Abstract
The yellow drum Nibea albiflora is a marine fish of great economic value in China. Despite efforts to improve yields, aquaculture of this species has been hindered by increases in winter-related mortalities associated with cold temperatures and associated natural fasting periods. To better understand the molecular mechanisms that regulate stress responses in yellow drum during periods of cold and starvation, the effect of these stresses on the liver was investigated by performing comparative analyses among fish subjected to different temperatures and feeding strategies. The experiment lasted for 22 d and involved 4 groups: one fed group (control) and one fasted group at 16°C, and one fed group and one fasted group at 8°C. Our results showed that all stress-treated groups exhibited body weight loss during the experiment, demonstrating that both cold stress and fasting caused growth inhibition, but only the fish in the fasted group at 16°C showed a loss in the liver/body ratio, suggesting that starvation can cause mass loss in the liver while cold stress can result in mass loss in both liver and other tissues. Histological alterations were observed in the liver cells from stress-treated groups, also indicating mass loss in the liver during cold stress and starvation. Transcriptomic analysis showed that genes related to the metabolism of carbohydrates, lipids and amino acids were the most enriched differentially expressed genes during the challenge conditions. These findings can help reveal molecular mechanisms regulating the stress responses of yellow drum exposed to cold and starvation.
Highlights
Winter mortalities have been reported in a large number of fish species and have resulted in severe economic losses, especially in regions and countries that are dependent on aquaculture (Kirjasniemi & Valtonen 1997, Hurst 2007, Ibarz et al 2010, Zhang et al 2019)
Huth & Place (2013) generated a reference transcriptome of emerald rockfish Trematomus bernacchii gill tissue and found that many genes associated with metabolism were up-regulated in response to cold stress
We found that low temperature and starvation significantly affected the growth of yellow drum (Fig. 1), which is consistent with previous findings from studies conducted on black rockfish Sebastes melanops (Boehlert & Yoklavich 1983) and sea bass Dicentrarchus labrax (Pastoureaud 1991)
Summary
Winter mortalities (those associated with low temperatures) have been reported in a large number of fish species and have resulted in severe economic losses, especially in regions and countries that are dependent on aquaculture (Kirjasniemi & Valtonen 1997, Hurst 2007, Ibarz et al 2010, Zhang et al 2019). This problem is especially critical for species cultured in net cages or ponds, where water temperatures are affected by weather and fish are Publisher: Inter-Research · www.int-res.com. A transcriptomic study on the large yellow croaker Larimichthys crocea showed that pathways involved in type I fatty acid synthesis, β-oxidation, polyunsaturated fatty acid synthesis, oxidative phosphorylation and molecular chaperones may take part in cold resistance (Zhang et al 2019). Bilyk & Cheng (2013) studied the transcriptome of the bald notothen Pagothenia borchgrevinki and found that genes associated with ubiquitin-protein ligase activity, protein ubiquitination and protein binding may play essential roles in cold temperature functioning
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