Axenyllodes bayeri ( Kseneman, 1935 )

Babenko, Anatoly, Shveenkova, Yulia & Arbea, Javier I., 2025, Two new and two little-known species of the genus Axenyllodes Stach, 1949 from Russia and Kazakhstan, Zootaxa 5583 (1), pp. 154-170 : 158-159

Axenyllodes bayeri ( Kseneman, 1935)

Basionym: Xenyllodes bayeri Kseneman, 1935: 3

Figs 13 , 16–23

Studied material. Russia: 8 females and 1 juvenile, Middle Volga River Basin, Penza Region, “Privolzhskaya Lesostep” State Nature Reserve, xerophytic steppe with fescue on sandy soil ( Festuca polesica , Stipa borysthenica ; Potentilla argentea ), 52.4816 o N 46.2027 o E, 22 September 2017; 11 females and 7 juveniles, same biotope, but 27 September 2018; 30 females and 1 juvenile, same habitat, but 01 October 2019; 2 females, same area, meadow steppe with Brachypodium pinnatum , 52.4858 o N 46.2113 o E, 15 September 2021.All Yu. Shveenkova leg.; 1 female, Arkhangelsk Region, Pinega State Nature Reserve [64.56 o N 43.26 o E], entrance to Golubinsky proval cave, Poa sp. , 21 September 2004. A. Babenko leg.

Kazakhstan: 12 females, Pavlodar Region, Motogul [53.39 o N, 75.87 o E], small birch grove, nest of Formica polyctena , 08–09 September 1977. S.K. Stebaeva leg.; 5 females, same area, date and collector, but steppe with Stipa spp. and Silaum silaus .

Spain: 2 females ( MNCN _ Ent 45863 and 75086), Leiva , La Rioja Province, fruit culture, 42.5003º N 3.0497º W, 20 January 2004, C. Gutiérrez Martín leg. ; 3 females ( MNCN _ Ent 109949, 109950 and 109951), Vallecas , Madrid Province, grass on gypsum soil (sierozem), 40.3589º N 3.6322º W, 4 April 1954, W. Steiner leg. ; 2 females ( MNCN _ Ent 45366 and 45373), Abejar, Cabreja Range , Soria Province, juniper leaf litter ( Juniperus thurifera ), 41.7961º N 2.7878º W, A. Signoret leg. The material is stored in the Museo Nacional de Ciencias Naturales ( MNCN) in Madrid .

Diagnosis. A species of the genus distinguished from all other known congeners by its large PAO that usually having four irregular lobes.

Description based on specimens from Russia and Spain. Length (without antennae) 0.43–0.53 mm. Habitus typical of the genus. Colour white, without any traces of dark pigment. Tegument granulation coarse, secondary granules rounded at tip. Head and all terga from Th. I to Abd. V with rounded fields with finer granulations located more or less symmetrically with respect to medial line ( Fig. 16 ).

Antennae about as long as head. Ant. IV with a large simple vesicle apically, six rather thin, but clearly differentiated sensilla with pointed apices (three dorso-external [S7, S8, S9] and three dorso-internal [S1, S2, S4]), ms rather large and broadened at apex, notably shorter in length than sensilla, subapical organite present ( Fig. 19 ); ventral side of Ant. IV with few ordinary setae ( Fig. 18 ). Antennal organ of Ant. III typical, all its sensilla and ms subequal ( Fig. 17 ). Ant. I–III with 7, 10 and 15–17 ordinary setae, respectively.

Head with 2+2 ocelli, their diameter equal to 0.38–0.50 of PAO length, distance between them usually longer than their diameter (1.0–1.6: 1). PAO large (9–13 μm in length) and irregularly lobed, located in a depression ( Fig. 20 ), sometimes partly hidden under cuticular folds. Buccal cone short, typical of the genus. Labrum with 8 usual setae, medial pair of setae in anterior row stronger, with tips curved laterally, only two prelabral setae always present. Maxillary palp simple. Labium with five apical spinules and three common setae subequal to them in length. Basomedial and basolateral fields of labium with 4+4 setae, respectively. Maxilla typical of the family with strong, triangular head, mandibles invisible. Ventral side of head in adults with 3+3 postlabial setae along ventral line ( Fig. 21 ), but juveniles often with 2+2 postlabial setae.

