Coecobrya ellisi Jantarit & Nilsai, 2021

Nilsai 1, Areeruk, Detcharoen 1, Matsapume, Godeiro 2, Nerivania Nunes & Jantarit 3, Sopark, 2021, Four new species of troglomorphic Coecobrya Yosii, 1956 (Collembola, Entomobryidae) from Thailand based on morphological and molecular evidence, with an updated key of Thai troglomorphic species, Subterranean Biology 41, pp. 1-42 : 1

Coecobrya ellisi Jantarit & Nilsai sp. nov.

Figures 1C , 8 , 9 , 10

Type material.

Holotype: male on slide. Thailand, Phetchabun province, Nong Phai district, Tham Tho, altitude 261 m a.m.s.l., 16.1231°N, 101.0222°E. 9.X.2019; S. Jantarit and A. Nilsai leg. (sample # THA_SJ_PNB06), dark zone of a cave, by entomological aspirator. Paratypes: same data as holotype, 12 specimens (1 male, 4 females and 7 subadults on slides). Additional material: same data as holotype, 8 specimens (in ethanol).

Holotype and 12 paratypes on slides deposited in NHM-PSU.

Description.

Habitus (Fig. 1C ). Medium size Entomobryidae . Body length 1.6-2.1 mm (holotype 1.8 mm). No scales. Eyes absent. Color: whitish in alcohol, with orange pigmentation on head, body, legs and furca. Four antennal segments. Body slender not bent nor humped at the level of Th. II. Th. II slightly larger than Th. III. Abd. IV 3.70-4.25 times as long as Abd. III along dorsal midline.

Pseudopores (Figs 9E , 10A-C ). Pseudopores present as round flat disks, smaller than mac sockets, except for the coxae and manubrium where psp are as large as mac sockets, 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 apical row of chaetae (2 psp on Ant. I, 2-3 psp on Ant. II, and 3 psp on Ant. III). On head, 1-2 psp located externally on each peri-antennal area. On tergites, 1+1 psp close to the axis from Th. II to Abd. IV (Figs 10A-C ). On coxae, 1-2 psp on coxae I, 2-3 psp on coxae II and 1-2 psp on coxae III, located close to longitudinal rows of chaetae. On manubrium, 2+2 dorso-apical ones (Fig. 9E ).

Clypeus and mouthparts (Figs 8A-C, E-G ). Clypeal area with three long, smooth prefrontal; seven middle chaetae (two long smooth chaetae and five ciliated chaetae; 1+1 long lateral chaetae (Fig. 8G ). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; the three median chaetae of the first row longer than two lateral ones, two lateral chaetae 1/2.5 length of others on second row (Fig. 8A ). Distal border of the apical non-granulated area of the labrum with a relatively narrow median U- or V-form intrusion into the granulated area dorsally; apical edge without spines (Fig. 8A ). Ventro-distal complex of labrum well differentiated, asymmetrical, with 1+1 distal combs of 13-15 minute on the right side and 14-16 strong and larger teeth on the left side (Fig. 8C ), and an axial pair of long sinuous tubules. Maxillary outer lobe with one basal chaeta, one apical chaeta (basal chaeta thicker than apical one) (34-44 µm vs. 12-15 µm) and four smooth sublobal hairs (Fig. 8F ). Labial palp strongly modified for the genus, 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. 8B ). Mandible apex strong, asymmetrical (left with four teeth, right with five teeth); molar plate with three strong pointed basal teeth, and 3-(5) smaller inner distal teeth, identical in both mandibles (Fig. 8E ). Maxilla capitulum with a three-toothed claw and several stout ciliated lamellae; lamella 2 large and broad, lamella 3 well developed; several other lamellae present.

Antennae (Fig. 8D ). Antennae extremely long, approximately 3.5-6.4 times as long as cephalic diagonal. Antennal segments ratio as I: II: III: IV. 1: 1.85: 1.76: 2.54 (N = 3). However, Ant II and III fused together in most cases. Antennal segments not subdivided nor annulated. Antennal chaetal types not analysed in detail. Smooth spiny mic at base of antennae: 3 dorsal, 3 ventral on Ant. I, 1 internal, 1 external and 1 ventral on Ant. II, 1 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. The paddle-like chaetae on Ant II absent. Ant. III organ with five sens not clearly seen in all specimens. Ant. IV without apical bulb. Subapical organite not distinctly knobbed, swollen, slightly enlarged apically, inserted dorsally (Fig. 8D ).

