Monodontocerus cinereus Yu

Yu, Daoyuan, Yan, Qibao & Liu, Manqiang, 2016, New cave-dwelling species of Tomoceridae from China, with a study on the pattern of mesothoracic bothriotricha in Tomocerinae (Collembola, Entomobryomorpha), ZooKeys 574, pp. 81-95 : 85-89

Taxon classification Animalia Collembola Tomoceridae

Monodontocerus cinereus Yu sp. n. Figs 1C, 4, 5

Type-locality.

China, Guangxi Province: Hechi, Duan County, Chengjiang Township, Ganwan Village, Nongsi Cave, 23°56'24"N, 108°10'12"E, alt. ca. 270 m, inside cave, 25 July 2015, Jujian Chen, Xinhui Wang and Mingruo Tang leg.

Type-specimens.

Holotype male (labelled 15cave6-1) and two paratypes female (labelled 15cave6-2 and -3) on slides, one paratype (labelled 15cave6) in alcohol. Deposited in NJAU.

Diagnosis.

Typical Monodontocerus species with multi-furcated dental spines and single mucronal basal tooth. Body length approximately 4.0 mm, with light grey pigment all over; antennae slightly shorter than body; eyes small; chaetotaxy typical for the genus; tenent hair pointed; unguis with 2-4 teeth; manubrium with 28-35 pseudopores on each side; dental spines formula as 4, II/6, I, 3, I or 5, I/6, I, 3, I; mucro with 3-4 intermediate teeth. Cave-dwelling species.

Description.

Body length 3.9-4.1 mm. Body colour uniformly light grey with unpigmented patches, appendages paler. Eye patches black. (Fig. 1C). Scales and chaetae of Tomocerinae type.

Antennae approximately 0.7-0.9 times as long as body. Length ratio of antenna segments as I:II:III:IV = 1.0:1.7 –2.0:10.5– 11.0:1.8. Only dorsal side of Ant. I and Ant. II scaled, Ant. III and Ant. IV unscaled. PAO not seen. Eyes 6+6, relatively small. Mouthparts typical for Tomocerinae. Labral formula as 4/5, 5, 4. Distal edge of labrum with four curved spine-like papillae. Mandibular heads asymmetrical, the left one with four teeth and the right one with five, left molar plate distally with a tapered tooth (Fig. 4A). Maxillary lamella five without beard-like appendage, basal teeth elongated (Fig. 4B). Maxillary outer lobe with trifurcate palp, one basal chaeta and four sublobal hairs. Both dorsal and ventral sides of head scaled. Cephalic dorsal macrochaetotaxy: anterior area: 2, 2; interocular area: 2, 3, central uneven macrochaeta present; postocular area: 2+2; posterior area: 2. Posterior margin of head with 40-50 small chaetae (Fig. 4C). Mentum with five chaetae, submentum with numerous chaetae.

Pattern of body chaetotaxy as in Fig. 4D. Number of bothriotricha as 2 (1?), 1/ 0, 0, 1, 2, 0, 0 on Th. II–Abd. VI. Macrochaetae densely arranged along anterior margin of Th. II (not shown in figure). Th. II with a row of macrochaetae behind anterior margin. Number of macrochaetae or large mesochaetae in the posterior row as 3, 3/ 3, 3, 4, 2, 4 (3 dorsal+1 lateral) from Th. II to Abd. V. Th. II with three central macrochaetae arranged approximately in a line, postero-central chaeta near pseudopore; Abd. III with two anterior macrochaetae; Abd. IV with two lateral macrochaetae; Abd. VI with numerous chaetae of moderate size. Most mesochaetae laterally and posteriorly on terga. Pseudopores near the axis of terga, number of them as 1, 1/ 1, 1, 1, 1, 0, 0 from Th. II to Abd. VI.

Trochantero-femoral organ with 1, 1 small slender chaetae (Fig. 4E). Front, middle and hind tibiotarsus ventro-distally with 0, 0, 2 blunt spine-like chaetae (Fig. 4F). Each tibiotarsus with a distal whorl of 11 chaetae, ventral six as ordinary chaetae, dorsal five modified: tenent hair very small and pointed; two accessory chaetae subequal to tenent hair, longer than pretarsal chaetae; two guard chaetae thin and pointed, approximately three times as long as tenent hair. Unguis slender, with baso-internal ridges approximately 1/3 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with one basal and 1-3 more distal teeth. Unguiculus slender, approximately 0.6-0.7 times as long as unguis, its inner edge with 1-2 corner tooth. Pretarsus chaetae 1+1 (Fig. 4G).

Ventral tube with scales on both anterior and posterior faces, lateral flaps unscaled, anterior face with ca. 70 chaetae on each side, posterior face with ca. 160 chaetae, each lateral flap with ca. 100 chaetae. Rami of tenaculum with 4+4 teeth, anterior face with one chaeta and without scale (Fig. 5A). Length ratio of furca segments as manubrium: dens: mucro=3.7-3.8: 5.1-5.3: 1.0. Manubrium ventrally scaled, without chaetae, laterally with large round scales and 9-10 strong chaetae; dorsal chaetal stripe with ca. 280 chaetae of different sizes, without distinct prominent chaetae; dorsal scales mixed with chaetae in chaetal stripe; pseudopores 28-35 on each side (Fig. 5B); external corner chaeta as a small mesochaeta in chaetal stripe (Fig. 5C). Dens basally without large modified inner scale or strong outer chaetae. Dental spines formula as 4, II/6, I, 3, I or 5, I/6, I, 3, I, proximal spines enlarged gradually; each spine consisting of a strong trunk surrounded by several denticles near base (Fig. 5D). Dens dorsally with ordinary chaetae and feather-like chaetae, ventrally with scales. Mucro elongated and multi-setaceous; single basal tooth with proximal lamella; apical and subapical tooth subequal; two dorsal lamellae running from subapical tooth, outer lamella ending at basal tooth, inner lamella ending at base of mucro; outer lamella with 3-4 moderate sized intermediate teeth (Fig. 5E).

Etymology.

Named for its light grey body colour, from the Latin cinereus, meaning ash-coloured.

Remarks.

Within the genus, Monodontocerus cinereus sp. n. is more similar to Monodontocerus mulunensis Yu, Deharveng & Zhang, 2014 in the cephalic chaetotaxy, the pointed tenent hair and the number of mucronal intermediate teeth, but can be distinguished from the latter by having longer antennae, fewer teeth on unguis and more macrochaetae on Abd. III and Abd. IV. In alcohol the new species can be identified from other known species of Monodontocerus by the grey body colour.