Crossodonthina hainana Xiong, Chen & Yin, 2005

Jiang, Jigang & Wang, Qingyun, 2025, A new species of Crossodonthina Yosii (Collembola, Neanuridae) from Central-South China, with the redescription of C. hainana Xiong, Chen & Yin, 2005, Zootaxa 5665 (2), pp. 187-204 : 196-202

Crossodonthina hainana Xiong, Chen & Yin, 2005

Redescription based on Hunan’s material

Figs 15–23 , Tables 3–4

Studied material. Fourteen females and one male; Mountain Sun Forest Park , Wuling District, Changde City, Hunan Province, China, coordinates: 29°11'33.45" N, 111°42'10.93" E, alt. 478m, under the leaves of Phyllostachys heteroclada Oliver on the side of a path in forest, leg. Jigang Jiang, Ziyue Wang, Yixuan Zhou, Yali Gao, Yuchuan Jin, 14.IV.2024 (No. 2024041402). Two females, Mountain Sun Forest Park , Wuling District, Changde City, Hunan Province, China, coordinates: 29°9'26.69" N, 111°42'37.55" E, alt. 115m, under the leaves of Osmanthus fragrans (Thunb.) Lour and Castanea mollissima Blume on the side of a road in forest, leg. Jigang Jiang, Ziyue Wang, Yixuan Zhou, Yali Gao, Yuchuan Jin, 14.IV.2024 (No. 20240411401). Specimens deposited at the Key Laboratory of Zoology, Hunan University of Arts and Science ( HUAS), Changde, Hunan Province, China .

Description. Body length: females 2.2–4.1 mm; male 3.1mm. Color: red while living and white in alcohol ( Fig. 15 ).

Chaetal morphology. Dorsal ordinary chaetae of five types. Long macrochaetae (Ml) smooth and clavate ( Fig. 17a ). Short macrochaetae (Mc) morphologically similar to and shorter than Ml ( Fig. 17b–d ). Very short macrochaetae (Mcc) shorter than Mc ( Fig. 17e ). Mesochaetae (me) smooth, pointed and variable in length ( Fig. 17f–i ). Microchaetae (mi) pointed and smooth, shorter than me (fig. 17j). S-chaetae (s) on terga thin, smooth and pointed, subequal to the longest Mc ( Fig. 17k ).

Head. Eyes 2+2, colorless, one anterior to, but not included in tubercle Oc, the posterior one on the back of tubercle Oc ( Fig. 16 ).

Antenna four-segmented.Ant. I always with 9 chaetae.Ant. II with 11 chaetae.Ant. III fused to Ant. IV dorsally. Guard chaeta sgd of Ant. III almost at the same level of the two sensory rods. Ant. IV dorsally with eight subequal, slightly thickened and blunt sensilla (S1–8). Apical bulb trilobed, organite (or) present between S6 and S7 ( Fig. 18 ). On ventral side of Ant. III, Vi, Vc and Ve with 4, 4, 5 chaetae, respectively, guard chaeta sgv almost at the same level of ms ( Fig. 19 ).

Oral cone short, labrum truncated, labral formula as 2/ 6, 2 ( Fig. 20 ). Labium with 11 chaetae, with two papillae x. Mandible with two large basal teeth, three slim teeth (two of them bifurcated), three whip-like branches and two fringed branches ( Fig. 21 ). Longer fringed branch with two rows of cilia, about 14 cilia on the dorsal row, arranging from base to end; and about 11 cilia on ventral row, arranging on middle part of branch. Short fringed branch with about 14 cilia on the inner side ( Fig. 21 ). Three whip-like branches smooth and curved, usually stuck to fringed branches. Maxilla with three lamellae, two longer lamellae needle-like. Shortest lamella apically ciliated ( Fig. 22 ).

Cephalic dorsal tubercles and chaetotaxy shown in Fig. 16 and Table 3 . Cephalic tubercles Cl, Fr, An and Oc independent; chaeta O not included in tubercle Fr and located between two An tubercles; tubercle Oc with 2 chaetae, chaeta Oca present as mi. Dorso-posterior area of head with four separate tubercles: two Di and two De, chaetae Di2, De1 and De2 included in tubercle De, line of chaetae Di2–De2 crossing line Di1–De1 on head (cross-type sensu Deharveng 1983). Tubercles Dl, L and So fused to each other, with 10–11 chaetae.

Ventral chaetotaxy of head. Group Vi with four chaetae, groups Vea with four, Vem and Vep with three chaetae respectively.

