The form and function of the kidney of selected Western Australian honeyeaters

Casotti, Giovanni (1993) The form and function of the kidney of selected Western Australian honeyeaters. PhD thesis, Murdoch University.

Abstract

This thesis examines the form and function of the kidney of corvid meliphagid honeyeaters. The kidneys of seven species inhabiting the wet zone environment were compared with the kidneys of seven species inhabiting the arid zone environment.

Gross anatomy and vasculature of the kidney were similar to other avian species. Histological structure was similar between arid .and wet zone species, as determined by light histology as well as by transmission and scanning electron microscopy. It differed from that found in muscicapid passerines, in the arrangement of tubules within the medulla and in the ultrastructural morphology of the loop of Henle. A quantitative analysis using stereology showed that most arid zone species: had a proportionately higher volume of renal medulla, a higher proportion of looped nephrons, and longer loops of Henle than did wet zone species. Wet zone species had a higher percentage volume of collecting ducts and arid zone honeyeaters had a higher percentage volume of medullary capillaries. Qualitatively there was no difference in the nephron components between species. The histological structure of the lower gastrointestinal tract was similar in both arid and wet zone honeyeaters.

Physiological experiments were conducted on two arid zone species: Phylidonyris albifrons and Meliphaga penicillata and three wet zone species: Phylidonyris novaehollandiae, Anthochaera lunulata and Anthochaera carunculata. When fed on artificial nectar diets ranging from more dilute (200mOsm) to within the osmolality range of nectar (600 - 1300 mOsm), the arid zone honeyeaters consumed more food, excreted more urine and gained more body mass than did the wet zone honeyeaters. On these diets all honeyeaters excreted a hyposmotic urine. There was no difference between species in: the concentration of urinary and plasma sodium and potassium ions, plasma osmolality, haematocrit and the concentration of uric acid. On diets more concentrated than nectar (2000 - >2000mOsm), all birds lost a significant amount of body mass. Arid zone species excreted a significantly higher concentration of sodium in the urine and wet zone species increased the level of plasma osmolality more so than did the arid zone species. Arid zone species also had a higher urine to plasma osmolality ratio than did wet zone species.

These results suggest that arid zone honeyeaters are better able to concentrate urine, and if the birds' habitat is altered, certain arid zone species may adapt successfully to a wet zone environment, however, wet zone species may find it difficult to adapt to an arid zone environment.

Item Type:	Thesis (PhD)
Murdoch Affiliation(s):	School of Veterinary Studies
Notes:	Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au, Thank you.
Supervisor(s):	Richardson, Ken and Johnson, Ken
URI:	http://researchrepository.murdoch.edu.au/id/eprint/53104

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