A new species and new record of the water mite genus Lebertia Neuman, 1880 (Acari: Hydrachnidia, Lebertiidae) from China

A new species Lebertia extendia n. sp. is described and illustrated and Lebertia (Pilolebertia) inaequalis Koch, 1837 is reported for the first time from China. The new species can be distinguished from other species by the mediodistal seta inserted close to the ventrodistal seta and the extended posterior margin of Cx-IV and the larger number of swimming setae on II-leg-5. Furthermore, a key to the Lebertia species of China is provided.


MATERIALS AND METHODS
All specimens were collected with a 200 µm mesh size hand net, preserved in Koenike's fluid, and mounted in glycerine jelly (Jin 1997b). The specimens were dissected under a Leica M125 stereoscope, described, and drawn under a Leica DM3000 microscope. The type material and non-type material is deposited in the Institute of Entomology, Guizhou University, Guizhou Province, P. R. China.

Family Lebertiidae Thor, 1900b
Genus Lebertia Neuman, 1880 Remarks -Lebertia inaequalis was originally described from Germany by Koch in 1837. The main characteristics of the Chinese specimens match the description of Gerecke (2009), based on the smooth integument; short Cx-II (Cx-I/II ML ratio 1.32-1.44 in Chinese specimens, 1.1-1.7, generally > 1.3 in German specimens); slight but distinct indentation in gnathosoma; P-4 ventral margin divided by ventral seta insertions into 2: 1: 1; P-2 relatively long (28% total L of the palp in Chinese specimens, 25 -28% in the German specimens); one minute peglike seta on P-4 and the swimming numbers of legs. However, the Chinese specimens still have one slightly difference compared with the description from Germany in the size of some of the palp segments. The Chinese specimens measure P-4 113 -138 µm long, while the type specimens from Germany are 133 -180 µm long. Nevertheless, as most of the main characteristics and measurements of the Chinese specimens fit well in the description of Gerecke (2009), we conclude that the Chinese specimens are of the same species as those from Germany.
Habitat -Pools of higher order streams, macrophyte belts in standing waters, especially in the wave-zone (Lundblad 1968;Gerecke 2009), clean rivers.
Remarks -The new species can be distin-guished from other species by the mediodistal seta inserted close to the ventrodistal seta and the extended posterior margin of Cx-IV.
Lebertia (Pilolebertia) insignis Neuman, 1880 is similar to the new species in the position of the mediodistal seta on P-3 and the distributions of ventral setae on P-4. Nevertheless, there are still many differences: 1) medial suture Cx-I is slightly longer than Cx-II in L. insignis (1.2 -1.3 in L. insignis), but in the new species medial sutures Cx-I/II are almost equal in length (ML 0.95); 2) P-2 of the new species is slightly longer than that of L. insignis (P-2/P-4 L 0.78 -0.80 in L. insignis, but 0.95 in the new species); 3) the Cx-IV posterior margin is truncated in L. insignis, but in the new species the coxal field extends with the posterior margin of Cx-IV almost reaching to the posterior end of the genital field; 4) II-L-5 with 2 swimming setae in L. insignis, while the new species has 6 -10 swimming setae on II-L-5. (Gerecke 2009;Bursali et al. 2011).
Distribution -China, known only from the type locality.