group) fed with either chironomid larvae Chironomus tentans or duckweed
Lemna minor. Fish had free access to food 24 h a day and fed for
60 days. At 30 days and 60 days after feeding respectively, 26 fishes
were randomly selected from each group for sample collection. The
following formula were used to calculate three ratios: the ratio of gut
length to body length (gut length/body length), the ratio of gut weight
to body weight (gut weight/body weight) and the ratio of hepatopancreas
weight to body weight (Hepatopancreas weight/body weight)
(Hidalgo et al., 1999; Hofer and Schiemer, 1981). The animal protocol
was approved by Huazhong Agricultural University.