Relationships between body weight and other morphological traits in young sea cucumbers Apostichopus japonicas

Abstract

Correlation, multiple regression, and path analyses were used to investigate the relationships between body weight and three other morphological traits in juvenile Japanese sea cucumbers Apostichopus japonicus. We measured live body weight (BW), body length (BL), numbers of papillae (NP), and numbers of tube feet (NF) at 60, 80, 100, and 130 days post-hatching (dph). We calculated path correlation coefficients, correlation indices (R2), and coefficients of determination with BW as the dependent variable and the other morphological traits as independent variables. The coefficient of variation for BW was high across all age groups, and all measured morphological traits were significantly correlated (P < 0.01). BL had the greatest direct effect on BW across all age groups (60 dph, 0.526; 80 dph, 0.404; 100 dph, 0.620; and 130 dph, 0.681), while NF had the greatest indirect effect on BW across all age groups (60 dph, 0.528; 80 dph, 0.452; 100 dph, 0.666; and 130 dph, 0.603). Regression analyses between morphological traits and BW indicated that R2 was greater than 0.85 only in the 100-dph specimens. The indirect effects of the other measured morphological traits on BW were age-dependent. The optimal regression equations, as determined with stepwise regression, were, for 60-dph specimens: BW60 =10 (-3.04+0.092BL+0.014NP+0.014NF) (R2 =0.632); for 80-dph specimens: BW80 =10 (- 3.035+0.056BL+0.017NP+0.02NF) (R2 =0.686); for 100-dph specimens: BW100 =10 (- 3.742+0.069BL+0. 633 × lg (NP)+0. 464 × lg (NF)) (R2 =0.893); and for 130-dph specimens: BW130 =10 (- 2.472+0.065BL+0.012NP) (R2 =0.774). Our work clarified the correlation between various morphological traits and body weight of a commercially-important sea cucumber species (A. japonicus). Our predictive models for body weight might be useful for the aquaculture and selective breeding of A. japonicus. These models might also provide theoretical support for the indirect selection of traits that are difficult to select directly.