Thalassaphorura udhagaiensis Thunnisa, Arbea & Sanil, 2022

Thunnisa, Abu Muhsina, Arbea, Javier Ignacio, Sumithra, Nallathambi, Mandal, Guru Pada & Sanil, Raveendranathanpillai, 2022, Two new species and two new records of Onychiurinae (Collembola, Onychiuridae) from the Nilgiris, India, Zootaxa 5182 (5), pp. 448-464 : 450-452

Thalassaphorura udhagaiensis Thunnisa, Arbea & Sanil sp. nov.

Figs 1–8 , Table 1

Diagnosis. Pseudocellar formula as 32/233/33343 dorsally and 11/000/01120 ventrally; two pso on each subcoxae 1. Five guard papillae on AIIIO. PAO with 21–24 simple vesicles. 3+3 p-chaetae between inner posterior pso on head. 7+7 chaetae on Th I tergum. Unguiculus without basal lamella and the unguiculus/unguis ratio is 0.6. Th I–III sterna with 1+1 chaetae each. AS set on small papillae and the AS /unguis ratio is 0.9.

Type locality. India, Tamil Nadu, Nilgiris, Udhagamandalam (11º24’50.0” N, 76º42’28.6” E)

Type Material. Holotype male and 12 paratypes (10 females and 2 males) on slides. India, Tamil Nadu, the Nilgiris, Udhagamandalam , 08.05.2019, moist soil filled in the concrete crevices, Berlese extractor, A.M. Thunnisa leg. Holotype male and 3 paratypes female in ZSI (Accession No. holotype 3235/H14 and paratypes 3236/H14); 6 paratypes (4 females and 2 male) in MBL; 3 paratypes in MNCN.

Etymology. The new species is named after type locality, Udhagamandalam, abbreviated as Udhagai.

Description. Length of type specimens: 0.7–1.1 mm in male and 1.0– 1.8 mm in female. Shape of body cylindrical, Abd III–IV more or less broadened ( Fig. 1 ). Color in alcohol white. AS set on small papillae, and the AS /unguis ratio is 0.9. Granulation fine and homogenous, without coarse granules even around dorsal pso.

Dorsal pso formula as 32/233/33343, and ventral as 11/000/01120 ( Figs 1 & 2 ). Subcoxa 1 of legs I, II and III with 2 pso each. Psx are not visible on head and body. Psp formula: 00/011/11110 dorsally and 00/111/0001 m 0 ventrally.

Head. Antennae almost as long as head. Length ratio of Ant I:II:III:IV as 1:1.5:1.5:2. Ant I, II and III with 5–7, 13 and 14 ordinary chaetae, respectively. AIIIO consisting of five guard chaetae, five papillae, two smooth sensory rods, and two weakly granulated and spherical sense clubs, ventro-lateral ms present. Ant IV with subapical organite, without differentiated S-chaetae; baso-lateral ms above the second proximal row of chaetae ( Fig. 3 ). PAO with 21–24 simple vesicles arranged in two rows perpendicularly to long axis of organ ( Fig. 5 ). Dorsal chaeta d0 on head present. 3+3 p-chaetae between inner posterior pso on head, p1 anterior to others ( Fig. 1 ). Labral formula of chaetae: 4/1,4,2. Maxillary palp simple with one basal chaeta and two sublobal hairs. Labial palp of type A, papillae A to E with 1, 4, 0, 3 and 2 guard chaetae, respectively ( Fig. 17 ). Labium with 6 proximal, 4 baso-median (E, F, G, and f) and 5 baso-lateral (b, c, d, e, e’) chaetae ( Fig. 4 ). Postlabial chaetae 4+4 along ventral groove.

Dorsal body chaetotaxy as in Fig. 1 . Ordinary chaetae differentiated in micro-, meso- and macrochaetae. Schaetae weakly thickened but distinguishable from ordinary chaetae, S-chaetae formula: 10/011/221110 dorsally and 11/000/000100 ventrally. Th I tergum with 7+7 chaetae ( Fig. 1 ). Th II–III with lateral ms. Th II to Abd III terga with 3+3 axial chaetae each ( Fig. 1 ). Abd IV tergum with unpaired axial chaeta m0; Abd V tergum without axial chaetae; Abd VI tergum with a0 and m0 ( Fig. 1 ).

Ventral body chaetotaxy according to Fig. 2 . Th I–III sterna with 1+1 chaetae each. Ventral tube with 6+6 distal, 1+1 anterior and 2+2 basal chaetae. MVO absent. Furca reduced to finely granulated area, with 4 small dental chaetae arranged in two rows posteriorly; one manubrial row of chaetae present ( Fig. 6 ). Genital plate with 13–15 ante-genital and 2 genital chaetae in females, 37–40 circum-genital and 8 genital chaetae in males. Anal valves with numerous acuminate chaetae; each lateral valve with chaetae a0, 2a1; upper valve with chaetae a0, 2a1, 2b1, c0, 2c1, 2c2 ( Fig. 7 ).

Legs. Subcoxae 1 of legs I–III with 3, 4, 4 chaetae and subcoxae 2 with 1, 4, 4 chaetae, respectively; coxae of legs I, II and III with 3, 8–9 and 11–12 chaetae; trochanters with 9 chaetae and femora with 14–15 chaetae each; tibiotarsi I, II and III with 18 (9, 8, 1) chaetae each ( Fig. 8 ); chaeta M present. Unguis without inner or lateral denticles. Unguiculus without basal lamella and the unguiculus/unguis ratio is 0.6 ( Fig. 8 ).

Discussion. The new species belongs to the group with pso formula as 32/233/33343 dorsally and 11/000/01120 ventrally ( Table 1 ). Thalassaphorura udhagaiensis sp. nov. according to characters listed in Sun et al. (2017b), the new species is the most similar to the cosmopolitan species T. encarpata ( Denis, 1931) . Both species are readily distinguishable from most members of the genus by a labial type A. T. udhagaiensis sp. nov. can be easily separated from T. encarpata by the presence of 10/011/221110 dorsal S-chaetae (indistinct in T. encarpata ), shorter unguiculus (ratio unguiculus/unguis as 0.6 in the new species, compared with 1.0 in T. encarpata ) and 1+1 anterior chaetae on ventral tube (without anterior chaetae in T. encarpata ). The main diagnostic characters of these species are summarized in Table 1 .

Figures

FIGURE 17. Phylogenetic analysis of the new species. Pink colour indicates new species. Blue colour*, new report from India.

FIGURES 1–3. Thalassaphorura udagaiensis sp. nov. 1, dorsal view; 2, abdominal ventral view; 3, Antena. Scales: 0.2 mm (1–2), 0.03 mm (3).

FIGURES 4–8. Thalassaphorura udagaiensis sp. nov. 4, labium (labial papillae chaetae not represented); 5, PAO; 6, furcal area; 7, anal valves; 8, tibiotarsus and claw of leg III. Scales: 0.03 mm (4–6, 8), 0.05 mm (7).