Troglopedetes kae, Jantarit & Surakhamhaeng & Deharveng, 2020

Jantarit, Sopark, Surakhamhaeng, Katthaleeya & Deharveng, Louis, 2020, The multiformity of antennal chaetae in Troglopedetes Joseph, 1872 (Collembola, Paronellidae, Troglopedetinae), with descriptions of two new species from Thailand, ZooKeys 987, pp. 1-40 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.987.54234
publication LSID	lsid:zoobank.org:pub:C46FAFC0-2322-47A6-8F5B-7DBC770C26EF
persistent identifier	https://treatment.plazi.org/id/99807B93-C5B7-4F80-8499-3FF951526C20
taxon LSID	lsid:zoobank.org:act:99807B93-C5B7-4F80-8499-3FF951526C20
treatment provided by	ZooKeys by Pensoft
scientific name	Troglopedetes kae
status	sp. nov.

Treatment

Troglopedetes kae sp. nov. Figures 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10

Type material.

Holotype male and seven paratypes on slides (one male, four females and two subadults). Thailand: Satun Province: La-Ngu district, Tham Kae, 6°53'41"N, 99°46'44"E, 24 m a.s.l., 25 Jul 2017, S. Jantarit, A. Nilsai and K. Surakhamhaeng leg., dark zone of cave, by aspirator (sample # THA_SJ_STN04). Holotype and five paratypes deposited in NHM-PSU, two paratypes deposited in MNHN. Measurements of holotype in Table 1 View Table 1 .

Description.

Habitus. Slightly troglomorphic, slender, with elongate legs, furca and antennae. Body length 1.3-1.6 mm. Fourth abdominal segment 3.5-6 × (n = 9, all adults) as long as the third one along dorsal axis. Furca well developed, ca. 1.6-2.2 (n = 8) × shorter than body length. Body colour white with spots of orange pigment. Eyes absent, no ocular patch.

Chaetal types. Four types of chaetae on somites, appendages (except antennae) and mouthparts: scales, present on antennae I and II, head, body and furca, absent on legs and ventral tube; ordinary chaetae on all body parts; S-chaetae and trichobothria on tergites; hairs devoid of sockets on outer maxillary lobe and labial papilla. Chaetal types on antennae are much more diverse and described further separately.

Pseudopores (Figs 2A View Figure 2 , 3B-D View Figure 3 , 4B View Figure 4 , 8A-D View Figure 8 , 10B View Figure 10 , 10D, E View Figure 10 ). Pseudopores present as round flat disks larger than mac sockets, on antennae, head and tergites. Dorsal pseudopore formula: 1-(2)/1, 1/1, 1, 1, 1+4 (Fig. 8A-D View Figure 8 ). On antenna, two psp detected ventro-distally on Ant. I, one ventro-distally on Ant. II and one ventro-distally on Ant. III (Figs 3B, D View Figure 3 , 4B View Figure 4 ). On head, 1-(2) psp close to antennal basis (Fig. 2A View Figure 2 ). On legs, psp present externally on coxae (two for legs I and II and 2-(3) for leg III). On manubrium, two psp on the dorso-distal plaque (Fig. 10B, D, E View Figure 10 ), on dens (new location for Troglopedetes ) two psp dorso-basally near the internal spine on each side (Fig. 10D, E View Figure 10 ).

