Retrograde movement of urine into the gut of salt water acclimated Mallards (Anas platyrhynchos)

Abstract

The influence of sex and salt-water intake on retrograde movement of urine into the hindgut was examined in captive adult wild Mallards (Anas platyrhynchos). Ducks were given intravenous injections of tritiated polyethylene glycol (3H-PEG) and killed 3 h later. The fluid content of each gut segment and its concentrations of 3H-PEG, sodium, and potassium were determined. Retrograde movement of urine into each gut segment was estimated from the quantity of 3H-PEG recovered there. In both ducks that drank tap water and those that drank saline, about 20% of the urine was moved into the hindgut, two-thirds of this into the ceca. Males deposited more urine in the ceca and reabsorbed more water from this urine than did females (P < 0.01). We conclude that retrograde movement of urine into the hindgut was unaffected by the salinity of drinking water and was greater in males than in females. Reabsorption of urinary sodium and water in the hindgut, particularly the ceca, may play an important role in osmoregulation in birds with salt glands.

Comparison of renal and salt gland function in three species of wild ducks

“…Saline acclimation and acute saline loading have little effect on GFR of ducks Hughes, 1980;Hughes et al, 1989Hughes et al, , 1999 Fig.·4) or other species with salt glands (Douglas, 1966;Hughes, 1995). GFR of goldeneyes is roughly twice that of mallards, canvasbacks and Pekin ducks (Table·1, Fig.·4), but is similar to that of other marine birds (gulls; Douglas, 1966;Hughes, 1980Hughes, , 1995Hughes et al, 1993).…”

“…Postrenal modification of urine has the potential to play an important osmoregulatory role in ducks. Pekin ducks (Hughes and Raveendran, 1994) and mallards (Hughes et al, 1999) reflux urine into their hindgut. Mallards reflux about 20% of their urine, regardless of drinking water salinity (Hughes et al, 1999).…”

“…Pekin ducks (Hughes and Raveendran, 1994) and mallards (Hughes et al, 1999) reflux urine into their hindgut. Mallards reflux about 20% of their urine, regardless of drinking water salinity (Hughes et al, 1999). The capacity for Na + uptake in the hindgut of Pekin ducks is only slightly diminished by saline acclimation (Skadhauge et al, 1984), and their cloacal fluid (Hughes et al, 1992) is more concentrated than their urine .…”

Morphological and Pathological Effects of Cadmium Ingestion on Pekin Ducks Exposed to Saline

“…This study simulated the return of seaducks to the marine habitat by presenting Pekin ducks simultaneously with increasingly concentrated NaCl and diets spiked with Cd. It included both sexes, since male and female Pekin ducks differ in kidney size , postrenal urine modification (Hughes et al, 1999), saline tolerance (Hughes et al, 1992), and the amount of Cd sequestered by the salt glands (Burger & Gochfeld, 1992). The following hypotheses were investigated: Ingestion of Cd induces (1) hypertrophy of osmoregulatory organs and (2) pathological changes in osmoregulatory organs.…”

Effect of Cadmium on Pekin Duck Total Body Water, Water Flux, Renal Filtration, and Salt Gland Function

“…H ow ever, ducks have another site of urinary N a + uptake. This is the hindgut (Skadhauge et al, 1984), into w hich urine is retropulsed (Hughes & Raveendran, 1994) and where N a + may be retrieved (Hughes et al, 1999). M allards move about 20% of their urine into the hindgut, w here a significant portion of its N a + is reabsorbed (Hughes et al, in press).…”