Sloman Katherine A, Sloman Richard D, De Boeck Gudrun, Scott Graham R, Iftikar Fathima I, Wood Chris M, Almeida-Val Vera M F, Val Adalberto L
School of Marine Sciences and Engineering, University of Plymouth, Devon, United Kingdom.
Physiol Biochem Zool. 2009 Nov-Dec;82(6):625-34. doi: 10.1086/605936.
Synchronized air breathing may have evolved as a way of minimizing the predation risk known to be associated with air breathing in fish. Little is known about how the size of individuals affects synchronized air breathing and whether some individuals are required to surface earlier than necessary in support of conspecifics, while others delay air intake. Here, the air-breathing behavior of Hoplosternum littorale held in groups or in isolation was investigated in relation to body mass, oxygen tensions, and a variety of other physiological parameters (plasma lactate, hepatic glycogen, hematocrit, hemoglobin, and size of heart, branchial basket, liver, and air-breathing organ [ABO]). A mass-specific relationship with oxygen tension of first surfacing was seen when fish were held in isolation; smaller individuals surfaced at higher oxygen tensions. However, this relationship was lost when the same individuals were held in social groups of four, where synchronous air breathing was observed. In isolation, 62% of fish first surfaced at an oxygen tension lower than the calculated P(crit) (8.13 kPa), but in the group environment this was reduced to 38% of individuals. Higher oxygen tensions at first surfacing in the group environment were related to higher levels of activity rather than any of the physiological parameters measured. In fish held in isolation but denied access to the water surface for 12 h before behavioral testing, there was no mass-specific relationship with oxygen tension at first surfacing. Larger individuals with a greater capacity to store air in their ABOs may, therefore, remain in hypoxic waters for longer periods than smaller individuals when held in isolation unless prior access to the air is prevented. This study highlights how social interaction can affect air-breathing behaviors and the importance of considering both behavioral and physiological responses of fish to hypoxia to understand the survival mechanisms they employ.
同步空气呼吸可能是作为一种将已知与鱼类空气呼吸相关的捕食风险降至最低的方式而进化出来的。关于个体大小如何影响同步空气呼吸，以及是否有些个体需要比必要时间更早浮出水面以支持同种个体，而其他个体则延迟空气吸入，目前所知甚少。在此，研究了群居或单独饲养的霍氏真唇脂鲤的空气呼吸行为与体重、氧张力以及各种其他生理参数（血浆乳酸、肝糖原、血细胞比容、血红蛋白以及心脏、鳃篮、肝脏和空气呼吸器官[ABO]的大小）之间的关系。当鱼单独饲养时，首次浮出水面时与氧张力存在质量特异性关系；较小的个体在较高氧张力时浮出水面。然而，当相同个体饲养在每组四条鱼的社会群体中时，这种关系消失了，在该群体中观察到了同步空气呼吸。单独饲养时，62%的鱼首次浮出水面时的氧张力低于计算出的临界压力（P(crit)，8.13千帕），但在群体环境中，这一比例降至个体的38%。在群体环境中首次浮出水面时较高的氧张力与较高的活动水平有关，而不是与所测量的任何生理参数有关。在单独饲养但在行为测试前12小时无法接触水面的鱼中，首次浮出水面时与氧张力不存在质量特异性关系。因此，在单独饲养时，具有更大能力在其ABO中储存空气的较大个体可能比较小个体在缺氧水域中停留更长时间，除非事先阻止其接触空气。这项研究突出了社会互动如何影响空气呼吸行为，以及考虑鱼类对缺氧的行为和生理反应以了解它们所采用的生存机制的重要性。
