Effect of hypoxia duration and pattern on channel catfish (Ictalurus punctatus) neuropeptide gene expression and hematology

Authors: Ott, Brian; Chisolm, Dakoda; GRIFFIN, MATT - Mississippi State University; Torrans, Eugene; ALLEN, PETER - Mississippi State University

Submitted to: Journal of Comparative Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2023
Publication Date: 10/10/2023
Citation: Ott, B.D., Chisolm, D.O., Griffin, M.J., Torrans, E.L., Allen, P.J. 2023. Effect of hypoxia duration and pattern on channel catfish (Ictalurus punctatus) neuropeptide gene expression and hematology. Journal of Comparative Physiology. 193:631-645. https://doi.org/10.1007/s00360-023-01521-5.
DOI: https://doi.org/10.1007/s00360-023-01521-5

Interpretive Summary: Commercial catfish ponds are dynamic environments that experience daily swings in dissolved oxygen concentration that can fall to lethal levels of hypoxia if supplemental aeration is not provided. Catfish respond by eating less feed the following day if dissolved oxygen falls lower than 3.0 mg O2/L, a process thought to be mediated by the neuropeptides corticotropin-releasing factor (CRF) and urotensin I (UI). USDA-ARS Warmwater Aquaculture Research Unit collaborated with Mississippi State University to measure the effect of different durations of hypoxia on gene expression of CRF and UI as well as other physiological parameters. A 12-hour exposure to hypoxia elicited a physiological response that was reversed within 12 hours of returning to normoxia. This response was mirrored by catfish that repeated this pattern cyclically for five days as well as those exposed to a prolonged (five day) period of hypoxia. Expression of the neuropeptides CRF and UI did not change during any of the hypoxia experiments performed here and suggests other factors regulate catfish appetite during hypoxia.

Technical Abstract: Commercial aquaculture production of channel catfish (Ictalurus punctatus) occurs in shallow ponds with daily cycling of dissolved oxygen concentration ranging from supersaturation to severe hypoxia. Once daily minimum dissolved oxygen concentration falls below 3.0 mg O2/L, channel catfish have reduced appetite, leading to reduced growth rates. In other fishes, upregulation of the neuropeptides corticotropin-releasing factor (CRF) and urotensin I (UI) have been implicated as initiating the mechanism responsible for decreasing appetite once an environmental stressor is detected. Channel catfish maintained at 27 °C in aquaria were subjected to varying durations and patterns of hypoxia (1.75 ± 0.07 mg O2/L) to evaluate underlying physiological responses to hypoxia and determine if hypothalamic CRF and UI are responsible for hypoxia-induced anorexia in channel catfish. During a short exposure to hypoxia (12 hours), venous PO2 was significantly lower within 6 hours and was coupled with an increase of hematocrit and decrease of blood osmolality, yet all responses reversed within 12 hours after returning to normoxia. When this pattern of hypoxia and normoxia was repeated cyclically for 5 days, these physiological responses repeated daily. Extended periods of hypoxia (5 days) resulted in similar hematological responses, which did not recover to baseline values during the hypoxia exposure. This study did not find a significant change in hypothalamic transcription of CRF and UI during hypoxia challenges but did identify multiple physiological adaptive responses that work together to reduce the severity of experimentally-induced hypoxia in channel catfish.