Allonychiurus elikonius, Babenko, Anatoly B., Chimitova, Ayuna B. & Stebaeva, Sophya K., 2011

Babenko, Anatoly B., Chimitova, Ayuna B. & Stebaeva, Sophya K., 2011, New Palaearctic species of the tribe Thalassaphorurini Pomorski, 1998 (Collembola, Onychiuridae), ZooKeys 126, pp. 1-38 : 18-21

Allonychiurus elikonius sp. n. Figs 3744

Material.

Holotype ♀, Russia, Yakutia (Sakha Republic), Suntar-Khayata Mt Range, upper reaches of Kyubyume River [63°13'N, 139°32'E], 1,300 m alt., sandbank in Elikon River bed (flotation), 06.vii.2002, leg. O. Makarova (MSPU).

Paratypes: 22 females on slides and more than 300 specimens in alcohol, same data as holotype; 11 females, same region, 1,480 m alt., plant community with predominance of Dryas sp. on slope, 07.vii.2002; 7 females, same region, 1,430 m alt., herbaceous meadow on south-facing slope, 07.vii.2002; 14 females on slides and more than 800 specimens in alcohol, same region, greenhouse of “Vostochnaya” Meteorological Station, 1,287 m alt., 24.vii.2002, leg. O. Makarova (MSPU).

Description.

Colour white. Size 0.72-0.84 mm. Body slender and elongated. Antennae about as long as head, antennal area not clearly demarcated. Ant.4 rather long and narrow, with several curved and slightly thickened sensilla, 2 of which (dorso-subapical and inner-subbasal) straighter and especially distinct, a subapical organite small, usually spherical, a basal microsensillum present (Fig. 37). Ant.3 organ consisting of 4 (or rarely 4+5) low papillae, 2 sensory rods, 2 smooth sensory clubs with ribs (Fig. 38), 5 guard setae, and a lateral microsensillum (Fig. 37). Ant.1 and 2 as a rule with 9 and 12-13 setae. PAO with 10-12 composed vesicles set at some distance from each other (Fig. 42). Labrum with 7 setae and 4 prelabral ones. Apical part of labium with thick terminal setae on papillae A and C (AC-type), 6 long (b3-4, d3-4, e1, 3; e2 absent) and 4 spiniform (a1, b1-2 and d2), guard setae, a1shorter than others (Fig. 41). Proximal field of labium usually with 6 setae, basal fields (mentum and submentum) with 4 and 6 setae. Maxillary palp simple, with 2 sublobal setae.

Pseudocellar formula (pso) as follows, dorsal: 32/233/33343, ventral: 11/000/0112, additionally one parapseudocellus (psx) present on each side of VT anteriorly to basal setae (Fig. 43). Each upper subcoxa with two pso. Localization of pso as in Figs 40, 43. Granulation fine and uniform, without areas of enlarged granules. Dorsal chaetotaxy almost symmetrical, setae smooth and clearly differentiated, especially on abdominal tip, sensilla not always distinct, sometimes hard to detect, particularly so on sterna and medially on Abd.1-3: 2/011/222010 (dorsal) and 2/000/00010 (ventral) (Fig. 40), a thickened sensillum on coxae of Lg.3 present. Th.1 with 5-6(7) setae on each side. Terga of Th.2-3 and Abd.1-3 with 3+3, Abd.4 with 2+2 and Abd.5 with 1+1, axial microsetae. Lateral microsensilla present on both Th.2-3. Unpaired dorsal setae: d0 on head, microseta m0 on Abd.4, microseta a0 on Abd.5, and 2 macrosetae a0 and m0 on Abd.6, supplemented by 2+2 prespinal microsetae (Fig. 40).

Sterna of Th. 2-3 with 1+1 setae along linea ventralis, ventral chaetotaxy of abdomen as in Fig. 43. Abd.3 sternum unclearly divided, anterior subsegment without setae. Furca reduced to a small area of fine granulation situated at some distance from border between Abd.3-4, with 2+2 small posterior setae arranged in 2 rows (Fig. 44), manubrial area with 4+4 setae arrange in 2 rows but only one of them set posteriorly to small dental setae (Fig. 43). Ventral tube with (5)6+6 distal setae and 2 proximal ones at corpus base. Upper subcoxae with (3)4-4-4, tibiotarsi with 18-18-18, setae: distal whorl with 9 setae (7 A and 2 T-setae), 7 setae in row B on each leg, setae M and Y present (Fig. 39). Unguis simple, with neither inner nor lateral tooth, unguiculus narrow with a long apical filament, latter usually reaching slightly beyond unguis (Fig. 39).Anal spine thick and slightly curved, set on unclear papillae.

