Acherontiella palaciosi Mehrafrooz Mayvan & Kováč, 2025

Mehrafrooz Mayvan, Mahmood & Kováč, Ľubomír, 2025, Two new species of the genus Acherontiella (Collembola, Hypogastruridae) from caves of the Alborz and Kopet Dagh mountains in Iran, ZooKeys 1255, pp. 1-25 : 1-25

Acherontiella palaciosi Mehrafrooz Mayvan & Kováč sp. nov.

Figs 11 , 12 , 13 , 14 , 15 , 16 , 17 B , Table 2

Diagnosis.

Eyes, PAO, furca, and retinaculum absent. Labrum with 4 / 554 setae, anterior row with 2 medial apically dentate spine-like setae. Ant IV with simple apical vesicle and 4 subapical globular sensilla. VT with 4 + 4 apical setae. Tibiotarsi with 2 knobbed tenent hairs. Claws with strong subapical internal tooth, empodium absent. Anal spines absent. Th I with setae m 1 and m 4.

Type material.

Holotype. • ♂, on slide; Iran, Razavi Khorasan province, Mashhad city, Moghan village, Moghan Cave ; 36°06'59"N, 59°22'06"E; 2193 m a. s. l.; 01 Aug. 2023; M. Mehrafrooz Mayvan leg.; dark zone, deep section of the cave, collected from rotten wood in 2 nd cave floor and from a stalagmite column in 1 st floor; temperature = 9 ° C, relative humidity = 84.0 %; slide no. IrMoAc 101 . Paratypes. • 4 ♂♂, 4 ♀♀, 1 juvenile, on slides; Iran, same collection data as for holotype; slide no. IrMoAc 102 –109 ; Holotype and 8 deposited in CoPJSU, 1 paratype ( IrMoAc 109 ) deposited in ZMFUM.

Description.

Body. Length 1.0 mm on average ( n = 9, maximum length 1.18 mm). Habitus and buccal cone typical of the genus Acherontiella . Eyes, PAO, retinaculum, and furca absent. Body fusiform, covered by serrate mesosetae (Fig. 13 D ), anal spines absent. Colour white, without traces of pigment. Cuticular granulation rather uniform.

Antenna e. Antennae slightly shorter than head, 0.18 mm and 0.20 mm, respectively (Fig. 11 A ). Length of Ant I: II: III and IV (dorsally fused) as 0.034: 0.036: 0.11 mm, respectively. All setae on Ant I – II slightly serrate. Ant I with 7 setae; Ant II with 11 setae. Ant III and IV dorsally fused, intersegmental suture on ventral side well marked, 26 dorsal and 25 ventral setae, all normal, smooth (lateral setae longer than other setae). Ant IIIO with 2 central short and curved rods (microsensilla) flanked by 2 long guard sensilla of characteristic constitution ( Deharveng and Díaz 1984) (Fig. 11 B ), a small ventrolateral microsensillum in a ventral pit. Ant IV with a protrusible ventroapical simple vesicle (Fig. 13 A ), 4 globular sensilla (Fig. 13 B ) – 2 dorsal (1 lateroexternal, 1 laterointernal) and 2 ventral (both lateroexternal), dorsoexternal subapical ms and apical os near external sensilla (see D’Haese 2003).

Head. Eyes and PAO absent. Setal formula of labrum 4 / 5, 5, 4, two medial setae in anterior row on labrum thickened as spines and apically dentate (Figs 12 B , 13 C ). Labium and labial triangle as in Fig. 12 C , with 5 main papillae (A – E), 6 proximal smooth setae, 4 basomedial and 5 basolateral smooth setae. Maxillary outer lobe with 1 sublobal hair (Fig. 12 E ). Left mandible with 3 teeth and right mandible with 4 teeth (Fig. 12 D ).

Legs. Legs I – III with normal setae, tibiotarsi with 2 knobbed tenent hairs (Fig. 13 E ). Setal pattern as in Fig. 14 A – C . Leg I: coxa with 3 setae, trochanter with 6 setae, femur with 12 setae, Tib with 18, including 2 knobbed apical tenent hairs. Leg II: coxa with 8 setae, trochanter with 6 setae, femur with 12 setae, Tib with 18, including 2 knobbed apical tenent hairs. Leg III: coxa with 7 setae, trochanter with 6 setae, femur with 11 setae, Tib with 17, including 2 knobbed apical tenent hairs; claw slender (Fig. 14 D – F ), internal edge with strong subapical tooth (Fig. 13 F ); empodium absent. Pretarsus with 2 setae (1 internal, 1 external), both reaching the half length of internal lamella.

Abdomen. Ventral tube with 4 + 4 setae. Retinaculum and furca absent. Anal spines absent, substituted by 2 serrate setae (Fig. 17 B ).

Setal pattern. Dorsal setal pattern generally of type I with mesosetae (after Jordana et al. 1997). Setae on head and body slightly serrate, sensory setae longer and smooth.

Head. Dorsal setal pattern as in Fig. 11 C . Seta a 0 present; d 1 – d 5; sd 3 – sd 5 (sd 1 and sd 2 absent); v 1 – v 2; c 2 – c 5 (c 1 absent); p 1 – p 5; oc 1 – oc 2 (oc 3 absent). Ventral setal pattern as in Fig. 12 A , all setae smooth.

Thorax. Dorsal setal pattern as in Fig. 15 . Position of ss in p row on Th II – III is 4 and 4, respectively. Th I with setae m 1 and m 4 [m 2 and m 3 absent]; Th II and III with 3 rows of setae – a: 4 + 4 as a 1, a 2, a 4 and a 5 [a 3 absent]; m: 3 + 3 between m 6 (s) as m 1, m 4 and m 5 [m 2 and m 3 absent]; p: 2 + 2 between p 4 (s) as p 1 and p 2 [p 3 absent]. Thoracic sterna without setae.