Dorsal head chaetotaxy (Fig. 9D ). Dorsal cephalic chaetotaxy with three antennal chaetae (An1, An3a, An3, An1 as mes); four anterior mac (A0, A2-3 and A5), three median (M1, M2 and M4) and eight sutural mac (S0, S1-7); Gr. II with 4(5) mac; A0 as mac; 6-8+6-8 scale-like structures (usually 6+6) present below sutural mac, probably inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head (Fig. 9D ).

Ventral head chaetotaxy (Figs 9A, B ). Chaetae of labial basis almost all smooth (m1m2rel1l2) or (mimrel1l2 sensu Zhang and Pan, 2020) (Fig. 9A ) except m1(mi) ciliated in one side in two specimens (Fig. 9B ), chaetae m1, e and l1 subequal, r thin and shortest, and l2 longest, m2 longer and thicker than m1. The r/m2 length ratio: 0.15-0.21 (Fig. 9A ). Postlabial chaetae X2, and X4 smooth and minute chaetae, X, X3 long and smooth and X1 absent (Fig. 9A ). On each side of the cephalic groove with 8-9 chaetae, of which the anterior five always long and smooth, 6thand 8th long and ciliated, 7thand 9th mics (Fig. 9A ).

Tergite chaetotaxy (Figs 10A-D ). Th. II with three (m1, m2, m2i) medio-medial, three (m4, m4p, m4i) medio-sublateral and 28-31 posterior mac; 1+1 ms and 2+2 sens antero-laterally (Fig. 10A ).

Th. III with 29-36 mac. 2+2 sens laterally (Fig. 10A ).

Abd. I with seven (a2-3, m2-4, m2i, m4p) mac, 1+1 ms and 1+1 sens laterally (Fig. 10B ).

Abd. II with two (m3, m3e) central and one (m5) lateral mac, 2+2 tric without modified chaetae, 1+1 sens laterally and 1+1 mic near internal tric (Fig. 10B ).

Abd. III with two (a2, m3) central, and three (am6, pm6, p6) lateral mac, 3+3 tric without modified chaetae, 1+1 sens laterally,1+1 mic near m3, ms present (Fig. 10B ).

Abd. IV with eight central mac (I, M, A5-6, A5p, B4-6) and nine (D3, E1-4, F1-3, F3a) lateral mac, 2+2 tric and at least 8 long S-like chaetae, without modified chaetae (Fig. 10C ).

Abd. V with at least 9 obvious mac mixed with several mes to small mac, and 3+3 sens (Fig. 10D ). Abd. VI not analysed.

S-chaetae formula from Th. II to Abd. V: 2+ms, 2/1+ms, 2,2+ms, ≈8, 3; as and ps sens on Abd. IV 1/3 as long as S-like chaetae (Figs 10A-D ).

Legs (Figs 8J, K ). Leg long; tita of leg III slightly longer than tita of legs I and II. Legs devoid of scales, covered with ordinary ciliated chaetae of various lengths, mic not seen. Trochanteral organ with 17-23 smooth, straight, unequal spine-like chaetae (Fig. 8K ). The distal whorl of tita III with 9-10 subequal ciliated mes, irregularly arranged, and dorso-apical pointed tenent hair (claw II-III clavate in one specimen). A smooth, thin and long chaeta close to tenent hair absent. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Claw rather slender and elongated. Unguis of all claw with one inner tooth at 68 % from the base of claw; a pair of unequal basal teeth at about 50-52 % of inner edge from basis, outer tooth present at 40 % from base of the claw (Fig. 8J ). Unguiculus approximately 2/3 as long as inner edge of the claw, pointed apically, devoid of inner and outer teeth (Fig. 8J ).

Ventral tube (Figs 8H, I , 9C ). Ventral tube about three times longer than wide. Lateral flaps with 7-8+7-8 chaetae (6-7+6-7 smooth chaetae and 0-2+0-2 ciliated chaetae present (Figs 8H-I , 9C ). Anterior face with 6-7+6-7 ciliated chaetae, 2(3) of them larger than others (Fig. 8H ); posteriorly with 4 apical long smooth chaetae, and about 8-9 proximal smooth chaetae mixed with long and mic chaetae arranged roughly asymmetrically (Fig. 9C ).

