Differential allocation of male-derived nutrients in two lampyrid beetles with contrasting life-history characteristics

Across diverse animal taxa, sperm is transferred from malesto females during mating within a spermatophore produced bymale accessory glands. In some insects, male spermatophoresprovide females with nutrients that may be used to increasereproductive output or for somatic maintenance, while in othersno such benefits have been detected. Boggs suggested that variationin the current function of spermatophores may be explained byconsidering ecological and life-history factors. This studyexamined spermatophore function in Ellychnia corrusca and Photinusignitus (Coleoptera: Lampyridae), two beetles that exhibit markeddifferences in adult diet, adult life span, and overwinteringstage. During mating, males of both species transfer to femalesa complex, proteinaceous spermatophore, which is subsequentlydigested in a specialized sac within the female reproductive tract.Males of each species were injected with ³H-radiolabeled aminoacid mixtures and mated with conspecific females. The fate of spermatophore-derivedproteins was determined by dissecting females at various timesafter mating with these radiolabeled males. Females of thesetwo species showed markedly different patterns of incorporationof spermatophorederived nutrients. P. ignitus females incorporatedthe majority (62%) of spermatophore-derived protein into maturingoocytes within 2 days after mating. In contrast, in E. corruscaa large percentage of radiolabel (46%) appeared in female fatbody at 6 days after mating, with a threefold lower allocationto maturing oocytes compared to P. ignitus. These findings supportthe prediction that short-lived, nonfeeding females are selectedto allocate a greater proportion of male-derived nutrients toreproduction, while longer-lived, feeding females are selectedto allocate a greater proportion to somatic reserves and maintenance.These results suggest that life-history characteristics maybe useful in explaining observed differences in spermatophorefunction across taxa.