Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Subject: search.filters.subject.310911 Animal structure and function

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Female masculinisation and reverse sexual dimorphism in the North Island Brown Kiwi (Apteryx mantelli) : a study using wild and captive birds : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University, Manawatū, New Zealand
    (Massey University, 2024) McLeod, Caitlin
    While sexual dimorphism is widely known in birds, little is known about when it is reversed. Species with reversed sexual dimorphism and/or sex roles often have females that show masculinisation in deviation from traditionally dimorphic pathways. This study investigates the endocrine profile of both male and female North Island brown kiwi across the breeding and non-breeding season as well as captive and wild status. Analysis of these profiles reveals androstenedione as a hormone of interest in female kiwi masculinisation, as well as significant differences between the endocrine profiles of birds in captivity from those in the wild. This study also describes the courtship behaviour of pairs of brown kiwi in the wild, adding nuance to our understanding of sexual dynamics between these birds.
  • Thumbnail Image
    Item
    Spatiotemporal mapping of spontaneous smooth muscle motility in capacious organs: the ex vivo urinary bladder and in vivo gravid uterus of the rabbit: a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand
    (Massey University, 2023-08-20) Hulls, Corrin
    The temporal and spatial dynamics of propagating myogenic contractions in the wall of the resting ex vivo urinary bladder and in vivo gravid uterus of the rabbit were characterised by spatiotemporal maps of area strain rate, of linear strain rate and contractile patch analysis, and related to cyclic variation in intravesical pressure (pves) in the bladder, and electrophysiological recordings in the gravid uterus. In the urinary bladder, patches of propagating contractions (PPCs) enlarged and involuted with a frequency in near synchrony with peaks in intravesical pressure. Maximum area percentage of the anterior surface of the bladder undergoing contraction and the sizes of individual PPCs also coincided with the peak in pves. Moreover, pves varied cyclically with total area of contraction and with the indices of the size and aggregation of PPCs, indicating that PPCs grew and involuted by a combination of peripheral enlargement or shrinkage and by coalescence or fission with other PPCs, their areas being maximal at or around the peak in pves. Bladder PPCs originated and propagated within temporary patch domains (TPDs) and comprised groups of near synchronous cyclic individual contractions (PICs). The TPDs were located principally along the vertical axis of the anterior surface of the bladder, either to the left or the right of midline and changed in location from one side to side and from side to tip or base. The sites of origin of PICs within PPCs were inconsistent, consecutive contractions often propagating in opposite directions along linear maps of strain rate. Similar patterns of movement of PPCs within TPDs of the same form occurred in areas of the anterior bladder wall that had been stripped of mucosa. The synchronisation and extended propagation of PICs within PPCs and the concurrent variation in pves of the bladder were sometimes lost or diminished, uncoordinated PICs then occurred, propagated shorter distances, and had little effect on pves. There was no evidence that any influence of bladder shape on stress influenced the principal direction of propagation of either PCCs or PICs or the disposition of TPDs. The disposition and dynamics of PPCs and their component individual myogenic contractions in the wall of the resting ex vivo tetrodotoxinized urinary bladder of the rabbit were characterised by spatiotemporal maps and related to cyclic variation in pves before and after the administration of carbachol, isoprenaline, carbenoxolone, and the RhoA-inhibitor Y-27632. The results confirm that the bladder wall can exhibit two contractile states that are of similar frequencies to those of the two types of electrophysiological discharge described by previous workers. In the first of these, large low frequency cyclic PPCs predominate. In the second, small irregular, higher frequency PICs predominate. Comparison of the effects of the drugs on the timing and disposition of contraction suggested indicated that the local spatial spread of contractions in PPCs was governed largely by myocytes, whilst the propagation, frequency, and duration of PPCs was likely governed via gap junctions between interstitial cells of cajal- intermuscular (ICC-IM) and myocytes. Spontaneous and oxytocin-induced contractile activity was quantified in the bicornuate uteri of pregnant rabbits maintained in situ, using data from electrophysiological recordings and spatiotemporal maps, and compared statistically. Spontaneous contractions occurred over a range of frequencies in gravid animals at 18-21 and at 28 days of gestation and propagated both radially and longitudinally over the uterine wall overlying each foetus. Patches of contractions were randomly distributed over the entire surface of the cornua and were pleomorphic in shape. No spatial coordination was evident between longitudinal and circular muscle layers nor temporal coordination that could indicate the activity of a localised pacemaker. The density and duration of contractions decreased, and their frequency increased with the length of gestation in the non-labouring uterus. Increasing intravenous doses of oxytocin had no effect on the mean frequencies, or the mean durations of contractions in rabbits of 18-21 days gestation but caused frequencies to decrease and durations to increase in rabbits of 28 days gestation, from greater spatial and temporal clustering of individual contractions. This was accompanied by an increase in the distance of propagation, the mean size of the patches of contraction, the area of the largest patch of contraction and the overall density of patches. Together these results suggest that progressive smooth muscle hypertrophy and displacement with increasing gestation is accompanied by a decrease in smooth muscle connectivity causing an increase in wall compliance and that oxytocin restores connectivity and decreases compliance, promoting volumetric expulsion rather than direct propulsion of the foetus by peristalsis. The latter effects were reversed by the β2 adrenergic receptor agonist salbutamol thus reducing area of contraction, duration, and distance of propagation. The characteristics of smooth muscle contraction that are associated with the maintenance of tone during accommodation appear to be to be similar in the capacious organs discussed. Hence, it appears there is patchy rather than uniform local revision of the state of tonal contraction over the surfaces of the various capacious organs during accommodation that can undergo neural modulation. There appears to be less similarity in regard to the mechanisms that secure the voiding contractions in these capacious structures. Whilst the actuation of the necessary shorter term increase in tone may be ultimately dependent upon a mechanosensitive myogenic reflex, the relative contributions of autonomic, hormonal, mechanical and voluntary reflexes that reset the threshold of this reflex and aid in the relatively rapid expulsion of the contents, appear to vary between organs.
