Predatory activity of Arthrobotrys oligospora and Duddingtonia flagrans on pre-parasitic larval stages of cyathostominae under different constant temperatures

摘要

The effect of different temperatures on the predatory activity of Arthrobotrys oligospora and Duddingtonia flagrans on the free-living larval stages of cyathostomes were evaluated in an experiment where feces of horses containing the parasites?’ eggs were treated with these fungi and incubated under different constant temperatures (10?°C, 15?°C, 20?°C, 25?°C and 30?°C ). The results indicated that the optimum temperature for egg development was 25?°C. At 10?°C the number of L3 recovered was practically zero, and at 15?°C and 20?°C, the percentage of larvae recovered was less than 3% of the total number of eggs per gram of feces. When these cultures subsequently were incubated for an additional period of 14 days at 27?°C, they allowed the development of L3. In all the cultures inoculated with fungi a significant reduction in the number of larvae was observed. When incubated at 25?°C or 30?°C, the fungi caused reductions above 90%, in the number of L3. The samples cultivated at 10?°C, 15?°C, 20?°C, 25?°C and 30?°C, when incubated for an additional period of 14 days at 27?°C the reduction percentage of larvae was above 90% for A. oligospora. However, the same did not occur for D. flagrans. Here a reduction percentage between 47.5% and 41.8% was recorded when the cultures were incubated at 10?°C and 20?°C, respectively. The two species of fungi tested showed to be efficient in reducing the number of L3 when mixed with equine feces and maintained at the same temperature for the development of larval pre-parasitic stages of cyathostomes.