Crossodonthina jiuyishanensis, Jiang & Wang, 2025

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 : 188-196

Crossodonthina jiuyishanensis sp. nov.

Figs 1–14 , Tables 1–2

Type material. Holotype: Female , Mountain Jiuyi National Nature Reserve , Ningyuan County, Yongzhou City, Hunan Province, China, coordinates: 25°15'12.91" N, 111°56'14.78" E, alt. 998 m, under leaves in forest, leg. Jigang Jiang, Lu He and Yali Gao, 29. IV. 2024 (No. 2024042901) . Paratypes: fourteen females, same data as the holotype ; three males and nine females, Mountain Jiuyi National Nature Reserve , Ningyuan County, Yongzhou City, Hunan Province, China, coordinates: 25°15'11.08" N, 112°1'13.17" E, alt. 1301 m, under leaves on the roadside from Yangyanping to Fenjiwo, leg. Jigang Jiang, Lu He and Yali Gao, 1.V.2024 (No. 2024050101) ; one female, Mountain Jiuyi National Nature Reserve , Ningyuan County, Yongzhou City , Hunan Province, China, coordinates: 25°15'6.66" N, 112°1'39.58" E, alt. 1070m, in leaves on the roadside of Yangyanping, leg. Jigang Jiang, Lu He and Yali Gao, 4.V.2024 (No. 2024050104). Type material deposited at the Key Laboratory of Zoology , Hunan University of Arts and Science ( HUAS), Changde, Hunan Province, China .

Etymology. The species name is derived from Mountain Jiuyi, where the type specimens were collected.

Diagnosis. Body tubercles well differentiated; all body chaetae smooth and pointed. Cephalic chaeta O present and included in tubercle Fr, tubercle Oc with 3 chaetae and Oca as Mc; cephalic tubercles Dl, L and So separated from each other; cephalic chaeta Di2 included in tubercle Di; tubercle De with only two chaetae: De1 and De2; mandible complex, with two basal teeth and six main branches; maxilla with three lamella, biggest lamella with two basal teeth and three apical teeth, shortest lamella with only one tooth, median lamella apically with 5–6 cilia; tubercles Di, De and Dl on Th. I with 1, 2, 2 chaetae respectively; tubercle Di on Abd. I–III each with 3 chaetae.

Description. Body length: holotype, female 3.5 mm, paratypes, females 2.8–4.5 mm, males 1.6–3.0 mm. Color: red while living, white in ethanol ( Fig. 1 ).

Chaetal morphology. Dorsal ordinary chaetae of four types. Long macrochaetae (Ml) smooth and pointed ( Fig. 2a–b ). Short macrochaetae (Mc) morphologically similar to and shorter than Ml ( Fig. 2c–e ). Very short macrochaetae (Mcc) similar to and shorter than Mc ( Fig. 2f ). Mesochaetae ( Fig. 2g –j ) smooth, pointed and variable in length, longest one shorter than Ml and longer than Mc. S-chaetae (s) on terga thin, smooth and pointed, slightly longer than Ml ( Fig. 2k ). Mi on anal lobe slim and pointed, shorter than shortest me ( Fig. 2l ).

Head. Eyes 3+3, black, two anterior, but not included in tubercle Oc, posterior one on the back of tubercle Oc ( Fig. 7 ).

Antenna four-segmented. Ant. I with 9 chaetae. Ant. II with 11 chaetae. Ant. III dorsally fused to Ant. IV ( Fig. 3 ). Guard chaeta sgd of Ant. III slightly displaced apically to the level of two sensory rods. Ant. IV dorsally with six subequal, slightly thickened and blunt sensilla (S3–S8), S1 and S2 always missing ( Fig. 3 ). Apical bulb trilobed, organite (or) present. Ventral side of Ant. IV with 13 pointed, flat or slightly blunt and hyaline chaetae ( Fig. 4 ). On ventral side of Ant. III, guard chaeta sgv located far and in front of ms. Vi, Vc and Ve with 4, 4, 5 chaetae respectively ( Fig. 4 ).

