Reproductive Biology Research Group

Our research group is interested in the comparative morphology and evolution of gametes, gonads and external genitalia of Australian mammals. We have found great diversity in these characteristics across the species investigated and we are now exploring the functional implications of this diversity. We have published extensively in this field with articles in Nature and New Scientist as well as in the more specialist scientific journals. In addition, we are involved in developing reproductive technological procedures for long-term storage of sperm and eggs from some of these species to assist with conservation programs.

In particular our current research interests include studies on:

• Factors determining the efficiency of gamete production across species

• Factors determining sperm shape and size

• Co-evolution of molecules involved in sperm-egg interaction at fertilisation

• Environmental control of reproduction

Project 1

Title: A comparative study of ovarian structure and organisation in marsupial species.

Description: Mammalian ovaries are composed of an outer cortical zone of connective tissue (CT) in which the follicles containing oocytes and the ovulated follicles (=corpora lutea) are located. This zone surrounds a more fibrous medullary region containing the main vasculature of the ovary. The structural appearance of the ovary varies cyclically, with growth and development of follicles, ovulation and formation of corpora lutea controlled by the hypothalamo-pituitary-ovarian axis. A surge in LH from the pituitary gland is responsible for ovulation and the transformation of thecal and granulosa cells of ovulated follicles into the luteinised endocrine tissue of the corpora lutea. In several species of mammals, the cortical interstitial CT contains, in addition to follicles of various developmental stages, large clusters of additional “luteinised” interstitial cells, with a cellular appearance similar to that of corpora lutea, but that are not part of these structures, or of follicles. From where these cells arise, how widely they occur across species, and what role they might play in regulating ovarian function is largely unknown, particularly with respect to marsupial species. This project will analyse and compare the cellular characteristics and proportions of follicular and interstitial tissue within the ovaries of species of various Australian marsupials. It is hypothesised that where many luteinised interstitial cells occur the species has a longer cycle length than in species where these cells are not present.

Number of students: 10

Category: Dry lab - morphometric image analysis of histological slides

Major: Reproductive Health; Medical Sciences

Project 2

Title: Testicular architecture in marsupial species: does it relate to intensity of sperm competition and hence post-copulatory sexual selection?

Description: In many animal groups, females often mate with more than one male in the same oestrous period, leading to the likelihood of competition between the sperm from different males to fertilise the oocytes in the female tract. According to the “raffle” principle, intermale sperm competition will result in increased testis size to maximise sperm numbers. Indeed, a strong positive association between multi-male breeding systems and large relative testis size - RTM (after controlling for body size) has been shown in numerous taxa where multimale mating occurs. However, adaptations of testicular and/or sperm structure to maximise the male’s chances of fertilising the available eggs might also occur. Therefore, the proportion of sperm producing tissue within the testes, and its kinetic capabilities, may reflect the breeding system that has evolved in a particular species. It has also been proposed that investment in larger numbers of small sperm is a selective advantage where intense intermale sperm competition occurs. The associations between RTM, testis structure and organisation, sperm production and sperm morphology have not yet been investigated in Australian marsupials although It is known that testis structure varies markedly across different marsupial groups. However, whether this variation correlates with RTM, and hence intensity of intermale sperm competition, has yet to be explored. This project will determine the relationships between RTM, the structural architecture of the testes, sperm morphology and sperm size across various groups of Australian marsupials. The hypothesis that will be tested is that testis and sperm morphology correlate with predicted levels of intermale sperm competition. 

Number of students: 10

Category: Dry lab - morphometric image analysis of histological slides and sperm smears

Major: Reproductive Health; Medical Sciences