Frequently mated males have higher protein preference in German cockroaches

Abstract

Protein is an abundant nutrient in sperm, and males therefore expend protein every time they mate. In addition, many males provide the female with a nitrogen-rich nuptial gift during mating, which often increases female fertility by supplementing her pool of limiting nutrients. However, it is unknown whether males compensate for the nitrogen cost of mating by increasing their preference for protein, which would facilitate the production of new sperm and nuptial gift material. Using artificial diets, we investigated whether male German cockroaches (Blattella germanica) would compensate for nitrogen expenses of mating by increasing protein preference when given the opportunity to self-select their diet from complementary foods differing only in protein and carbohydrate content. We distributed adult males across 4 mating regimes differing in the frequency of mating opportunities with receptive females and measured protein and carbohydrate consumption as well as reproductive output over the lifespan of each male. Receptive females were either never available (no mating opportunity), or they were available overnight at a frequency of each 28 days (rare mating opportunities), each 14 days (occasional mating opportunities), or each 7 days (frequent mating opportunities). Males selected highly carbohydratebiased diets. However, males that mated more frequently had higher consumption and reproduction and self-selected higher lifetime protein to carbohydrate ratios. Our study demonstrates that male German cockroaches actively select a more protein-biased diet that compensates for their nutritional requirements following mating. The study shows that male mating significantly affects foraging decisions for specific nutrients to compensate for the expenses of mating.