Coecobrya phitsanulokensis 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 phitsanulokensis Jantarit & Nilsai sp. nov.

Figures 1D , 11 , 12 , 13

Type material.

Holotype: female on slide. Thailand, Phitsanulok province, Noen Mapang district, Tham Yai Nakarat, altitude 85 m a.m.s.l., 16.5052°N, 100.6864°E. 7.X.2019; S. Jantarit, A. Nilsai, K. Sarakhamhaeng and K. Jantapaso leg. (sample # THA_SJ_PLK01), dark zone of a cave, by entomological aspirator. Paratypes: same data as holotype, 7 specimens (3 females and 4 subadults on slides). Additional material: same data as holotype, 13 specimens (in ethanol)

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

Description.

Habitus (Fig. 1D ). Medium size Entomobryidae . Body length 1.8-2.3 mm (holotype 1.8 mm). No scales. Eyes absent. Color: whitish in alcohol, without pigmentation. Four antennal segments. Body slender not bent nor humped at the level of Th. II. Th. II slightly larger than Th. III. Abd. IV 3.58-3.88 times as long as Abd. III along the dorsal midline.

Pseudopores (Figs 12H , 13A, B, D ). 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 the apical row of chaetae (2 psp on Ant. I, 2-3 psp on Ant. II, and 3 psp on Ant. III). On the 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 13A, B , 13D ). 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. 12H ).

Clypeus and mouthparts (Figs 11A-C, F , 12A ). Clypeal area with three long, smooth prefrontal chaetae; 9 middle chaetae (two long smooth chaetae, 7 small ciliated chaetae from mic to mes arranged asymmetrically), and two long, smooth lateral chaetae (Fig. 11A ). Prelabral and labral chaetae 4/5, 5, 4, all thin and smooth; three median chaetae of the first and second rows longer than the two lateral ones (32-38 vs. 12-15 µm) (Fig. 11C ). 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. 11C ). Ventro-distal complex of labrum well differentiated, asymmetrical, with 1+1 distal combs 15-16 minute on the right side and 13 strong and larger teeth on the left side, and an axial pair of long sinuous tubules. Maxillary outer lobe with one basal chaeta, one apical chaeta (basal chaeta thicker than apical one) and four smooth sublobal hairs (65-70 vs. 25-32 µm) (Fig. 11F ). 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. 11B ). Mandible apex blunt and 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. 12A ). 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. Antennae long, approximately 3.1-4.2 times as long as cephalic diagonal. Antennal segments ratio as I: II: III: IV. 1: 0.5-0.73: 0.48-0.7: 0.41-0.68 (N = 6). Antennal segments not subdivided nor annulated. Antennal chaetal types not analyzed in detail. 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.

Dorsal head chaetotaxy (Fig. 11E ). Dorsal cephalic chaetotaxy with five antennal chaetae (An1-3, An3a2, An3a, An1 as mes), four anterior mac (A0, A2-3 and A5) three median (M1, M2 and M4) and eight sutural mac (S0, S1-S7); Gr. II with 4 or 5 mac; A0 as mac; 5-7+5-7 scale-like structures present below sutural mac, probably inside the integument; a pair of short cephalic trichobothria, external and close to the middle of the head (Fig. 11E ).

Ventral head chaetotaxy (Fig. 11D ). Chaetae of labial basis all smooth (m1m2rel1l2), (mimrel1l2 sensu Zhang and Pan, 2020), chaetae m1(mi), e and l1 subequal, r thin and shortest, and l2 longest, m2 longer and thicker than m1. The ratio of r to m2: 0.13-0.19 (Fig. 11D ). Postlabial chaetae X2, X and X4 minute chaetae, X1 and X3 absent. On each side of cephalic groove with 8-11 chaetae, of which the anterior five always long and smooth, others either smooth or finely ciliated, at least 3-4 minute chaetae always present on the posterior ones (Fig. 11D ).

Tergite chaetotaxy (Figs 13A-D ). Th. II with three (m1, m2, m2i) medio-medial, three (m4, m4p, m4i) medio-sublateral and 31-33 posterior mac; 1+1 ms and 2+2 sens antero-laterally (Fig. 13A ).

Th. III with 32-33 mac. 2+2 sens laterally (Fig. 13A ).

