干旱区生态环境知识资源中心

Nidicolous ectoparasites such as fleas and gamasid mites that feed on small and medium-sized mammals spend much of their time in their hosts’ burrows, which provide an environment for living, and often feeding, to their pre-imaginal and/or adult stages. Thus, these ectoparasites should be adapted to environmental conditions in burrows, including high fractional concentrations of CO2 (F-CO2). We examined how a high F-CO2 (0.04) affected survival and reproductive success of a hematophagous ectoparasite of burrowing rodents using fleas Xenopsylla ramesis and Sundevall’s jirds Meriones crassus. In the first experiment, fleas fed on hosts housed in high-CO2 (F-CO2 = 0.04) or atmospheric-CO2 (F-CO2 approximate to 0.0004) air, and were allowed to breed. In a second experiment, fleas were maintained in high CO2 or CO2-free air with no hosts to determine how CO2 levels affect survival and activity levels. We found that at high F-CO2 fleas laid fewer eggs, reducing reproductive success. In addition, at high F-CO2, activity levels and survival of fleas were reduced. Our results indicate that fleas do not perform well in the F-CO2 used in this experiment. Previous research indicated that the type and intensity of the effects of CO2 concentration on the fitness of an insect depend on the F-CO2 used, so we advise caution when generalizing inferences drawn to insects exposed to other F-CO2. If, however, F-CO2 found in natural mammal burrows brings about reduced fitness in fleas in general, then burrowing hosts may benefit from reduced parasite infestation if burrow air F-CO2 is high.