Coecobrya satasookea, 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 : 367-372

Coecobrya satasookea sp. nov. Nilsai, Bellini & Jantarit

Figs 1A, 2‒5, Table 1

Type material. Holotype: female on slide. Thailand, Chaiyaphum province, Khon San district, Tham Prakai Phet (tham = “cave” in Thai), altitude 570 m a.s.l., 16.4842°N 101.7825°E, 30 November 2020 S. Jantarit, A. Nilsai, K. Sarakhamhaeng and K. Jantapaso leg. (sample # THA_SJ_ CPM03 ), dark zone of the cave, by entomological aspirator.

Paratypes: same data as holotype, 10 specimens (four females, one male and five subadults on slides) .

Additional material: same data as holotype, 6 specimens (in ethanol) deposited in NHM-PSU. and 6 paratypes (in ethanol) deposited in CRFS-UEPB .

Holotype and eight paratypes on slides deposited at NHM-PSU, two paratypes (two subadults) on slides deposited at CRFS-UEPB.

Description. Habitus ( Fig. 1A, 2A).

Large sized Entomobryidae . Body length 1.4‒1.9 mm (holotype 1.5 mm). Eyes absent. Color: whitish in alcohol. Body slender, not bent nor humped at the level of the Th. II., very elongated antennae, legs and furca. Th. II slightly larger than the Th. III; Abd. IV about 3.45‒4.33 times as long as the Abd. III along the dorsal midline .

Pseudopores ( Figs 3H, 4B‒F, 5A‒B).Pseudopores present as round flat disks, smaller than mac sockets ( Fig. 4B), except for the coxae and manubrium where psp are as large as mac sockets. 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. 4B). On tergites, 1+1 psp close to the axis from Th. II to Abd. IV ( Figs 4C‒F, 5A‒B). 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. 3H).

Clypeus and mouthparts ( Figs 2B‒C, 2F‒G, 2I). Clypeal area with three long, smooth prefrontal chaetae; 10‒12 rather short smooth chaetae of unequal size in the facial area, two of them short and ciliated laterally; and 1+1 long smooth lateral chaetae anteriorly ( Fig. 2I). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; three median chaetae slightly longer than the two lateral ones (35‒39 vs. 27‒30 µm) ( Fig. 2G). Distal border of the apical nongranulated median area of the labrum with a relatively narrow, median U- or V-form intrusion into the granulated area dorsally (V-form in the fig. 2G); apical edge without spines, lacking clear papillae ( Fig. 2G). Maxillary outer lobe with one basal and one apical chaetae (basal chaeta slightly thicker than the apical one) and three smooth sublobal hairs (55‒58 vs. 40‒44 µm) ( Figs 2C, G). 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 ( Figs 2B, F, G). Mandible apex strong, asymmetrical (left with four, right with five teeth).

Antennae ( Figs 2A, D, E). Antennae very long, approximately 4.73–5.50 times as long as the cephalic diagonal. Antennal segments ratio as I: II: III: IV = 1: 2.0–3.10: 2.58–3.20: 6.60–8.50 (N = 4). 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 two paddle-like chaetae. Ant. III organ with five sens; sens one and four subequal, hyaline; sens five acuminate, dark and shorter; sens two and three swollen ( Figs 2A, E). Ant. IV very long, not subdivided, without the apical bulb. Subapical organite not much swollen, slightly enlarged apically, inserted dorsally ( Figs 2A, D).

Dorsal head chaetotaxy ( Figs 4A, 4C‒D). Dorsal cephalic chaetotaxy with five antennal chaetae (An1–2, An3a2, An3a; An3 as mic), four anterior (A0, A2–3 and A5), three median mac (M1–2, M4) and six sutural mac (S2– 4, 4e, 5–6), Gr. II with two mac (Pi1–2); 5+5 scale-like structures present below the sutural mac (sensu Jantarit et al. 2019), inside the integument ( Fig. 4D), (socket of scale-like structures not detected under SEM) ( Fig. 4C); a pair of short cephalic trichobothria, external and close to the middle of the head ( Fig. 4A).

Ventral head chaetotaxy ( Figs 2F, 2H). Chaetae of labial basis all smooth (mrel 1 l 2)chaetae m, e and l 1 subequal, r thin and shortest, ratio of r to m 0.13‒0.17, l 2 longest ( Fig. 2F). Postlabial chaetae X, X 3, as spiny mic; X 2 and X 4 absent ( Fig. 2H). Each side of the cephalic groove with 9‒11 chaetae, the anterior six always long and smooth, 7 th –11 st small or long ciliated chaetae.

Tergites ( Figs 4E‒F, 5A‒E). Th. II with three (m1, m2, m2i) medio-medial, two (a5, m4) medio-sublateral and 20 posterior mac; 1+1 ms and 2+2 sens laterally ( Fig. 4E).

