Biology of Deladenus Siricidicola (Neotylenchidae) an Entomophagous-Mycetophagous Nematode Parasitic in Siricid Woodwasps

Abstract

Deladenus siricidicola has two life cycles each of which can continue indefinitely without the intervention of the other. One cycle is free-living involving a neotylenchid form of female that reproduces oviparously while feeding on the symbiotic fungus of Sirex woodwasps. The other cycle is parasitic, with a sphacrulariid form of female reproducing ovoviviparously within the haemocoel of four species of Sirex and two associated insects. Macro- and microspermatozoa are associated with the free-living and parasitic forms of female respectively. Juvenile nematodes may become adults of either cycle depending upon environmental conditions. Detailed observations have been made on the mycetophagous life cycle from plate cultures and within timber. Details of the mode and localization of penetration by infective females into Sirex larvae are included. The development of parasitic females particularly with regard to ovarial development has been followed. It has been shown that the time at which reproduction by the parasitic nematode commences in relation to host development may be dependant either on the species of host or the strain of nematode involved. This factor is correlated with the severity of the effect produced by parasitism on the reproductive system of the female host.