Abstract

Broodstock of North Chilean scallops Argopecten purpuratus were transferred from Tongoy (30°16?S, 71°32?W) to Dichato (36°32?S, 72°57?W), Chile, to be conditioned in a hatchery. The scallops were subjected to four different microalgal feeding treatments for 45 d. The feeding treatments were as follows: (1) equal parts of Isochrysis galbana and Dunaliella tertiolecta, (2) equal parts of I. galbana, Chaetoceros gracilis, and D. tertiolecta, (3) equal parts of I. galbana and C. gracilis, and (4) equal parts of C. gracilis and D. tertiolecta. All microalgae were collected in the exponential phase of growth (feed quantities, 1-3 × 105 cells/mL) in the hatchery. One group of scallops kept in "lanterns" in the sea served as a control. After 20 and 45 d of conditioning, gonad samples were taken from both immature and mature scallops (distinguished by coloring) from the treatment and control groups for biochemical analysis. Higher-molecular-weight polypeptides (72-89 kilodaltons [kDa] in the treatment groups and 69-107 kDa in the control group) were found more frequently in mature than in immature scallops. Moreover, a greater amount of polypeptides of a higher total molecular weight was observed in mature gonads. Polypeptide quality was unaffected by treatment but differed from that of scallops in the control group. Polypeptides of specific molecular weights in each maturity stage were detected. Although the quantity of total lipid was high in both treatment and control scallops, qualitative and quantitative differences in several fatty acids were observed. The presence of 20:5, 22:6, and 18:3 (where the number before the colon is the number of carbon atoms and the number after the colon is the number of double bonds) shows that the development of female gonads was good when the scallops were fed I. galbana and C. gracilis. Female gonad development was similar in scallops fed D. tertiolecta and C. gracilis.