Nile crocodile (Crocodylus niloticus) : egg mass relative to egg component mass in unbanded and fertile eggs

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dc.contributor.author Brown, Geoffrey James
dc.contributor.author Forbes, Patricia B.C.
dc.contributor.author Myburgh, J.G.
dc.contributor.author Nothling, Johan O.
dc.date.accessioned 2019-08-05T10:26:58Z
dc.date.issued 2019-04
dc.description.abstract Crocodylus niloticus eggs are a useful starting point to study reproduction in this species. Using samples collected from a single farm during a single breeding season, the present research aimed to describe and compare the masses of unbanded and fertile eggs and their components. The clustering effect of clutch on egg and egg component mass was investigated, and the relationship between the mass of unbanded eggs and their components, together with the effect of possible confounding variables was explored. Estimated egg volume (ellipsoid volume) was strongly positively correlated with egg mass. A strong positive linear relationship existed between egg mass and the combined mass of the foetus and intra-abdominal yolk, as well as between egg mass and the isolated yolk-free foetal mass. If egg mass and incubation period were kept constant, foetal mass increased by 1.1 g for each gram that yolk decreased. The wet yolk and dried shell masses of fertile eggs were significantly lower than those of size-matched unbanded eggs. Clutch had a strong clustering effect on all component masses, particularly total egg mass and hatchling mass. Unbanded egg mass and its individual component masses tended to be similar within a clutch, however some variability existed which should not be discounted. The mass of an egg was strongly positively linearly correlated with the mass of each of its components. The period within the laying season an egg was laid had no effect on its mass nor the mass of any of its components, whereas the breeding pond in which the female resided did affect these measurements. The strong clustering effect of clutch on total egg mass and the masses of all egg components must be accounted for when selecting samples for future studies. The potential confounding effect of breeding pond of origin (which related to female size in the current study) should be considered, particularly where the age or size of females differ among ponds. en_ZA
dc.description.department Chemistry en_ZA
dc.description.department Production Animal Studies en_ZA
dc.description.embargo 2020-04-30
dc.description.librarian hj2019 en_ZA
dc.description.sponsorship The University of Pretoria in the form of a bursary to the first author, and by the South African National Research Foundation (NRF) in the form of an incentive fund for rated researchers to the last author. en_ZA
dc.description.uri http://www.elsevier.com/ locate/aqua-online en_ZA
dc.identifier.citation Brown, G.J., Forbes, P.B.C., Myburgh, J.G. et al. 2019, 'Nile crocodile (Crocodylus niloticus) : egg mass relative to egg component mass in unbanded and fertile eggs, Aquaculture, vol. 505, pp. 423-430. en_ZA
dc.identifier.issn 0044-8486 (print)
dc.identifier.issn 1873-5622 (online)
dc.identifier.other 10.1016/j.aquaculture.2019.03.006
dc.identifier.uri http://hdl.handle.net/2263/70887
dc.language.iso en en_ZA
dc.publisher Elsevier en_ZA
dc.rights © 2019 Elsevier B.V. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Aquaculture. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Aquaculture, vol. 505, pp. 423-430, 2019. doi : 10.1016/j.aquaculture.2019.03.006. en_ZA
dc.subject Nile crocodile (Crocodylus niloticus) en_ZA
dc.subject Clutch en_ZA
dc.subject Egg en_ZA
dc.subject Egg mass en_ZA
dc.subject Yolk en_ZA
dc.subject Shell en_ZA
dc.subject Unbanded eggs en_ZA
dc.subject Fertile eggs en_ZA
dc.title Nile crocodile (Crocodylus niloticus) : egg mass relative to egg component mass in unbanded and fertile eggs en_ZA
dc.type Postprint Article en_ZA


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