Should I stay or should I go?: Physiological, metabolic and biochemical consequences of voluntary emersion upon aquatic hypoxia in the scaleless fish Galaxias maculatus.

Hypoxia represents a significant challenge to most fish, forcing the development of behavioural, physiological and biochemical adaptations to survive. It has been previously shown that inanga (Galaxias maculatus) display a complex behavioural repertoire to escape aquatic hypoxia, finishing with the fish voluntarily emerging from the water and aerially respiring. In the present study we evaluated the physiological, metabolic and biochemical consequences of both aquatic hypoxia and emersion in inanga. Inanga successfully tolerated up to 6 h of aquatic hypoxia or emersion. Initially, this involved enhancing blood oxygen-carrying capacity, followed by the induction of anaerobic metabolism. Only minor changes were noted between emersed fish and those maintained in aquatic hypoxia, with the latter group displaying a higher mean cell haemoglobin content and a reduced haematocrit after 6 h. Calculations suggest that inanga exposed to both aquatic hypoxia and air reduced oxygen uptake and also increased anaerobic contribution to meet energy demands, but the extent of these changes was small compared with hypoxia-tolerant fish species. Overall, these findings add to previous studies suggesting that inanga are relatively poorly adapted to survive aquatic hypoxia.

Inflammation of the bronchi in broiler chickens, associated with barn dust and the influence of barn temperature.

Broiler chickens were raised in separate rooms kept at temperatures of either 27 C or 16 C from 28 through 39 days of age. At the high temperature mouth breathing was recorded, but it was absent at the lower temperature. The number of dust particles in the air was greater in the warm rooms. More than 50% of the chickens in warm rooms had microscopic lesions in the bronchi of their lungs, whereas fewer than 5% of chickens in cold rooms had such lesions. Large dust particles were visible in some of the lesions. It was postulated that the increased incidence of lung lesions in chickens from warm rooms was due to mouth breathing rather than the higher dust levels in the air of these rooms.

Mouth breathing in chickens under rebreathing conditions, cervical vagotomy of heat load.

By recording the lower beak movement, open-mouth breathing was monitored in adult hens restrained in a supine position with the cannulated trachea under rebreathing conditions, bilateral cervical vagotomy or heat load. Tidal volume and respiratory carbon-dioxide and oxygen contents were recorded simultaneously. The beak movement can be a significant indication of hypercapnia and/or increase in respiratory CO2 content, but not of hypoxia or decrease in respiratory O2 content. Vagotomy causes big oscillatory movements of the beak, which do not mainly depend on hypercapnic hypoxia induced by the vagotomy. If the dysfunction of the vagus is aggravated progressively, it will be unable for the pattern and amplitude of beak movement to be any differential indication of this dysfunction from hypercapnia and/or increase in respiratory CO2 content seen at respiratory failure. Two patterns of beak movement are noticed. One appears at an early stage of beak movement and at a certain direct level superimposed with or without small beak-oscillation. The other indicates a bigger oscillatory beak movement than the former. This oscillatory movement is synchronous with the inspiration after vagotomy and hypercapnia. This is the case with hyperthermia at a remarkably high breathing frequency. The amplitude of beak movement is not always proportional to the tidal volume. The onset and end of inspiration cannot precisely be indicated by those of a beak movement.