Osmo-respiratory compromise in the mosshead sculpin (Clinocottus globiceps): effects of temperature, hypoxia, and re-oxygenation on rates of diffusive water flux and oxygen uptake.

In nature, mosshead sculpins (Clinocottus globiceps) are challenged by fluctuations in temperature and oxygen levels in their environment. However, it is unclear how mosshead sculpins modulate the permeability of their branchial epithelia to water and O in response to temperature or hypoxia stress. Acute decrease in temperature from 13 to 6 C reduced diffusive water flux rate by 22% and ṀO by 51%, whereas acute increase in temperature from 13 to 25 C increased diffusive water flux rate by 217% and ṀO by 140%, yielding overall Q values of 2.

Gill surface area allometry does not constrain the body mass scaling of maximum oxygen uptake rate in the tidepool sculpin, Oligocottus maculosus.

The gill oxygen limitation hypothesis (GOLH) suggests that hypometric scaling of metabolic rate in fishes is a consequence of oxygen supply constraints imposed by the mismatched growth rates of gill surface area (a two-dimensional surface) and body mass (a three-dimensional volume). GOLH may, therefore, explain the size-dependent spatial distribution of fish in temperature- and oxygen-variable environments through size-dependent respiratory capacity, but this question is unstudied. We tested GOLH in the tidepool sculpin, Oligocottus maculosus, a species in which body mass decreases with increasing temperature- and oxygen-variability in the intertidal, a pattern consistent with GOLH.

Ventilatory responses of the clown knifefish, Chitala ornata, to hypercarbia and hypercapnia.

The aim of the present study was to determine the roles of externally versus internally oriented CO/H-sensitive chemoreceptors in promoting cardiorespiratory responses to environmental hypercarbia in the facultative air-breathing fish, Chitala ornata (the clown knifefish). Fish were exposed to environmental acidosis (pH ~ 6.0) or hypercarbia (≈ 30 torr PCO) that produced changes in water pH equal to the pH levels of the acidotic water to distinguish the relative roles of CO versus H.

Development of Dive Capacity in Northern Elephant Seals (Mirounga angustirostris): Reduced Body Reserves at Weaning Are Associated with Elevated Body Oxygen Stores during the Postweaning Fast.

Developmental increases in dive capacity have been reported in numerous species of air-breathing marine vertebrates. Previous studies in juvenile phocid seals suggest that increases in physiological dive capacity during the postweaning fast (PWF) are critical to support independent aquatic foraging. Although there is a strong relationship between size at weaning and PWF duration and body reserves at weaning vary considerably, few studies have considered whether such variation in body reserve magnitude promotes phenotypic modulation of dive capacity development during the PWF.

Metabolic responses to adrenocorticotropic hormone (ACTH) vary with life-history stage in adult male northern elephant seals.

Strong individual and life-history variation in serum glucocorticoids has been documented in many wildlife species. Less is known about variation in hypothalamic-pituitary-adrenal (HPA) axis responsiveness and its impact on metabolism. We challenged 18 free-ranging adult male northern elephant seals (NES) with an intramuscular injection of slow-release adrenocorticotropic hormone (ACTH) over 3 sample periods: early in the breeding season, after 70+ days of the breeding fast, and during peak molt.