Effect of lectins on the invasion of Ichthyophthirius theront to channel catfish tissue

This study determined the effects of lectin binding to therohts of Ichthyop hthirius-multifiliis on theront immobilization, invasion, trophont developm ent and survival in channel catfish Ictalurus punctatus excised fins in vit ro. Soybean agglutinin (SBA), lentil agglutinin (LCA), gorse agglutinin (UE A-I) and wheat germ agglutinin (WGA) were used to treat theronts. Percentag es of theronts immobilized by 4 lectins ranged from 12.0 to 19.4% at a conc entration of 1000 mug ml(-1). These lectins bound more than half of the the ronts at a concentration of 50 mug ml(-1). More theronts were labeled by SE A and WGA than by lectin LCA at concentrations of 50 and 100 mug ml(-1), re spectively. The binding of these lectins to theronts indicated that monosac charides (D-galactose, L-fucose, D-mannose and D-glucose) and amino sugar d erivatives (N-acetylgalactosamine and N-acetylglucosamine) were present on the surface of theronts. Invasion was reduced significantly for theronts tr eated with LCA, UEA-I and WGA. No difference in invasion was found between control and SEA bound theronts (p > 0.05). The binding of lectin LCA, UEA-I and WGA to theronts significantly reduced the development of trophonts (p < 0.05). The mean volumes of trophonts labeled with these 3 lectins were sm aller than volumes in control trophonts from 8 to 48 h after exposure. Surv ival was lower in trophonts labeled with lectins than in control trophonts at 48 h after exposure.