Pseudachorutella intricata, Stryczek & Smolis, 2024

Stryczek, Beata & Smolis, Adrian, 2024, A new intriguing species of the genus Pseudachorutella Stach, 1949 (Collembola: Neanuridae: Pseudachorutinae) from Kyrgyzstan with the supplementation of generic definition and the description of the first instar larva, Zootaxa 5492 (3), pp. 421-430 : 422-427

Pseudachorutella intricata sp. nov.

Figs 1–17

Type material. Holotype, adult female on slide, under bark of spruce trees, Dzhety Oguz , Karakol Region, Issyk-Kul District, Kyrgyzstan, 11.VI.2006, leg. R. J. Pomorski . Paratypes: 2 juveniles and 4 adult females, under bark of spruce trees, in decaying wood, same data as holotype ; 2 adult females, same locality as holotype , mosses on waterfall, 25.VII.2005, leg. R. J. Pomorski .

Diagnosis. A large-sized species. Ant. IV with eight cylindrical sensilla S in adults. Labrum with 5/4,2,4 setae, labium with 12–13 ordinary setae and subapical spine, labial organites absent. Maxillae styliform without apical hooks, mandibles with two basal and three small apical teeth. Dorsal chaetotaxy of abdomen characterized by the presence of supplementary setae, especially in dorso-external parts of abdominal terga. Abd. V lacking setae p 2. Furca reduced, dens short and globular in shape with 5–6 + 5–6 setae, mucro absent.

Description of the first instar larva. Body length: 1.45 mm Colour of the body bluish-grey. Granulation relatively coarse and uniform. Dorsal organ of Th. I present ( Fig. 6 ).

Antennae equal to head. Ant. I with 7 chaetae, Ant. II with 12–13 chaetae. Chaetotaxy of Ant. III–IV as in Figs 1, 2 . AOIII with two small internal curved sensilla, one ventral microsensillum and two cylindrical guard sensilla, ventral one longer than dorsal ( Figs 1–2 ). Ant. IV with trilobed apical vesicle, subapical organite, microsensillum and chaeta i. Ant. IV with two cylindrical sensilla S and six sensilla mou, without ventral “file”.

8 + 8 ocelli dark pigmented. Buccal cone elongated, labral sclerifications ogival ( Figs 5, 7 ). Labium with 12 + 12 setae ( Fig. 5 ). Maxilla and mandible as in adults. Ventral side of head with 6+6 setae Vi ( Fig. 5 ).

Dorsal chaetotaxy as in Fig. 6 , setae relatively short and smooth differentiated into macro- and mesosetae, body sensilla slightly shorter than ordinary setae, fine and smooth. Sensillar formula: 022/11111. Microsensillum on Th. II present. Head with dorsal setae d 1 present and a 0 absent ( Fig. 6 ). Th. II with setae a 2 present and m 3 absent. Th. III with setae a 2 absent. Dorsal side of body without additional setae, plurichaetosis absent.

Thoracic sterna without setae.

Ventral chaetotaxy of abdomen as in Fig. 8 . Ventral tube with 4 + 4 setae. Each anal valve with 2 small setae hr. Retinaculum with 3 + 3 teeth, furca as in Fig. 8 .

Tibiotarsi I, II, III with 19, 19, 18 setae respectively, seta M present. Femora I, II, III with 13, 12, 11 setae respectively, trochanters with 6 setae each, coxae I, II, III with 3, 8, 8 setae, subcoxae 2 of legs I, II and III with 0, 2 and 2 setae, subcoxae 1 of legs I, II and III with 1, 2 and 2 setae. Claws with one inner tooth and without lateral teeth.

Description of adults. Body length: 2.85 mm–3.45 mm (holotype: 3.25 mm). Colour of the body dark bluish-grey. Granulation relatively coarse and uniform.

Antennae equal to head. Ant. I with 7 chaetae, Ant. II with 12–13 chaetae. Chaetotaxy of Ant. III–IV as in Figs 3, 4 . AOIII with two small internal curved sensilla, one ventral microsensillum and two cylindrical guard sensilla, ventral one longer than dorsal. Ant. IV with eight cylindrical sensilla S and numerous sensilla mou ( Fig. 3 ), without ventral “file” ( Fig. 4 ).

8 + 8 ocelli dark pigmented. Buccal cone elongated, labral sclerifications ogival ( Fig. 9 ). Labium 13+13 setae, additional setae p 1 present ( Fig. 9 ). Maxilla and mandible as in Figs 10–12 . Ventral side of head with 6+6 setae Vi ( Fig. 9 ).