Oral cone short, labrum truncated, labral formula as 0/2, 2 ( Fig. 8 ). Labium with 11 chaetae, without papillae x. Mandible complex, with two basal teeth and six main branches. First branch the most complex one, with two rows of sub-branches, about 9–10 sub-branches on dorsal row ( Figs 5 , 9 ); eight short sub-branches on ventral row ( Fig. 10 ). Second branch ciliated on inner side. Third branch with some denticles on inner side of basal and middle parts. Fourth branch similar to and longer than second branch. Fifth one similar to and longer than fourth branch. Sixth branch as the longest one, with a few cilia on inner side of the apical part, with some denticles on basal and middle parts ( Fig. 5 ). Maxilla with three lamellae, largest lamella with two basal teeth and three apical teeth, shortest lamella with only one tooth, median one apically with 5–6 cilia ( Fig. 6 ).

Cephalic dorsal tubercles and chaetotaxy shown in Table 1 and Fig. 7 . Central area of head with one Cl, one Fr, two Oc and two An tubercles; chaeta O present on tubercle Fr as a Mc; tubercle Oc with 3 chaetae, chaeta Oca present as Mc. Dorso-posterior area of head with four separate tubercles: two Di and two De, chaetae Di1 and Di2 included on tubercle Di, chaetae De1 and De2 included on tubercle De, line of chaetae Di2–De2 crossing the line Di1–De1 on head (cross-type sensu Deharveng 1983). Dorsolateral tubercle (Dl) independent, with 4 chaetae; lateral tubercle (L) on dorsal lateral area separate from tubercle So and with 2 chaetae; tubercle So with 6 chaetae.

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

Thorax ( Fig. 11 and Table 2 ). Th. I with 3+3 tubercles, Di, De, Dl, with 1, 2, 2 chaetae, respectively. Th. II with 4+4 tubercles, tubercle Di with three chaetae, all chaetae included on it, De with five (4+s), Dl with five (3+s+ms), tubercle L with three or four chaetae, respectively. Th. III with 4+4 tubercles, Di with three chaetae, arranging similar to that on Th. II, De with five (4+s), Dl with four (3+s), and L with three or four chaetae, respectively. Chaetotaxy of thorax and legs as in Table 2 . One basal inner tooth present on basal unguis; unguiculus absent. Chaeta M present on tibiotarsus.

Abdomen ( Figs 12–14 and Table 2 ). Abd. I–III each with 4+4 tubercles, Di with three, De with four (3+s), Dl with two chaetae, respectively; tubercle L with a chaeta s and 6–8 ordinary chaetae. Abd. IV with 4+4 tubercles, Di with two, De with three (2+s), Dl with three chaetae, respectively; tubercle L with 7–9 chaetae, without chaeta s. Abd. V dorsally with 3+3 tubercles, two separated Di, each with three chaetae, tubercle De independent, with only one chaeta s, tubercle Dl with 3–4 chaetae. Tubercle L on Abd. V on the ventral side of abdomen, with 7–8 ordinary chaetae. Abd. VI with 1+1 tubercles, 7 chaetae present on each tubercle ( Figs 13–14 ). VT with 4+4 chaetae (sometimes 4+3 chaetae) ( Fig. 14 ). Furcular remnant with 3 chaetae ( Fig. 14 ). Chaetotaxy of ventral side of abdomen as in Table 2 .

Ecology. The new species lives in the forest litter.

