Are yellow-vented bulbuls facultatively ammonotelic, apparently ammonotelic, or both?
Preest and Beuchat (1997) were the first to challenge the long-held notion of avian uricotely. They showed that under certain conditions Anna’s hummingbirds could excrete more nitrogen as ammonia than as uric acid. They termed the ability to switch from uric acid to ammonia as the primary waste product `facultative ammonotely’. Roxburgh and Pinshow (2002) found that the Palestine sunbirds also switched from uric acid to ammonia excretion under some conditions. In sunbirds, ammonotely was correlated with low protein intake, whereas in hummingbirds it was associated with low ambient temperature. Roxburgh and Pinshow (2002) found that ammonia excretion remained relatively constant, whereas uric acid excretion increased with increased protein intake. They claimed that the ammonotely observed in sunbirds was only `apparent’. Since uric acid was the major nitrogen waste form in the ureteral urine, no modification took place in the metabolic pathway of nitrogen waste production in the birds;
Related Questions
- Apparently nearly everyone forgot to ask, "Decodable by what phonics?" We predicted that phonemes without concurrent graphemes would soon be discovered not to work (see
- Today I noticed that the Naso had an apparently inflamed eye (copper poisoning?
- How should Decision Support Systems present apparently "Bad News"?
