Tomocerus caecus, Yu, Daoyuan & Deharveng, Louis, 2015

Yu, Daoyuan & Deharveng, Louis, 2015, The first eyeless species of Tomocerus from China (Collembola, Tomoceridae) with notes on genera Tomocerus and Pogonognathellus, Zootaxa 3914 (2), pp. 175-184 : 176-180

publication ID	https://doi.org/ 10.11646/zootaxa.3914.2.7
publication LSID	lsid:zoobank.org:pub:AD355247-9EA4-403C-9377-3F1E60769496
DOI	https://doi.org/10.5281/zenodo.6098314
persistent identifier	https://treatment.plazi.org/id/03AEA13A-FF77-672F-FF1A-FBDCFC6AFE37
treatment provided by	Plazi
scientific name	Tomocerus caecus
status	sp. nov.

Treatment

Tomocerus caecus sp. nov.

Figs 1–5 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5

Type material. Holotype female and one paratype female on slide, three paratypes in alcohol. Collected in Ganchao Dong (Cave), Zhonglun Village, Mulun Township, Huanjiang Autonomous County, Hechi, Guangxi Zhuang Autonomous Region, China, 107.927003°N, 25.1243°E, 24.vi.2011, by Youbang Li, Zheng Tang & Shiyi Lu (sample code: CHIgx11-LYB07). Holotype and two paratypes in NJAU, two paratypes in MNHN.

Description. Body length 2.5 to 3.3 mm for adults, ratio of tergum lengths: 2.6–3.3:1.8–2.0:1.3–1.4:1.3–1.6:2.7–3.0:2.2–2.5:1.0–1.3:1.0 from Th. II to Abd. VI. Color white without trace of pigment ( Fig. 1 View FIGURE 1 ).

Ocelli and PAO absent. Antennae quite short, Ant. IV lost in all types, Ant. I+II+III about 0.33 times as long as body, antennal length ratio as Ant. I:II:III =1.0:1.7:5.4. Ant. I and Ant. II with scales on dorsal side and S-chaetae mostly on ventral side besides uniform smooth pointed chaetae, 3–4 PLS shaped chaetae with sockets sinking deeply into cuticle present disto-laterally on Ant. II ( Fig. 2 View FIGURE 2 A). Ant. III annulated with about 35 equal subsegments except in its most distal and basal parts, each subsegment with whorl of normal chaetae and S-chaetae of different sizes; Ant. III latero-distally with two minute PLS shaped chaetae and one SH besides two PLS similar to those on Ant. II, probably components of Ant. III organ ( Fig. 2 View FIGURE 2 B).

Labral chaeta formula 4/5,5,4; prelabral and labral chaetae pointed and smooth; labral chaetae with thick sockets fused to cuticle, proximal two rows of chaetae subequal in thickness and length, distal four distinctly stronger; distal edge of labrum with four papillae, curved and apically blunt; ventro-distal margin of labrum densely ciliated, brush-like ( Fig. 2 View FIGURE 2 C). Mandible heads asymmetrical, left mandible with four teeth, right mandible with five teeth, molar plate of left mandible distally with strong darker tooth ( Fig. 2 View FIGURE 2 D). Maxilla head normal in shape for the genus, with three teeth and six distinct lamellae: lamella 1 protruding, distally comb-like; lamella 2 and 4 fan-like, with acuminate serrated edges; lamella 3 densely covered with bristle-like teeth; lamella 5 broad and curved, its basal teeth slightly prolonged, without distinct beard; lamella 6 smaller than other surrounding lamellae, its apex with short teeth ( Fig. 2 View FIGURE 2 E). Maxillary outer lobe with trifurcate palp, one basal chaeta and four sublobal hairs. Mentum with five chaetae, other parts of labium multi-setaceous, details not clearly seen.

