Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters

Purchase, Cromwell; Napier, Kathryn R.; Nicolson, Susan W.; McWhorter, Todd J.; Fleming, Patricia A.

doi:10.1242/jeb.075176

Cited by 8 publications

(15 citation statements)

References 41 publications

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“…However, three passerine nectarivores (Palestine sunbird, Cinnyris oseus; whitebellied sunbird; and New Holland honeyeater) show evidence of modulation of water absorption (Fig. 4B-D), absorbing a lower proportion of ingested water on dilute diets compared with concentrated diets (McWhorter et al, 2003;Purchase et al, 2013b). These data therefore support the intestinal shunting hypothesis (Beuchat et al, 1990) for sunbirds and honeyeaters, but not for hummingbirds.…”

Section: Regulation Of Intestinal Water Absorptionmentioning

confidence: 72%

“…In nectarivores, plasma AVT concentration increases with increasing sugar concentration, presumably reflecting a hormonal response to increased plasma osmotic concentration (Gray et al, 2004). Surprisingly, in view of the high variation in water intake, GFR does not vary with water loading for the three avian nectarivore lineages (Goldstein and Bradshaw, 1998;Hartman Bakken and Sabat, 2006;Purchase et al, 2013b), although GFR is greatly reduced at night (see below).…”

Section: Commentarymentioning

confidence: 98%

“…The possible occurrence of such modulation of intestinal water absorption has been tested experimentally by means of pharmacokinetic techniques, using the model developed by McWhorter and Martínez del Rio (McWhorter and Martínez del Rio, 1999). Assumptions and limitations of the steady-state pharmacokinetic method have recently been explored in detail (Purchase et al, 2013b;Napier et al, 2012). Data collected to date suggest that there is no modulation of intestinal water absorption in two hummingbird species [green-backed firecrowns, Sephanoides sephaniodes (Fig.…”

Section: Regulation Of Intestinal Water Absorptionmentioning

confidence: 99%

“…Hummingbirds (which lack intestinal shunting of preformed water) tend to modulate water reabsorption in the kidneys in relation to water intake (Hartman Bakken and Sabat, 2006); Palestine sunbirds also modulate water reabsorption , but there is no evidence that whitebellied sunbirds and New Holland honeyeaters do so (Purchase et al, 2013b).…”

Section: Commentarymentioning

confidence: 99%

“…Nothing is known of the partitioning of evaporation between cutaneous and respiratory routes, but cutaneous EWL is influenced by hydration state in other birds (Williams et al, 2012). Unfortunately, the high excretory output of avian nectarivores complicates the direct measurement of EWL, and the pharmacokinetic method has proved unreliable for its estimation (Purchase et al, 2013b). Further research in this area is required to determine the role of evaporation in osmoregulation for the three avian nectarivore lineages.…”

Section: The Potential Role Of Evaporationmentioning

confidence: 99%

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Drinking problems on a ‘simple’ diet: physiological convergence in nectar-feeding birds

Nicolson

Fleming

2014

Journal of Experimental Biology

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Regulation of energy and water are by necessity closely linked in avian nectarivores, because the easily available sugars in nectar are accompanied by an excess of water but few electrolytes. In general, there is convergence in morphology and physiology between three main lineages of avian nectarivores that have evolved on different continents -the hummingbirds, sunbirds and honeyeaters. These birds show similar dependence of sugar preferences on nectar concentration, high intestinal sucrase activity and rapid absorption of hexoses via mediated and paracellular routes. There are differences, however, in how these lineages deal with energy challenges, as well as processing the large volumes of preformed water ingested in nectar. While hummingbirds rely on varying renal water reabsorption, the passerine nectarivores modulate intestinal water absorption during water loading, thus reducing the impact on the kidneys. Hummingbirds do not generally cope with salt loading, and have renal morphology consistent with their ability to produce copious dilute urine; by contrast, as well as being able to deal with dilute diets, honeyeaters and sunbirds are more than capable of dealing with moderately high levels of added electrolytes. And finally, in response to energy challenge, hummingbirds readily resort to torpor, while the passerines show renal and digestive responses that allow them to deal with short-term fasts and rapidly restore energy balance without using torpor. In conclusion, sunbirds and honeyeaters demonstrate a degree of physiological plasticity in dealing with digestive and renal challenges of their nectar diet, while hummingbirds appear to be more constrained by this diet.