Dorsal chaetotaxy as in Figs 14–15 , setae relatively short and smooth not differentiated into macro- and mesosetae, body sensilla slightly shorter than ordinary setae, fine and smooth. Sensillar formula: 022/11111. Microsensillum on Th. II present. Head with dorsal setae d 1 present and a 0 absent ( Fig. 14 ). Th. II with setae a 2 and m 1 present. Th. III with setae a 2 absent. Dorsal side of body with some additional setae, moderate plurichaetosis present especially in groups De ( Fig. 15 ).

Thoracic sterna without setae. Ventral chaetotaxy of abdomen as in Fig. 16 . Moderate plurichaetosis present. Ventral tube with 8 + 8 setae ( Fig. 16 ). Each anal valve with 2 small setae hr. Retinaculum with 3 + 3 teeth ( Fig. 13 ). Furca as in Figs 13 and 16 .

Tibiotarsi I, II, III with 19, 19, 18 setae respectively, seta M present ( Fig. 17 ). Femora I, II, III with 13, 12, 11 setae respectively, trochanters with 6 setae each, coxae I, II, III with 3, 8, 8 setae, subcoxae 2 of legs I, II and III with 0, 2 and 2 setae, subcoxae 1 of legs I, II and III with 1, 2 and 2 setae. Claws with one inner tooth and without lateral teeth ( Fig. 17 ).

Note. The comparison of morphology of the first instar larva and adults of Pseudachorutella intricata sp. nov. provides important data in the context of the taxonomy of the analyzed genus and even the subfamily. In general, the chaetotaxy of the first instar larva, both the antennae and other parts of the body, is highly incomplete compared to the adults. For example, antennal segment IV the first instar larva lacks six sensilla S and many sensilla mou. Similarly, the dorsal chaetoataxy of thorax and abdomen of this stage is devoid of numerous setae found in adults. Thus, during development, a transition from a non plurichaetotic to a moderate plurichaetotic form can be observed. Therefore, to avoid incorrect taxonomic decisions, the description of new species of the genus Pseudachorutella should be based on material containing adult stages. Although knowledge of first-instar larval morphology is of less importance for generic taxonomy, it may be helpful in classification and phylogenetic considerations within subfamily and family (see Discussion).

Etymology. The name of the new species referring to its intricate characters i.e. strong reduction of furca, unknown in other members of the genus.

Remarks. Pseudachorutella intricata sp. nov. is unique, distinguished from other species of the genus by presence of strong reduction of furca i.e. dens shortened and globular in shape, mucro absent. Nevertheless, the new species appears to be most similar to P. plurichaetosa Babenko & Kuznetsova, 2024 , species recently described from the Caucasus ( Babenko & Kuznetsova 2024). Besides these unique characters of the new species, they can additionally be distinguished by the following features: ventral “file” on Ant. IV (absent in P. intricata sp. nov., present in P. plurichaetosa ), apical hooks on maxillae (absent in P. intricata sp. nov., present in P. plurichaetosa ), labral formula (5/4,2,4 setae in P. intricata sp. nov., 4/2,3,3,4 in P. plurichaetosa ) and lateral teeth on claw (absent in P. intricata sp. nov., present in P. plurichaetosa ).

In addition, the differences between all known Palearctic species of the genus are provided in the key.

Figures

FIGURES 1–4. Pseudachorutella intricata sp. nov.: 1, dorsal chaetotaxy of Ant. III–IV (I instar larva); 2, ventral chaetotaxy of Ant. III–IV (I instar larva); 3, dorsal chaetotaxy of Ant. III–IV (adult); 4, ventral chaetotaxy of Ant. IV (adult).

FIGURES 5–8. Pseudachorutella intricata sp. nov. (I instar larva): 5, labium and group Vi; 6, dorsal chaetotaxy of head, thorax and abdomen; 7, labrum; 8, ventral chaetotaxy of abdomen.

FIGURES 9–13. Pseudachorutella intricata sp. nov. (adult): 9, labium and group Vi; 10, maxilla; 11, mandible; 12, mandible (front view); 13, retinaculum and furca.

FIGURES 14–17. Pseudachorutella intricata sp. nov. (adult): 14, dorsal chaetotaxy of head and Th.I–II; 15, dorsal chaetotaxy of Abd. III–VI; 16, ventral chaetotaxy of abdomen; 17, tibiotarsus and claw of leg I.