Tomocerus postantennalis, Yu, Daoyuan, Zhang, Feng & Deharveng, Louis, 2014

Yu, Daoyuan, Zhang, Feng & Deharveng, Louis, 2014, A peculiar cave species of Tomocerus (Collembola, Tomoceridae, Tomocerinae) from Vietnam, with a discussion of the postantennal organ and prelabral chaetae in Tomocerinae, ZooKeys 408, pp. 61-70 : 62-65

Tomocerus postantennalis sp. n. Figs 1-18

Type locality.

Vietnam, Tuyen Quang Province: Na Hang, Khuoi Sung, Hang Khuoi Sung, in cave, 22.5013°N, 105.3649°E, 24 Dec. 2003, Louis Deharveng and Anne Bedos leg.

Type specimens.

Holotype female and three paratype females on slides, labelled with collectors’ sample number Vn0312-56. Deposited in MNHN (holotype and two paratypes) and NJAU (one paratype).

Description.

Body length 3.4-4.3 mm. Body with diffuse dark pigment all over; Ant. II, base of Ant. III and ventral side of Ant. I darker than other parts of antenna; eye patches black and small; clypeus, antero-dorsal region and posterior margin of head darker than other parts of head; anterior half of trunk darker than posterior half; head and trunk with bilaterally symmetrical white pattern formed by numerous unpigmented patches (Fig. 1).

Antenna longer than body, Ant. IV lost, Ant. I:II:III ≈ 1.0:1.8:21.0, Ant. I and II dorsally scaled, Ant. III unscaled. Antennal chaetae poorly preserved and not studied. PAO oval, with thickened inner margin, its long axis as long as the diameter of anterior ocelli (Fig. 2). Ocelli 6+6, anterior two larger than others (Figs 2, 3). Prelabral chaetae 3+3; labral chaetotaxy 5, 5, 4, distal four chaetae stronger, anterior margin of labrum with four papillae (Fig. 4). Mandibular head asymmetrical, left mandible with four teeth, right mandible with five teeth, molar plate of left mandible distally with a cone-like tooth (Fig. 5). Basal teeth of maxillary lamella 5 prolonged, distinct beard absent (Fig. 6). Mentum (baso-lateral area of labium) with 5 smooth chaetae, other parts of labium not clearly seen. Cephalic dorsal chaetotaxy: anterior area 2, 2; interocular area 2, 0, macrochaetae absent along transverse medial line; postocular area 2+2; posterior area 1+1; posterior margin with about 30+30 short chaetae (Fig. 3). Head scaled both dorsally and ventrally.

Trochanteral-femoral organ with 1, 1 chaetae (Fig. 7); fore, middle and hind tibiotarsi ventrally with 6-7, 5, 5 spine-like chaetae (Fig. 8). Distal whorl of tibiotarsus with 11 chaetae, tenent hair thin and probably pointed (judging from its small socket), two small accessory chaetae beside tenent hair larger than pretarsal chaetae, sockets of two outer guard chaetae larger than tenent hair (Fig. 9). Unguis slender, with baso-internal ridging, two lateral teeth pointed, of moderate size; inner edge of unguis with one basal and one distal tooth, the distal tooth at about one third of the length of unguis from base. Unguiculus length 0.50-0.67 that of unguis, with one inner tooth larger than ungual teeth (Fig. 10). Scales present on all segments except pretarsus of all legs.

Ventral tube scaled both anteriorly and posteriorly, lateral flap unscaled. Each side of anterior face with ca. 50 chaetae, posterior face with ca. 90 chaetae, each lateral flap with ca. 60 chaetae; all chaetae smooth.

Tenaculum unscaled, with 4+4 teeth, anterior face with 5 small smooth chaetae (Fig. 11). Ratio manubrium:dens:mucro 3.3 –4.0:4.8– 5.4:1.0. Manubrium laterally with large scales and 11 chaetae, the proximal one chaeta small and smooth, the distal 10 chaetae enlarged and serrated; dorsal scales absent; each dorsal chaetal stripe with 250-300 smooth chaetae of different sizes, including 2+2 pointed prominent chaetae larger and straighter than other chaetae (arrowed in Fig. 12); 22-27 pseudopores on each side (Fig. 12); external corner chaetae as large as mesochaetae in the chaetal stripe (Fig. 13). Ventral side of manubrium covered only with scales. Dental spines formula 4 –5/5– 7, I, 1-2, I. Distal most spine strongest, about 0.1 times length of dens, sizes of the proximal spines increasing gradually from basal to distal. All spines compound, with numerous denticles of moderate size at basal half and smaller at distal half (Fig. 14). Dens internally divided into three subsegments, basally without outer strong chaetae or inner pointed scales, dorsally with ordinary smooth chaetae and a longitudinal central stripe of feathered chaetae (Fig. 15) from base of middle subsegment to apex of distal subsegment between ordinary chaetae, ventrally covered with small oval scales. Mucro elongate and multi-setaceous; both basal teeth with proximal lamellae, outer basal tooth with a toothlet (Fig. 16); apical and subapical teeth subequal; two dorsal lamellae beginning from subapical tooth, outer lamella ending in inner basal tooth, inner lamella ending freely beside inner basal tooth. Outer dorsal lamella with 5-7 subequal intermediate teeth (Fig. 17).

Macrochaetae distributed densely along anterior margin of Th. II (not drawn) and sparingly in posterior rows on terga. Th. II-Abd. V with 2,1/0,0,1,2,0 bothriotricha and 3,3/3,3,4,2,4 (3 central+1 lateral) posterior macrochaetae on each side; dorsal flap of Abd. VI with 13 macrochaetae (6+6 and 1 on middle line). Medial area of Th. II with two macrochaetae, the posterior one close to pseudopore; Abd. IV antero-laterally with one macrochaeta and one mesochaeta (Fig. 18). Most mesochaetae present at lateral margin of terga, especially from Abd. II to Abd. IV. Microchaetae uniformly distributed.

Etymology.

Named with reference to the presence of the postantennal organ.

Remarks.

Tomocerus postantennalis sp. n. is distinct from any other Tomocerus spp. in the presence of PAO and six prelabral chaetae. Besides, it is characterized by the unequal size of the ocelli, the lower number of cephalic macrochaetae and the reduction in the number of ungual inner teeth. Its compound dental spines are very similar to those of the Vietnamese species Tomocerus ocreatus Denis, 1948 and of the Chinese species Tomocerus folsomi Denis, 1929, which probably indicates a close phylogenetic relationship. The discrimination of these species is shown in Table 1.