Warmwater Aquaculture Research Unit, United States Department of Agriculture, Agricultural Research Service, Thad Cochran National Warmwater Aquaculture Center, Post Office Box 38, Stoneville, MS, 38776, USA.
Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Mail Stop 9690, Mississippi, MS, 39762, USA.
J Comp Physiol B. 2023 Dec;193(6):631-645. doi: 10.1007/s00360-023-01521-5. Epub 2023 Oct 12.
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 O/L, channel catfish have a 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 O/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 h), venous PO was significantly lower within 6 h and was coupled with an increase of hematocrit and decrease of blood osmolality, yet all responses reversed within 12 h 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.
商业养殖的斑点叉尾鮰（Ictalurus punctatus）生活在浅池塘中，其溶解氧浓度每天都在经历从过饱和到严重缺氧的循环变化。一旦每日最低溶解氧浓度降至 3.0mg O/L 以下，斑点叉尾鮰的食欲就会下降，导致生长速度减缓。在其他鱼类中，促肾上腺皮质释放因子 (CRF) 和尾加压素 I (UI) 等神经肽的上调被认为是在环境胁迫因子被检测到时，启动负责降低食欲的机制的原因。将 27°C 下饲养在水族箱中的斑点叉尾鮰暴露于不同持续时间和模式的缺氧环境（1.75±0.07mg O/L）中，以评估其对缺氧的潜在生理反应，并确定下丘脑的 CRF 和 UI 是否是导致斑点叉尾鮰缺氧性厌食的原因。在短暂缺氧（12h）暴露期间，静脉 PO 在 6h 内显著降低，并伴随着红细胞压积的增加和血液渗透压的降低，但所有反应在恢复到常氧后 12h 内都得到逆转。当这种缺氧和常氧的模式重复 5 天时，这些生理反应每天都在重复。延长的缺氧期（5 天）导致类似的血液学反应，但在缺氧暴露期间并未恢复到基线值。本研究未发现下丘脑 CRF 和 UI 转录在缺氧挑战期间发生显著变化，但确实确定了多种生理适应反应，这些反应共同作用，减轻了斑点叉尾鮰实验诱导性缺氧的严重程度。