Abd. I with seven (a2-3, m4, m2-3, m2i, m4p) mac, 1+1 ms and 1+1 sens laterally (Fig. 13B ).

Abd. II with 3(4) (a2, m3, m3ep, and m3e sometimes present) central and one (m5) lateral mac. 2+2 tric without modified chaetae, 1+1 sens laterally and 1+1 mic near internal tric (Fig. 13B ).

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. 13B ).

Abd. IV with nine central mac (I, M, A4-6, A5p, B4-6) and nine (D3, E1-4, E2p, F1-3) lateral mac, 2+2 tric and about 8 long S-like chaetae, without modified chaetae (Fig. 13D ).

Abd. V with 12 obvious mac mixed with several mes to small mac, and 3+3 sens (Fig. 13C ). 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 13A-D ).

Legs (Figs 12B, D ). 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 19 smooth, straight, unequal spine-like chaetae (Fig. 12D ). The distal whorl of tita III with 10 subequal ciliated mes, irregularly arranged, and dorso-apical pointed tenent hair. A smooth, thin and long chaeta close to tenent hair absent. Ventro-distal smooth chaeta of tita III thick, erected, pointed, rather short. Claw slender and elongated. Unguis of all claws without inner tooth, and a pair of subequal basal teeth at about 29-36 % of inner edge from basis. Unguiculus approximately 1/2 as long as the inner edge of the claw, rather swollen basally, pointed apically, devoid of inner tooth, with at least 3-4 minute outer teeth, often inconspicuous, at 3/4 of its length (Fig. 12B )

Ventral tube (Figs 12E, F ). Ventral tube about four times longer than wide. Lateral flaps with 6-8+6-8 smooth chaetae (Fig. 12F ). Anterior face with 6-7+6-7 ciliated chaetae, four of them larger than others (Fig. 12E ); posterior face with 4 long, smooth apical chaetae and about 11 smooth chaetae arranged roughly asymmetrically, mixed with mic or small acuminate mes (Fig. 12F ).

Furcal complex (Figs 12C, G, H ). 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 1.11-2.27 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. 12H ). Distal part of manubrium ventrally with 13-15+13-15 ciliate chaetae (Fig. 12C ). Dens without spines, annulated and covered with ciliated chaetae on both sides. Distal smooth part of dens slightly longer than mucro. Mucro strong and falcate, basal spine long, nearly reaching the tip of the mucronal tooth (Fig. 12G ).

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

Ecology.

Coecobrya phitsanulokensis sp. nov. was found from the twilight zone (ca. 20 m from the cave entrance) to the dark zone of the cave on wet and muddy ground and on the decaying organic material inside the cave. The length of the main passage in the cave is about 300 m. The temperature was 26.2-27.9 °C, the soil temperature was 24.1-24.3 °C and the relative humidity in the cave was 78-89 %. The cave has a seasonal stream in it, but there was no water during our visit. This cave is developed in a very small isolated limestone hill (0.4 × 0.9 km) surrounded by a flood plain agricultural landscape, with at least seven other caves having been reported in this hill.

Etymology.

This species is named after the type locality, Phitsanulok province, where the material was collected.

Remarks.

Among the troglobitic Coecobrya species C. phitsanulokensis sp. nov. is similar to C. ellisi sp. nov. from Tham Tho, Nong Phai district, Phetchabun province. For the species diagnosis see the remarks under Coecobrya ellisi sp. nov. and Table 1 .

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 11. Coecobrya phitsanulokensis sp. nov. A Clypeal chaetae B Labial palp C Prelabral and labral chaetae D Anterior side of ventral tube E Dorsal cephalic chaetotaxy F Outer maxillary lobe.

Figure 12. Coecobrya phitsanulokensis sp. nov., continued A Mandibles B Distal part of tita III and claw complex C Distal part of manubrium ventrally D Trochanteral organ E Anterior side of ventral tube F Posterior side of ventral tube and Lateral flap G Mucro H Manubrium plaque.

Figure 13. Coecobrya phitsanulokensis sp. nov., continued A Chaetotaxy of dorsal Th. II- III B Chaetotaxy of dorsal Abd. I- III C Chaetotaxy of dorsal Abd. V D Chaetotaxy of dorsal Abd. IV.