Mouthparts. Labral formula 4/5,5,4 (Fig. 2G View Figure 2 ); prelabral chaetae short, bent and ciliated, labral chaetae thinner, longer, smooth and acuminate, those of the distal row slightly shorter than those of the median row. Ventro-distal complex of labrum well differentiated, asymmetrical, with 2 distal combs (a larger one with 6-8 teeth on the left side, a smaller one with more than ten minute teeth on the right side) and an axial pair of sinuous tubules as in Cyphoderopsis ( Jantarit et al. 2013) (Fig. 2F View Figure 2 ). Distal part of labrum not adorned with spines dorso-distally. Labial palp similar to that described by Fjellberg (1999) for Troglopedetes sp., with strong papillate chaetae. Indicative number of guards for each major papillate chaetae: A (0), B (5), C (0), D (4) and E (4); lateral process subcylindrical, reaching slightly above the apex of papilla E (Fig. 2C View Figure 2 ); five smooth proximal chaetae. Chaetae of labial basis as M1M2REL1l2, with M1, M2, E and L1 subequal and ciliated, R shorter than others and ciliated, l2 short, smooth and acuminate (Fig. 2I View Figure 2 ). Outer maxillary lobe with one papillate chaeta, one basal chaeta and two sublobal hairs, shorter than others (Fig. 2B View Figure 2 ). Maxillary head with a 3-toothed claw, several stout shortly ciliated lamellae not observed in detail and three thin elongate structures (two dorsally and one ventrally) (Fig. 2D, E View Figure 2 ). Mandible head strong, asymmetrical (left side with four teeth, right side with five teeth); molar plate with three strong pointed basal teeth, and other two or three inner distal teeth, identical in both mandibles (Fig. 2H View Figure 2 ).

Ventral chaetotaxy of head (Fig. 2I View Figure 2 ). Head densely covered with oval scales (40-50 µm), postlabial chaetae along the linea ventralis as three mes anteriorly, one mac and an oblique line of five mes posteriorly on each side.

Antennae (Figs 3 View Figure 3 - 7 View Figure 7 ). Antennae shorter than body, 2.2 × (n = 6) as long as cephalic diagonal. Ant. IV subdivided into two subequal segments, without apical bulb (Fig. 5 View Figure 5 ). Lengths of antennal segments I-IV (IVa+IVb) as 1:1.9:1.3:2.5 (average, n = 6). Two other specimens with Ant. II and III fused (Figs 6 View Figure 6 , 7 View Figure 7 ). Antennal chaetae (scales, five types of ordinary chaetae, 14 types of S-chaetae and subapical organite) described separately. Antennal scales oval, present dorsally only on Ant. I and II and ventrally on Ant. II, absent ventrally on Ant. I, and absent on Ant. III and IV (Figs 3A, C, D View Figure 3 , 6B-D View Figure 6 ).

Body dorsal chaetotaxy (Figs 2A View Figure 2 , 8A-D View Figure 8 ). Dorsal macrochaetae formula: 4,4/8,4/0,2,4,3 (Figs 2A View Figure 2 , 8A View Figure 8 ). Trichobothrial pattern: 1/0, 0/0, 2, 3, 3 (Figs 2A View Figure 2 , 8A View Figure 8 ). Trichobothrial complexes well developed with modified mes of various sizes (Fig. 8A-D View Figure 8 ) described below for each segment. The figured mes pattern is not complete.

Head with 12-13 peri-antennal mac in line on each side, with 4+4 central mac (chaetae A, B, E, F of Deharveng and Gers (1993), absence of the chaetae C, D and G, cephalic mes short, feebly serrated, equal, symmetrically arranged (not analysed). One lateral cephalic trichobothrium much shorter than closest mac on each side; suture zone not visible (Fig. 2A View Figure 2 ). Head dorsally densely covered with round to oval scales (20-35 µm). Body densely covered with oval scales (15-50 µm).

Th. II with a collar consisting of a few rows of mac along its anterior and antero-lateral margins, a compact group of six central mac on each side ("P3 complex" of Soto-Adames et al. (2014) and two antero-lateral mac; one antero-lateral ms; one antero-lateral sens; two or three short mic laterally, and a few others not counted centrally (Fig. 8A View Figure 8 ).

Th. III with four mac by side (a group of three central and one anterior to them), one sens at antero-lateral margins, and ca. eight or nine mac or long mes at lateral margins (Fig. 8A View Figure 8 ).

Abd. I without central mac, with one ms laterally on each side, and three mes laterally, mic not counted (Fig. 8A View Figure 8 ).

