Ephemerotoma huadongensis ( Chen, 1985 ) Chen, 1985

Potapov, Mikhail, Kahrarian, Morteza, Deharveng, Louis & Shayanmehr, Masoumeh, 2015, Taxonomy of the Proisotoma complex. V. Sexually dimorphic Ephemerotoma gen. nov. (Collembola: Isotomidae), Zootaxa 4052 (3), pp. 345-358 : 351-353

Ephemerotoma huadongensis ( Chen, 1985) comb. nov.

Figs 17–21 , 25–28

Syn.: Proisotoma huadongensis Chen, 1985

Syn.: Dimorphotoma huadongensis: Potapov (2001) Syn. nov.: Scutisotoma potapovi Xie & Chen, 2008

Material. More than 500 individuals in alcohol, 9 fully adult males and females on slides: China Guangxi Province, Fushui, Bapen, Bapen Ft., 04.iii.2005, litter, leg. Chen (CHIgx05 – 034). Six subadult individuals: E China, ~ 50 km from Shanghai city. 16.xii.2002, leg. L.Yunxia. Deposited in MSPU and MNHN. Two paratypes of Scutisotoma potapovi from the collection of Nanjing University ( China).

Redescription. Size of body of adult individuals more than 2.0 mm. Purplish. Cuticle finely reticulated, granules small, most of them orthogonal. Ocelli 8+8, G and H smaller. PAO narrowly elliptical, not constricted, as long as 1.9–2.4 the ocellus diameter and as 0.6–0.8 U3. Maxillary outer lobe with simple maxillary palp and 4 sublobal hairs, one of which is thicker than the other three. Maxillary head with unmodified lamellae. Labral formula as 2/554. Labium with all papillae (A–E), papillae A–D with normal number of guards (1,4,0,4), E with 4 guards, with 3 proximal and 5 (more rarely 4) basomedian chaetae. Ventral side of head with 4–5+4–5 postlabial chaetae. Ant.1 with more than 30 chaetae, 2 small basal microsens (bms), one each dorsally and ventrally, and 2 ventral sens (s). Ant.2 with 3 bms and 1 laterodistal s, Ant.3 without bms and with 5 distal s (including one lateral spine-like), guard sens of AO as long as inner ones. Sens on Ant.4 weakly differentiated, subapical organite small.

Body with numerous short chaetae on body. Dorsal axial chaetom of Th.II–Abd.III as 10–12,10–11/7–9,8–9,9– 10,~18,~10. Common chaetae of normal shape, smooth ( Fig. 20 ). Th.I–III without ventral axial chaetae. Macrochaetae not differentiated (see also the description of epitokous males below), largest chaetae on Abd.V as long as 0.18–0.23 of tergal midline. Sens on tergites clearly differentiated, short. S-formula as 3,3/2,2,2,2,4 (s), 1,1/ 1,1,1 (ms). Sens on Abd.I–III in front of p -row of chaetae. Microsens on Abd. I–III in front of lateral sens. On Abd.V sens arranged as in Fig. 20 , as one long pair and one short pair. Unguis simple, without inner or lateral teeth. Ti.1–3 with many chaetae, more than 40 on Ti.1 and 2, and more than 50 on Ti.3 ( Figs 25, 26 ). Tibiotarsal tenent chaetae 1,2,2, clearly clavate, 1.2–1.4 as long as U3. Femur 1 with many chaetae: 11–14 a-ae -chaetae, 8–10 e - chaetae, and 18–20 chaetae of pe-p-pi-i -group. Due to polychaetosis borders between groups of chaetae hardly recognizable, particularly a and e groups "fused". Ventral tube with 7–9 chaetae on each side and with 7 – 10 posterior chaetae. Tenaculum with 3+3 teeth and a chaeta. Anterior furcal subcoxae with 35–50 chaetae, posterior subcoxae with 18–23 chaetae. Furca well developed. Anterior side of manubrium with a pair of distal chaetae, posterior side with about 30–35+30–35 chaetae on main part and 6–7+6–7 chaetae laterobasally. Dens slender, crenulated, with 4 anterior chaetae arranged as 1,1,2, all in distal half. Posterior side of dens with 7–9 chaetae, arranged as 5–7 chaetae in proximal half, one at the middle and one distally ( Figs 27, 28 ). Mucro with 3 teeth, slightly lamellate. Ratio of manubrium: dens: mucro = 7.4–11.0: 5.6–8.0: 1.0.

Epitokous males. In the material from Guangxi (South China) we collected reproductive males and females (2.2–2.4 mm) showing fully developed sexual dimorphism. Macrochaetotaxy of body, head and antennae are affected by epitoky. Males are well recognized by the appearance of very distinct lateral macrochaetae: one pair each on Th. II and III, and two pairs on Abd.V (absent in juveniles, females, and subadult males) ( Fig. 20 ). The anterior part of the body is strongly affected ( Fig. 19 , 21 ); the front of the head is swollen and armed with erect spines, similar spines are also located at the middle and posterior edge of head, the lateral sides bear longitudinal rows of 4 macrochaetae contrasting with other clothing of head (for dorsal view of front part head of male head see Fig. 25 in Chen 1985). The antennae are strongly bent downwards and Ant.2 and 3 are swollen and polychaetotic. The antennae are also armed with a few thick, stout chaetae of different shapes. Two chaetae on the ventral side of Ant.3 and one on Ant.2 are modified as thin, wavy macrochaetae. Male spurs (common in many species of the subfamily) also are present, set on all antennal segments. Sens and basal microsens keep their normal arrangement and number. Subadult males (males of the same size as adults but with closed genital orifice) principally have the same shape of head and antennae but are devoid of "male" macrochaetae on body and of stout chaetae on antennae and head. Populations from Shanghai consist of smaller (ca 1.7 mm) and non-reproductive individuals. Immature males are also slightly affected by having thicker and slightly bent antennae ( Fig. 18 ). Reproducing populations from Guangxi also have a longer dens and tibiotarsi ( Figs 25 – 28 ).

Affinity. This species is distinctive due to the tridentate mucro, unmodified Abd. V and other features. Characteristics of epitokous males are also different. The s-pattern of Abd. V resembles that of E. multituberculata .

The species was described from Shanghai. Our materials agree well with the description by Chen (1985), including peculiarities of adult males such as the stout antennae, spine-shaped chaetae on head, and very specific macrochaetotaxy. The description of Scutisotoma potapovi from nearby province Jiangsu is much more detailed and includes sensillar chaetotaxy, mouth parts, and antennal chaetotaxy. Variation in the number of chaetae given in the description of potapovi and observed in Guangxi specimens strongly overlap and suggests that the Guangxi populations are not different from the species of Jiangsu. The only considerable difference is the presence of basal microsens (bms) and 2 lateral sens (s) on Ant. 3 in first description of S. potapovi (bms is absent in our specimens, and there is only one lateral sens).

Distribution. Known from four localities in China (Jiangsu, Guangxi, two from Shanghai).

Figures

FIGURES 17 – 19. Habitus of female (17), immature (18) and reproductive (19) male of Ephemerotoma huadongensis.

FIGURES 20 – 21. Reproductive male of Ephemerotoma huadongensis: 20, Abd. IV – VI; 21, head and antennae, lateral view. msp—male spurs.

FIGURES 22 – 28. Ephemerotoma multituberculata (22 – 24) and E. huadongensis (25 – 28): 22 – 24, variation of dens, anterior view; 25, 26, distal part of leg 3 in individual from Shanghai (25) and Guangxi (26); 27, 28, dens, from Shanghai (27) and Guangxi (28).