Thorax ( Fig. 16 and Table 4 ). Th. I with 3+3 tubercles, Di, De, Dl with 1, 2, 1 chaetae, respectively. Th. II with 4+4 tubercles, tubercle Di with three chaetae, two chaetae included in the tubercle, another one (mi) free from the tubercle; De with five (4+s), Dl with four (2+s+ms), tubercle L with three chaetae, respectively. Th. III with 4+4 tubercles, chaetae arrangement on tubercles Di, De, L similar to that of Th. II; tubercle Dl with three (2+s) chaetae. Chaetotaxy of thorax and legs as in Table 4 . One basal inner tooth present on basal unguis; unguiculus absent. Chaeta M present on tibiotarsus.

Abdomen ( Figs 16 , 23 and Table 4 ). Abd. I–III each with 4+4 tubercles, Di with two, De with four (3+s), Dl with two and L with three chaetae, respectively. Abd. IV with 4+4 tubercles, Di with two, De with three (2+s), Dl with three, L with 6 chaetae, respectively. Abd. V dorsally with 2+2 tubercles, two separated Di, each with three chaetae, tubercle De only with one chaeta s and fused to tubercle Dl, fused De+Dl totaling 5 (s+4) chaetae. Tubercle L on Abd. V on the ventral side of the abdomen, with 5 chaetae. Abd. VI with 1+1 tubercles, seven chaetae present on each tubercle. VT with 4+4 chaetae ( Fig. 23 ). Furcular remnant with 3+3 chaetae ( Fig. 23 ). Chaetotaxy of ventral side of abdomen listed in Table 4 .

Remarks. Due to the insufficient original description of Crossodonthina hainana Xiong, Chen & Yin, 2005 , it was firstly redescribed by Luo & Chen (2010). Crossodonthina hainana is well characterized within the genus by having two eyes on each side of head, 2/ 6, 2 chaetae on labrum, two chaetae on tubercle Oc, five-branched mandibles and six chaetae on Fu. Undoubtedly, it falls into the C. montana species group ( Jiang & Wang 2024). Crossodonthina hainana was firstly described from Dongzhaigang Mangrove Natural Reserve, Hainan Province, China, so it is probably well adapted to saline-alkaline environment of beach habitats. However, its recent discovery in inland China suggests a broader ecological adaptability. So, this species may be widely distributed in the Southern region of China.

Because most of the characters of our studied specimens from Hunan Province fit the redescription of Luo & Chen, i.e., the similar chaetotaxy on body, the five-branched mandible (with three smooth whip-like and two fringed branches), the similar labral chaetotaxy (2/ 6, 2), and only two chaetae on tubercle Oc, we assigned them to Crossodonthina hainana . However, our redescription reports some minor discrepancies compared to the specimens from Hainan Province sensu Luo & Chen (2010), for example: all macrochaetae are smooth and clavate; the maxillary shortest lamella has 2–3 cilia on its tip; and tubercle De on Th. II has 5 (4+s) chaetae in Hunan’s specimens. Contrarily, the Hainan specimens studied by Luo & Chen (2010) have all macrochaetae ciliated and knobbed; the maxillary shortest lamella has a tooth on its tip; and tubercle De on Th. II has 4 (3+s) chaetae. In this sense, further studies are in need to determine whether specimens from Hunan and Hainan actually belong to the same species.

Figures

FIGURE 15. Crossodonthina hainana, habitus and color in ethanol.

FIGURE 16. Crossodonthina hainana, dorsal body tubercles and chaetotaxy.

FIGURES 17–19. Crossodonthina hainana: 17, chaetal types: Ml (a), Mc (b–d), Mcc (e), me (f–i), mi (j), s (k); 18, Ant. III–IV, dorsal view; 19, ventral side of Ant. III.

FIGURES 20–22. Crossodonthina hainana: 20, labrum; 21, mandible; 22, maxilla.

FIGURE 23. Crossodonthina hainana, ventral side of Abd. I–VI.

Tables

TABLE 3. Cephalic tubercles and chaetotaxy of C. hainana.

Tubercle or group of chaetae	Number and type of chaetae	Chaetae names
Cl	2 Mc 2 Mc	F G
An	1 Ml 3 Mc (or me)	B C, D, E
Fr	2 Ml (orMc) 1 Mc	A O
Oc	1 Ml 1 mi	Ocm Oca
Di	1 Mc	Di1
De	1 Ml 1 Mcc 1 mi	De1 Di2 De2
Dl+L+So	2 Ml+1 Mc+7–8 me	Uncertain