Abd. II with two tric on each side and six or seven modified mes around them (three or four around the internal tric and three near external tric), two mac (one near internal tric and one near external tric), one sens near internal tric (Fig. 8A, B View Figure 8 ), three mic (one close to internal tric and two close to external tric), others mes sockets internally visible, not counted.

Abd. III with three tric on each side (one internal, two external) and eight or nine modified mes around tric (two near internal tric, six or seven near the two external tric); four mac (one near internal tric and three near external tric); one sens anterior to internal tric and one ms posterior to the two external tric; several mes at lateral margins, not counted (Fig. 8A, C View Figure 8 ).

Abd. IV with three tric on each side (two antero-lateral, one postero-lateral) and ca. 7-9 modified mes around the two antero-lateral tric; postero-lateral tric without modified mes. Mac distributed as three central on each side (one antero-external to pseudopore, two anterior to posterior tergite margin), one near postero-lateral tric, and at least four external, mixed with many mes or smaller mac on lateral to posterior margins (not counted); probably three sens anteriorly; at least six S-like chaetae sensu Lukić et al. (2015) anteriorly, and several mes or S-like chaetae uniformly distributed (not counted); six serrated mes in line in the posterior row, four near axis and two along pseudopore line, from medium to short size (Fig. 8A, D View Figure 8 ).

Abd. V with only one sens detected on each side, and several ordinary chaetae from mes to mac, not counted (Fig. 8A View Figure 8 ). Abd. VI chaetotaxy not analysed.

Legs (Fig. 9A-C View Figure 9 ). Legs long. Tita III as long as head diagonal, slightly longer than Tita I and II. Legs devoid of scales, mostly covered with ordinary ciliated chaetae of various length, from mes to mac. Trochanteral organ of leg III with eight smooth, straight, unequal, spiny chaetae (n = 1) (Fig. 9C View Figure 9 ). Tibiotarsus chaetotaxy mostly composed of strong ciliated-serrated mes, the basal ones longer and thicker (50-60 µm), slightly shorter distally (up to 15-20 µm). Distal row with 8-10 subequal ciliated mes and a dorso-apical tenent hair thin, smooth and acuminate on all tita; a ventro-distal strong smooth erected chaeta present on Tita III (Fig. 9A View Figure 9 ). Praetarsal mic minute (2.5-3 µm) (Fig. 9A View Figure 9 ). Unguis slender and relatively short (25-30 µm long, 6-7 µm wide at basis), 8-9 × shorter than tita, with one rather strong tooth at 30% of inner edge and a pair of inner basal teeth of unequal size; unguiculus pointed, narrow, lanceolate and elongate, ca. 0.6 × as long as claw, its external edge smooth (Fig. 9A View Figure 9 ).

Ventral tube (Fig. 9D-F View Figure 9 ). Ventral tube ca. 4 × longer than wide, with 3+3 long serrated mac anteriorly (Fig. 9D View Figure 9 ) and six mes (two ciliated and four smooth) on each lateral flap (Fig. 9E View Figure 9 ); posteriorly with at least 31 long ciliated mes and two distal smooth mes (Fig. 9F View Figure 9 ).

