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Marine Mammal Physiology: Requisites for Ocean Living
osmoregulation, their longer-term responses to guard against excess salt environments are
not well-defined, although the many systems must have evolved to allow for their tolerance
to an aquatic lifestyle of varying osmotic habitats. While many challenges exist that limit
the capacity to fully elucidate many unresolved questions of the osmoregulatory abilities
of marine mammals, further investigation in this area is fully warranted and encouraged.
Glossary
Aldosterone: A steroid hormone secreted by the adrenal cortex that primarily regulates
the reabsorption of Na + in the kidney and colon.
Angiotensin II: An eight amino acid peptide cleaved from angiotensin I by angiotensinconverting enzyme that primarily regulates blood pressure and the adrenal secretion of aldosterone.
Angiotensinogen: An alpha-2 globulin produced by the liver and serves as the precursor
protein for the formation of angiotensin I.
Arginine vasopressin: A nine amino acid peptide secreted by neurohypophysis (posterior pituitary) that primarily regulates the reabsorption of free water in the collecting duct of the renal tubule in mammals.
Atrial natriuretic peptide: A 28 amino acid peptide produced by the atrium that functions primarily to induce urinary Na + excretion (natriuresis).
Concentration gradient: From the compartment with the lower concentration of dissolved particles to the compartment with the greater concentration.
Countercurrent heat exchanger: A design in which fluids at sufficiently different temperatures flow closely in opposite directions to facilitate heat exchange down the
temperature gradient.
Diuresis: Increased urine output.
Glomerular filtration rate: The rate at which a volume of blood passes through the
glomeruli.
Hemodilution: The dilution or decreased concentration of the plasma and its constituents.
Hyperosmotic: Increased osmotic content of a solution.
Instantaneous dilution space: The calculated estimate of the space or volume into which a
particle would be diluted at the moment the particle is introduced into that space.
Defined by the y-intercept of a multi-point regression during isotopic dilution studies.
Isotopic dilution: A technique to study the kinetics of an isotopically labeled molecule that
emulates the endogenous, unlabeled molecule. The rate at which an isotope is diluted
in a compartment estimates the turnover of the endogenous, unlabeled molecule.
Mariposia: The voluntary and deliberate consumption of seawater.
Metabolic water: The water produced during substrate-level metabolism.
Milieu interieur: The internal environment, in reference to Claude Bernard’s description
of the physiological control of homeostasis.
Osmotic pressure: The pressure produced by the concentration of dissolved particles in
solution.
Pre-formed water: The water that occurs naturally in food, for example.
Relative medullary thickness: The thickness of the medulla relative to the size of the kidney.
Reniculi: Refers to a specific design of the mammalian kidney in which the entire kidney is compartmentalized into discrete, independent functional units (cortex and
medulla) that empty into a common renal pelvis. Externally the kidney appears
lobulated where each lobe in cetaceans, pinnipeds, otters, and polar bears is a reniculus and collectively the kidney is referred as multireniculate.
Marine Mammal Physiology: Requisites for Ocean Living
osmoregulation, their longer-term responses to guard against excess salt environments are
not well-defined, although the many systems must have evolved to allow for their tolerance
to an aquatic lifestyle of varying osmotic habitats. While many challenges exist that limit
the capacity to fully elucidate many unresolved questions of the osmoregulatory abilities
of marine mammals, further investigation in this area is fully warranted and encouraged.
Glossary
Aldosterone: A steroid hormone secreted by the adrenal cortex that primarily regulates
the reabsorption of Na + in the kidney and colon.
Angiotensin II: An eight amino acid peptide cleaved from angiotensin I by angiotensinconverting enzyme that primarily regulates blood pressure and the adrenal secretion of aldosterone.
Angiotensinogen: An alpha-2 globulin produced by the liver and serves as the precursor
protein for the formation of angiotensin I.
Arginine vasopressin: A nine amino acid peptide secreted by neurohypophysis (posterior pituitary) that primarily regulates the reabsorption of free water in the collecting duct of the renal tubule in mammals.
Atrial natriuretic peptide: A 28 amino acid peptide produced by the atrium that functions primarily to induce urinary Na + excretion (natriuresis).
Concentration gradient: From the compartment with the lower concentration of dissolved particles to the compartment with the greater concentration.
Countercurrent heat exchanger: A design in which fluids at sufficiently different temperatures flow closely in opposite directions to facilitate heat exchange down the
temperature gradient.
Diuresis: Increased urine output.
Glomerular filtration rate: The rate at which a volume of blood passes through the
glomeruli.
Hemodilution: The dilution or decreased concentration of the plasma and its constituents.
Hyperosmotic: Increased osmotic content of a solution.
Instantaneous dilution space: The calculated estimate of the space or volume into which a
particle would be diluted at the moment the particle is introduced into that space.
Defined by the y-intercept of a multi-point regression during isotopic dilution studies.
Isotopic dilution: A technique to study the kinetics of an isotopically labeled molecule that
emulates the endogenous, unlabeled molecule. The rate at which an isotope is diluted
in a compartment estimates the turnover of the endogenous, unlabeled molecule.
Mariposia: The voluntary and deliberate consumption of seawater.
Metabolic water: The water produced during substrate-level metabolism.
Milieu interieur: The internal environment, in reference to Claude Bernard’s description
of the physiological control of homeostasis.
Osmotic pressure: The pressure produced by the concentration of dissolved particles in
solution.
Pre-formed water: The water that occurs naturally in food, for example.
Relative medullary thickness: The thickness of the medulla relative to the size of the kidney.
Reniculi: Refers to a specific design of the mammalian kidney in which the entire kidney is compartmentalized into discrete, independent functional units (cortex and
medulla) that empty into a common renal pelvis. Externally the kidney appears
lobulated where each lobe in cetaceans, pinnipeds, otters, and polar bears is a reniculus and collectively the kidney is referred as multireniculate.