Development of an entomopathogenic nematode, Steinernema carpocapsae, in cultured insect cells under axenic conditions

Abstract

AbstractA new method for culturing an entomopathogenic nematode, Steinernema carpocapsae, in cultured insect cells under axenic conditions was devised. When Steinernema eggs were put into the established cell line Sf9, they grew, moulted, developed to adults and produced eggs. Their life cycle took about 6 days and successive subcultures were possible. Their developmental state was comparable to that of culture in insects, and an individual nematode and each developmental event could be observed easily through the transparent culture vial under a microscope. Living insect cells were food for nematodes because juveniles grew slowly and did not develop to adults in the culture medium only or in medium containing dead cells. Infective juveniles (IJ) were not observed during the first generation in culture but they appeared and increased in number during 30 days of culture with cell deterioration. The propagation of nematodes and the occurrence of IJ varied with culture conditions such as medium volume. When IJ obtained from insects were transferred to cultured cells, they shed their cuticle and recovered from the dauer state. Culturing Steinernema with cultured insect cells is a useful tool to investigate its life cycle.