Maternal effects and early-life social experiences in the live-bearing and lactating Pacific beetle cockroach
Supervisors: Dr Sinead English, Prof Rebecca Kilner
Experiences in early life have lasting impacts on behaviour, health and reproductive success across a great many species. For organisms starting life in the womb, the diet and environment experienced by the mother contributes significantly to these long-term effects. While there is extensive research across the natural world documenting the diversity and pervasiveness of these parental and early-life effects, important questions remain. For example, how do maternal and post-natal early-life influences interact to contribute to later development? To what extent are these early-life effects reversible when conditions change? Why are certain periods of development more sensitive to external experiences than others?
This project will tackle some of these questions using an exciting experimental system, the lactating and live-bearing Pacific beetle cockroach, Diploptera punctata. Females give birth to a brood of around 7-13 nymphs after a 60-day gestation, during which time the developing young feed from a milk-like secretion from the female's intrauterine tract. Studies have shown that maternal nutrition and early social experiences have lasting effects on offspring development rate and final body size. Males are more susceptible to these effects, but the reasons for sex differences are not clear. The PhD will explore these effects further by manipulating maternal nutrition and offspring environment in the laboratory.
What the student will be doing:
The scope of the project is flexible and a range of manipulations is possible. Maternal and offspring nutrition can be manipulated by varying the amount of standard laboratory food provided, or the composition of protein to sugar. Early-life social experience can be varied by adding or removing nymphs from a clutch after birth. By monitoring the growth and social behaviour of individuals from birth through to sexual maturity, the long-term effects of early-life manipulations can be contrasted with manipulations repeated later in development. Maternal investment can be monitored across subsequent broods to assess the extent to which females trade-off current investment versus future reproduction, and the role of infanticide or siblicide in these adjustments under food stress.
Holbrook, G. L. & Schal, C. 2004 Maternal investment affects offspring phenotypic plasticity in a viviparous cockroach. Proc. Natl. Acad. Sci. U. S. A. 101, 5595–5597. (doi:10.1073/pnas.0400209101)
Holbrook, G. L. & Schal, C. 1998 Social influences on nymphal development in the cockroach, Diploptera punctata. Physiol. Entomol. 23, 121–130
Stay, B. & Coop, A. 1973 Developmental stages and chemical composition in embryos of the cockroach, Diploptera punctata, with observations on the effect of diet. J. Insect Physiol. 19, 147–171. (doi:10.1016/0022-1910(73)90230-8)