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Entomophthora muscae resting spore formation in vivo in the host Delia radicum
1Department of Ecology, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark. LT@KVL.DK
Abstract:
The formation in vivo of Entomophthora muscae resting spores was investigated in the host, Delia radicum (cabbage root fly), by analysis of field data on the seasonal occurrence of E. muscae resting spores over 4 years. E. muscae resting spores in D. radicum were spherical with an average diameter of 39.4 microm, and the average numbers produced were estimated at 5.7 x 10(4) resting spores/female cadaver. Resting spores were found only after midsummer in D. radicum and almost exclusively in females. The proportion of infected females with resting spores was negatively correlated with average weekly day length after midsummer. We did not detect any significant year effect; thus, the results support the hypothesis that the photoperiod is the most important abiotic factor controlling E. muscae resting spore formation in D. radicum.
Insights
Photoperiod, or day length, is the key environmental factor influencing the formation of Entomophthora muscae resting spores in cabbage root flies. This fungus produces spores primarily in female flies after midsummer, with shorter days accelerating spore development.
Area of Science:
- Entomology
- Plant Pathology
- Mycology
Background:
- Entomophthora muscae is an important fungal pathogen infecting various insect hosts.
- Understanding the environmental triggers for resting spore formation is crucial for predicting pathogen dynamics.
Purpose of the Study:
- To investigate the in vivo formation of Entomophthora muscae resting spores within its host, Delia radicum.
- To identify key abiotic factors influencing seasonal resting spore production.
Main Methods:
- Analysis of 4 years of field data on the seasonal occurrence of E. muscae resting spores in D. radicum.
- Quantification of resting spore diameter and number per female cadaver.
- Correlation analysis between resting spore presence and environmental factors like day length.
Main Results:
- E. muscae resting spores were spherical (avg. diameter 39.4 microm) and produced at an estimated 5.7 x 10^4 spores/female cadaver.
- Resting spores were predominantly found in female D. radicum cadavers after midsummer.
- The proportion of infected females with resting spores showed a negative correlation with average weekly day length after midsummer.
Conclusions:
- Photoperiod is the most significant abiotic factor controlling E. muscae resting spore formation in D. radicum.
- Resting spore formation is primarily a late-season event in this host-pathogen system, linked to decreasing day length.