Adult cat flea (Siphonaptera: Pulicidae) excretion of host blood proteins in relation to larval nutrition.

Protein content and ion composition of host blood and feces from blood-fed adult cat fleas, Ctenocephalides felis (Bouché), were examined. Total fecal protein differed slightly from host blood indicating that there was little digestion of host blood by adult fleas. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels of host blood and flea feces also revealed little digestion, as evidenced by the quantitatively and qualitatively similar protein banding patterns. Blood and fecal ion compositions also were similar, except for fleas fed in vivo on cats, where both potassium and chloride compositions of feces were approximately 50% lower. Host blood or flea feces alone were not of sufficient food value to allow > 12.5% of larvae to develop to adults. The addition of yeast or dog chow increased larval development to the pupal stage to 100% and 87.5% of first instars tested, respectively. Although some larval survival occurred with diets of dog chow + yeast (37.5%), feces + hair (20%), and feces + stratum corneum (16.7%), the period to cocoon formation was twice as long as that of larvae fed diets containing blood or flea feces + yeast. In contrast to fleas, feces of adults of two other hematophagous insects--bed bugs, Cimex lectularius L., and mosquitoes, Aedes aegypti (L.)--contained significantly less protein and more digested protein than the blood that they had fed upon. We propose that host blood excretion evolved in response to larval nutritional requirements.