Effect of N-ethyl-N-nitrosourea (ENU) toxicity on early development of Asian catfish Clarias batrachus (Linnaeus, 1758)

Abstract

The chemical mutagenesis is an efficient way to produce new mutants for future genetic improvement in aquaculture species. Although these chemicals also induce toxicity. N-ethyl-N-nitrosourea (ENU) is an alkylating agent (SN1 type) and used as a chemical mutagen to study development and physiology of fishes. Although the concentration of ENU used in common protocols to mutagenize fish is limited by its toxicity in literature. In this article, an attempt has been made to identify the ENU associated toxicity to understand the fertilization, hatchability, survivability, and early developmental deformity to provide a baseline data. The fertilization and hatching rate decreased with increased concentration of ENU in Clarias batrachus. The LC50 value was observed as 5.7 (6.1, 5.3). The incubation periods were extended in the embryonic development with increasing concentrations of ENU. The observed deformities included unfertilized eggs, disintegrated yolk and blastodisc, retention of chorion, lordosis, retarded larvae and bent tail larvae, larva with no eye formation and larva with cardiac abnormality pooled blood in brain with tube heart. These embryos with deformities usually survived until hatching; however, embryos with more severe malformations died without hatching.