Abdomen. Dorsal setal pattern as in Fig. 16 A . Position of ss in p row on Abd I – V is 5, 5, 5, 4 and 3, respectively. Abd I – III with 2 rows of setae – a: 5 + 5 as a 1 – a 5; p: 4 + 4 between p 5 (s) as p 1 – p 4. Abd IV with 3 rows of setae – a: 3 + 3 as a 1, a 2 and a 4 [a 3 absent]; m: 1 + 1 (or 2 + 2) as m 4 (m 5) [m 1, m 2 and m 3 absent]; p: 3 + 3 between p 4 (s) as p 1 – p 3. Abd V with 2 rows of setae – a: 3 + 3 as a 1, a 3 and a 4 [a 2 absent]; p: 2 + 2 between p 3 (s) as p 1 – p 2. Ventral abdominal setal pattern as in Fig. 16 B .

Etymology.

The new species is dedicated to our colleague and friend professor José G. Palacios-Vargas (Universidad Nacional Autónoma de México) for his immense contribution to taxonomy of soil and subterranean Collembola.

Taxonomic remarks.

Acherontiella palaciosi sp. nov. is similar to 11 species in lack of anal spines: A. candida ( Delamare Deboutteville, 1952) , A. carusoi Dallai, 1978 , A. cassagnaui Thibaud, 1967 , A. colotlipana Palacios-Vargas & Thibaud, 1985 , A. dentata Djanaschvili, 1971 , A. globulata Thibaud & Massoud, 1979 , A. kowalskiorum Weiner & Najt, 1998 , A. massoudi Thibaud, 1963 , A. onychiuriformis Absolon, 1913 , A. variabilis Delamare Deboutteville, 1948 , and A. xenylliformis Gisin, 1952 . Among them, A. palaciosi sp. nov., A. carusoi , A. cassagnaui , A. dentata , A. massoudi , A. variabilis , and A. xenylliformis differ from others by 2 knobbed tenent hairs on tibiotarsi, while the rest of the species have 1–2 sharp tenent hairs on tibiotarsi. Moreover, claws in A. palaciosi sp. nov., A. carusoi , A. cassagnaui and A. dentata are equipped with a strong subapical tooth; however, claws are toothless in A. massoudi , A. variabilis , and A. xenylliformis . In A. palaciosi sp. nov., A. cassagnaui , and A. dentata , 2 medial setae in anterior row on labrum are thickened as spines and apically dentate, while in A. carusoi all 4 anterior labral setae are sharp and smooth. Acherontiella palaciosi sp. nov. differs from A. cassagnaui by Th I with 2 + 2 m setae, absence of seta a 3 on Abd IV, presence of seta m 4 (m 5) on Abd IV, and absence of seta a 2 and m setae on Abd V. In A. cassagnaui 3 + 3 m setae on Th I and seta a 3 on Abd IV are present, as well as setae m 1 (m 3) and m 4 on Abd IV and seta a 2 and m setae on Abd V. Finally, A. palaciosi sp. nov. differs from A. dentata by following characters: setae a 0 and sd 3 are present, while oc 3 is absent on dorsal side of head, maxillary outer lobe with one sublobal hair, seta m 3 on Th I is absent, seta m 4 on Abd IV is present, and seta a 2 on Abd V is absent. In contrast, in A. dentata setae a 0 and sd 3 are absent, while oc 3 is present on the dorsal side of head; maxillary outer lobe with 2 sublobal hairs, seta m 3 on Th I is present, Abd IV with seta m 2 in the m row, and seta a 2 on Abd V is present.

Figures

Figure 11. Acherontiella palaciosi sp. nov. A. Ant I – IV (left antenna), setal pattern on ventral side; B. Ant III sensory organ; C. Head, setal pattern of dorsal side. Scale bars: A = 0.02 mm (N); B = 0.05 mm (N); C = 0.025 mm (N).

Figure 12. Acherontiella palaciosi sp. nov. A. Head, setal pattern on ventral side; B. Labrum, setal pattern; C. Labium and labial triangle, setal pattern; D. Mandibles; E. Maxillary outer lobe. Scale bars: 0.025 mm (A); 0.01 mm (B – E).

Figure 13. Acherontiella palaciosi sp. nov. A. Ant IV apical vesicle; B. Ant IV sensillum; C. Two medial setae in anterior row of labrum; D. Serrate mesosetae of Th II; E. Knobbed tenent hair on tibiotarsi; F. Claw with subapical tooth. Scale bars: 0.01 mm (A – F).

Figure 14. Acherontiella palaciosi sp. nov. A – C. Legs I – III, setal pattern of coxa, trochanter, femur and tibiotarsus; D – F. Legs I – III, foot complex. Scale bars: 0.01 mm (A – F).

Figure 15. Acherontiella palaciosi sp. nov. Th I – III, setal pattern of dorsal side. Scale bar: 0.025 mm.

Figure 16. Acherontiella palaciosi sp. nov. A. Abd I – VI setal pattern of dorsal side; B. Abd I – VI setal pattern of ventral side. Scale bars: 0.025 mm (A, B).

Figure 17. A. Acherontiella nezamdoosti sp. nov. – two small anal spines on Abd VI; B. Acherontiella palaciosi sp. nov. – two serrate mesosetae in position of anal spines on Abd VI. Scale bars: 0.01 mm (A, B).