Adaptation mechanism of the adult zebrafish respiratory organ to endurance training

Abstract

In order to study the adaptation scope of the fish respiratory organ and the O 2 metabolism due to endurance training, we subjected adult zebrafish (Danio rerio) to endurance exercise for 5 weeks. After the training period, the swimmer group showed a significant increase in swimming performance, body weight and length. In scanning electron microscopy of the gills, the average length of centrally located primary filaments appeared significantly longer in the swimmer than in the non-trained control group (+6.1%, 1639 μm vs. 1545 μm, p = 0.00043) and the average number of secondary filaments increased significantly (+7.7%, 49.27 vs. 45.73, p = 9e-09). Micro-computed tomography indicated a significant increase in the gill volume (p = 0.048) by 11.8% from 0.490 mm 3 to 0.549 mm 3. The space-filling complexity dropped significantly (p = 0.0088) by 8.2% from 38.8% to 35.9%., i.e. making the gills of the swimmers less compact. Respirometry after 5 weeks showed a significantly higher oxygen consumption (+30.4%, p = 0.0081) of trained fish during exercise compared to controls. Scanning electron microscopy revealed different stages of new secondary filament budding, which happened at the tip of the primary lamellae. Using BrdU we could confirm that the growth of the secondary filaments took place mainly in the distal half and the tip and for primary filaments mainly at the tip. We conclude that the zebrafish respiratory organunlike the mammalian lung-has a high plasticity, and after endurance training increases its volume and changes its structure in order to facilitate O 2 uptake.

Plastic loss of motile cilia in the gills of Polypterus in response to high CO2 or terrestrial environments

“…This is the first report of ciliated cells of the internal gills in a ray‐finned fish (Actinopterygii). Although several SEM images of gills have been presented in model organisms such as zebrafish ( Danio rerio ) and medaka ( Oryzias latipes ) (Leguen, 2018 ; Messerli et al, 2020 ), the cilia were not described in these studies. Cilia were not found in gills and/or specialized respiratory organs in walking catfish (Clariidae) nor in mangrove killifish ( K. marmoratus ), which are also adapted to the terrestrial environment in a manner similar to Polypterus (Maina, 2018 ; Ong et al, 2007 ).…”

Loss of developmentally derived Irf8+ macrophages promotes hyperinnervation and arrhythmia in the adult zebrafish heart

“…To determine if irf8 mutants were susceptible to developing arrhythmias, we challenged the fish with a swim tunnel exercise assay and immediately followed the physiological challenge with an ECG (Figure 2A-B). Swim tunnels are enclosed chambers with continuous laminar water flow at controllable flow rates that provide important information on bioenergetics, biomechanics, and respirometry 46,47 . For the swim assay, we designed a custom, rack-compatible swim tunnel that achieved laminar flow, had adjustable flow rate, and was equipped with a digital flow meter for monitoring (See 'Methods').…”

Rapid altitude displacement induce zebrafish appearing acute high altitude illness symptoms

“…Additionally, the actions and functions of macrophages and neutrophils play a crucial role in lung inflammatory diseases and exhibit remarkable similarities between humans and zebrafish. A key experimental benefit is the direct exposure of gill tissue to ambient water, which enables direct targeting with waterborne substances without invasive procedures [ [26] , [27] , [28] ]. At the same time, zebrafish is also a classic animal model for studying blood-brain barrier integrity and local pathology ( e.g.…”