Effect of sediment type, feeding level, and larval density on growth and development of a midge (Chironomus riparius)

A 10-d growth test and an emergence test were performed with Chironomus rip arius Meigen in four unpolluted lake sediments (organic carbon content 0.5- 57%) using different feeding levels (Tetramin(R) at 0.03, 0.06, 0.12, or 0. 33 mg/larva/d in the growth test and 0, 0.015, or 0.30 mg/larva/d in the em ergence test) to study how sediment type and feeding level affect larval gr owth. To examine effects of larval density on growth, another growth rest w as performed using densities of one larva per 24, 12, 4.8, or 2.4 cm(2) and a feeding level of Tetramin at 0.12 mg/larva/d. Regardless of sediment typ e. feeding was necessary in the experiments started with first-instar larva e. The effects of sediment physicochemical characteristics on larval growth and development could not be totally compensated for by food addition. Whe n fed, larvae grew best in sandy sediment with low organic carbon content ( 0.5%). Acceptable survival was achieved with a very low food dose (0.03 mg/ larva/d), but a somewhat higher dose (0.12 mg/larva/d) is recommended. Incr ement of feeding accelerated larval growth and development. Larval growth w as correlated to the food dose per individual and to the density of food pa rticles on the sediment surface.