DNA-BASED IDENTIFICATION OF ECOLOGICALLY IMPORTANT CADDISFLY LARVAE (TRICHOPTERA,HYDROBIOSIDAE)
SHAN Lin Na, YANG Lian Fang, SUN Chang Hai Entomology Department, Nanjing Agricultural University, Nanjing 210095,China
Identification of the larvl stage of aquatic insects is one of most important factors in biomonitoring water quality. So far, the morphological diagnostic characters for many mature and early instars larvae are still lacking in China. Therefore mitochondrial DNA sequence analysis is used in this study for the identification of hydrobiosid larvae. The partial se quences of the mitochondrial CO I, CO II and tRNA gene of the adults and larvae of Apsilochorema unculatum and A. hwangi are compared in this study, with the length of 2?236, 2?236 and 2?235 bp respectively. The results indicate that intraspecific divergence is ≤1% between the adult and the larva of A. unculatum, and interspecific divergence is 14% and 13% between the larva of A. unculatum and the adult of A. hwangi. The study proves that the mitochondrial DNA sequence analysis is a feasible approach for immature taxonomy. The larva of A. unculatum is described and figured here for the first time (Figs 2\|11). Full grown larva with body length 8 11?mm; alive individuals green, but turned into diffusion dark violet dots on its dorsum while preserved in alcohol. Head capsule length 0 99 1 09?mm, oblong, about 1 4 times as long as wide; plain yellowish. Eyes dark brown, situated at 1/3 distance to the distal margin. Antennae tiny, positioned at the base of mandibles. Pronotum light yellowish, much narrower posteriorly, with posterior margins darkened; lateral margin dark brown, with a longitudinal, dark stripe close to it. The antero lateral angles darkened and roundly projected, each bearing 6 short thin setae and 2 stout setae; with an additional fine, primary seta, as long as pronotum, located at a small notch just next to antero lateral angle; on each side of median line, with only a single seta positioned anteriorly but two setae posteriorly. Meso and metathorax much broader than prothorax, dorsum entire membranous with distinct light pattern; each divided transversely into two parts. Forelegs predacious form, femur and claw forming the chelate. Coxa elongate, rod like, bearing 2 thick setae near base. Femur sub oval, strongly flattened laterally, 1 5 times as long as its width in lateral view; with inner surface convex and smooth while outer surface divided into a thick dorsal portion and a thin, concave ventral portion, its ventral edge furnished with a row of short, fine hairs and with a long, stout seta and a long, thin seta set at one third distance to the base of the joint for controlling the tip of claw. Tibia small and short, cylindrical, slightly concave ventrally; with two row of spinules in ventral view, the apical tooth on the inner margin most obvious. Tarsus only one segment, cylindrical, smaller than tibia, also slightly concave ventrally and with two row of spinules in ventral view, but with the distal three teeth on the inner margin and one apical tooth on the out margin most obvious. Claw very long and thin, seta shaped, blunt at apex, with a short, stout basal spine. Distribution. Material examined: 6 larvae and 6 pupae, Lishui River, Penglong Town, Qimen County, Anhui Province, 410?m elev., 6 June 2003, coll. SHAN Lin Na and LU Shuang. Discussion. Among the known Apsilochorema larva species, this species is very similar to A. sutshanum Martynov from Russia. It could be distinguished by: 1) the antero lateral angle of pronotum each bearing 8 setae, rather than 7 setae as in the latter; 2) with only one seta anteriorly on each side of median line of the pronotum rather than two setae in the latter; 3) tibiae and tarsi of forelegs each with two rows of minute spinules ventrally but was absent in the latter; and 4) femur of midleg and hindleg normal, without a row of minute spinules, but was present in the latter.