Fig. 1. Experimental control of animal and cardiac growth in adult zebrafish. (A) Representative images of hearts collected from animals maintained for 14 days in conditions for rapid growth (RG), slow growth (SG) or to maintain size (MS). Hearts in images may be missing some atrial tissue lost during tissue collection. a, atrium; b, bulbous arteriosus v, ventricle. (B) Quantification of animal mass of RG, SG and MS fish. RG fish had a much higher increase in body mass from day 0 than their SG clutchmates at day 14, whereas MS fish maintained mass (^*P<0.001, t-test, significantly different from day 0). The numbers of animals per group are shown in parentheses. (C) Quantification of ventricular size in RG, SG and MS fish. Ventricles in the RG group showed much greater size increases than those of SG clutchmates at day 14, while ventricular size remained stable in MS fish (^*P<0.005, t-test, significantly different from day 0).