Affinities.

The main morphological features of Agraphorura elikonius sp. n. are similar to those of Agraphorura volinensis , Agraphorura subvolinensis sp. n. and Agraphorura asiaticus (Babenko, 2007), comb. n. (see Table 2). Thus, all four species are characterized by virtually identical dorsal chaetotaxy and similar numbers of pso on all terga, sterna and subcoxae. The presence of a complete set of B-setae and M-seta on all tibiotarsi is also shared by them. Agraphorura elikonius sp. n. has a different type of the labium (AC in Agraphorura elikonius sp. n. versus ABC in three other species) and differs from Agraphorura volinensis and Agraphorura subvolinensis in the mutual position of antennal pso (cf. Figs 40 and 45). There are also some variations of the number of distal setae on the tibiotarsi in these four species (7 setae in Agraphorura volinensis and Agraphorura asiaticus , 9 in Agraphorura elikonius and Agraphorura subvolinensis ). Agraphorura asiaticus is the only species in the group showing five papillae in AO (found in elikonius only in exceptional cases), and only Agraphorura subvolinensis is characterized by the presence of setae on all thoracic sterna (absent from Th.1 in all other species).

It is more difficult to distinguish Allonychiurus elikonius sp. n. from three Korean and one Chinese species of the group, namely Allonychiurus mariangeae (Thibaud & Lee, 1994), Allonychiurus donjiensis (Lee & Kim, 1994), Allonychiurus jindoensis (Lee & Kim, 1994), and Allonychiurus foliatus (Rusek, 1967), because their descriptions are incomplete and probably not fully correct in certain details. The most complete description is that of Allonychiurus mariangeae . It is rather similar to Allonychiurus elikonius sp. n. in having an almost identical chaetotaxy, the same number of dorsal pso and tibiotarsal setae (see Table 2). The only difference of the sternal pso formula is the presence of true pseudocellus on Abd.1 in Allonychiurus mariangeae instead of an elongated parapseudocellus without clear cuticular ring in Allonychiurus elikonius sp. n. However, these organs are homologous and sometimes difficult to distinguish. The most characteristic feature of Allonychiurus mariangeae is the presence of MVO in mature males. Unfortunately, Allonychiurus elikonius sp. n. in the region under study is only represented by parthenogenetic populations: among more than 100 specimens checked, all were females. Formally, these species differ in size (0.75-0.83 mm in Allonychiurus elikonius sp. n. versus 0.5-0.65 mm in Allonychiurus mariangeae ), in the absence of ventral setae on Th.1 in elikonius, in the different number of setae on Ant.1 (9 in Allonychiurus elikonius versus 8 in Allonychiurus mariangeae ), by unguiculus length (equal to or slightly longer than unguis in Allonychiurus elikonius versus 0.75 of U3 in Allonychiurus mariangeae ), and by the absence of a0 on Abd.5 in Allonychiurus mariangeae , but all these characters are probably variable.

Three remaining species of the volinensis-group were described as having a lesser number of dorsal and ventral pso (see Table 2). Yet this probably needs verification. In any case, clear differences in the ecological preferences of compared species confirm the specificity of Allonychiurus elikonius sp. n. The monsoon subtropical climate of southern Korea (the habitats of Allonychiurus mariangeae , Allonychiurus donjiensis , and Allonychiurus jindoensis are sand beaches) and central China (vicinity of Shanghai, the only known locality of Allonychiurus foliatus ) has nothing to do with the extremely continental conditions of mountainous Yakutia (about 160 km from Oymyakon, one of the coldest places on Earth), where Allonychiurus elikonius sp. n. was found. Nevertheless, the probability that some of these nominate species can probe to be conspecific with Allonychiurus elikonius sp. n. cannot be completely ruled out until their adequate redescriptions.

Etymology.

The new species was named after its type-locality, Elikon River.

Distribution.

Still known only from the region of the type-locality, where it inhabits a number of different communities up to 1,500 m alt.