Damage to the gills, skin and other tissues by lysenin and the coelomic fluid of the earthworm Eisenia foetida in two teleosts, Tanichthys albonubes and Oreochromis mossambicus.

Lysenin is a 33-kDa protein found in the coelomic fluid (CF) of the earthworm Eisenia foetida. Purified lysenin binds specifically to sphingomyelin (SM). In the present studies, we found that the white cloud mountain minnow Tanichthys albonubes and the Mozambique tilapia Oreochromis mossambicus died in solutions of lysenin (at concentrations above 2.5 µg/ml) and CF (0.6%, v/v) within 2 h. The gills of both species of fish were damaged similarly by lysenin and by CF. Most gill lamellae became irregularly bent or curled, with swelling of the epithelial cells of the lamellae. Red blood cells in the lamellar vascular sinuses, in the central venous sinuses, and in the blood vessels of the entire body became swollen and lysed, choking the sinuses. Epithelial cells in the skin were also damaged. When fish of both species were treated with lysenin or CF that had been incubated with SM-liposomes, they did not die. Their behavior remained normal and there was no damage to any cells or tissues. These findings suggest that SM might be involved in the lethal effects of lysenin and CF. It is likely that purified lysenin and lysenin in CF bound to SM in the cell membranes of the tissues mentioned above, damaging the cells. The presence of SM in the gills and skin was confirmed, supporting this hypothesis. The damage to gills and hemolysis might have resulted in lethal respiratory problems. Damage to the skin might disturb the exchange of ions through the skin, hastening death. Damage by lysenin and CF to epithelial cells of the cornea and the wall of the oral cavity was also recognized, but there was no such damage to the intestine. J. Exp. Zool. 295A:117–126, 2003. © 2003, Wiley-Liss, Inc.