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A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2012 / Various insect taxa are known to modify bone with their mandibles, including members of the orders of Dermestidae, Tenebrionidae, Calliphoridae, Tineidae and Termitidae. Despite bone modification being a known behavioural trait of many of these taxa, little work has been done to record the distinctive ways in which they modify the bone surface, and a lack of concise descriptions of modification suites inhibits decisive identification and interpretation. The most widely inferred causal agents in palaeontological literature are either termites or dermestid beetles, whilst cockroaches as potential bone modifying agents have not yet been considered. The primary aims of this investigation were to establish whether or not cockroaches and dermestids modify bone, and if so in what ways, develop an interpretative framework to aid future researchers in the identification and differentiation between the variously reported agents of bone modifications, test whether or not the agents will modify bone of varying densities (thin cortical, thick cortical, compact and cancellous bone) or in a particular state of preservation/condition (fresh, dry, weathered or fossilised), and investigate whether or not the occurrence of insect modifications on bone can be used as a proxy to establish a broad climatic signature based on their known thermal physiological limits. A single experimental trial of 18 bone specimens were exposed to the African cockroach Periplaneta americana for a period of six months and a further four experimental trials (totalling 80 bone specimens) were exposed to the Coleopteran Dermestes maculatus for periods of four months each under the absence or presence of substrate and variable feeding conditions. Experiments were conducted within an insectary at 28° C, 40 % humidity and 12 hour light/ 12 of darkness. Subsequently, all specimens were viewed using an Olympus SZX 16 Multifocus microscope fitted with a digital camera at magnifications between 7 and 115x. Three modification types were identified for P. Americana, namely discolouration, destruction of bone and gnawing. A total of five modification types were established for D. maculatus including the occurrence of surface tunnels, destruction of bone, bore holes, surface pits (Classes 1–3) and gnawing. Three distinctive surface pits morphologies were identified; Class 1 pits are highly variable but most often semi-circular to elliptical shallow depressions with a U-shape profile with striations radiating around the outer circumference of the depression. Class 2 surface pits are semi-circular shallow depressions with randomly orientated striations occurring over the entire feature. Class 3 surface pits are irregular shaped depressions with complex profiles not associated to gnawing striations. Broad climatic signatures for both of these agents were developed based on their known physiological thermal limits. The indistinct modification signature of P. americana in combination with limited occurrence and frequency patterns may prove difficult to identify from an archaeological or palaeontological context. Periplaneta americana and D. maculatus do significant damage to aves bones, which could result in their under representation in the archaeological and palaeontological records. The highly distinctive signature as well as occurrence and frequency patterns of modifications produced by D. maculatus has enabled the reinterpretation of existing palaeontological analyses, suggesting that dermestids are in fact not responsible for reported instances in which they are suggested as the causal agent during the Mesozoic and Cenozoic.

Large cockroaches, such as Periplaneta Americana, typically harbour in their hindgut two or more species of parasitic pinworm (Nematoda: Oxyurida). Our laboratory colony was infected with three, possibly four species. The mechanism(s) permitting the sympatry of these potentially competing species were investigated by: i) repeatedly sampling over time hosts of various size to determine the structure, if any, in the pinworm guild and ii) infecting uninfected hosts with known doses of infective eggs and monitoring population changes via daily host dissections. Results indicate that chemically-mediated intraspecific interference competition maintains pinworm populations at densities well below the apparent carrying capacity of the majority of hosts. The concomitant reduction of interspecific pressures thus permits the cohabitation of multiple pinworm species in what is essentially a single niche. This intraspecific population limitation is likely a response to pressures produced by the large size of the parasite in relation the hindgut of early instar hosts. / Science, Faculty of / Zoology, Department of / Graduate

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Successive releases of male German cockroaches heterozygous for the translocation T(8;9) and the recessive deleterious gene sty were made into laboratory populations of Blattella germanica to study the effect of this genetic load on population growth. Five experimental populations and one control were followed by monthly census for eight months. Individual progeny groups were held in separate containers. Various aspects of reproductive behavior of different genotypes were evaluated in separate experiments including fecundity, competitiveness and assortative mating. Linkage between T(8;9) and sty was also measured. The translocation T(8;9) and sty were successfully introduced into the experimental populations by the introduction of heterozygous males. Experimental populations were only 50% the size of the control at the F₁ generation and only 25% as large by the F₂ generation. At the F₃ generation, experimental populations were only 15.4% as large as the control. Cross connected contingency table analyses of population data showed a significant retardation of population growth from releases of T(8;9) sty males. T(8;9) provided a successful mechanism for driving the deleterious gene, sty, into the normal segment of the population. The frequency of sty/sty females in F₂ groups was predicted at 0.20. Observed frequencies approached the expected frequency at 0.11 to 0.22. This deleterious gene provided additional genetic load by reducing possible F₃ progeny by approximately 15%. Linkage tests of T(8;9) with sty showed cross-over frequencies of less than 1% for both males and females. Results were less than optimum due to the following: a possible reduction in competitiveness of released males; higher than expected fecundity in the sty· homozygote female; possible shift in the frequency of alternate disjunction in T(8;9) sty heterozygote males; possible assortative mating between non-translocation bearing wildtype males and T+/+sty females in the population as well as T+/+sty males and non-translocation bearing wild-type females; fewer T+/+sty males and more sty males released than planned due to phenotyping errors in larger releases. Laboratory studies of the reproductive behavior of three genotypes involved in the experimental populations evaluated competitiveness among males, initial productivity, maximum number of matings per male, and assessed the prospect of assortative mating among the genotypes. Competitiveness of the T+/+sty males in small number tests was consistently better than wild-type males but in later assessments by mass mating and population studies, they demonstrated equal competitiveness with wild-type males. A statistically significant tendency toward assortative mating between VPI wild-type males and T+/+sty females was observed. The feasibility of techniques for mass rearing of semi-sterile males for releases of up to 10,000 males per month was demonstrated. / Ph. D.

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