Furcal complex (Figs 9E-G ).Tenaculum with four large teeth of decreasing size from the basal to the distal one of each ramus, on a prominent, irregular body, with a postero-basal strong serrated chaeta bent distally. Mucrodens 1.22-1.31 times longer than manubrium. Furcula without smooth chaetae. Manubrium with a dense cover of ciliated chaetae both dorsally and ventrally. Manubrial plaque with 2+2 psp and five to six ciliate chaetae (Fig. 9E ). Distal part of manubrium ventrally with 10-12 + 10-12 ciliate chaetae (Fig. 9G ). Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens longer than mucro. Mucro strong and falcate, basal spine long, nearly reaching the tip of the mucronal tooth (Fig. 9F ).

Genital plate. Female genital plate with 2+2 genital mic, male genital plate not clearly seen.

Ecology.

Coecobrya ellisi sp. nov. was found deep in a cave which has many chambers, on the muddy ground floor, on stalagmites and on wet rock walls. Many individuals were found feeding on the patches of bat guano in mesotrophic to eutrophic habitats. The relative humidity of the cave was 86-89% and the temperature was 25.8-27.5 °C. The cave where this species was found is located in an isolated limestone hill and has a narrow, vertical, entrance about 25 m deep which is equipped with iron ladders. The cave is approximately 250 m long and 30 m deep and many of the chambers are dug out and enlarged. Bad air, with a low oxygen level (<18%), was also detected in some chambers, including the one where the new species was found which is at the base of the iron ladders.

Etymology.

This species is named in honor of Martin Ellis, a British speleologist who played a role in the Tham Luang cave rescue in Thailand (in 2018), and for his outstanding contribution to the study of cave fauna in Thailand. Our biological surveys have benefited tremendously from his support, including the discovery of this new species.

Remarks.

Coecobrya ellisi sp. nov. is close to and shares most morphological characters with C. phitsanulokensis sp. nov. from Tham Yai Nakarat, Noen Mapang district, Phitsanulok province. The two caves where these new two species were discovered are only 55 km apart in a straight line. They are similar in chaetotaxy of dorsal head, number of sublobal hairs on maxillary outer lobe, labial chaetotaxy, medio-medial and medio-sublateral mac on Th. II, number of mac on Abd. I, Abd. III, pointed tenent hair, anterior face of ventral tube and number of chaetae on manubrium plaque. However, C. ellisi sp. nov. can be easily distinguished from C. phitsanulokensis sp. nov. by the number of An mac on dorsal head (3 vs. 5), number of central mac on Abd. II (2 vs 3(4), number of central mac on Abd. IV (8 vs. 9), lateral mac on Abd. IV (9 vs. 8), number of inner teeth of claw (3 vs. 2) and number of chaetae on ventro-distal part of manubrium (10-12 vs. 13) (Table 1 ). Moreover, C. ellisi sp. nov. possesses orange dots clearly pigmented on the antennae, head, body, legs and manubrium while all other troglomorphic Coecobrya species so far described in Thailand are devoid of any trace of pigmentation (Fig. 1C ).

Figures

Figure 1. The distribution map of the troglomorphic Coecobrya in Thailand and the habitus of the four new species. (1) A Coecobrya whitteni sp. nov. (2) B C. troglobia sp. nov. (3) C C. ellisi sp. nov. (4) D C. phitsanulokensis sp. nov. (5) C. chumphonensis Zhang & Nilsai, 2017 (6) C. sirindhornae Jantarit, Satasook & Deharveng, 2019 (7) C. polychaeta Zhang & Nilsai, 2017 and (8) C. cavicta Nilsai & Zhang, 2017. Scale bar: 1 mm.

Figure 8. Coecobrya ellisi sp. nov. A Prelabral and labral chaetae B Labial palp C Ventro-distal complex of labrum D Subapical organ of Ant. IV E Mandibles F Outer maxillary lobe G Clypeal chaetae H Anterior side of ventral tube and Lateral flap I Lateral flap J Distal part of tita III and claw complex K Trochanteral organ.

Figure 9. Coecobrya ellisi sp. nov., continued A Chaetae of labial basis and ventral chaetotaxy of head B Chaetae of labial basis C Posterior side of ventral tube and Lateral flap D Dorsal cephalic chaetotaxy E Manubrium plaque F Mucro G Distal part of manubrium ventrally.

Figure 10. Coecobrya ellisi sp. nov., continued A Chaetotaxy of dorsal Th. II- III B Chaetotaxy of dorsal Abd. I- III C Chaetotaxy of dorsal Abd. IV D Chaetotaxy of dorsal Abd. V.