Ordinary setae on dorsal side of body smooth and acuminate, slightly longer on last abdominal terga, sensilla undifferentiated ( Fig. 16 ). Main characteristics of dorsal chaetotaxy: Th. II–III with three setae present in a-row (a1, a3 and a5), two setae and sensilla in m-row (m1, m4 and S [=m6]) and five setae in p-row, lateral microsensilla invisible; Abd. I–III with 4–5 setae in a-row (seta a4 often absent); Abd. IV without setae m1.

Thoracic sterna without setae. Ventral tube with 3+3 distal setae, one seta also present on each side of VT on sternum of Abd. I, Abd. II–III with 4 and 5 ventral setae on each side, respectively ( Fig. 22 ). Tenaculum with 2+2 teeth. Furca small ( Figs 13 , 22 ), manubrium with 4+4 setae on main part, 1+1 basal setae and 3+3 basolateral setae (8+8 setae in total); dorsal side of dens with two setae and rather fine granulation. Mucro about as long as dens, strongly curved, lateral lamella not especially high. Anal spines strong and curved, set on subequal papillae.

Legs I–III with more or less stable sets of setae: 1, 2, 2 setae on upper subcoxae, 0, 2, 2 setae on lower subcoxae, 4, 4, 4 setae on coxae, 5, (4)5, 4–5 on trochanters, 8, 8, 8 setae on femora, and 10–10–9(10) setae on each tibiotarsus, the latter setae clearly differing in length. Unguis toothless, unguiculus needle-shaped and rather long ( Fig. 23 ).

Remarks. Axenyllodes bayeri , the type species of the genus, differs quite radically from all other representatives of the genus by its unique shape of the PAO. It is widespread in the Palaearctic and, in addition to the original description from the Czech Republic, there are several more or less detailed redescriptions ( Stach 1949; Gisin 1960; Pallissa 1964; Jordana et al. 1997; Fjellberg, 1995), between which and the above description, being mainly based on material from the Volga region, there are but few discrepancies. The most important of these is the presence or absence of lateral microsensilla on the thoracic segments.According to fig. 117 in Jordana et al. (1997), the Spanish specimens have microsensilla on both thoracic segments. It appears that Thibaud’s statement (2006, p. 114) of the presence of lateral sensilla is based on this figure: thorax II et III avec chacun 1 paire de microsensilles ms. We have revised the specimens from Spain (La Rioja, Soria, Madrid) which served for the description in the Ibérian Fauna, but did not find the ms on Th. II–III. Thus, we can confidently say that the material described above from the Central Palaearctic belongs to the same species that occurs in Europe.

Figures

FIGURES 10–15. Axenyllodes ghilarovi (10–12), A. bayeri (13), A. nematodes (14) and A. echinatus (15): 10, dorsal chaetotaxy of head and thorax, holotype; 11, abdominal tip, holotype; 12–15, chaetotaxy of manubrial field: m—setae on main part, b— basal setae and bl—basolateral setae. Scales: 10–11, 0.1 mm, 12–15, 0.01 mm.

FIGURES 16–23. Axenyllodes bayeri: 16, cuticular granulation and dorsal chaetotaxy; 17, AOIII; 18, chaetotaxy of antenna, ventral view; 19, ibid., dorsal view; 20, PAO and ocelli; 21, ventral chaetotaxy of head; 22, ventral chaetotaxy of abdomen; 23, tibiotarsi I. Scale: 16, 21–22, 0.05 mm, 18–19, 0.025 mm, 17, 20, 23, 0.01 mm.