ラクトフェリン投与による海産魚の体表粘液分泌亢進

The effect of bovine lactoferrin (0.2mg, 2mg, 20mg, 200mg/kg boby weight/day) on promoting the amount of mucus secreted on the body epidermis of several species of juvenile marine fish, such as yellowtail (Seriola quinqueradiata), red sea bream (Pagrus major), the Japanese flounder (Paralichthys olivaceus), rockfish (Sebastes inermis), and common goby (Acanthogobius flavimanus) was studied at 20°C for a period of 12 days. In the lactoferrin-treated groups (2mg and 200mg/kg body weight/day), mortality decreased slightly. The amount of protein secreted on the epidermis was measured as the index of the amount of skin mucus. The amount of protein secreted on the epidermis of the fish at the start of the experiment (initial control) was as follows: 1.47±0.25μg/mm2 for yellowtail, 1.73±0.24μg/mm2 for red sea bream, 1.54±0.27μg/mm2 for Japanese flounder, 1.69±0.34μg/mm2 for rockfish and 1.45±0.31μg/mm2 for common goby. Oral administration of lactoferrin at 20mg and 200mg/kg body weight/day resulted in increased mucus production within 6days. The amount of skin mucus increased significantly in the fish fed with lactoferrin at 2mg/kg body weight/day after 9 or 12days. Increased secretion of mucus on the epidermis was also observed in the red sea bream that was administrated lactoferrin at 0.2mg/kg body weight/day after 12days. In the red sea bream and other four species, the maximum values for the amount of skin mucus for the fish that were administrated lactoferrin were about 2times and 1.4 to 1.7times of those of the control, respectively. Among the species used in this experiment, the promotive effect of lactoferrin on the amount of mucus secreted on the body epidermis was most remarkable for the red sea bream, followed by Japanese flounder, common goby, yellowtail, and rockfish in that order.