Crossodonthina acuminata

Ecology. The new species was found only in the litter of studied forests.

Description. Body length: holotype, female, 2.6 mm; paratypes, females, 2.6 – 3.8 mm. Body color: red while living and white in alcohol (Fig. 2). Chaetal morphology. Body dorsal side with four types of ordinary chaetae: long macrochaetae (Ml), short macrochaetae (Mc), very short macrochaetae (Mcc) and mesochaetae (me). All chaetae thin, smooth and pointed. S-chaetae (s) on terga smooth, thinner than ordinary chaetae, and equal to Ml in length. Head (Table 4, Fig. 11). Eyes 3 + 3, black. Antenna 4 - segmented. Ant. I with 10 chaetae. Ant. II with 11 chaetae. Two guard chaetae sgd and sgv present dorsally and ventrally on Ant. III respectively. Two short rods exposed in separate pits. Dorsally, 8 subequal, thickened and curved sensilla present on Ant. IV, apical bulb trilobed, organite (or) present (Fig. 14). Ventral chaetotaxy of Ant. IV: ap with 7 bs and 2 miA, ca with 2 bs and 1 miA, cm with 4 bs and without miA, and cp with 7 miA (Fig. 15). On ventral side of Ant. III, Vi, Vc, Ve respectively with 2, 4, 3 chaetae (Fig. 15). TABLE 4. Cephalic tubercles and chaetotaxy of C. acuminata sp. nov. Buccal cone developed, labrum truncated, labrum chaetae formula as 0 / 2, 2. Mandible with three basal teeth, five long rami and three short rami (Fig. 16). Maxilla with three lamellae, the longest lamella bifurcated, with filaments on the edge of the big ramus; the middle lamella with two teeth; the shortest lamella with only one pointed tooth (Fig. 17). Labium with 11 chaetae and no papillae x. Dorsal chaetotaxy of head as in Table 4 and Fig. 11. Tubercles Cl, An, Fr and Oc on dorsal central area independent from each other. Dorsal posterior area with 4 separate tubercles: 2 Di and 2 De, its chaetotaxy arranged as intermediate between cross and non-cross type (Deharveng 1983). Dorsal lateral area with 3 separated tubercles: Dl, L and So, each tubercle L with 2 chaetae. Ventral chaetotaxy of head. Group Vi with 6 chaetae, groups Vea, Vem and Vep with 4, 4 and 3 chaetae respectively. Thorax (Table 5 & Fig. 12). Th. I with 3 + 3 tubercles: Di with 1 chaeta, De with 3 (or 2) chaetae, Dl with 2 chaetae. Th. II and Th. III respectively with 4 + 4 tubercles. Tubercle Dl of Th. II with 5 chaetae (including the microsensilla). Chaetotaxy of thorax and legs as in Table 5. Unguis with a basal inner tooth, unguiculus absent. Chaeta M present on tibiotarsus. Abdomen (Table 5 & Fig. 12). Abd. I – IV respectively with 4 + 4 tubercles, tubercle L of Abd. I with 5 – 7 chaetae (4 – 6 + s), tubercle L of Abd. II with 6 – 8 chaetae (5 – 7 + s), tubercle L of Abd. III with 8 – 9 chaetae (7 – 8 + s), tubercle L of Abd. IV with 8 chaetae, without sensory chaeta. Abd. V dorsally with 3 + 3 tubercles, two tubercles Di separate from each other, tubercle De separate from Dl, tubercle L with 3 – 4 chaetae. Abd. VI with 1 tubercle on each side. Ventral tube with 4 + 4 chaetae (Fig. 13). Furcular remnant without chaeta.

Figures 2, 11 – 17, Tables 4 – 6

Diagnosis. Three black eyes per side on head; all cephalic tubercles independent; chaeta O on tubercle Fr present; cephalic tubercle Di, De on posterior area of head with 2 chaetae each, arranged as intermediate between cross and non-cross type; mandible with 3 teeth and 8 rami; tubercle De of Th. I with 3 chaetae; furcular remnant without any chaeta.

