How does a butterfly embryo cope with environmental stress?

Butterfly abundance and species diversity have been in decline and several anthropogenic factors have been implicated in the observed downwards trend. This thesis focusses on environmental stress directed at butterfly eggs, using the model systems Pararge aegeria and Bicyclus anynana. Eggs are a vulnerable life stage in which environmental stressors can have a major impact on both survival and development. The majority of winged insects, including butterflies, develop a protective sheet of cells surrounding the embryo during early embryogenesis. This sheet of epithelial cells is called the serosa and appears to protect the embryo against toxins, desiccation and pathogens. I first developed a morphological staging including a description of the extra-embryonic serosa for P. aegeria. Such a description will aid in understanding the developmental perturbations environmental stressors may cause. One of the stressors butterflies are (inadvertently) exposed to are insecticides, which is reviewed in full here. A research programme is proposed to incorporate the developmental genetic mechanisms underlying the pesticide response in a conservation context. The effects of two hormone analogs (i.e. of juvenile hormone and 20E) to study their effect on endocrine disruption during embryogenesis; both a maternal effect and through direct exposure. Eggs displayed increased sensitivity early in development before serosa formation and were in general more significantly affected as a result of a maternal effect. Finally, using transcriptomics and in-situ hybridisations, the effects of a natural stressor in B. anynana eggs was investigated; bacterial exposure in combination with wounding. The serosa, rather than the embryo, was able to mount an immune response, evidenced by significant upregulation of immune-related genes, such as hemolin, and genes in the Toll, IMD, Mapk-Jnk-P38 and JAKSTAT pathways. In conclusion, the butterfly embryo copes with environmental stress, such as toxins and immune challenges, with the help of the serosa.

Grantor dc:publisher

Oxford Brookes University

Year dc:date

2018

Author dc:creator

• Braak, Anne Leonora

Contributors dc:contributor

• Breuker, Casper
• Gibbs, Melanie
• Jones, Andrew

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/0cym-jt45

OAI identifier oai:identifier

tle:e331ee81-0948-420d-b5cf-d250e1602acb:d6bd9758-527a-46cd-bfe2-c433766e8fca:1