Mr The Anh Than1,2, Associate Professor Fleur Ponton1

1Macquarie University, North Ryde, Australia, 2Vietnam National University of Agriculture, Hanoi, Vietnam

Biography:

Anh is a PhD candidate in Biological Science at Macquarie University, NSW, Australia. His research focuses on insect biology, ecology, and behaviour. He has worked with various insect models, including the beet armyworm (Spodoptera exigua), the Queensland fruit fly (Bactrocera tryoni), and is currently studying Drosophila melanogaster. His work explores the effects of ecological factors such as nutrition, density, and bacterial infection on life history traits, oviposition behaviours, and transgenerational effects in insects.

Abstract:

The fitness and survival of insect offspring often depend on the quality of their developing habitat, influencing the timing and location of maternal egg-laying. The nutritional composition of the developing substrate is particularly important in influencing developmental time and adult expression traits. It has been suggested that the condition of the mother can also affect offspring physiology and might interact with oviposition choice. In this study, we manipulated the maternal physiology in Drosophila melanogaster flies through three treatments: infected (flies injected with live Serratia marcescens bacteria), heat-killed (flies injected with heat-killed S. marcescens bacteria), and control (naïve flies). We then examined the effects of the treatment on maternal oviposition choice for substrates that varied in their nutritional composition (i.e., protein-to-carbohydrate ratio, P:C ratio), in both choice and no-choice assays. Offspring development and bacterial resistance were also followed. In the no-choice experiment, flies laid the most eggs on the protein-biased substrate. However, when given a choice, females preferred the carbohydrate-biased substrates, especially in the infected treatment. These last results are surprising since offspring larvae failed to develop into pupae on the carbohydrate-biased substrate. Among the substrates biased for protein, the developmental time decreased as the P:C ratio increased, though the total number of pupae remained consistent across these substrates. Further, the interaction between the developing substrate and maternal infectious status influenced offspring bacterial resistance. In the infected treatment, males on the highest P:C ratio substrate showed a higher resistance, while females exhibited a lower resistance compared to other substrates. These findings highlight how the physiological status of mothers influences their oviposition choice and underscore its importance for offspring performance.