The impairment of continuous malnutrition on larval fish swimming performance at the mouth-opening stage

Nutritional status at the mouth-opening stage is critical for fish development and fitness due to the nutritional strategy switch from endogenous to exogenous feeding. In the present study, we explored the impairments of continuous malnutrition on larval development and swimming performance. Results showed that larval survival and body growth were reduced from 5 days post fertilization (dpf) to 14 dpf under malnutrition, and the swimming performance of moved distance, velocity, motility, maximum duration of movement, highly mobile and mobile states were significantly suppressed. As to the transcripts analyses, the mRNA expression of gh1 distinctly downregulated with the compensatory effect of increased expression of ghrb, and the ghrelin expression responded fast with upregulation to the malnutrition. The downregulated mRNA expressions of neurodevelopment related genes (nes, neurog1, gap43, syn2a, manf, hirip3) meant the disturbed neuronal functions that account for the swimming response and suggest the vulnerable molecular marker of Neurog1 responsible for the alternation of swimming behavior. And the upregulated mRNA expressions of apoptotic genes (bax, casp3, casp9) signified cellular injury in the malnutrition-treated larvae. Besides, the decreased mitochondrial DNA copy number indicated the mitochondrial dysfunction, which might be responsible for the reduced larval development and swimming performance that link to the potential chronic impairments throughout the lifespan. Collectively, current works discussed the specific impairments of malnutrition on swimming capability and its potentially chronic adverseness to remind the larval management in the aquaculture industry.