First record of Acrocyrtus Yosii, 1959 (Collemobla, Entomobryidae) from Chinese mainland

Abstract The genus Acrocrytus is reported from Chinese mainland for the first time, with description of two new species Acrocyrtus zhujiensis sp. n. and Acrocyrtus finis sp. n. from Zhejiang Province, East China. They can be separated from other species of this genus by colour pattern, unscaled appendages (antennae, legs and ventral tube), interocular chaetae, labial basal chaetae, bothriotrichal complex chaetae on Abd. II–IV, microchaeta a2 on Abd. II, im on Abd. III and C1p on Abd. IV. Illustrations and a table showing main differences with closest Acrocyrtus species are provided.


introduction
Acrocyrtus was established by Yosii 1959 as a subgenus of Lepidocyrtus Bourlet, 1839 for Lepidocyrtus (Acrocyrtus) malayanus Yosii, 1959 having pointed dental tubercle. Yoshii and Suhardjono (1989) raised it to generic level and established three subgenera (Acrocyrtus, Onerocyrtus, Carocyrtus) based on scales distribution of ventral tube. Christiansen and Bellinger (1991) analyzed the phylogenetic relationships among Hawaiian Lepidocyrtus s. l. species and questioned the reliability of dental tubercle. Later, Soto-Adames (2000) made a phylogenetic analysis of Neotropical members of the genus, disagreeing with the previous conclusion and considering that this character has phylogenetic information useful in defining Yoshii's subgenera; he also suggested that dental tubercle should be used in combination with other characters. Considering the availability of this character in most literature descriptions and how easily it can be observed in practice, we considered that its use at generic level is relevant.
Acrocyrtus is characterized by the presence of conical pointed dental tubercles, rounded and finely striated scales on body and ventral side of furcula, 8+8 ommatidia (G and H smaller), 4-segmented antennae and apical bulb absent on Ant. IV, bidentate mucro with or without accessory spinelet. It is widely distributed in Southeast Asia, such as Singapore, Malay and Indonesia. So far, more than 26 species of the genus Acrocyrtus were described all over the world (Pan et al. 2011). Only one species Acrocyrtus heterolepis Yosii, 1959 was recorded from Hong Kong (Yosii 1966) and Taiwan (Yoshii 1982), China. Recently, an unidentified species assigned to "cf. Acrocyrtus" was also recorded from a cave in Huanjiang (Guangxi) by Deharveng et al. (2008). The two new species of Acrocyrtus that are studied here represent the first ones described from mainland of China.
Etymology. Named after the type locality. Description. Body length up to 0.93 mm. Colour pattern. Ground colour pale yellow, with a pair of dark patches present on lateral Abd. III. Violet pigment distributed on antennae and gradually darker towards tip. Eye patches dark (Fig. 1). Scales hyaline, oval to circular (Fig. 2), present on head, body tergites, ventral side of furcula; antennae, ventral tube and legs unscaled.
Ecology. In the leaf litter of Cunninghamia lanceolata, Cinamomum camphora along a lake.
Remarks. This new species is characterized by colour pattern, clavate tenent hair, unscaled appendages (antennae, legs and ventral tube), 4 conical labral papillae, ventral tube with ciliate chaetae present on lateral flap and without smooth chaeta on posterior side, and ciliate mic a2 on Abd. II.
It is similar to Vietnamese Acrocyrtus baii Nguyen, 2005 in clavate tenent hair, claw, unscaled appendages (antennae and ventral tube). However, it can be easily distinguished from it by pigment absent on Th. II-III and Abd. II (versus present), ciliate labial chaetae EL 1 L 2 (versus smooth), M 1 subequal to M 2 on labial base (versus M 1 smaller than M 2 ), absence of smooth chaetae on posterior face of ventral tube (versus 1+1 smooth chaetae) and unscaled legs (versus scaled).
Etymology. Named after the type locality, which is the border (latin word "finis") of the three adjacent cities.
Description. Body length up to 1.2 mm. Colour pattern. Ground colour from yellow to slightly brown, a pair of dark lateral patches of Abd. III and a pair of dark postero-lateral patches of Abd. IV, slightly violet pigment distributed on antennae and gradually darker towards tip, eye patches dark (Fig. 28). Scales hyaline, oval to circular (Fig. 29), present on head, body tergites and ventral side of furcula, and absent on antennae, legs and ventral tube.
Ecology. In leaf litter of Pinus massoniana, Schima superba and Cinamomum camphora, in bryophyta and on farmland.
Remarks. The new species is easily distinguished from other Acrocyrtus by 4 abdominal lateral patches, morphology of interocular chaetae v, r and s, cephalic mac as R 0 R 1 R 2 ST, 4 papillae and thicken c-row chaetae on labrum, smooth mic a2, im and C1p on Abd. II, Abd. III and Abd. IV, respectively, unscaled appendages (antennae, ventral tube and legs).
The species is most similar to Acrocyrtus zhujiensis sp. n. in cephalic chaetotaxy, labral papillae, claw, furcula, macrochaetotaxy and S-chaetotaxy. However, the two species are different in colour pattern, morphology of chaetae a2, m3 and m5 on Abd. II, a2 and im on Abd. III, C1p on Abd. IV. Main differences between two new species are listed in Table 1.

Discussion
Dental tubercles are pointed in Acrocyrtus and rounded in Ascocyrtus. However, it is sometimes uneasy to recognize the shape of dental tubercles. Their shape maybe wrongly observed in different visual angles, pointed in lateral view but "rounded" in facial view. They need to be observed under various angles. Another interesting point is that some species of Yoshii (1982Yoshii ( , 1989 with colour patterns similar to our species (pigment on Abd. III) were assigned to Ascocyrtus rather than Acrocyrtus. Our new species would be placed in Ascocyrtus due to habitus compared with those Southeast Asia taxa (Deharveng, personal communication). Actually, more Chinese species with similar patterns in our collection have pointed and relatively long dental tubercles. Since the works of Yosii, no significant advance has been made for the classification of Lepidocyrtus s. l. Molecular tools are expected to help discriminate Lepidocyrtinae genera in the future.