Monodontocerus absens, Yu, Daoyuan, Deharveng, Louis & Zhang, Feng, 2014

Yu, Daoyuan, Deharveng, Louis & Zhang, Feng, 2014, New species of Monodontocerus (Collembola: Tomoceridae) from southern China with diagnostic notes on the genus and introduction of new taxonomic characters, Zootaxa 3768 (5), pp. 557-575 : 559-563

publication ID	https://doi.org/ 10.11646/zootaxa.3768.5.3
publication LSID	lsid:zoobank.org:pub:8A447FE6-C25D-4542-9DDB-37A41687C35E
DOI	https://doi.org/10.5281/zenodo.5678993
persistent identifier	https://treatment.plazi.org/id/03BE075B-FFCD-FFA7-17B8-FBC2FF75B7D0
treatment provided by	Plazi
scientific name	Monodontocerus absens
status	sp. nov.

Treatment

Monodontocerus absens sp. nov.

Figs 1–3 View FIGURES 1 – 5. 1 – 3 , 6–29 View FIGURES 6 – 14 View FIGURES 15 – 22 View FIGURES 23 – 29 , 54, 57 View FIGURES 54 – 59 , Table 2 View TABLE 2

Type material. Holotype female and two paratype females on slides, collected in Ba Xian Dong (cave), Ba Xian, Duan County, Hechi, Guangxi Zhuang Autonomous Region, China, x= 108.132811°E; y= 23.914039°N, elevation 151 m, 26.iv.2010, by Louis Deharveng & Li Youbang (sample code: CHIgx10.67). Holotype and one paratype in NJAU, one paratype in MNHN.

Description. Body length 3.1–3.8 mm. Ground color pale ( Fig. 1 View FIGURES 1 – 5. 1 – 3 ); head and body covered with spotted brown pigment ( Fig. 2 View FIGURES 1 – 5. 1 – 3 ); sockets of macrochaetae and large mesochaetae, antero-dorsal part of head and anterior margins of clypeus and Th. II darker than other parts ( Fig. 3 View FIGURES 1 – 5. 1 – 3 ); eye patches black, relatively small; legs, ventral tube, furca, Ant. I, Ant. II and base of Ant. III with diffuse pigment, remaining parts of antenna pale.

Postantennal organ absent. Ommatidia 6+6, relatively smaller than in edaphic Tomocerinae. Antennae about 1.1–1.2 times as long as body, antennal length ratio as I: II: III: IV=1.0: 2.2: 17.6–17.8: 3.3. Ant. I and Ant. II dorsally scaled, ventrally with dense s-chaetae. Ant. III and Ant. IV annulated as normal for Tomocerinae, with six types of chaetae identified ( Table 1, Figs 6–9 View FIGURES 6 – 14 ). Ant. III dorso-basally scaled, each subsegment near the middle of Ant. III with a whorl of about 30 chaetae; ordinary chaetae type a (SE) and s-chaetae of type b, type c (RLS) and type d (RSS) uniformly distributed; dorso-apically, with one (SH) chaeta of type f (TRS), one of type e, two of type c and two of type b ( Fig. 7 View FIGURES 6 – 14 ). Ant. IV unscaled, chaetotaxy similar to that of Ant. III, with one subapical papilla, apex with one type f chaeta and one type e chaeta ( Fig. 9 View FIGURES 6 – 14 ).

