Energy reserves and reproductive investment in male three-spined sticklebacks, Gasterosteus aculeatus

In a 6-month study of male sticklebacks from a single cohort of an annual p opulation, energy reserves (carbohydrate, lipid and protein) in the carcass and gonad were found to increase from December to May. Energy reserves in the liver increased from December to March before declining between March a nd April, a period of marked gonadal growth in this population. Examination at the individual level of the interrelationships among the various compon ents of the energy store (corrected for differences in body size) identifie d overall body condition as a major component of variation and highlighted a negative relationship between energetic investment in gonadal tissue and energy reserves in various somatic compartments. Early in the season, relat ive gonadal weight was largely unrelated to somatic energy reserves, but fr om March onwards there was a negative correlation between these two variabl es. These data suggest that a significant flux of glycogen and lipid from t he somatic to the gonadal tissue occurs in male sticklebacks in the period just prior to the breeding season, with the extent of gonadal growth varyin g between individuals and occurring at the expense of overall nutritional s tatus.