Remarks. So far, 13 species of Crossodonthina were reported from the C. nipponica species group ( Jiang & Wang 2024), making C. jiuyishanensis sp. nov. the fourteenth one of this group. Comparing C. jiuyishanensis sp. nov. to other species of this group, C. jiuyishanensis sp. nov. is most similar to C. acuminata Jiang & Wang, 2021 from China (Hunan Province) in: head chaetotaxy (tubercle Oc with 3 chaetae, tubercle Fr with 3 chaetae, cephalic tubercles Di and De with 2 chaetae each); Three chaetae on tubercles Di of Abd. I–III each; and the presence of a chaetae s on tubercles L of Abd. I–III. However, C. jiuyishanensis sp. nov. differs from C. acuminata Jiang & Wang, 2021 by the following characters: chaetotaxy on Th. I (with 1, 2, 2 chaetae on tubercles Di, De, Dl, respectively, in the new species, versus usually 1, 3, 2 in the latter one); number of chaetae on tubercle So of head (6 chaetae on tubercle So of head in C. jiuyishanensis sp. nov., versus 8 in C. acuminata ); number of chaetae on tubercle L of Abd. V (7 or 8 chaetae in the new species versus 3 or 4 in the latter species); number of chaetae on Fu (3 chaetae in the new species versus no chaeta in C. acuminata ); number of basal mandible teeth (2 in the new species versus 3 in the latter one); and teethed branches on mandible (2 in the new species (the third branch and the sixth branch, Fig. 5 ) versus no teethed branch in C. acuminata ); number of chaetae s on dorsum of Ant. IV (6 in the new species versus 8 in the latter species).

C. jiuyishanensis sp. nov. is also close to C. laterisensillata Ohira, Kataoka, Tanooka & Nakamori, 2022 from Japan in the mouthpart structures (both have 6 rami on mandible and 3 lamellae on maxilla) and the presence of a chaetae s on tubercles L of Abd. I–III. However, the two species differ in a number of characteristics as follows: mandible basal teeth (2 teeth in C. jiuyishanensis sp. nov., 3 teeth in C. laterisensillata ); number of dendritic branches on mandible (only 1 dendritic branch in C. jiuyishanensis sp. nov., 2 in C. laterisensillata ); number of chaetae s on Ant. IV (6 s in C. jiuyishanensis sp. nov., 8 s in C. laterisensillata ); number of chaetae on tubercle Dl of Th. I (2 in C. jiuyishanensis sp. nov., 1 in C. laterisensillata ); number of chaetae on tubercles Di of Abd. I–III (3 in C. jiuyishanensis sp. nov., 2 in C. laterisensillata ); cephalic tubercles on lateral area (Dl, L and So separated from each other in C. jiuyishanensis sp. nov., Dl, L and So fused together in the latter species); and chaeta s on tubercle L of Abd. IV (absent in C. jiuyishanensis sp. nov., present in C. laterisensillata ).

In Crossodonthina nipponica -group, C. jiuyishanensis sp. nov. has several unique characters, such as: antennal S1 and S2 always absent; chaeta Di2 on head included in tubercle Di; tubercles Di, De and Dl of Th. I with 1, 2, 2 chaetae, respectively; tubercles Di of Abd. I–III each with 3 chaetae, tubercles L of Abd. I–III each with a chaeta s and 6–8 ordinary chaetae. These characters distinguish it from all other known species of the nipponica -group.

Figures

FIGURE 1. Crossodonthina jiuyishanensis sp. nov., habitus and color in ethanol.

FIGURES 2–6. Crossodonthina jiuyishanensis sp. nov.: 2, chaetal types: Ml (a–b), Mc (c–e), Mcc (f), me (g–j), mi on anal lobe (l), s (k); 3, Ant. III–IV, dorsal view; 4, Ant. III–IV, ventral view; 5, mandible; 6, maxilla.

FIGURES 7–11. Crossodonthina jiuyishanensis sp. nov.: 7, head; 8, labrum; 9, mandible, showing the dorsal row of subbranches of first main branch; 10, mandible, showing the ventral row of sub-branches of first main branch; 11, dorsal tubercles and chaetotaxy of Th. I–II.

FIGURES 12–13. Crossodonthina jiuyishanensis sp. nov.: 12, dorsal tubercles and chaetotaxy of Abd. I–II; 13, dorsal tubercles and chaetotaxy of Abd. III–VI.

FIGURE 14. Crossodonthina jiuyishanensis sp. nov., ventral side of Abd. I–VI.