The effects of nutritional and social environment on ovarian dynamics and life history strategy in Nauphoeta cinerea
Barrett, Emma Louise Beverley
Thesis or dissertation
University of Exeter
Journal of Insect Physiology (http://www.elsevier.com/wps/find/authorsview.authors/copyright#whatrights); Journal of Evolutionary Biology (http://www.blackwellpublishing.com/jeb_enhanced/submit.asp); Proceeding of the Royal Society B (http://royalsocietypublishing.org/site/authors/policy.xhtml); Insect Science (http://www.wiley.com/bw/submit.asp?ref=1672-9609); Physiological Entomology (http://www.wiley.com/bw/submit.asp?ref=0307-6962&site=1)
Reason for embargo
The majority of this thesis is published, or is in press. Journal of Evolutionary Biology, Proceedings of the Royal Society B and Physiological Entomology allow authors to have copyright and allow publishing of work elsewhere after a period of time (for JEB after 6 months (Aug 2009), for Proceedings 12 months (June 2010), and for Physiological Entomology 12 months (it is still in press). Journal of Insect Physiology and Insect Science retain copyright, therefore only links can be made to those sites.
The trade-off between gametes and soma is central to life-history evolution. Oosorption has been proposed as a mechanism that can mediate this trade-off. When conditions are not conducive to successful reproduction, females are expected to be able to recoup nutrients from unfertilized oocytes and reinvest them into the somatic processes that promote survival and hence future reproduction. Although positive correlations between oocyte degradation and lifespan have been documented in oviparous insects, the adaptive significance of this process in species with more complex reproductive biology has not been explored. Oocyte degradation via apoptosis (programmed cell death) occurs in response to enforced virginity in females of the ovoviviparous cockroach, Nauphoeta cinerea. Observed apoptosis may represent oosorption, however, an alternative but not mutually exclusive argument is that oocyte apoptosis may represent oocyte ageing and clearance in order to maintain reproductive synchrony. The aim of this thesis was to test the hypothesis that the function of oocyte apoptosis is oosorption in N. cinerea. I found that in addition to enforced virginity, starvation induces oocyte apoptosis. However, the life history outcome following one form of stress is the opposite of the other. Hence, the functional role of oocyte apoptosis appears to be different depending on whether apoptosis is induced through starvation or age. Following a period of starvation-induced apoptosis females exhibit the increase in survival and future reproduction predicted by oosorption. Whereas, following a period of age-induced apoptosis females suffer fecundity and longevity cuts. However, age-induced apoptosis does not appear to simply be cellular ageing and clearance. In conjugation with age-induced apoptosis, ovariole number declines whilst the size of surviving oocytes increases. Hence, it appears that resources from sacrificed oocytes are being recycled into the survivors, and that this reinvestment in current reproduction trade-offs with future reproductive capacity. My thesis shows the importance of studying proximal mechanisms alongside more traditional measures of life history, as the relationship between isolated biological levels is not always clear.
Barrett, E. L. B., Preziosi, R. F., Moore, A. J. & Moore, P. J. (2008) Effects of mating delay and nutritional signals on resource recycling in a cyclically breeding cockroach. Journal of Insect Physiology 54, 25-31.
Barrett, E. L. B., Moore, A. J. & Moore, P. J. (2009) Diet and social conditions during sexual maturation have unpredictable influences on female life history trade-offs. J. Evol. Biol. 22(3):571-581
Barrett, E. L. B., Hunt, J., Moore, A. J. & Moore, P. J. (Published online ahead of press) Separate and combined effects of nutrition during juvenile and sexual development on female life-history trajectories: the thrifty phenotype in a cockroach. Proc. Roy. Soc. B., June 24, 2009, doi: 10.1098/rspb.2009.0725
Barrett, E. L. B., Moore, A. J. & Moore, P. J. (In Press) Does the scent of a potential mate prevent the resorption. Insect Science (DOI 10.1111/j.1744-7917.2009.01276.x)
Barrett, E.L.B., Moore, A.J. and Moore, P.J. (In Press) A potential function for oocyte apoptosis in Nauphoeta cinerea. Physiological Entomology.
Moore, Patricia J
Moore, Allen J
PhD in Biological Sciences