Head dorsally scaled, file of smooth chaetae around bases of antennae. Cephalic dorsal macrochaetotaxy: anterior area: 2, 2; interocular area: 2, 5 (including uneven chaeta); postocular area: 0+0; posterior area: 0. Posterior margin of head with about 12+12 smooth chaetae ( Fig. 2 View FIGURE 2 F); numerous microchaetae uniformly distributed. Head ventrally unscaled, with numerous smooth chaetae of different sizes.

Trochantero-femoral organ with 1, 1 slender smooth chaetae. Fore, middle and hind femora with 2, 1, 1 long outstanding chaetae on inner side. Fore, middle and hind tibiotarsi with 0, 0, 2 spine-like blunt inner chaetae ( Fig. 3 View FIGURE 3 A), distal whorl with 11 chaetae, tenent hair slender, smooth and pointed with 1+1 small accessory chaetae slightly longer than pretarsal chaetae, 1+1 outer guard chaetae of the same type as tenent hair ( Fig. 3 View FIGURE 3 B). Unguis slender, its outer edge about 0.40, 0.40, 0.22–0.25 times as long as tibiotarsus respectively for fore, middle and hind leg, basally with internal ridging; lateral teeth relatively weak, their apex pointed; inner side of unguis with two small teeth, basal one lamellar, distal one minute ( Fig. 3 View FIGURE 3 C). Unguiculus about 0.6 times as long as inner edge of unguis, approximately triangular, tapering distally, inner side with 1–3 teeth, longer and thicker than those on unguis ( Fig. 3 View FIGURE 3 C). Pretarsus with 1+1 microchaetae ( Fig. 3 View FIGURE 3 C).

Ventral tube with about 10 scales and 30–45 chaetae of different sizes on each side of anterior face; posterior face unscaled, with dozens of chaetae (approximately 100 in holotype, 50 in paratype); lateral flap unscaled, each side with about 50 chaetae ( Fig. 3 View FIGURE 3 D). Rami of tenaculum with 4+4 teeth, corpus unscaled, with one anterior chaeta about as long as rami ( Fig. 4 View FIGURE 4 A). Chaetae on ventral tube and tenaculum all smooth and pointed.

Furca about half as long as body, ratio manubrium:dens:mucro as 2.4:3.3:1.0. Manubrium stout, width:length as about 1.0:1.4, ventrally scaled, laterally with large round scales and row of 9–10 chaetae, proximal ones thin, pointed and smooth, distal ones strong and serrated. Each side of manubrium with dorsal stripe of about 90 smooth chaetae of various sizes, including 10–13 external large chaetae and one pointed prominent macrochaeta longer and straighter than others; scales absent either within or between chaetal stripes; external to each stripe, 5–8 pseudopores present in a longitudinal row; each externo-distal corner of manubrium with single small smooth pointed chaeta ( Fig. 4 View FIGURE 4 B). Dens internally divided into three subsegments, basal subsegment about four times shorter than medial+distal ones, ventro-internally with one small pointed scale, followed by a cluster of long and narrow scales ( Fig. 4 View FIGURE 4 C). Dental spine formula as 4–5/1–2,I–II,0–1,I–II approximately in single row. Dental spines multi-spinulated mainly at basal half, from 2–6 subequal spinules to 15–20 spinules of various sizes ( Fig. 4 View FIGURE 4 D); all spines with fine longitudinal ribs on surface. Largest dental spines about 0.15 times as long as dens. At least four types of dorsal dental chaetae besides dental spines: type 1 as ordinary chaetae, long, slender and smooth, including 1+1 prominent chaetae on basal subsegment similar to manubrial ones; type 2 spine-like and strong, with distinct longitudinal ribs on surface ( Fig. 5 View FIGURE 5 Aa); type 3 spine-like and with numerous tiny spinules ( Fig. 5 View FIGURE 5 Ab); type 4 slender and curved, ciliated on only one side ( Fig. 5 View FIGURE 5 Ac). Ventral side of dens covered only by oval scales. Mucro elongated, distally curved, bearing numerous smooth chaetae with elongated sockets; two dorsal lamellae beginning from subapical tooth, outer lamella ending in inner basal tooth, inner lamella ending freely beside inner basal tooth; two basal teeth with proximal lamellae at base, outer one with toothlet; single intermediate tooth at about 1/5 of length of mucro from base; subapical tooth with broad basal lamella, apical tooth distinctly stronger than subapical tooth, with hooked apex ( Fig. 5 View FIGURE 5 B).

