Hormones and osmoregulation in marine birds

Abstract

The neural and hormonal mechanisms responsible for the control of electrolyte excretion by the nasal glands of marine birds are outlined. At least three stages in the sequence of events leading to excretion, and therefore successful adaption to the marine environment, are sensitive to the presence of environmental pollutants and pathogens. The initiation and continuation of nasal gland function depends on the development of increased rates of Na + and water transfer across the small intestinal mucosa. This adaptive response is sensitive to the presence of crude oil and crude oil distillation fractions and ingestion of these substances may prevent the development of increased rates of intestinal transfer. Degradation products of DDT may also inhibit the normal pattern of adrenal steroid biosynthesis and thus lead to impaired nasal gland function. Ingestion of the neurotoxin produced by Clostridium botulinum inhibits the release of acetylcholine and therefore blocks the essential visceral motor impulses to the nasal gland function. Thus, when intoxicated birds are fed either hypertonic saline or “pothole” drinking water derived from many prairie sloughs and lakes, they show higher rates of mortality than do similarly intoxicated birds given fresh drinking water.