Furcal complex (Fig. 10A-E View Figure 10 ). Tenaculum with four teeth on each ramus, of decreasing size from the basal to the distal one, on a prominent, irregular body, with a postero-basal strong, densely serrated, distally bent chaeta (Fig. 10A View Figure 10 ). Manubrium ca. 0.82 × (n = 8) shorter than mucrodens (mucro+dens). Manubrium dorsally with subequal ciliated mes (none smooth), irregularly arranged in three or four rows in two longitudinal stripes separated by a glabrous axial stripe, external row of chaetae distally with at least 7-11 long ciliated mes, dorso-distal plaque with 4+4 mes and 2+2 pseudopores (Fig. 10B View Figure 10 ). Ventrally, dense cover of round to oval (22-38 µm) and thin elongated scales (20-25 µm). Dens straight, elongate, hairy, slightly and progressively tapering, dorsally with two rows of spines, mixed with ciliated mes of various length, thickness and shape. Dorso-external row with 15-22 spines, dorso-internal row with 26-40 spines (asymmetries between dentes); external spines larger and less sclerotised than internal ones. Some short ciliated mes interspersed with spines in the external row; dorsally between the two rows of spines a mix of short and long ciliated mes, irregularly arranged in one row distally turning to three or four rows proximally; laterally, many short ciliated mes; dorso-distally, 3-(4) stronger ciliated mes; 2+2 psp on dorso-basally between the two rows of spine, sometimes inconspicuous (Fig. 10C, D View Figure 10 ). Dens ventrally entirely and densely scaled, the scales elongate (20-38 µm) (oval shape distally), arranged in short lines from 3-5 (distally) to 6-8 scales (proximally) (Fig. 10D View Figure 10 ). Mucro rather stout, short, 9.3-13.7 (average 12, n = 8) × shorter than dens (Fig. 10D, E View Figure 10 ), with five main teeth, the apical one blunt and strong, the subapical one acute and strong, a latero-distal one small and acute, and two dorso-basal, one minute and acute and one strong, acute and longer without toothlets basally (Fig. 10E View Figure 10 ).

Genital plate (Fig. 10F, G View Figure 10 ). Male genital plate of the circinate type, with six genital mic and 16 circumgenital short, thin, smooth mes (Fig. 10F View Figure 10 ); female genital plate with 2+2 mic (Fig. 10G View Figure 10 ).

Ecology.

Troglopedetes kae sp. nov. is only known from a small chamber in the dark zone of a cave, accessible by a very low and narrow passage. Specimens were found as small populations in an oligotrophic habitat, i.e., on wall and ground with very humid and wet environment, without any trace of organic matter.

Etymology.

The species name is taken from the type locality (Tham Kae).

Remarks.

Troglopedetes kae sp. nov. has four medial head macrochaetae, three medial Abd. IV macrochaetae, one inner teeth of claw and mucro with five teeth. It is near T. centralis Deharveng & Gers, 1993 from a cave in Doi Chiang Dao, Chiang Mai province in the absence of eyes, chaetotaxy of labial basis and of outer maxillary lobe, dorsal macrochaetotaxy from head to Abd. IV, chaetotaxy of anterior side of ventral tube and claw morphology. However, T. kae sp. nov. differs from T. centralis by its smaller size (1.3-1.6 vs. 1.7-2.1 mm), body colour with spots of orange pigment (vs. white), longer antennae (0.5-0.6 × as long as body vs. 0.4), thinner claw with an internal tooth at 30 vs. 50-65% from the basis, chaetae on lateral flap of the ventral tube (6+6 vs. 7+7), higher ratio dens:mucro (9.3-13.7 vs. 8.8), and mucro with five teeth (vs. four).

In the same cave and same habitat, we found another morphotype with very different claw complex; thick and clavate tenent hair, two strong inner teeth on claw at 74% and 91% of inner edge, and external edge of unguiculus with two or three minute outer basal teeth, sometimes inconspicuous (Fig. 9B View Figure 9 ). However, material was not enough to describe it in detail.

The locality where T. kae sp. nov. was collected is located 400 km south of the Isthmus of Kra, i.e., more south than other described Troglopedetes from Thailand. The Isthmus of Kra is well-known to be a biogeographical transition zone between Indochinese and Sundaic fauna (Fig. 1 View Figure 1 ). It was previously considered to be the southern distribution limit for the genus Troglopedetes , and the northern limit for the closely related genus Cyphoderopsis in Thailand ( Deharveng and Gers 1993, Jantarit et al. 2013). This discovery provides evidence that the two genera may actually overlap in southern Thailand, and questions the role of the Isthmus of Kra as biogeographical barrier for cave fauna.