Labral formula 4/5, 5, 4; prelabral and labral chaetae pointed, smooth; labral chaetae with thick basal papillae fused to cuticle, proximal two rows of chaetae subequal in thickness and length, distal four chaetae distinctly stronger; distal edge of labrum with four spiny papillae with rounded apices; ventro-distal margin of labrum densely ciliated as a brush ( Fig. 10 View FIGURES 6 – 14 ). Mandible heads asymmetrical, left mandible with four teeth, right mandible with five teeth; molar plate with numerous strong teeth, including a distal tapered one on left mandible ( Fig. 11 View FIGURES 6 – 14 ). Maxilla head with three teeth and six distinct lamellae; lamella 5 broad, curved with prolonged basal teeth, distinct beard absent ( Fig. 12 View FIGURES 6 – 14 ). Maxillary outer lobe with trifurcate palp, one basal chaeta and four subequal sublobal hairs ( Fig. 13 View FIGURES 6 – 14 ). Labial palp with about 20 proximal chaetae, papillae A–E respectively with 0, 5, 0, 4, 7 (a1 present but attached to papilla B (Fjellberg 1999)) guard chaetae, hypostomal chaeta H rod-like, with h1 stronger than h2 ( Fig. 14 View FIGURES 6 – 14 ). Mentum with five large chaetae, submentum with approximately 25 chaetae of different sizes, 9–12 of them distinctly smaller ( Fig. 15 View FIGURES 15 – 22 ).

Head dorsally scaled, a file of smooth chaetae around the base of antenna, anterior area with 2, 2 and interocular area with five macrochaetae arranged as 2, 1, 2, the axial chaeta located more anteriorly than in other Tomocerinae species; postocular chaetae 2+2; posterior chaetae two; numerous microchaetae uniformly distributed; posterior margin of head with 10+10 chaetae ( Fig. 54 View FIGURES 54 – 59 ). Head ventrally scaled, with numerous smooth chaetae of different sizes.

Trochanteral-femoral organ with 1, 1 slender smooth larger chaetae and several additional smaller chaetae on trochanter ( Fig. 16 View FIGURES 15 – 22 ). Fore, middle and hind femur respectively with at least 3, 1, 1 long outstanding chaetae on inner side. Fore, middle and hind tibiotarsus distally with 0, 0, 2 blunt spiny inner chaetae ( Fig. 17 View FIGURES 15 – 22 ). Each tibiotarsus with a distal whorl of 11 chaetae, ventral six as ordinary chaetae, dorsal five including one small, pointed tenent hair, 1+1 small accessory chaetae on either side of tenent hair and 1+1 long, slender, pointed chaetae external to tenent hair and accessory chaetae; on front leg these two small accessory chaetae subequal in size ( Fig. 18 View FIGURES 15 – 22 ) but on mid and hind leg the posterior small chaeta is larger than the anterior one ( Figs 19, 20 View FIGURES 15 – 22 ). Unguis slender, outer edge 0.24, 0.21, 0.16 times length of tibiotarsus, respectively, for front, mid and hind leg ( Fig. 17 View FIGURES 15 – 22 ), with basointernal ridging visible in lateral view; lateral teeth pointed, of moderate size; inner side of unguis with five teeth, the subbasal tooth strongest. Unguiculus slender, two-thirds length of inner edge of unguis, its inner side with one tooth ( Fig. 21 View FIGURES 15 – 22 ). Prestarsus with 1+1 microchaetae.

Ventral tube scaled on both faces, anterior face with 50–70 chaetae on each side, posterior face with 110–150 chaetae; lateral flap unscaled, each side with about 75 chaetae. Rami of tenaculum with 4+4 teeth, corpus without scales or chaetae ( Fig. 22 View FIGURES 15 – 22 ).

Furca about half as long as body, ratio manubrium: dens: mucro as 4.7: 6.7: 1.0. Manubrial width: length about 1.0: 1.7, ventrally scaled, laterally with large round scales and a row of about 10 chaetae, distal chaetae strong and serrated, proximal chaetae smaller. Each side of manubrium with a dorsal stripe of about 190 smooth chaetae of various sizes mixed with numerous scales; external to the stripe, 26–28 pseudopores present in a longitudinal row ( Fig. 23 View FIGURES 23 – 29 ); one chaeta at each externo-distal corner of manubrium as long as a medium-size mesochaeta in the dorsal chaetal stripe ( Fig. 24 View FIGURES 23 – 29 ).

