LE3 .A278 2015

2015

Gibson, Glenys

Acadia University

Bachelor of Science

Honours

Biology

Biology

Developmental plasticity is environmentally-induced variation in phenotype due to changes that occur during development, and is observed in many taxa. Epigenetic mechanisms have been linked to developmental plasticity and are thought to lead to the development of alternate phenotypes in offspring. My objective is to investigate whether epigenetic effects on larval phenotype in Polydora cornuta are parental or embryonic in origin. P. cornuta exhibits plasticity in larval development, in which it generates two morphs of young. My first hypothesis is that larval phenotype is determined by transgenerational epigenetic modifications. My second hypothesis is that larval phenotype is more strongly influenced by epigenetic modifications to the zygotic genome than to the maternal genome. I used immunofluorescence to detect the epigenetic mark, H3K9 monomethylation, in early embryos to test my first hypothesis. I compared larval data at hatching among treatments to evaluate my second hypothesis. Adults and/or broods were exposed to a methyl-releaser (bisphenol A, BPA) or a methyl-donor (folate/vitamin B12), as well as a seawater control. All broods collected were A-broods and contained large numbers of nurse eggs. Results showed significant differences in brood traits between control and BPA treatments. No significant difference was noted between control and folate treatments, however folate data showed a greater variance in some brood traits than the controls, an indication that some treatment effect was occurring. Low survivorship and brood production limited sample sizes therefore I was unable assess the relative importance of the parental or embryonic epigenome in determining larval phenotype. However, preliminary results suggest that epigenetic effects to the maternal genome are more influential in determining larval phenotype than those to the zygotic genome.

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https://scholar.acadiau.ca/islandora/object/theses:1257