Sex differences in biochemical composition, energy content and allocation to reproductive effort in the brooding sea star Leptasterias polaris

Abstract

We assessed sex differences in reproductive investment of the brooding sea star Lepta- sterias polaris (in the northern Gulf of St. Lawrence, eastern Canada) by examining the biochemical composition and energetic content of the principal body components in 3 contrasting periods: just before spawning, after spawning and after brooding. The reproductive effort for a standard sea star with an underwater mass of 10 g (equivalent to 8.2 cm in radius) was similar for both sexes (15.1 kJ in males and 12.2 kJ in females). However, the sexes differed in how energy was allocated for repro- duction. The energy loss due to gamete release was almost 4-fold greater for males (15.1 kJ) than females (4.1 kJ). The major reproductive expenditure in females came from maintenance costs dur- ing the prolonged brooding period (8.1 kJ). For the body wall and stomach, lipid, protein and energy contents were similar for males and females over the spawning and brooding periods. The ratio of males to females in the population was 1:1 in smaller size classes but was about 2:1 for individuals measuring >11 cm in radius. This is possibly explained by slower somatic growth of females due to the repeated use of energetic reserves and lack of feeding during the 5 to 6 mo brooding period. The replenishment of body wall carbohydrates in males during the winter (not observed in females) suggests that males feed during this period.