Remarks. The new species can be differentiated from all known species of genus Crossodonthina by the following character combination: all cephalic tubercles independent, cephalic tubercle Di, De with 2 chaetae each, arranged as intermediate between cross and non-cross type chaetotaxy on posterior area of head, mandible with 3 teeth, five long rami and three short rami. Maxilla with 3 lamellae. Tubercle De and Dl of Th. I with 3 (2) and 2 chaetae respectively, furcular remnant without chaeta, tubercle L of Abd. I – III with a sensory chaeta each. Crossodonthina acuminata sp. nov. is the eleventh species with 3 + 3 eyes in the genus Crossodonthina. The new species is similar to C. formosana Yosii, 1965 from Taiwan in macrochaetae on terga smooth and pointed, tubercle Di on Th. II – Abd. III present, maxilla with 3 lamellae, Ant. IV with trilobed apical bulb, ventral tube with 4 + 4 chaetae. However, the former can be differentiated from the latter by having separated tubercle Dl, L and So on head, 8 rami and 3 teeth on mandible, 3 (2) chaetae on tubercle De of Th. I and no chaeta on Fu, versus having fused tubercle Dl + L + So on head, 4 rami and 1 big tooth on mandible, 1 chaeta on tubercle De of Th. I and 3 chaetae on Fu. C. acuminata sp. nov. also resembles C. nipponica Yosii, 1954 from Japan by the following characters: macrochaetae on terga smooth and pointed, cephalic tubercles Dl, L and So independent, mandible with 3 basal teeth and claw with an inner tooth. However, the former can be differentiated from the latter by having well defined tubercle Di on Th. II – Abd. IV, 8 rami on mandible, 2 chaetae on tubercle Dl of Th. I and no chaeta on Fu, versus having obscure tubercle Di on Th. II – Abd. IV, 2 rami on mandible, 1 chaeta on tubercle Dl of Th. I and 3 chaetae on Fu. In the genus Crossodonthina, C. altamontana Yoshii, 1981 has no chaetae on Fu, that is similar to C. acuminata sp. nov. However, the new species can be differentiated from the former by having 3 chaetae on tubercle Oc, separated tubercle Dl, L and So on cephalic lateral area, chaeta O present on tubercle Fr, versus 2 chaetae on tubercle Oc, fused tubercle Dl, L and So on cephalic lateral area, chaeta O absent on tubercle Fr. Furthermore, C. clavata sp. nov. and C. acuminata sp. nov. can be discriminated from each other and From known species with 3 eyes by the key provided below.

Etymology. The name of the species derives from its acuminate body macrochaetae.

Type material. Holotype: Female, China, Hunan, Yizhang County, Mangshan National Nature Reserve. Coordinates: 24.967959 N, 112.957361 E, alt. 1070 m, on the highway side at Tiantaishan, in forest of bamboo, leg. Ji- Gang Jiang, Yu-Yao Zhao, Fang-Jun Chen, 8. iv. 2018 (J 2018040806). Paratypes: 4 females, Hunan, Yizhang County, on the road sides near the waterfall at Jiangjunzhai, leg. Ji-Gang Jiang, Yu-Yao Zhao, Fang-Jun Chen, 7. iv. 2018 (J 2018040711) (24.954720 N, 112.923782 E, alt. 1121 m); one female, ibid, Mangshan National Nature Reserve, near the entrance of Jiangjunzhai, in decayed leaves, leg. Ji-Gang Jiang, Yu-Yao Zhao, Fang-Jun Chen, 6. iv. 2018 (J 2018040602) (24.956291 N, 112.955372 E, alt. 1230 m); one female, ibid, Mangshan National Nature Reserve, in a pit on the sides of highway near the hydropower station, in decayed leaves, leg. Ji-Gang Jiang, Yu-Yao Zhao, Fang- Jun Chen, 7. iv. 2018 (J 2018040704) (24.977702 N, 112.939269 E, alt. 930 m). Type materials are housed in the Key Laboratory of Zoology, Hunan University of Arts and Science (HUAS), Changde, Hunan Province, China.