Four‐year successive rearing of Glyptotendipes tokunagai Sasa (Diptera: Chironomidae) under laboratory condition

Abstract

The dipteran Chironomidae have been commonly used as water quality indicators and toxicity test organisms. Two chironomids, Chironomus riparius Meigan and C. tentans Fabricius, are standard test organisms for toxicity (OECD), but their distribution is limited in Korea. The purpose of this study was to establish a Korean native chironomid species as a toxicity test organism. Glyptotendipes tokunagai Sasa, distributed widely in Korean streams, was selected and reared successively under laboratory conditions for over 30 generations over 4 years.Four G. tokunagai egg masses were collected from the Jungrang stream in Seoul, Korea in April 2007 and introduced to the laboratory for rearing. Room temperature (23.5 ± 3.2°C), larval and adult rearing cages, mating cages, and larval food were appropriately modified from conventional chironomid rearing methods. The number of eggs in an egg mass, hatching rate, and adult body sizes (head width, thorax width, wing width and length, and body length) were monitored every generation.As a result, the number of eggs in an egg mass decreased rapidly in early generations, and then tended to stabilize after the fourth generation (p < 0.05). The mean hatching rate was higher than 75% in all generations. The gender ratio (no. of females/total no. of adults) was 0.24–0.52. The adult body size became significantly reduced in the initial three generations and tended to be stabilized in the following generations (p < 0.05), although it depended on food supply and larval density. This is the first case of chironomid domestication in Korea that has been successfully reared longer than 4 years under laboratory conditions. This reared population of G. tokunagai can be used for various environmental studies such as bioassays, ecological risk assessments, and environmental monitoring.