PARASITIC WORMS IMPAIR NUTRIENT ASSIMILATION AND REPRODUCTIVE INVESTMENT WITHOUT ALTERING MACRONUTRIENT PREFERENCE IN FEMALE HOUSE CRICKETS.

Growth and reproduction in insects are strongly influenced by dietary protein and carbohydrate intake, yet parasitism may alter how hosts acquire and allocate these resources. Hairworms (Nematomorpha) develop within arthropod hosts and consume host-derived nutrients, but the effects on host nutrition and development remain poorly understood. We tested the effects of Paragordius varius (Leidy, 1851) parasitism on diet choice, growth, and reproduction in experimentally infected female house crickets, Acheta domesticus (Linnaeus, 1758). Crickets were offered complementary high-protein and high-carbohydrate diets, and we quantified food intake, nutrient preference, and host performance metrics. Infected crickets consumed similar protein-to-carbohydrate ratios as controls but ingested 14% less total food. Control crickets exhibited higher standard growth rates (SGR), whereas SGR decreased with increasing parasite intensity in infected individuals. Infected crickets produced no eggs and had significantly reduced lipid content, ovipositor growth, and fecal output relative to controls. Nutritional indices on the basis of wet mass indicated no difference in the conversion of intake to body mass; however, indices on the basis of parasite-free dry mass revealed that control crickets converted food intake 3.7 times more efficiently than infected crickets. These results indicate that hairworm parasitism reduces host growth and reproductive output and decreases the efficiency of energy assimilation, likely due to direct or indirect resource competition with developing parasites.