Tomocerus tiani 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 : 82-85

Taxon classification Animalia Collembola Tomoceridae

Tomocerus tiani Yu sp. n. Figs 1A, B, 2, 3

Type-locality.

China, Guizhou Province: Zunyi, Suiyang County, Wenquan Town, Guihua Village, Hejiao Cave, inside cave, 7 November 2008, Mingyi Tian leg.

Type-specimens.

Holotype male (labelled 15cave15-1) and paratype juvenile (labelled 15cave15-2) on slide. Deposited in NJAU.

Diagnosis.

Species similar to Tomocerus kinoshitai Yosii, 1954, with short antennae, multi-furcated dental spines and apically curved mucro. Body length approximately 3.0 mm, with purplish grey pigment all over; antennae approximately half as long as body; eyes small; terminal hair of maxillary outer lobe with a small basal denticle; Th. II with only one bothriotrichum; tenent hairs pointed; unguis with two teeth, baso-internal ridges at approximately 1/2 distance from base; manubrium with 12-17 pseudopores on each side; dental spines formula as 4/2, II; dens dorsally with only a few feather-like chaetae; mucro without intermediate tooth. Cave-dwelling species.

Description.

Body length 2.9 mm. Body with uniform purplish grey pigment and unpigmented patches, appendages paler. Eye patches black (Fig. 1A). Types of scales and chaetae typical for Tomocerinae.

Antennae approximately half length of body. Length ratio of antenna segments as I:II:III+IV = 1.0:1.9 –2.0:9.6– 9.7. Only dorsal side of Ant. I and Ant. II scaled, Ant. III+IV unscaled. PAO not seen. Eyes 6+6, relatively small. 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. 2A). Maxillary lamella five without beard-like appendage. Maxillary outer lobe with trifurcate palp, one basal chaeta and four sublobal hairs; terminal hair with a small basal denticle (Fig. 2B). Both dorsal and ventral sides of head scaled. Cephalic dorsal macrochaetotaxy: anterior area: 2, 2; interocular area: 2, 4, central uneven macrochaeta absent; postocular area: 2+2; posterior area: 0. Posterior margin of head with ca. 70 small chaetae (Fig. 2C). Mentum with five chaetae, submentum with numerous chaetae.

Pattern of body chaetotaxy as in Fig. 2D. Number of bothriotricha as 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, 3, 4 (3 dorsal+1 lateral) from Th. II to Abd. V. Th. II with four central and one lateral macrochaetae, postero-central chaeta near pseudopore; Abd. III with two anterior macrochaetae; Abd. IV with one lateral macrochaeta; 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. 2E). Front, middle and hind tibiotarsus ventrally with 0, 0, 2 pointed spine-like chaetae (Fig. 2F). Each tibiotarsus with a distal whorl of 11 chaetae, ventral six as ordinary chaetae, dorsal five modified: tenent hair thin and pointed, approximately 0.33 times as long as inner edge of unguis; two accessory chaetae small, longer than pretarsal chaetae; two guard chaetae of same morphology and size as tenent hair. Unguis slender, with baso-internal ridges at approximately 1/2 distance from base; lateral teeth pointed, of moderate size. Inner edge of unguis with one basal and one central minute teeth. Unguiculus rather slender, approximately 0.5-0.72 times as long as unguis, its inner edge with one corner tooth. Pretarsus chaetae 1+1 (Fig. 2G).

Anterior face of ventral tube with scales, posterior face and lateral flaps unscaled, anterior face with ca. 25 chaetae on each side, posterior face with ca. 30 chaetae, each lateral flap with ca. 15 chaetae. Rami of tenaculum with 4+4 teeth, anterior face with one chaeta and without scale (Fig. 3A). Length ratio of furca segments as manubrium: dens: mucro = 2.5: 3.6-3.7: 1.0. Manubrium ventrally scaled, without chaetae, laterally with large round scales and 7-9 strong chaetae; dorsal chaetal stripe with ca. 200 chaetae of different sizes, including 2+2 pointed prominent chaetae; inner side of chaetal stripe with several scales; pseudopores 12-17 on each side (Fig. 3B); external corner chaeta as a microchaeta (Fig. 3C). Dens basally with a pointed prominent dorsal chaeta, without large modified inner scale or strong outer chaetae. Dental spines formula as 4/2, II; spines with moderate to large sized denticles around basal half (Fig. 3D). Dens dorsally with ordinary chaetae, swollen spine-like ciliated chaetae and a few feather-like chaetae (Figs 1B, 3E), ventrally with scales and several apical chaetae. Mucro elongated, distally curved and multi-setaceous; both basal teeth with proximal lamellae, outer tooth with a toothlet; apical and subapical tooth subequal; two dorsal lamellae running from subapical tooth, outer lamella ending in inner basal tooth, inner lamella ending at base of mucro; without intermediate teeth (Fig. 3F).

Etymology.

Named after the collector Prof. Mingyi Tian.

Remarks.

Tomocerus tiani sp. n. is similar to Tomocerus caecus Yu & Deharveng, 2015, Tomocerus kinoshitai (materials from Changbai Mountain, China) and Tomocerus similis Chen & Ma, 1997 (type materials) in the length of antennae, the general pattern of chaetotaxy on Th. II, the number and position of spine-like tibiotarsal inner chaetae, the size of external corner chaeta on the manubrium, the type and general arrangement of dental spines and the shape of mucro, but it is clearly different from the first species in having eyes and pigment, and is different from the other two species mainly in the body colour, the cephalic chaetotaxy, the sharply pointed tibiotarsal strong inner chaetae and tenent hair, and the more slender unguiculus; besides, with similar body size, Tomocerus tiani sp. n. has more manubrial pseudopores than the three known species. The small basal denticle of the terminal hair of maxillary outer lobe is so far unique to Tomocerus tiani sp. n. and is useful for diagnosis if dissected and exposed carefully. The baso-internal ridges of unguis are located at approximately 1/2 distance from the base in Tomocerus tiani sp. n., whereas in most other species the distance between the ridges and the base is only 1/3 or less. The dorsal dental chaetae in Tomocerus tiani sp. n. is also characteristic, that the dense stripes of feather-like chaetae in most other tomocerids are almost replaced by ordinary chaetae and swollen serrated chaetae, leaving only a few feather-like ones. Similar condition was also reported in Tomocerus kinoshitai and Tomocerus caecus that some spine-like chaetae are present on dens ( Yosii 1967, Yu and Deharveng 2015).

The juvenile specimen is almost identical to the adult in most characters, including the macrochaetotaxy, the number of teeth on claws and the dental spines formula. However, some characters on manubrium are distinctly different between juvenile and adult. In the juvenile specimen, there are ca. 80 dorsal chaetae on each side of manubrium, the number of pseudopores is only 4-5 on each side, and the external corner chaeta is as large as a mesochaeta in the dorsal chaetal stripe. These differences provide interesting information in the postembryonic development of manubrium in Tomocerinae, and indicate these characters are not suitable for the identification of immature specimens at different instars.