Coecobrya chompon, Nilsai & Zeppelini & Bellini & Lima & Jantarit, 2022

Nilsai, Areeruk, Zeppelini, Douglas, Bellini, Bruno C., Lima, Estevam C. A. & Jantarit, Sopark, 2022, First record of the boneti-group of Coecobrya Yosii, 1956 (Collembola Entomobryidae) from Thailand, with the description of three new cave species of the genus, Zootaxa 5214 (3), pp. 365-392 : 381-389

Coecobrya chompon sp. nov. Nilsai, Lima & Jantarit

Figs 1C , 10‒12 , Table 2

Type material. Holotype: female on slide. Thailand, Ratchaburi province, Chom Bung district, Tham Chom Pon , altitude 100 m a.s.l., 13.6256°N 099.5875°E, 25 November 2018 S. Jantarit, K. Sarakhamhaeng and K. Jantapaso leg. (sample # THA _ SJ_ PBR03 ), entrance, middle and dark zones of the cave, by entomological aspirator.

Paratypes: same data as holotype, 6 specimens (four females and two subadults on slides).

Additional material: same data as holotype, 20 specimens (in ethanol) in NHM-PSU and 24 specimens (in ethanol) in CRFS-UEPB. Holotype and six paratypes on slides deposited in NHM-PSU.

Description. Habitus ( Figs 1C , 10A, C , 12A ). Small sized Entomobryidae . Body length 1.0‒ 1.4 mm (holotype 1.4 mm). Eyes 1+1 well-developed ( Figs 10A, 10C , 12A ). Color: whitish in alcohol. Body slender, not bent nor humped at the level of the Th. II, elongated antennae, legs and furca. Th. II slightly larger than the Th. III; Abd. IV about 3.16‒3.50 times as long as the Abd. III along the dorsal midline.

Pseudopores ( Figs 10F , 12A‒G ). Pseudopores present as round flat disks, smaller than mac sockets, except for the coxae and manubrium where psp are as large as mac sockets ( Fig. 10F ). Pseudopores present on various parts of the body: antennae, head, tergites, coxae and manubrium. On antennae, psp located ventro-apically between the tip of antennal segments and the chaetae of the apical row, or just below the apical row of chaetae (two on Ant. I, 2‒3 on Ant. II, and three on Ant. III). On head, 1‒2 psp located externally on each peri-antennal area ( Fig. 12A ). On tergites, 1+1 psp close to the axis from Th. II to Abd. IV ( Figs 12B‒G ). Coxae I, II and III with 1‒ 2, 2‒ 3, and 1‒2 psp respectively, located close to longitudinal rows of chaetae. On manubrium, 2+2 dorso-apical ones on the manubrial plaques ( Fig. 10F ).

Clypeus and mouthparts ( Figs 10E , 11A‒B, 11D‒E ). Clypeal area with 11 chaetae arranged in three rows, with three rather long smooth chaetae in the prefrontal area; seven chaetae arranged asymmetrically (five smooth, rather long chaetae of unequal sizes, one ciliated and one mic; and 1+1 rather long smooth lateral chaetae anteriorly ( Fig. 10E ). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; one median shorter than the lateral ones (23‒25 vs. 18‒20 µm) ( Fig. 11B ). Distal border of the apical non-granulated median area of the labrum with a relatively narrow median U- or V-form intrusion (V form in Fig. 11B ) into the granulated area dorsally; apical edge without spines, lacking clear papillae. Maxillary outer lobe with one basal and one apical chaeta (basal chaeta thicker than the apical one) and three smooth sublobal hairs ( Fig. 11A ). Labial palp with 0, 5, 0, 4, 4 guards for papillae A‒E. Lateral process of labial palp subcylindrical, as thick as normal chaetae with tip beyond the apex of the labial papilla ( Fig.11E ). Mandible apex strong, asymmetrical (left with four, right with five teeth) ( Fig.11D ).

Antennae ( Figs 10A–B, 10D ). Antennae moderately long, approximately 2.09–2.84 times as long as the cephalic diagonal ( Fig. 10A ). Antennal segments ratio as I: II: III: IV = 1: 1.30–2.27: 1.40–1.75: 2.09–2.83 (N = 6). Antennal segments not subdivided nor annulated. Antennal chaetal types not analysed in detail. Smooth spiny mic at the base of antennae: three dorsal, three ventral on Ant. I, one internal, one external and one ventral on Ant. II, one smooth ventral on Ant. I, smooth straight long chaetae on antennae present. Ant. I ventrally with many smooth spiny mic of various sizes in its basal part, many subcylindrical, hyaline sens in its middle to apical part, and many long smooth straight chaetae. Dorsal Ant. II with 2–3 s-like chaetae ( Fig. 10D ). Ant. III organ with five sens; sens one and four subequal, hyaline; sens five acuminate, dark and shorter; sens two and three swollen ( Fig. 10B ). Ant. IV short, not subdivided, without the apical bulb. Subapical organite not much swollen, slightly enlarged apically, inserted dorsally.

