Water and Energy Flux in Elephant Seal Pups Fasting under Natural Conditions

Ortiz, Charles L.; Costa, Daniel P.; Bœuf, Burney J. Le

doi:10.1086/physzool.51.2.30157864

Cited by 231 publications

(181 citation statements)

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“…Mass gain during the nursing period averaged 4.39 kgrday and mean mass loss over the fast was 0.69 kgrday. Rates of mass gain and loss across suckling and fasting were similar to previously reported values, suggesting that experimental subjects were representative of typical seal Ž pups Ortiz et al, 1978Ortiz et al, , 1984Rea and Costa, . 1992 .…”

Section: ( ) 31 Mass and Extracellular¨olume Ecvsupporting

confidence: 86%

“…During the 4-week suckling period, pups nearly triple their mass and deposit a considerable amount of adipose tissue, increasing adipose composition from 9% of mass at birth to nearly 50% Ž of mass at weaning Ortiz et al, 1978;Rea and Costa, 1992;Kretzmann et al, 1993;Crocker, . 1995 .…”

Section: Discussionmentioning

confidence: 99%

“…stirostris completely abstain from food and water during periods of intense terrestrial activity and energy expenditure, and during postweaning de-Ž velopment Le Boeuf and Peterson, 1969;Ortiz et . al., 1978;Costa et al, 1986 .…”

Section: Northern Elephant Seals Mirounga Angu-mentioning

confidence: 99%

“…Ortiz et al, 1978;Castellini et al, 1987 . Significant reductions in both evaporative and urinary water loss help to maintain positive water balance Ž .…”

Section: Northern Elephant Seals Mirounga Angu-mentioning

confidence: 99%

“…Significant reductions in both evaporative and urinary water loss help to maintain positive water balance Ž . Ortiz et al, 1978 . Respiratory evaporative water loss is reduced by a combination of apneustic breathing and the presence of an exceptional Ž counter-current nasal heat-exchanger Huntley et .…”

Section: Northern Elephant Seals Mirounga Angu-mentioning

confidence: 99%

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Renal function in suckling and fasting pups of the northern elephant seal

Houser

Crocker

Webb

et al. 2001

Comparative Biochemistry and Physiology Part A: Molecular &

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Elephant seals fast for prolonged periods without access to water. This is made possible, in part, by reductions in urine production. However, the mechanisms involved in reducing urine production are not understood. In this study, Ž . Ž . glomerular filtration rate GFR was measured in five northern elephant seal pups Mirounga angustirostris via the inulin clearance technique. Measurements were made during day 9 and day 18᎐22 of nursing and the second and eighth week of the postweaning fast. Plasma aldosterone and cortisol concentrations, quantified by radioimmunoassay, were measured in eight other weanlings during the second and eighth week of the fast. Mean GFR was 79.3" 29.3 mlrmin during the early suckling period and 78.2" 17.1, 89.8" 52.7, and 80.4" 12.2 mlrmin during the late suckling, early fasting and late fasting periods, respectively. Differences between nursing and fasting were insignificant, possibly because reduced protein oxidation during suckling and rapid recruitment of protein for tissue synthesis obviated the need for postprandial hyperfiltration. Alternatively, maintenance of GFR during fasting may facilitate urea concentration by compensating for reductions in the fractional excretion of urea. It is further hypothesized that aldosterone is primarily responsible for mediating renal water reabsorption in this system. ᮊ

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Section: ( ) 31 Mass and Extracellular¨olume Ecvsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Northern Elephant Seals Mirounga Angu-mentioning

confidence: 99%

“…Ortiz et al, 1978;Castellini et al, 1987 . Significant reductions in both evaporative and urinary water loss help to maintain positive water balance Ž .…”

Section: Northern Elephant Seals Mirounga Angu-mentioning

confidence: 99%

Section: Northern Elephant Seals Mirounga Angu-mentioning

confidence: 99%

See 3 more Smart Citations

Renal function in suckling and fasting pups of the northern elephant seal

Houser

Crocker

Webb

et al. 2001

Comparative Biochemistry and Physiology Part A: Molecular &

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Osmoregulation by Vertebrates in Aquatic Environments

