Exposure to acute severe hypoxia leads to increased urea loss and disruptions in acid-base and ionoregulatory balance in dogfish sharks (Squalus acanthias)

Alex M. Zimmer, Chris M. Wood

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

The effects of acute moderate (20% air O2 saturation; 6-h exposure) and severe (5% air O2 saturation; 4-h exposure) hypoxia on N-waste, acid-base, and ion balance in dogfish sharks (Squalus acanthias suckleyi) were evaluated. We predicted that the synthesis and/or retention of urea, which are active processes, would be inhibited by hypoxia. Exposure to moderate hypoxia had negligible effects on N-waste fluxes or systemic physiology, except for a modest rise in plasma lactate. Exposure to severe hypoxia led to a significant increase in urea excretion (Jurea), while plasma, liver, and muscle urea concentrations were unchanged, suggesting a loss of urea retention. Ammonia excretion (Jamm) was elevated during normoxic recovery. Moreover, severe hypoxia led to disruptions in acid-base balance, indicated by a large increase in plasma [lactate] and substantial decreases in arterial pHa and plasma [HCO3-]a, as well as loss of ionic homeostasis, indicated by increases in plasma [Mg2+ ], [Ca2+ ], and [Na+]. We suggest that severe hypoxia in dogfish sharks leads to a reduction in active gill homeostatic processes, such as urea retention, acid-base regulation and ionoregulation, and/or an osmoregulatory compromise due to increased functional gill surface area. Overall, the results provide a comprehensive picture of the physiological responses to a severe degree of hypoxia in an ancient fish species.

Original languageEnglish (US)
Pages (from-to)623-639
Number of pages17
JournalPhysiological and Biochemical Zoology
Volume87
Issue number5
DOIs
StatePublished - Sep 1 2014

ASJC Scopus subject areas

  • Physiology
  • Biochemistry
  • Animal Science and Zoology

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