Heritability estimates for growth and salt-resistance traits of Urechis unicinctus

Abstract

The echiura worm Urechis unicinctus has high economic and nutritional value and has emerged as a promising species for aquaculture development. Selective breeding plays a crucial role in enhancing growth and production, and estimating the narrow-sense heritability is the initial step in implementing selective breeding programs. To assess the proportion of additive genetic variation in growh and salt-tolerance traits, this study used 20 families to measure genetic parameters for growth traits at the 100-day and 200-day stages (weight, length, and width) and two salinity conditions (high and low salt). For growth traits, moderate to high heritability estimates were observed at both the 100-day and 200-day stages, ranging from 0.24 ± 0.08 (body width) to 0.42 ± 0.12 (body weight) and 0.40 ± 0.11 (body width) to 0.72 ± 0.16 (body weight), respectively. The genetic and phenotypic correlation coefficients between these traits were found to be intermediate to high across the two testing periods, and these results were supported by significant Pearson correlation (P < 0.01). Regarding salt-tolerance traits, different families exhibited varying survival times under salinity stress, indicating distinct viability responses. The heritability estimates for high-salt and low-salt tolerance were 0.73 ± 0.22 and 0.16 ± 0.06, respectively. The genetic correlation coefficients between salt tolerance and body weight were 0.39 ± 0.16 and 0.89 ± 0.05. Additionally, a positive Pearson correlation was observed between these traits (P < 0.01), suggesting the feasibility of indirect breeding. Overall, these findings indicate the presence of genetic variation in the growth and salt-tolerance traits of U. unicinctus and highlight the potential for genetic improvement through selective breeding techniques. The results provide valuable information to guide effective selection of U. unicinctus.