Research Article |
Corresponding author: Mingyi Tian ( mytian168@aliyun.com ) Academic editor: Achille Casale
© 2017 Mingyi Tian, Sunbin Huang, Dianmei Wang.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Tian M, Huang S, Wang D (2017) Discovery of a most remarkable cave-specialized trechine beetle from southern China (Coleoptera, Carabidae, Trechinae). ZooKeys 725: 37-47. https://doi.org/10.3897/zookeys.725.21040
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Xuedytes bellus Tian & Huang, gen. et sp. n. is described from a limestone cave in Du’an Karst of Guangxi, a kingdom of cavernicolous trechine beetles in southern China. From a morphological point of view, Xuedytes Tian & Huang, gen. n. seems to be the most extremely cave-adapted trechines in the world. Superficially, it looks much like Giraffaphaenops Deuve, 2002 in general body shape, in particular the structure of the prothorax, but simultaneously it is similar to Dongodytes (s. str.) Deuve, 1993, based on elytral characters, including chaetotaxy. Hence the new genus seems to represent a lineage intermediate between Giraffaphaenops and Dongodytes (s. str.).
aphaenopsian, Guangxi, ground beetle, troglobite
The globe’s largest and highly varied karst landscapes that blanket nearly the entire area of southern China (
In early August 2017, a cave biological survey carried out in Du’an Karst of northern Guangxi, southern China led to the discovery of a very peculiar species belonging to the subfamily Trechinae, family Carabidae. Moreover, it shows a number of most remarkable troglomorphic features amongst subterranean trechines generally. Superficially, its strongly elongated and slender body looks very much like that of a Giraffaphaenops species, especially due to the extremely elongated prothorax. However, Giraffaphaenops species are known from the Leye-Tianlin karsts of northwestern Guangxi, about 200 km away from Du’an Karst (
The beetles were collected in the cave using an aspirator, and kept in vials with 50% ethanol before study, except for a specimen put in a vial with 95% ethanol for molecular analysis.
Techniques and terminology are the same as in
Xuedytes bellus Tian & Huang, sp. n.
Highly modified aphaenopsian trechines, body shape, in particular prothorax, similar to that in Giraffaphaenops, but elytra generally like in Dongodytes (s. str.) (Fig.
Xuedytes Tian & Huang, gen. n. is undoubtedly the most remarkable cavernicolous trechine genera as regards the extremely elongated prothorax and elytra. It may be considered as a lineage intermediate between Giraffaphaenops and Dongodytes (Fig.
Although Xuedytes is similar to Giraffaphaenops, there are several important differences: (1) Prothorax and elytra much more strongly elongated in Xuedytes than in Giraffaphaenops; (2) Head subquadrate, slightly convex laterally, not contracted posteriad in Xuedytes (vs. inversed triangular, with a well-marked neck constriction in Giraffaphaenops); (3) Entire lateral margins of pronotum visible from above in Xuedytes (vs. invisible from above in front half in Giraffaphaenops); and (4) Two pairs of latero-marginal setae present behind middle of pronotum in Xuedytes (vs. absent in Giraffaphaenops) (Fig.
Apart from the differences in prothoracic features, Xuedytes is easily distinguished from Dongodytes (s. str.) by the following characteristics: (1) Head thicker and broader, not narrowed posteriad in Xuedytes (vs. thinner and evidently narrowed posteriad, forming a long and distinct neck constriction in Dongodytes); (2) Three pairs of frontal pores present in Xuedytes, instead of only one pair in Dongodytes; (3) Elytral striae completely obliterated in Xuedytes (vs. partially visible in Dongodytes) (Fig.
Furthermore, differences between the new genus and both Giraffaphaenops and Dongodytes are also evident regarding the structure of the male genitalia (Fig.
“Xue + dytes”. “Xue” in Chinese means “cave”, to indicate that the beetles are cavernicolous. Gender masculine.
China (Guangxi Zhuang Autonomous Region).
Male, Cave II, southeastern Du’an Yao Autonomous County, Hechi Shi (=Prefecture), northern Guangxi Zhuang Autonomous Region, southern China, VIII-08-2017, leg. Mingyi Tian, Sunbin Huang, Dianmei Wang and Mengzhen Chen; paratypes: 2 males and 1 female, IBID. All type material is deposited in the insect collection of South China Agricultural University, Guangzhou.
A large-sized, blind, cave-adapted trechine, remarkably modified morphologically, with both prothorax and elytra highly elongated and slender so that body five times longer than wide, antennae slightly shorter than body including mandibles, extending beyond elytral apices; head, pronotum and base of elytra covered with sparse erect setae. Habitus as in Figs
Length: 8.3–9.0 mm (from apex of right mandible to elytral apex) or 7.5–8.6 mm (from labrum to elytral apex); width: 1.4–1.5 mm.
Body yellowish brown, but antennae, palps and tarsi pale; strongly shining; head, pronotum and base of elytra covered with rather long and sparse setae, other parts of elytra glabrous, underside of fore body excluding pleurae, meso- and metasterna pubescent, abdominal ventrites densely pubescent; microsculptural engraved meshes transverse striate on head, pronotum and elytra; fore body very strongly elongated, much longer than elytra, (HLm+PrL)/EL = 1.55–1.60.
Head oblong subquadrate, much longer than wide, HLm/HW = 3.02–3.03, HLl/HW = 2.02–2.04; genae fairly well developed, broadly dilated on sides, widest at about middle of head from neck to clypeal margin, gradually tapered posteriorly; frons and vertex moderately convex, frontal furrows moderately defined, strongly diverging posteriorly, ending level with middle frontal pores; clypeus transverse, 6-setose; labrum transverse, frontal margin nearly truncate, 6-setose; three pairs of frontal setiferous pores present; mentum and submentum completely fused, mentum bisetose on either side of tooth at base, mental tooth short and blunt at apex, basal fovea broadly concave; submentum 8-setose; palps thin and very slender, glabrous except for labial palpomere 2 which is bisetose on inner margin; 2nd labial palpomere 1.40 times longer than 3rd; 3rd maxillary palpomere 1.25 times longer than 4th; suborbital pore much closer to base than to submentum (Fig.
Prothorax (Fig.
Elytra (Fig.
Legs slender and long, bearing short pubescence; fore and middle femora sparsely setose; fore tibia smooth, with neither a longitudinal furrow nor a sulcus; 1st tarsomere shorter than, slightly longer than, and much longer than 2nd–4th tarsomeres combined in fore, middle, and hind legs, respectively.
Male genitalia (Fig.
“Bellus”, in Latin meaning “beautiful”, to refer to this beautiful aphaenopsian beetle.
China (Guangxi: Du’an). Known only from Cave II.
This cave maintains a natural condition, opening on a small hill on the northern bank of the Hongshui River. The entrance is surrounded by dense bushes and not readily accessible (Fig.
We are most grateful to Dr. Thierry Deuve (National Museum of Natural History, Paris) for his comments and suggestions that proved to be helpful in improving an early draft of this manuscript. Our particular thanks go to Dr. Sergei Golovatch (Russian Academy of Sciences, Moscow) for checking the English. This study is sponsored by the Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, through a biodiversity conservation project which focused on cave biodiversity, and a project of the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant no. 20134404110026).