Morphological changes in haemocytes of the host, Pseudaletia separata, parasitized by Microplitis mediator or Apanteles kariyai.

The granular cells of the host Pseudaletia separata were associated with the initial recognition of foreign materials. When the host was parasitized by Microplitis mediator, the filopodial elongation of the haemocytes was strongly suppressed. An inhibition of filopodial elongation was also observed following injection of the calyx and venom fluids of M. mediator. The reduction in the encapsulation capacity of parasitized hosts was confirmed by the experimental injection of Sephadex particles and tended to support to the observation of inhibition of filopodial elongation. However, in hosts parasitized by Apanteles kariyai, no suppression of filopodial elongation of haemocytes was evident and the Sephadex particles injected were fully encapsulated. Thus, the inhibitory mechanisms of Microplitis mediator and Apanteles kariyai against the cellular defence reactions of the host seemed to depend on different strategies.