Lillywhite

Evans

2021

Encyclopedia of Life Sciences

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Because the salt concentration of body fluids in aquatic vertebrates differs from that of their environment, they face net influx or efflux of water and salt across their permeable skin or exposed membranes. In fishes, these diffusional movements of both salts and water largely involve the gills. Other vertebrates have less permeable body surfaces, but water and salts are gained in drinking that is incidental to eating prey, which also can be an important source of salt intake. Kidneys function importantly in freshwater fishes to remove excess water, and ions are actively transported inwards across gill tissue as well as acquired in food. Marine fishes tend to dehydrate in seawater, so they drink seawater to make up a water deficit and secrete excess salt across the gills. Marine elasmobranch fishes accumulate urea in body fluids to minimise the gradient for osmotic exchange and secrete excess ions via a specialised rectal gland that functions accessory to the kidney. In other vertebrates, inhabitants of fresh water must counteract a key problem of acquiring sufficient ions while excreting nitrogenous waste as ammonia or urea, whereas marine species must avoid excess salt intake while avoiding dehydration. Vertebrates without gills have evolved either extrarenal salt glands that excrete excess salt, or in the case of mammals, a specialised kidney that can excrete highly concentrated urine. Relatively few, non‐fish taxa drink seawater as a route for water gain, while most others have dependency on dietary, metabolic or free drinking water. Osmoregulation involves the maintenance of volume, distribution and ionic composition of body fluids in organisms. With the exception of hagfish, extant vertebrates maintain osmotic concentrations of body fluids at levels that are roughly one‐third that of seawater. Aquatic vertebrates living in fresh water must counteract excessive influx of water and losses of ions to the surrounding environment, whereas those living in marine environments tend to dehydrate and gain excess salt. Freshwater fishes eliminate excess water by means of producing a copious flow of dilute urine, while acquiring ions from surrounding water by transporter mechanisms located in the gills. Marine fishes acquire needed water by drinking seawater and excreting excess salt gained by diffusion and drinking by transport mechanisms in the gills. Marine vertebrates other than fishes and mammals have evolved extrarenal salt glands that excrete excess salts, and water is gained largely from dietary, metabolic and freshwater drinking sources. Marine mammals excrete salt loads and urea from kidneys that have effective concentrating abilities, while gaining water from diet and metabolism.

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Colony‐specific differences in decadal longitudinal body composition of a capital‐breeding marine top predator

Hanson

Smout

Moss

et al. 2019

Aquatic Conservation

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1. Capital breeding animals such as true seals (Phocidae) rely on accumulated body reserves to rear offspring. A mother's body composition at the start of a breeding episode may depend on recent environmental conditions and sets the resources available for the reproductive episode.2. At two grey seal (Halichoerus grypus) breeding colonies with contrasting demographic characteristics, factors influencing individual variation and temporal trends in the body composition (expressed as the lipid-to-protein mass ratio) of females were examined.3. Maternal reproductive expenditure, and the consequences for mothers and their pups, were investigated. Individual variation in postpartum maternal body composition was considerable.Mean values of 27% (±5%) lipid and 18% (±1%) protein were estimated by hydrogen isotope dilution. No evidence of age effects was detected.5. Mothers with a high lipid-to-protein mass ratio expended a higher proportion of lipid resources, conserved protein and returned with more protein the following year.6. Average maternal postpartum body composition was similar between the two colonies, but temporal patterns differed at one colony where pup production was decreasing from another where pup production was increasing. Mothers at the declining colony consistently weaned larger pups than mothers at the increasing colony across the range of mother sizes, but measures of maternal body composition did not predict pup weaning masses.

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Water and Energy Flux in Elephant Seal Pups Fasting under Natural Conditions

Cited by 231 publications

References 25 publications

Renal function in suckling and fasting pups of the northern elephant seal

Renal function in suckling and fasting pups of the northern elephant seal

Osmoregulation by Vertebrates in Aquatic Environments

Colony‐specific differences in decadal longitudinal body composition of a capital‐breeding marine top predator

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