Deuteraphorura akelaris ( Jordana & Beruete, 1983 )

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 : 157

Deuteraphorura akelaris ( Jordana & Beruete, 1983)

Onychiurus akelaris Jordana & Beruete, 1983 . Mitt. Schweiz. Entomol. Ges., 56(3-4): 307

Deuteraphorura akelaris (Jordana & Beruete) : Jordana et al., 2012. Terrestrial Arthropod Reviews, 5: 65

Figs 2–7 , Tables 2, 3 and 10

Type material. Loc. 1. Akelar cave , 27.XII.1979, holotype male (slide MZNA730843 ), 2 paratypes (MZNA730842 and MZNA717039, male) .

Other material. Loc. 1. Akelar cave , 8.VIII.1929, 7 females, 1 male and 4 juveniles (slides MNCN _Ent 89369, MNCN_Ent 89370 and MNCN_Ent 89373 as sintypes of Onychiurus boneti ); other dates: 27.XII.1979, 1 male (MZNA717039); 28.III.1987, 1 male (MZNA717035). Loc. 13. Fria cave, 3.X.1985, 2 females, 2 males and 1 juvenile identified as O. boneti (MZNA730848, MZNA730849, MZNA730850, MZNA730851 and MZNA730852). Loc. 29. Mugiro cave, 8.V.1980 1 ex. (MZNA717036); 10.XI.1985, 17 ex. (MZNA730846, MZNA730847); 1 female (MZNA717036); 25.XI.1980, 1 female (MZNA717037); 10.XI.1985,1 male (MZNA717038) .

Redescription. Whitish body. Length of body, without antennae, 1.2–1.3mm (female and male). Quite fine and uniform cuticular granulation.

Dorsal pso formula 3,3–4/1,3,3/3,4–5,3(4),5,(3)4; Abd III tergite generally with 3 pairs of pso (a, b ‘, c) and sometimes with another more lateral pso (c’) ( Figs 2 , 3 ). Ventral pso formula 1,2/0,1,1/3+1,1–2,2(1),2; Abd I sternite with 3 pso on each side of the VT, and 1+1 anterior pso; Abd II with the medial pso sometimes missing; Abd III usually with 2+ 2 pso, rarely the medial pso missing ( Fig. 2 ). Each subcoxa 1 of legs I−III with 2 pso. Neither psx nor psp could be distinguished.

Dorsal body chaetotaxy as in Table 3 and Figs 2–3 . The chaetae-s do not differ from the ordinary chaetae. Th II–III tergites with lateral ms. Th II to AbdV tergites axial chaetotaxy with 2,2/2,2,2,2,1 pairs of pointed microchaetae.Abd IV tergite with an axial impaired mesochaeta (p 0). Abd V without axial impaired chaetae and p 2 as short mesochaeta; ratio p 2:P 5 =0.31−0.47. AbdVI with an axial macrochaeta (a 0) ( Fig. 3 ).

Ventral body chaetotaxy as in Fig. 2 . Th I–III sternites without chaetae. VT with 5−6+5−6 distal chaetae, ante- rior and basal chaetae absent. Furcal vestige reduced to a finely grained area, with 4 posterior dental microchaetae and two rows of manubrial chaetae; row mm with 1 +1(2) and row mp with 2 +2 chaetae, of which the outer ones are macrochaetae ( Fig. 6 ). Genital plate with about 14 chaetae and 2 posterior microchaetae in females, and 34–42 chaetae in males. Males with ventral organ formed by short and thickened chaetae: 2 on the Abd II sternite and 7–9 on the Abd III sternite ( Fig. 5 ). Anal valves with numerous acuminate chaetae; each lateral plate with a 0 and 2a 1; posterior plate with a 0, 2b 1, 2b 2, c 0, 2c 1 and 2c 2.

Legs. Subcoxae 1 of the legs I−III with 3,4,4 chaetae, sub−coxae 2 with 0,3,3 chaetae, coxae with 2−3,10,12−13 chaetae, trochanter with 9,8−9,7−8 chaetae, and femur with 14−15,14−15,13−14 chaetae. Tibiotarsi of the legs I−III with 18 (9,8,1), 18 (9,8,1) and 17 (9,7,1) chaetae, respectively ( Fig. 7 ). Claws without internal or lateral teeth. The empodial appendage reaches 55–60 % of the internal edge of the claw, presents a narrow basal lamella reaching 40 % of its length ( Fig. 7 ).

Discussion. D. akelaris belongs to the species group of D. boneti , characterised by presenting a reduced dorsal chaetotaxy and a tendency to present 4+4 pso in at least one Abd I–III tergite ( Beruete et al. 2001). The morphological features that characterise the species in this group show a high degree of variability, so that overlaping between various species are frequent ( Table 10). D. akelaris has been considered synonnymous with D. boneti by Jordana et al. (1997), however, we prefer to leave it as a good species until more detailed studies of the morphological and genetic variability of the species of this group can be carried out, based on more abundant material of all species.

The most similar species is D. boneti from which it differs by a lesser development of the dorsal body chaetae. This is especially evident in the medial and posterior abdominal chaetae rows, areas with the highest specific value and less intraspecific variability in the Onychiuridae ( Yosii 1963) . Table 2 shows the length (in micrometers) of m 2 and p 2 chaetae on Abd III, and p 2 and p 5 chaetae on AbdV, in both species. The ratio between the lengths of the Abd III m 2 /p 2 chaetae, and especially AbdV p 2 /p 5 allows to differentiate the two species (there are no overlapping of the measurements). D. akelaris is characterised by a smaller size of the Abd III p 2 chaeta, ratio m 2 /p 2 ratio: 1.62– 1.83, compared to 1.24–1.32 in D. boneti . Also, p 2 is a short mesochaeta on AbdV, ratio p 2 /p 5: 0.41–0.42, compared to 0.77–0.80 in D. boneti .

Distribution and ecology. Troglobiont species found on organic remains and the surface of gours. It is endemic to natural cavities of the karst massif of the Navarre part of the Sierra de Aralar ( Jordana & Beruete 1983, Jordana et al. 2012).

Figures

FIGURE 2. Deuteraphorura akelaris, lateral view of a male paratype. Scale: 0.2mm.

FIGURES 3−7. Deuteraphorura akelaris. 3, dorsal view of a specimen from Mugiro cave; 4, PAO; 5, male ventral organ; 6, AbdII−IV sternites central chaetotaxy; 7, tibiotarsus and claw of leg III. Scales: 0.2mm (3), 0.05mm (4−7).