Genetic parameter estimation of tolerance traits for ammonia‑nitrogen and nitrite‑nitrogen in Urechis unicinctus

Abstract

The echiura worm, Urechis unicinctus, is an aquatic germplasm resource with high economic value in China and exhibits a high degree of nutritional and medicinal value. However, the limited exchange of water resources, bait residues, and accumulation of metabolic wastes in high-density intensive aquaculture make it difficult to accurately regulate the concentration of inorganic nitrogen in the environment, resulting in huge economic losses for the U. unicinctus farming industry. In this study, 20 full-sib families were used to investigate the genetic parameters of U. unicinctus under two inorganic nitrogen stress conditions: ammonia‑nitrogen and nitrite‑nitrogen. The 72-h semi-lethal concentrations of U. unicinctus under the two inorganic nitrogen stresses were calculated to be 1.39 g/L and 1.94 g/L, respectively. The estimated heritability for ammonia‑nitrogen and nitrite‑nitrogen tolerances were 0.21 ± 0.08 and 0.66 ± 0.18, which were medium to high levels of heritability. The genetic and phenotypic correlation coefficients between inorganic nitrogen tolerance and body weight ranged from 0.02 ± 0.30–0.80 ± 0.08 and 0.42 ± 0.07–0.49 ± 0.04, while Pearson correlation coefficients were 0.38 and 0.58 (P < 0.01), respectively. These results indicate that selective breeding has great potential for enhancing the inorganic nitrogen tolerance traits of U. unicinctus, while body weight can be used for indirect selection of the ammonia‑nitrogen tolerance trait. The results provide valuable information for the cultivation of new high-yield and stress-resistant varieties of U. unicinctus.