  • Thumbnail Image
    Item
    Stress and reproduction in domestic cats (Felis catus) as a model for endangered felids : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.) Animal Science Group, Massey University, Palmerston North, New Zealand
    (Massey University, 2021) Andrews, Christopher
    Captive breeding programs are a vital component of the conservation strategies for felids, but these programs are often hindered by poor reproductive performance. Knowledge of reproductive biology is crucial to improving in situ and ex situ felid breeding programs. This thesis provided the first comprehensive systematic review of the literature available on the reproductive biology of the extant felid species. It was concluded that the high prevalence of teratospermia and highly variable oestrous cycles in felids contribute towards their poor reproductive performance in captivity. The captive environment has been linked to reduced ejaculate quality and ovarian quiescence in felids, but it is difficult to elucidate whether this is due to captivity-related stress (i.e., elevated glucocorticoid (GC) concentrations) or other factors associated with captivity. This thesis aimed to determine whether a simulated endocrine stress response (GC treatment) altered the testicular and ovarian function of felids using the domestic cat as a model species. While epididymal sperm motility was unaffected by GC treatments, the percentage of morphological abnormal sperm was higher in GC-treated cats than in control cats. This would likely have an adverse effect on fertility as morphologically abnormal sperm are rarely involved in the fertilisation process. Glucocorticoid treatments did not affect the ovarian response of cats in which follicular growth and development was stimulated by exogenous gonadotrophins. However, ooplasm and zona pellucida morphology was graded poorer in GC-treated animals than control animals. Whether this corresponds to a reduction in fertility is unclear as the fertilisation capabilities of oocytes were not assessed. It would be worth investigating whether GC administration affects the natural oestrous cycles of cats, as elevated GC concentrations associated with captivity have been linked to ovarian quiescence. However, this would require an accurate and minimally invasive (i.e., low stress) method for monitoring the ovarian cycles of domestic cats. Thus, this thesis investigated whether accelerometry and infrared thermography could be used to monitor the ovarian function of cats. It was found that accelerometry could be used to detect an increase in activity of cats following the induction of follicular growth with equine chorionic gonadotrophin (eCG). Infrared thermography also identified changes in perivulvar temperature (PVT) driven by follicular development and ovulation, with PVT increasing as follicular growth occurred and decreasing following ovulation. Both methods show promise; however, further investigation into the use of accelerometry and IR thermography for monitoring ovarian function is needed. In conclusion, the results of thesis indicate that GC have adverse effects on the testicular and ovarian function of domestic cats. Thus, there is an urgent need to further investigate the effects of captivity-related stress on the reproductive performance of non-domestic felids. Furthermore, this thesis assessed two promising non-invasive methods for monitoring the ovarian activity of cats, with the findings being highly applicable for the management and breeding of non-domestic felids in captivity.
  • Thumbnail Image
    Item
    Investigating patterns of avian ornamental colouration : intraspecific and interspecific approaches : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Zoology at Massey University, Albany, New Zealand
    (Massey University, 2019) Ahlstrom, Millie Beatrice May
    Research into the evolutionary function of elaborated colouration in birds is continually ongoing. Novel approaches to addressing various aspects of this broad research area may help us consider this topic in a new light. This thesis aimed to consider two different aspects of avian colouration research using novel methods and testing relatively new hypotheses. Firstly, I consider the cost of carotenoid pigmented ornamental colouration - an area of research that is currently under intense debate. Classically carotenoid-based pigmentation has considered carotenoids to function as indicators of sexual quality, with costs being due to carotenoids being diet dependent in birds. Recent research however has argued that carotenoid pigmented colour traits function in agonistic social contexts, and that the cost of using carotenoid pigmentation as an honest indicator of quality is a social one. In this study I test this hypothesis using blackbirds (Turdus merula) and their natural variation in carotenoid-based bill colouration. I replicate a study using model presentations to simulate territory intrusions. Additionally, I examine the feasibility of using three-dimensionally printed models in avian behavioural studies. This study was unsuccessful due to a lack of response rates from territorial males, however it was successful in questioning several differing aspects between my study and the study I replicated. Secondly, I explore the spatial organisation of colouration on the bodies of birds as a way of potentially inferring different functions of elaborate colour traits. In the third chapter I develop a novel method that allows objective analysis of the spatial organisation of colour on the bodies of birds, by removing morphological variation between species. Using this method I present a case study on the spatial organisation of colour elaboration in 2,471 species of passerines. This case study uses a difference in sexual dichromatism as a proxy for colour elaboration and determined where signaling hotspots occur on the bodies of birds. These results demonstrate that conspicuous colouration is most common in the supercilium, chin, and upper breast of passerine birds. In chapter four, I used this method to determine correlations between different life-history traits and different regions of the body. This study aimed to infer the function of different regions of the head in signaling. My results show that the irises in species with tropical life-histories and cooperative breeding strategies are more likely to be elaborately coloured; bills of larger bodied species are more likely to be elaborately coloured than are smaller species; and the spatial organisation of colour effects females more than it does males.