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Keywords:

  • eupyrene sperm;
  • inherited sterility;
  • moth longevity;
  • painted apple moth;
  • sterile insect technique

Abstract

The advantage of inherited sterility over complete sterility in lepidopteran sterile insect technique programs results from the improvement of mating fitness of male-only releases with wild females, and the resulting large multiplier effect from viable but sterile progeny from every mating. The deleterious effects induced by irradiation are inherited by the F1 generation, but it is very difficult to measure population introgression at that stage, and the alternative has been to await population suppression at the F2 generation. This work, conducted in support of the successful elimination of painted apple moth (Teia anartoides) in New Zealand, aimed to determine the feasibility of a cytological assessment on the F1 sperm bundles of this species, as a new forensic biosecurity tool providing information for decision support. The technique successfully distinguished the homogeneous nuclei clusters of eupyrene bundles of the normal fertile males from the heterogeneously stained nuclei clusters of the F1 progeny. However, the challenge for the technique involved obtaining good specimens for cytological diagnosis. The percentage of positive staining results was correlated strongly with survival, which was <5 days. Moths that had spent 24 h on a sticky base in a monitoring trap were equivalent to freshly killed specimens, but the efficacy of the technique decreased after that. Some specimens that were ‘dead’ to the naked eye but potentially alive internally produced reliable results. The technique may be potentially useful as a forensic biosecurity tool in the future when a communicating trap is deployed, ensuring that fresh specimens could be used to monitor the success of inherited sterility in population suppression or eradication.