The weight of the heart in Callithrix Erxleben, 1777

The allometric relationship between the weight of the heart and the body measurements was analyzed in 31 primates of genus Callithrix (C. jacchus and C. penicillata). The data were analyzed after logarithmic transformation using the model: Ln Y = Ln a + (b) Ln X. We compared with the t-test the slopes of the males and females and the slopes of the C. Jacchus and C. penicillata. Positive allometry was found to the weight of the heart in relation to the body weight (except to females of C. penicillata = isometry) and to sitting height in females of C. jacchus and males of C. penicillata. The relationship of the weight of the heart with the sitting height was isometric in males of C. jacchus and negative in females of C. penicillata. We cannot reject the null hypothesis analyzing the differences between the slopes of males and females. Therefore, in these two species of Callithrix we accept the concept of monomorphism.