Thalassaphorura microspinata, Sun & Bedos & Deharveng, 2017

Sun, Xin, Bedos, Anne & Deharveng, Louis, 2017, Two new species of the genus Thalassaphorura Bagnall, 1949 (Collembola: Onychiuridae) from South China, with an updated key to world species of the genus, Zootaxa 4338 (2), pp. 319-332 : 320-324

Thalassaphorura microspinata sp. nov.

Figs 1–13

Diagnosis. Pso formula as 32/133/33343 dorsally and 11/000/01110 ventrally, two pso on each subcoxae 1, five guard papillae on AIIIO, 4+4 p-chaetae between inner posterior pso on head, 5+5 (rarely 4+5) chaetae on Th. I tergum, unguiculus without basal lamella and the unguiculus/unguis ratio is 0.4, Th. I–III sterna with 0+0, 1+1, 1+1 chaetae, AS set on small papillae and the AS /unguis ratio is 0.2, and small body size.

Type material. Holotype female and 9 paratypes on slides (4 females and 5 males). China: Guangxi: Huanjiang: near Xia Lan Dong , 2 November 2009, leaf litter fallen through the entrance of a small subvertical cave, berlese extraction after sifting, Louis Deharveng & Anne Bedos leg. (sample CHIgx09-052). Type specimens (holotype, 2 female paratypes and 3 males paratypes) are deposited in CAS-IGA, Changchun, and 2 females and 2 males paratypes in MNHN, Paris.

Other material. Ibidem, numerous specimens in alcohol.

Description. Holotype length 0.82 mm, length of paratypes: 0.73–0.83 mm in females and 0.64–0.73 mm in males. Shape of body cylindrical, Abd. III–IV parallel ( Figs 1 & 7 ). Color in alcohol white. AS set on small papillae, and the AS /unguis ratio is 0.2 ( Figs 1 & 13 ).

Granulation fine and homogenous, without coarse granules even around dorsal pseudocelli, on dorsal part of antennae, and on Th. I–III. Antennae almost as long as head. Ant. I with 9 chaetae, Ant. II with 13 chaetae. AIIIO consisting of five guard chaetae, five papillae, two smooth sensory rods, and two smooth and spherical sense clubs ( Figs 5 & 6 ), ventro-lateral ms present. Ant. IV with subapical organite, without differentiated S-chaetae; basolateral ms above the second proximal row of chaetae ( Fig. 5 ).

PAO with 14–18 simple vesicles arranged in two rows perpendicularly to long axis of organ ( Fig. 2 ). Dorsal chaeta d0 on head present. 4+4 p-chaetae between inner posterior pso on head, p1 anteriorly to others ( Fig. 1 ).

Labral formula of chaetae: 4/1,4,2 ( Fig. 4 ). Maxillary palp simple with one basal chaeta and two sublobal hairs. Labial palp of type AC, papillae A to E with 1, 4, 0, 3 and 2 guard chaetae respectively ( Fig. 3 ). Labium with 6 proximal, 4 baso-median (E, F, G, and f) and 5 baso-lateral (b, c, d, e, e’) chaetae ( Fig. 8 ). 4+4 postlabial chaetae along ventral groove ( Fig. 8 ).

Dorsal pso formula as 32/133/33343, and ventral as 11/000/01110 ( Figs 1 & 7 ). Subcoxa 1 of legs I, II and III with 2, 2 and 2 pso respectively. Parapseudocelli only visible on Abd. I sternum at the base of VT as 1+1. Pseudopore formula: 00/011/11110 dorsally and 00/111/0001m0 ventrally ( Figs 1 & 7 ).

Ordinary chaetae differentiated in micro-, meso- and macrochaetae. S-chaetae weakly thickened but distinguishable from ordinary chaetae, S-chaetae formula: 11/011/222121 dorsally and 11/000/000100 ventrally ( Figs 1 & 7 ). Th. I tergum with 5+5 (rarely 4+5 chaetae) ( Fig. 1 ). Th. II–III with lateral ms. Th. II–Abd. III terga with 2–3 paired axial chaetae each ( Fig. 1 ). Abd. IV tergum with unpaired axial chaeta m0, Abd. V tergum with or without a0, Abd. VI tergum with a0 and m0 ( Fig. 1 ). Th. I–III sterna with 0+0, 1+1, 1+1 chaetae.

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, 10 and 13 chaetae, trochanters with 9 chaetae and femora with 14 chaetae each. Tibiotarsi I, II and III with 18 (1, 8, 9) chaetae each. Chaeta M present. Unguis without inner or lateral denticles. Unguiculus without basal lamella and the unguiculus/unguis ratio is 0.4 ( Figs 9 & 11 ). Ventral tube with 6+6 distal and 1–2+1–2 proximal chaetae, without anterior chaetae. Modified chaetae in males ventrally absent. Furca reduced to finely granulated area, with 4 small dental chaetae arranged in two rows posteriorly; one manubrial row of chaetae present ( Figs 7 & 12 ). Genital plate with 13–20 ante-genital and 2 genital chaetae in females, 20–28 circum-genital and 8 genital chaetae in males. Anal valves with numerous acuminate chaetae; each lateral valve with chaetae a0 and 2a1; upper valve with chaetae a0, 2a1, 2b1, c0, 2c1, 2c2 ( Fig. 10 ).

Etymology. Species is named for its short anal spines.

Distribution and ecology. Only known from the type locality. The species was present in leaf litter accumulated at the base of a cave entrance, but not found inside the cave itself nor in the nearby large cave Xia Lan Dong.

Discussion. The new species is most similar to T. grandis which was also found in Guangxi province ( Sun et al. 2010), in having pso formula 32/133/33343 dorsally and 11/000/01110 ventrally, 2 pso on subcoxae 1, 9 chaetae in the distal whorl of tibiotarsi and 4+4 p-chaetae between inner posterior pso on head. They differ in the the body size (0.64–0.83 mm in the new species versus 1.4–1.6 mm in T. grandis ), the length of AS ( AS /unguis ratio as 0.2 in the new species versus 0.75 in T. grandis ), the number of chaetae on baso-lateral part of labium (5 in the new species versus 6 in T. grandis ), the form of S-chaetae (distinguishable from ordinary chaetae in the new species versus indistinguishable in T. grandis ), the chaetae on Th. I sternum (absent in the new species versus 1+ 1 in T. grandis ), the number of chaetae on subcoxae 1 of leg I (3 in the new species versus 4 in T. grandis ) and the reproductive mode (bisexual in the new species versus probably parthenogenetic in T. grandis ). Comparisons between the known species of Thalassaphorura having dorsal pso formula as 32/133/33343 are given in Table 1.

Figures

FIGURES 1 – 7. Thalassaphorura microspinata sp. nov. 1, dorsal side of body; 2, PAO; 3, labium; 4, labrum; 5, antenna; 6, clubs, and papillae of AIIIO; 7, ventral side of Abd. II – IV. Scales: 0.1 mm (1, 5, 7), 0.01 mm (2 – 4, 6).

FIGURES 8 – 13. Thalassaphorura microspinata sp. nov. 8, ventral side of head; 9, tibiotarsus of leg I; 10, anal valves; 11, distal part of leg III; 12, central part of abdominal sternum IV; 13, AS. Scales: 0.1 mm (8), 0.01 mm (9 – 13).