Dorsal head chaetotax y ( Fig. 12A ). Dorsal cephalic chaetotaxy with five antennal chaetae (An1–2, An3a2, An3a; An3 as mic), four anterior (A0, A2–3, A5), three median (M1–2, M4) and eight sutural mac (S0, S1–4, S4e, S5–6), sometimes S5, S6 as mic; Gr. II with three mac (Pi1–3); 5+5 scale-like structures not present below the sutural mac inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head ( Fig. 12A ).

Ventral head chaetotaxy ( Fig. 11F ). Chaetae of labial basis all smooth (mrel 1 l 2) chaetae m, e l 1 and l 2 subequal, r as mic, thin and shortest, ratio of r to m 0.46 ( Fig. 11F ). Postlabial chaetae X 2 smooth, X long and smooth, and X 4 smooth chaetae, X 1 and X 3 absent. Each side of the cephalic groove with 6–8 chaetae, the anterior four always long and smooth, 5 th –8 th always ciliated mixed of small to long chaetae ( Fig. 11F ).

Tergites ( Figs 12B–G ). Th. II with three (m1, m2, m2i) medio-medial, four (a5, m4, m4i, m4p) medio-sublateral and 22 posterior mac; 1+1 ms and 2+2 sens laterally ( Fig. 12B ).

Th. III with 26 mac, a6i and m6i as mac, 2+2 sens laterally ( Fig. 12C ). Abd. I with six (a3, a5, m2–4, m2i) central mac, 1+1 ms and 1+1 sens laterally ( Fig. 12D ). Abd. II with four (a2, m3, m3e, m3ep) central and one (m5) lateral mac; 2+2 tric without modified surrounding chaetae; 1+1 sens laterally and 1+1 sens near m3 ( Fig. 12E ). Abd. III with one (m3) central, and three (am6, pm6, p6) lateral mac. 3+3 tric without modified surrounding chaetae, 1+1 sens laterally, 1+1 sens near m3 ( Fig. 12F ). bd. IV with seven central mac (A3, A6, B4‒6, Si, Sm) and seven (D3, E2–4, Ee8, F1, F3a) lateral mac, 2+2 tric and about 12 long S-like chaetae anteriorly (only six represented), without modified chaetae ( Fig. 12G ). Abd. V and VI not clearly seen in all specimens and not analysed. S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms, 2, 2, ≈ 12, 3; ps and as sens on Abd. IV 1/3 as long as S-like chaetae ( Figs 12B–G ).

Legs ( Figs 10I‒K, 10H , 11G ). Legs long; tita of leg III ( Fig. 10K ) slightly longer than tita of legs I and II. Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths and one mic of leg III near the ventrodistal region as smooth chaeta ( Fig. 10H ). Trochanteral organ with 21‒25 smooth, straight, unequal spine-like chaetae ( Fig. 11G ). The distal whorl of tita with 8‒9 subequal ciliated mes, irregularly arranged, and usually dorsoapical clavate tenent hair present (one specimen with pointed tenent hair in claw I). Smooth, thin and long chaeta close to the tenent hair absent. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Claw small, moderately elongated. Unguis with one strong unpaired inner tooth at about 70% from base of the claw, and a pair of subequal basal teeth at about 57‒60% of inner edge from basis. External edge of unguis with a strong tooth at about 50% of claw I and II and about 20% of claw III. Unguiculus approximately 1/2 as long as the inner edge of the claw, rather swollen baso-externally, pointed apically, with one tiny inner tooth at 15% only in claw I, and at least five to six minute outer teeth, often inconspicuous in the middle of its length ( Figs 10I‒K ).

Ventral tube ( Figs 11C, 11H ). Ventral tube two to three times longer than wide. Lateral flaps with 6‒10 + 6‒10 chaetae, usually with 6‒8 long smooth chaetae; sometimes with 1‒2 ciliated present (in the holotype) ( Fig. 11C ). Anterior face with 5‒6+5‒6 ciliated chaetae, 2 of them apically larger than the others ( Fig.11H ); posterior face with 2+2 long, smooth chaetae distally, the middle region with 2+2 mics, and 2+2 long and smooth chaetae proximally ( Fig. 11C ).

