata , despite the presence of only 3+3 ocelli, seems to be even more similar to A. hirsuta sp. nov. According to the original ( Kinoshita 1916) and later descriptions ( Uchida 1951; Yosii 1954a, 1956b; Hasegawa & Tanaka 2013), it has a similar colouration (orange-yellow in life and almost white in alcohol), six blunt sensilla on Ant.4, almost the same number of lobes in PAO: 27–30 ( Kinoshita 1916), 25–32 ( Yosii 1954a) or 27–32 ( Uchida 1951) vs 28–35 lobes in A. hirsuta sp. nov., and a similar shape of the mandibles and maxillae. As far as can be judged from the only available illustration of the chaetotaxy pattern in A. trioculata ( Yosii 1956b, fig. 6), it is also quite similar to that of A. hirsuta sp. nov.: dorsal setae strongly differentiated in size, all terga from Th.2 to Abd.5 with 3+3 axial setae, middle ones (m 1 in Yosii [=p 2 in our interpretation]) much longer. The most significant difference in the chaetotaxy between A. hirsuta sp. nov. and A. trioculata , based on Yosii’s (1956) figure, is a posterior position of sensilla on Th.2 (and probably also Th.3), i.e. p3 on Th.2 set level with seta p4. This character makes A. trioculata to differ from all other known species of the hammerae -group and it obviously needs confirmation. We have not yet been able to study the types or topotypes of the latter species, but there is a fairly similar form in our collection from the shores of Lake Biwa (35.5039°N, 136.1809°E), ca. 300 km from Tokyo, the type locality of A. trioculata . This form we tentatively identify as A. cf. trioculata differs from the true A. trioculata mainly in the presence of some additional setae on the head and all terga ( Fig. 12–13 ). This confirms the posterior position of p3 on Th.2–3 being correct as depicted by Yosii for A. trioculata , as the same is also typical of A. cf. trioculata . On the other hand, its assignment to the hammerae -group remains debatable, since this is the only species of the group with a posterior position of sensilla p3 on Th.2–3.

Some other differences between A. hirsuta sp. nov., A. trioculata and A. cf. trioculata are as follows: sensilla on Ant.4 (S2 much thinner in A. hirsuta sp. nov., vs subequal at least in A. cf. trioculata ), maxillary L2 (long in A. hirsuta sp. nov., vs only slightly surpassing beyond the capitulum tip in A. trioculata [see fig. 31 in Kinoshita (1916) and fig. 18 in Yosii (1954a)], as well as in A. cf. trioculata ), seta a0 on head (present in A. hirsuta sp. nov. vs absent in A. trioculata and A. cf. trioculata ), relative lengths of Oc-setae in ocular area (only Oc2 being macrosetae, with Oc1 and Oc3 shorter and subequal in A. hirsuta sp. nov., vs two more or less subequal macrosetae and one microsetae in A. trioculata and A. cf. trioculata ), and relative length of tergal sensilla (about as long as macrosetae in A. trioculata , but subequal to microsetae in A. hirsuta sp. nov. and A. cf. trioculata ).

Distribution. The species is only known from the type locality

Figures

FIGURES 1–7. Anurida hirsuta sp. nov.: 1, Ant.3–4; 2, PAO and anterior group of ocelli; 3, maxillae; 4, mandible; 5, sensillum and basal part of macroseta (Abd.5); 6, tibiotarsus and unguis of hind leg; 7, reticulation on Abd.5. Scales: Figs 4–5, 9–10—0.1 mm, 6–8—0.01 mm.

FIGURES 8–10. Anurida hirsuta sp. nov.: 8, dorsal chaetotaxy; 9, ventral chaetotaxy of abdomen; 10, dorsal chaetotaxy of Abd.4–6 (another specimen). Scales: 0.1 mm.

FIGURES 11–13. Anurida sp. gr. hammerae (11) & A. cf. trioculata (12–13): 11, dorsal chaetotaxy (juvenile specimen from Magadan Region); 12, dorsal chaetotaxy of head and thorax; 13, chaetotaxy of Abd.4–6. Scales: Figs 11—0.1 mm, 12–13—0.5 mm.