Developmental basis of mushroom body expansion in Heliconius butterflies

Mushroom bodies (MBs) are the most enigmatic structures in the insect brain. They have ‘higher order’ functions, integrating sensory information and storing memories of past experience. MBs share a conserved ground plan, but their size and structure varies extensively across species. MB volume in Heliconius butterflies are among the highest across insects, 3-4 times larger than typical for Lepidoptera, including their most closely related genera in the wider tribe of Heliconiini. This provides a novel system for investigating the developmental mechanisms that control neural proliferation and brain component size. However, nothing is known about the developmental changes that have produced such a dramatic expansion.

The project will involve core laboratory, microscopy and neuroanatomical techniques, insect rearing and experimental manipulation.

You will construct the first time course of Heliconius brain development, from late larvae through pupation to adulthood. Using immunocytochemistry and confocal imaging you will determine key properties of MB growth trajectories, providing a template for developing hypotheses of when and how MB development in Heliconius diverged from related genera.

By adopting an evo-devo approach you will then conduct a series of comparative studies across Heliconiini to assess how increases in neuron number are produced, considering four potential mechanisms: i) an increase in the number of neural progenitor cells, ii) accelerated cell-cycle rates during neurogenesis, iii) an extension in the overall duration of neurogenesis including the possibility of adult neurogenesis, iv) reduced or delayed patterns of apoptosis among neural progenitor cells.

Finally, once key periods of developmental divergence have been identified between Heliconius and related genera, you will perform a second series of analyses to identify divergent patterns of gene regulation and expression as part of a project that aims to identify the genetic basis of MB expansion.

Some field/insectary work in Panama may be necessary/desirable.