Furcal complex ( Figs 10F‒G , 11I ). Tenaculum with four large teeth of decreasing sizes from the basal to the distal one on each ramus, on a prominent, irregular corpus, with a postero-basal strong serrated chaeta bent distally. Mucrodens 1.22‒1.52 times longer than the manubrium. Furcula without smooth chaetae. Manubrium densely covered by ciliated chaetae both dorsally and ventrally. Manubrial plaque with 2+2 pseudopores and two or three ciliated chaetae ( Fig. 10F ). Distal part of the ventral manubrium with 6+6 ciliate chaetae ( Fig. 11I ). Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens as long as the mucro. Mucro strong and falcate, basal spine long, beyond the tip of the mucronal tooth ( Fig. 10G ).

Genital plate. Female genital plate with 2+2 genital mic.

Ecology. Coecobrya chompon sp. nov. was found on the floor of Tham Chom Pon, in an area covered by bat guano (a meso to eutrophic habitat), with a large number of individuals in the dark zone of a cave. The temperature in the chamber was 26.4‒26.6ºC and the humidity was 75‒82%. The cave is well known as an attractive show cave with a length of 290 m. At least 21 species of fauna are already recorded from Tham Chom Pon: one planarian, seven copepods, one beetle and one fly, plus 11 species of bat (Ellis, personal communication), the latter providing food sources for the subterranean invertebrates found in the cave, including the new species.

Etymology. The name of the new species refers to the type locality where it was discovered.

Remarks. Coecobrya chompon sp. nov. belongs to the boneti -group by presenting 1+1 eyes. Within this group, the new species differs from the others especially by the number of lateral mac chaetae on Abd.IV (7), (see Table 2). It looks closer to C. boneti ( Denis, 1948) from Dalat, Vietnam by presenting 1+1 eyes, similar body length, presence of long smooth straight and s-like chaetae on antennae, labial chaetae formula (mrel1l2), number of mac on dorsal head (An = 4, M = 3), medio-medial mac on Th. II (3), medio-sublateral mac on Th. II (3); mac on Abd. I (6), central mac of Abd. II (4), central mac in Abd. III (1), lateral mac on Abd. III (3), presence of ms on Abd. III, and number of ungual inner teeth (3). However, the new species clearly differs from C. boneti in a longer antennal length (2.1‒2.84 vs 1.9‒2.1); number of mac on Gr.II (3 vs 4); posterior mac on Th. II (15‒18 vs 20‒24); central mac on Abd. IV (7 vs 6); lateral mac in Abd.IV (7 vs 6); tenent hair (clavate vs pointed), number of chaetae in posterior face of ventral tube (18‒20 vs 8); number of smooth, spiny chaetae on trochanteral organ (21‒25 vs 11‒15); and mucronal spine (nearly vs reaching the mucronal apex). A discussion concerning the variability within the boneti - group is presented below.

Figures

FIGURE 1. Distribution of the new species of Coecobrya described in this study: A, Coecobrya satasookea sp. nov.; B, Coecobrya cavicola sp. nov.; C, Coecobrya chompon sp. nov. Scale bars: 500 µm. Light green in Thai map refers limestone areas.

FIGURE 10. Coecobrya chompon sp. nov. SEM photographs: A, habitus; B, Ant. III organ; C, Eye and pseudopore near to the basal Ant. I.; D, s-like chaeta on Ant II; E, clypeal chaetae; F, manubrial plaque; G, mucro and distal dens; H, additional cheata on tibia III; I, empodial complex I; J, empodial complex II; K, empodial complex III; Scale bars: 10 µm, with the exception of the habitus.

FIGURE 11. Coecobrya chompon sp. nov. morphology: A, maxillary outer lobe and sublobal plate; B, labrum and prelabral chaetae, red arrow indicating V-form shaped intrusion; C, posterior face of ventral tube and lateral flap; D, mandibles; E. lateral process of labial papilla E; F, main chaetae on ventral head; G, trochanteral organ; H, anterior face of ventral tube; I, distal part of manubrium ventrally Scale bars: 20 µm.

FIGURE 12. Coecobrya chompon sp. nov. dorsal chaetotaxy:A, head (including the right eye); B, Th. II; C, Th. III; D, Abd. I; E, Abd. II; F, Abd. III; G, Abd. IV; Scale bars: 100 µm.