Juvenile development and life cycle of Heterorhabditis bacteriophora and H-indica (Nematoda : Heterorhabditidae)

Heterorhabditis bacteriophora and H. indica were cultured in vitro in monox enic liquid cultures. Nematodes were examined for morphological characters which can be used to determine the sexes in all juvenile stages. When hatch ing from the egg no sex-specific characters could be distinguished. Twelve hours later sex determination resulted in male phenotypes which were identi fied by the asymmetric shape of the primordial testis. Female phenotypes, w ith symmetrical primordial gonads, were observed 12 h later. Of the eggs la id by the parental hermaphrodite 57% developed to amphimictic adults. The o ther individuals were determined to become automictic dauer juveniles which further develop to hermaphrodites. The pre-dauer J1 was the last of the fi rst juvenile stages to be determined. They moult to the pre-dauer second st age juvenile (J2D) which is distinguished from the other J2 stages by a thi n and spindle-like shape, elongated pharynx and needle-like tip of the tail . The late JD2 stage is immobile, pharyngeal pumping ceases and intercalate d fat reserves make it appear darker then the amphimictic J2. The further d evelopment to adults is described and the occurrence of the different stage s in liquid culture documented.