This dissertation was submitted to the Faculty of Science, University of the Witwatersrand, in fulfillment of the requirements for the degree of Master of Science / Dung beetle feeding is still not a widely understood behaviour. Feeding on the waste of other animals creates a challenge of acquiring the necessary nutrients for growth, development and for survival. Because of their soft mouthparts, it has always been thought that adult dung beetles cannot chew the hard parts of dung but only select smaller particles to feed on. Dung beetle larvae on the other hand can chew harder components, but where they get the nutrients required for development has not yet been discovered. The aim of this study was to discover which dung particles adult dung beetles select when feeding, and when creating a nest for their offspring, and also how much they can alter the dung nutrient content in the process. Foregut and hindgut contents were dissected out of the dung beetle Scarabaeus goryi, and their contents compared with untreated dung from the cow and the excreta of adult beetles. Brood balls and maternal gifts of Euoniticellus intermedius were also dissected. Nitrogen and carbon content, the carbon to nitrogen ratio, and results of the carbon and nitrogen stable isotopes were compared between all samples. When feeding dung beetles selected particles which were bigger than 800 μm in diameter and had three times more nitrogen than raw dung, and used particles over 2000 μm in size in the maternal gift packed for their offspring. Nitrogen content in the selected dung was increased from 1.40 % to 5.14% by adult dung beetle feeding and up to 2.62% in dung selected for the larvae to feed on. The carbon to nitrogen ratio also decreased when feeding adults and in the brood balls made for the larvae to feed on. Both carbon and nitrogen were absorbed from ingested dung during digestion. The heavier nitrogen isotope was selected for when feeding. The heavier nitrogen isotopes and the lighter carbon isotope were selected for during absorption. Dung beetles increase the nitrogen content of the dung on which they feed by careful selection of particles of a certain size and nitrogen content, which is probably the limiting nutrient when feeding and nesting. The increase in the nitrogen content is not only from the change in particle size but also in selection of particles with higher nitrogen content. / MT2018
Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/24177 |
Date | January 2017 |
Creators | Madzivhe, Fhulufhedzani Macphee |
Source Sets | South African National ETD Portal |
Language | English |
Detected Language | English |
Type | Thesis |
Format | Online resource (65 pages), application/pdf |
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