Effect of saline intake on water flux and osmotic homeostasis in Pekin ducks (Anas platyrhynchos)

Bennett, Darin C.; Gray, David A.; Hughes, Maryanne R.

doi:10.1007/s00360-002-0306-8

Cited by 14 publications

(3 citation statements)

References 44 publications

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“…In other coastal shorebirds the sustained rate can reach 22.5 g NaCl day −1 kg −1 in the whimbrel Numenius phaeopus (330 g body mass, Zwarts and Dirksen 1990), and 27 g NaCl day −1 kg −1 in the red knot Calidris canutus (120 g body mass; Verboven and Piersma 1995). By comparison, mallard Anas platyrhynchos and snowy plover Charadrius alexandrinus (an inland shorebird species) could not sustain the rate of NaCl intake>5.2 (Bennett et al 2003) and>4.1 (Purdue and Haines 1977) g day −1 kg −1 respectively without freshwater supplement. Marine birds readily subside on just seawater for drinking (e.g., glaucous‐winged gull Larus glaucescens , Hughes 2003), and can ingest NaCl at the rate of 15.9 g day −1 kg −1 (Cassin's auklet Ptychoramphus aleuticus , Hodum et al 1998) without signs of physiological stress.…”

Section: Discussionmentioning

confidence: 94%

“…While oceanic seabirds can be considered osmotic specialists, species that either inhabit environments with varying salinities (Johnston and Bildstein 1990), or regularly migrate between freshwater and saltwater sites (Piersma 2002, Bennett and Hughes 2003) can be considered osmotic generalists, and are, by definition, less adapted to osmotic extremes. Experiments on such species indicate that high dietary salt‐loads cause slower growth rates (Johnston and Bildstein 1990), loss of body mass and dehydration (Purdue and Haines 1977, Bennett et al 2003). This implies that in osmotic generalists environmental salinity may affect individual fitness (Nyström and Pehrsson 1988, Tietje and Teer 1996).…”

Section: Predicted Differences In Long‐term Intake Rates (Lir) Of Foomentioning

confidence: 99%

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Lack of an osmotic constraint on intake rate of the eastern curlew Numenius madagascariensis

Blakey¹,

Zharikov²,

Skilleter³

2006

Journal of Avian Biology

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Rates of food intake in animals consuming abundant prey can be constrained by the rates of digestion or excretion of ingested substances, such as salt, particularly so in the animals that regularly migrate between freshwater and saltwater environments. We tested this hypothesis in a long‐distance migrant shorebird, the eastern curlew Numenius madagascariensis (suborder Charadrii), foraging on intertidal decapods in eastern Australia. We predicted that if food intake rates are constrained osmotically, individuals with access to freshwater and less saline prey (FW group) would have higher rates of food and water intake than individuals with seawater‐only access (SW group). Food intake rates did not differ between the FW and SW groups (0.14 g ash‐free dry mass min−1), nor did the water influx rates (0.75 g min−1). Salt intake rates were lower at FW sites (19.3 versus 23.3 mg NaCl min−1) and overall they were similar to those of marine birds. Food intake rate in the eastern curlew appeared limited by digestive rather than by osmoregulatory capacity.

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Section: Discussionmentioning

confidence: 94%

Section: Predicted Differences In Long‐term Intake Rates (Lir) Of Foomentioning

confidence: 99%

Lack of an osmotic constraint on intake rate of the eastern curlew Numenius madagascariensis

Blakey¹,

Zharikov²,

Skilleter³

2006

Journal of Avian Biology

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“…They found that the Barrow’s goldeneye ( Bucephala islandica ), a marine‐adapted species, was able to completely excrete an infused Na + load via salt glands, while the mallard ( Anas platyrhynchos ), usually a freshwater species, used a combination of salt glands and decreased renal (or postrenal) Na + recovery associated with additional urinary water loss to eliminate an infused Na + load. By contrast, the canvasback ( Aythya valisineria ) was unable to completely eliminate an infused Na + load, yet tolerated higher drinking water salinities than the mallard (Bennett, 2002). This suggests that in canvasbacks water and Na + regulation are carried out by organs other than the kidneys and salt glands, and thus that the hindgut plays a relatively more important osmoregulatory role.…”

mentioning

confidence: 97%

The integration of digestion and osmoregulation in the avian gut

2009

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We review digestion and osmoregulation in the avian gut, with an emphasis on the ways these different functions might interact to support or constrain each other and the ways they support the functioning of the whole animal in its natural environment. Differences between birds and other vertebrates are highlighted because these differences may make birds excellent models for study and may suggest interesting directions for future research. At a given body size birds, compared with mammals, tend to eat more food but have less small intestine and retain food in their gastrointestinal tract (GIT) for shorter periods of time, despite generally higher mass-specific energy demands. On most foods, however, they are not less efficient at digestion, which begs the question how they compensate. Intestinal tissue-specific rates of enzymatic breakdown of substrates and rates of active transport do not appear higher in birds than in mammals, nor is there a demonstrated difference in the extent to which those rates can be modulated during acclimation to different feeding regimes (e.g. diet, relative intake level). One compensation appears to be more extensive reliance on passive nutrient absorption by the paracellular pathway, because the avian species studied so far exceed the mammalian species by a factor of at least two- to threefold in this regard. Undigested residues reach the hindgut, but there is little evidence that most wild birds recover microbial metabolites of nutritional significance (essential amino acids and vitamins) by re-ingestion of faeces, in contrast to many hindgut fermenting mammals and possibly poultry. In birds, there is some evidence for hindgut capacity to breakdown either microbial protein or protein that escapes the small intestine intact, freeing up essential amino acids, and there is considerable evidence for an amino acid absorptive capacity in the hindgut of both avian and mammalian hindgut fermenters. Birds, unlike mammals, do not excrete hyperosmotic urine (i.e. more than five times plasma osmotic concentration). Urine is mixed with digesta rather than directly eliminated, and so the avian gut plays a relatively more important role in water and salt regulation than in mammals. Responses to dehydration and high- and low-salt loads are reviewed. Intestinal absorption of ingested water is modulated to help achieve water balance in one species studied (a nectar-feeding sunbird), the first demonstration of this in any terrestrial vertebrate. In many wild avian species the size and digestive capacity of the GIT is increased or decreased by as much as 50% in response to nutritional challenges such as hyperphagia, food restriction or fasting. The coincident impacts of these changes on osmoregulatory or immune function of the gut are poorly understood.

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