Th. III with 22 mac, a6, p5–6 as mac, 2+2 sens laterally ( Fig. 4F). Abd. I with six (a3, a5, m2–4, m2i) central mac, 1+1 ms and 1+1 sens laterally ( Fig. 5A). Abd. II with two (m3, m3e) central and one (m5) lateral mac, 2+2 tric without modified surrounding chaetae, 1+1 sens laterally and 1+1 sens above m3 ( Fig. 5B). 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. 5C). Abd. IV with five central mac (A3, A5‒6, B5‒6), sometimes A6 as mic (N = 2), and six (E2–4, Ee8, F1, F3a) lateral mac, 2+2 tric and about 8 long S-like chaetae anteriorly (just two represented), without modified chaetae ( Fig. 5D). Abd. V with at least 6 obvious mac (a5, m2–3, m5, p1, p3) and several mes to small mac, and 3+3 sens ( Fig. 5E). Abd. VI not analysed.

S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms, 2, 2, ≈ 8, 3; ps and as sens on Abd. IV 1/3 as long as S-like chaetae ( Figs 4C–F, 5A–C).

Legs ( Figs 3A‒C, G, I, K). Legs long; tita of leg III ( Fig. 3C) slightly longer than tita of legs I ( Fig. 3A) and II ( Fig. 3B). Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths and at least one mic of leg III near the ventro-distal region as smooth chaeta ( Fig. 3K). Tibiotarsi II and III with one large inner ciliate mac at 1/3 from basal side ( Figs 3G, I). Trochanteral organ with 14‒21 smooth, straight, unequal spine-like chaetae. The distal whorl of tita with 10 subequal ciliated mes, irregularly arranged, and usually dorso-apical clavate tenent hair present (one specimen claw III with pointed tenent hair). Smooth, thin and long chaeta close to the tenent hair absent. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather long. Claw slender and elongated. Unguis with a tiny unpaired inner tooth, a pair of subequal basal teeth at about 33‒38% of inner edge from basis, and a tooth of outer edge at about 20% from basis. Unguiculus without outer tooth, approximately 1/2 as long as the inner edge of the claw, rather swollen baso-externally, pointed apically ( Figs 3A‒C).

Ventral tube ( Figs 3D‒E). Ventral tube about three times longer than wide. Lateral flaps with 7‒9+7‒9 rather long, smooth and thin chaetae ( Fig. 3E). Anterior face with 7‒9+7‒9 ciliated chaetae, two of them apically larger than the others ( Fig. 3E); posterior face with 2+2 long smooth distal chaetae, 1 unpaired smooth chaeta and 1+1 lateral smooth spines (as in Cyphoderus ), 1 unpaired plus 2+2 smooth chaetae, 2+2 ciliate chaetae, 1+1 lateral smooth spines and 2+2 ciliate chaetae at the apex ( Fig. 3D).

Furcal complex ( Figs 3F, H, J). 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 1.34‒1.50 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 five ciliated chaetae ( Fig. 3H). Distal part of the ventral manubrium with 10+10 to 12+12 ciliate chaetae ( Fig. 3J). 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, nearly reaching the tip of the mucronal tooth ( Fig. 3F).

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

Ecology. Coecobrya satasookea sp. nov. was found in the dark zone of Tham Prakai Phet on the surface of the muddy ground, near the edge of a (seasonal) stream. It was also found in the upper levels of the cave (a small chamber with a passage) on stalagmites, clay, gravel and rock surfaces. This species was found mainly in eutrophic habitats with a rather large population size where piles of guano and organic matter were frequent. The temperature in the cave varies from 22.6‒27.1ºC, while the chamber where the species was collected was 22.6‒24.8ºC, with a humidity of 76‒78%.

Etymology. Coecobrya satasookea sp. nov. is named in honour of Chutamas Satasook, a director of the Princess Maha Chakri Sirindhorn Natural History Museum, who has been interested in natural sciences and has greatly supported the study of Collembola in Thailand.

Remarks. Coecobrya satasookea sp. nov. belongs to the highly troglomorphic group of Thai Coecobrya species in presenting very long appendages (antennae, legs and furca), larger body size, and due to its blindness and depigmentation. This new species differs from other highly troglomorphic species especially in the number of posterior mac on Th. II (20), (see Table 1). It is most similar to C. whitteni and C. troglobia from caves in Khon Kaen province. The cave where this new species is found is, in a straight line, only about 44 km from C. whitteni from Tham Nayn Noi and about 41 km from C. troglobia from Tham Phaya Nakharat. They share similar morphological features like body and antennal length, in presenting long smooth straight chaetae on antennae, having the same number of prefontal clypeus chaetae, number of sublobal hairs on maxillary outer lobe, number of mac on Th. III, Abd. I, number of central mac on Abd. II, Abd. III and of lateral mac on Abd. III, having tenent hairs either clavate or pointed, and with the mucronal spine nearly reaching the mucronal apex (see Table 1 for a detailed comparison). However, C. satasookea sp. nov. differs from the two closely related species by presenting two paddle-like chaetae on Ant. II, (not present in the two described species); number of chaetae in facial area of clypeus (8‒10s2C in C. satasookea sp. nov. vs 2s6c in C. whitteni and 2s4c in C. troglobia ); number of dorsal head chaetae (An = five vs An = two in C. whitteni and An = four in C. troglobia ); number of Gr.II chaetae (two vs four in both C. whitteni and C. troglobia ); number of mac on medio-sublateral Th. II (two vs one in C. whitteni and four in C. troglobia ); ms chaeta in Abd. III (present vs absent in both C. whitteni and C. troglobia ) and number of claw inner teeth (two vs three in C. whitteni and four in C. troglobia ).