A self-fertile species of Steinernema from Indonesia: further evidence of convergent evolution amongst entomopathogenic nematodes?
More than 20 species of the entomopathogenic nematode Steinernema have been described; to date, all reproduce exclusively by cross-fertilization of male and female individuals. Steinernema sp. strain T87 from Indonesia was found to consist largely of self-fertile hermaphrodites. Progeny were produced by morphological females both in insects (Galleria mellonella) and in hanging drops of insect haemolymph inoculated with a single infective juvenile. Sperm were present in the oviduct of unmated morphological females. Approximately 1% of infective juveniles developed into males, and males were also present in the second generation where they constituted 1-6% of the population. Under the same conditions the related species Steinernema longicaudum strain CB2B displayed typical steinernematid reproduction: cross-fertilization and a 1:1 sex ratio. It is argued that the development of hermaphroditism in Steinernema sp. T87 represents convergent evolution with Heterorhabditis, the other major genus of entomopathogenic nematode.
Institute of Bioengineering and Agroecology, and Department of Biology, National University of Ireland Maynooth, Co. Kildare. christine.griffin@may.ie
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D000818:Animals; D005075:Biological Evolution; D005260:Female; D005298:Fertility; D007214:Indonesia; D008297:Male; D009348:Nematoda / Q000145:classification* / Q000235:genetics / Q000502:physiology; D012098:Reproduction; D012744:Sex Ratio