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Section: Regulation Of Intestinal Water Absorptionmentioning

confidence: 72%

Section: Commentarymentioning

confidence: 98%

Section: Regulation Of Intestinal Water Absorptionmentioning

confidence: 99%

Section: Commentarymentioning

confidence: 99%

Section: The Potential Role Of Evaporationmentioning

confidence: 99%

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Drinking problems on a ‘simple’ diet: physiological convergence in nectar-feeding birds

Nicolson

Fleming

2014

Journal of Experimental Biology

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Variable evidence for convergence in morphology and function across avian nectarivores

Hewes

Cuban

Groom

et al. 2022

Journal of Morphology

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Nectar-feeding birds provide an excellent system in which to examine form-function relationships over evolutionary time. There are many independent origins of nectarivory in birds, and nectar feeding is a lifestyle with many inherent biophysical constraints. We review the morphology and function of the feeding apparatus, the locomotor apparatus, and the digestive and renal systems across avian nectarivores with the goals of synthesizing available information and identifying the extent to which different aspects of anatomy have morphologically and functionally converged. In doing so, we have systematically tabulated the occurrence of putative adaptations to nectarivory across birds and created what is, to our knowledge, the first comprehensive summary of adaptations to nectarivory across body systems and taxa. We also provide the first phylogenetically informed estimate of the number of times nectarivory has evolved within Aves. Based on this synthesis of existing knowledge, we identify current knowledge gaps and provide suggestions for future research questions and methods of data collection that will increase our understanding of the distribution of adaptations across bodily systems and taxa, and the relationship between those adaptations and ecological and evolutionary factors. We hope that this synthesis will serve as a landmark for the current state of the field, prompting investigators to begin collecting new data and addressing questions that have heretofore been impossible to answer about the ecology, evolution, and functional morphology of avian nectarivory.

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Detoxification and elimination of nicotine by nectar-feeding birds

2017

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Many dilute nectars consumed by bird pollinators contain secondary metabolites, potentially toxic chemicals produced by plants as defences against herbivores. Consequently, nectar-feeding birds are challenged not only by frequent water excess, but also by the toxin content of their diet. High water turnover, however, could be advantageous to nectar consumers by enabling them to excrete secondary metabolites or their transformation products more easily. We investigated how the alkaloid nicotine, naturally present in nectar of Nicotiana species, influences osmoregulation in white-bellied sunbirds Cinnyris talatala and Cape white-eyes Zosterops virens. We also examined the metabolic fate of nicotine in these two species to shed more light on the post-ingestive mechanisms that allow nectar-feeding birds to tolerate nectar nicotine. A high concentration of nicotine (50 µM) decreased cloacal fluid output and increased its osmolality in both species, due to reduced food intake that led to dehydration. White-eyes excreted a higher proportion of the ingested nicotine-containing diet than sunbirds. However, sugar concentration did not affect nicotine detoxification and elimination. Both species metabolised nicotine, excreting very little unchanged nicotine. Cape white-eyes mainly metabolised nicotine through the cotinine metabolic pathway, with norcotinine being the most abundant metabolite in the excreta, while white-bellied sunbirds excreted mainly nornicotine. Both species also utilized phase II conjugation reactions to detoxify nicotine, with Cape white-eyes depending more on the mercapturic acid pathway to detoxify nicotine than white-bellied sunbirds. We found that sunbirds and white-eyes, despite having a similar nicotine tolerance, responded differently and used different nicotine-derived metabolites to excrete nicotine.

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Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters

Cited by 8 publications

References 41 publications

Drinking problems on a ‘simple’ diet: physiological convergence in nectar-feeding birds

Drinking problems on a ‘simple’ diet: physiological convergence in nectar-feeding birds

Variable evidence for convergence in morphology and function across avian nectarivores

Detoxification and elimination of nicotine by nectar-feeding birds

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