Curran-J. 1989. Chromosome numbers of Steinernema and Heterorhabditis species. Revue-de-Nematologie. 1989, 12:2, 145-148.
AB: Chromosome number is conserved amongst species within the genera Steinernema (n=5) and Heterorhabditis (n=7), with the exception of the Steinernema sp. NC 513 group of isolates (n=3). Interbreeding data and chromosome numbers indicate that the S. glaseri and Steinernema sp. NC 513 group of isolates should be considered separate species. Absence of pre-zygotic mating barriers, similar geographic distribution and similar morphology suggest that Steinernema sp. NC 513 may have evolved from a population of S. glaseri by chromosome fusion events. There is no difference in the ability of these species to grow, reproduce and retain the primary form of Xenorhabdus nematophilus subsp. poinarii NC 513 bacteria in the infective stage.