Pattern of tergal macrochaetotaxy as in Fig. 5 View FIGURE 5 C. Shape of most macrochaetae unknown, except one blunt ciliated macrochaeta on Abd. VI in mounted paratype. Th. II–Abd. V with constantly 3,3,3,3,4,3,4 posterior macrochaetae and 2,1/0,0,1,2,0 bothriotricha. Abd. VI with 7 macrochaetae on dorsal flap and one on lateral flap. Anterior macrochaetae present on Th. II, Abd. III and Abd. IV. Mesochaetae and microchaetae smooth and pointed. Mesochaetae of various size present mainly laterally on terga and posteriorly on Abd. VI. Microchaetae uniformly distributed. Pattern of S-chaetae not clearly visible: on Th. II four S-chaetae close to inner bothriotricha, anterior one as pointed S-microchaeta in oval socket, three others as rod-like S-chaetae with sockets sinking deeply into cuticle; on Th. III one normal S-chaeta and one S-microchaeta antero-lateral to bothriotrichum; on Abd. III, one normal S-chaeta, one rod-like S-chaeta posterior to bothriotrichum and one S-microchaeta posterior to anterolateral macrochaeta; on Abd. IV, long S-chaetae present near middle line, their number uncertain (7 remaining in paratype female). Pseudopores: 1,1/1,1,1,1 per half tergum from Th. II to Abd. IV ( Fig. 5 View FIGURE 5 C).

Etymology. Named in reference to the absence of ocelli, from the Latin word caecus : blind.

Remarks. Fifteen eyeless Tomoceridae species have been described previously, including eight species from Japan and Korea: Plutomurus suzukaensis ; P. yamatensis Yosii, 1956 ; P. ehimensis Yosii, 1956 ; P. kawasawai Yosii, 1956 ; P. marmorarius Yosii, 1967 ; P. gu l Yosii, 1966; P. i w a t e n s i s Yoshii, 1991 and Lethemurus finitimus Yosii, 1970. The new species lacks the baso-lateral strong dental chaetae which is a main generic character of Plutomurus , Aphaenomurus Yosii, 1956 and Tomolonus Mills, 1948 , and its poorly developed trochantero-femoral organ differs from that of Lethemurus Yosii, 1970. We did not place the new species in Tritomurus , which at present contains three European species, for the problematic situation of this genus ( Absolon 1903, Bonet 1931, Christiansen 1964, Denis 1929, Lukić et al. 2010). The compound dental spines and the presence of two mucronal dorsal lamellae separate T. caecus sp. nov. from Pogonognathellus . The paired mucronal basal teeth and the toothlet on the outer basal tooth separate T. caecus sp. nov. from Tomocerina and Monodontocerus Yosii, 1955, and fit it to Tomocerus .

Despite the absence of ocelli and pigment, Tomocerus caecus sp. nov. is similar to East Asian edaphic species Tomocerus similis Chen & Ma, 1997 and Tomocerus kinoshitai Yosii, 1954 (also found in caves) in several characters: the number of anterior cephalic chaetae; the number of tibiotarsal spine-like chaetae; the basally multispinulated dental spines; the reduced number of teeth on unguis and mucro, and the distally curved shape of mucro. However T. caecus sp. nov. is remarkably different from them in the dental spine formula, the pointed tenent hair, the absence of the postocular chaetae and, according to material of T. kinoshitai collected in northeast China, the absence of an anterior macrochaeta or large mesochaeta on Th. III.