Dens internally divided into three subsegments, length of basal part: medial part: distal part about 1.0: 1.4: 3.8. Dental spine formula 4, I/5, I, 3, I in a single row ( Fig. 25 View FIGURES 23 – 29 ). Each dental spine consisting of a strong trunk surrounded by 2–6 denticles near the base; largest dental spine about 0.08 times length of dens. Three types of dorsal chaetae on dens besides dental spines: type 1 long, slender and smooth; type 2 similar to type 1 but shorter and spiny; type 3 feather-like, ciliated heavily on outer side and slightly on internal side ( Fig. 26 View FIGURES 23 – 29 ). Basal subsegment with only type 1 chaetae; medial subsegment with type 1 and type 2 chaetae, the later distributed externally; distal subsegment with all three types of chaetae, type 3 mainly along the outer and inner margin. Ventral side of dens covered only with oval scales.

Mucro elongated, bearing numerous smooth chaetae with elongated sockets. Two dorsal lamellae beginning from base of mucro and ending in subapical tooth; single basal tooth with one proximal lamella; two intermediate teeth unequal with the distal tooth larger; apex of apical tooth broken in all specimens, not observed ( Fig. 27 View FIGURES 23 – 29 ).

Macrochaetae distributed densely along anterior margin of Th. II and sparingly in posterior rows on terga. On each side, Th. II–Abd. V with 3, 3/ 3, 3, 4, 2, 4 macrochaetae in posterior rows; Th. II with three anterior macrochaetae in a near-longitudinal line near the Th. II midline; two anterior macrochaetae on Abd. III, subequal in size; two antero-lateral macrochaetae on Abd. IV. On Abd. VI, seven macrochaetae present on upper flap. Sizes of body macrochaetae unequal, those on anterior segments generally smaller than those on posterior segments and especially for those in posterior rows; on Abd. V, chaeta p3 larger than the others and shifted slightly anterior to p1 and p2 ( Fig. 57 View FIGURES 54 – 59 ). Bothriotricha extremely thin, ciliated, pattern 2, 1/ 0, 0, 1, 2, 0, 0 from Th. II to Abd. VI as in other Tomocerinae. Mesochaetae of various sizes mainly distributed laterally on terga and posteriorly on Abd. VI. Microchaetae uniformly distributed on terga, pattern not studied. Numerous s-chaetae on terga, but patterns difficult to see; the following have been observed: on Th. II two rod-like s-chaetae, one s-microchaeta and one normal s-chaeta (?) close to bothriotricha; on Abd. III one s-microchaeta posterior to antero-external macrochaeta and three normal s-chaetae close to bothriotricha; on Abd. IV long s-chaetae uniformly distributed, their number uncertain; Abd. V with a single anterior normal s-chaeta.

Pseudopores near the middle line of terga, 1, 1, 1, 1, 1, 1, 0, 0 on each side ( Fig. 57 View FIGURES 54 – 59 ). On Th. II pseudopore close to the posterior most medial macrochaeta; on Th. III–Abd. IV pseudopores more near middle line and on Abd. I and Abd. II more posterior than on other terga.

Two types of female genital plate observed, one highly wrinkled with 2+2 microchaetae ( Fig. 28 View FIGURES 23 – 29 ) and the other less wrinkled without chaetae ( Fig. 29 View FIGURES 23 – 29 ), the latter probably from an immature form.

Etymology. Named after the absence of chaetae on tenaculum, from the Latin absens : absent, missing.

Remarks. This species is different from other Monodontocerus species mainly in the pattern of interocular chaetotaxy (2, 1, 2 while the others have 2, 3 or 2, 5) and the absence of chaetae on tenaculum (at least one present in other species). Besides, its antenna is distinctly longer than body, while other species have antennae shorter than body ( Table 2 View TABLE 2 ). The most distal spine on the basal part of dens is nearly as large as large spines on the medial part, but the difference in size between small and large spines on the basal part is not as distinct as it is on the medial part.