MORPHOMETRIC AND BIOCHEMICAL-CHANGES IN 2 AGE CLASSES OF THE TROPICALSCALLOP, ARGOPECTEN-VENTRICOSUS, UNDER LABORATORY CONDITIONS

A laboratory study was carried out in Lewes, Delaware, U.S.A., to (a) compare, through controlled laboratory experiments, morphometric and b iochemical changes in the digestive gland, adductor muscle, mantle-gil ls and gonad of eight- and 16-month-old tropical scallops Argopecten v entricosus (Sowerby, 1842), and (b) determine the effect of age on the content of carbohydrates and protein in the gonad. The gonadal index of eight- and 16-month-old scallops declined through the first 40 days of the experiment. Also, carbohydrate content declined significantly in the digestive gland and adductor muscle. This suggests energy was u sed either for somatic growth and/or reproduction. Some carbohydrates could have been used for reproduction, but were not transferred direct ly to the gonad before day 40. Adductor muscle dry weight and protein content of eight- and 16-month-old scallops increased for the first 40 days of the experiment, then declined around day 55. Simultaneously, around day 55, both groups of scallops had noticeable increases in gon adal dry weight and protein. This suggests that the adductor muscle st ores protein during the first 40 days, then protein catabolism in the adductor muscle contributes to reproductive activity of the gonad. Pro tein content in the mantle was higher in eight- than in 16-month-old s callops. This suggests mantle-gill protein provides better support for somatic growth in eight- than in 16-month old tropical scallops. The laboratory study in Delaware suggests that one-year-old scallops will spawn in the field in March.