McGill University
Ph.D. candidate
Supervisor: Ehab Abouheif
Dr. Rachel Collin, Smithsonian Tropical Research Institute
Start: 2009-09-01
End: 2016-04-01
Personal page

Project

Direct Development with Nutritive Embryos: Developmental Polyphenisms in Evolution and Development
Polyphenisms are discrete phenotypic responses to varied environmental stimuli. Nutritive embryos, embryos that arrest development and are ingested by their normally developing siblings, represent a developmental polyphenism. Although they are found in diverse groups including frogs, ants, and marine snails, little is known about their development and evolution. I combined ecology, embryology, gene expression, and development, to study nutritive embryos in the calyptraeid gastropods. I focused on two species, Crepidula navicella and Calyptraea lichen. Both are able to produce nutritive embryos, but C. lichen can also switch developmental mode, producing either mixed broods that include nutritive embryos, or broods of viable embryos that hatch as free-swimming larvae. Field collection of developing embryos during seasonal changes in upwelling conditions showed that C. lichen increases production of mixed broods and variability of brood composition during upwelling. C. navicella does not adjust embryo allocation in response to seasonal environmental changes. Detailed observations of early development of C. navicella showed that nutritive embryos are morphologically indistinguishable from viable embryos until shortly after gastrulation, when embryos can be categorized as viable embryos, gastrula-like nutritive embryos, or post-gastrula-like nutritive embryos. Early distinctions between viable and nutritive embryos may be influenced by precocious activation of MAPK (ERK 1/2), which correlates with apoptotic signals in some cleavage-stage embryos of C. navicella. A similar pattern of early MAPK activation and apoptosis is found in C. lichen. Finally, high throughput RNA sequencing of viable and gastrula-like nutritive embryos of C. navicella revealed transcriptional differences: viable embryos express transcripts associated with tissue differentiation, while nutritive embryos express transcripts associated with control of apoptosis and cellular events. Together, my data show that nutritive embryos are a complex character, highlighting the importance of combining multiple levels of biological organization in order to understand the evolution of development.

Keywords

evolution, development, life history evolution

Publications

1- Growth and differentiation during delayed metamorphosis of feeding gastropod larvae: signatures of ancestry and innovation
Lesoway, Maryna P., Louise R. Page
2007 Marine Biology

2- Cleavage pattern and fate map of the mesentoblast, 4d, in the gastropod Crepidula: a hallmark of spiralian development
Lyons, Deirdre C, Kimberly J Perry, Maryna P Lesoway, Jonathan Q Henry
2012 EvoDevo

3- Poecilogony in the caenogastropodCalyptraea lichen(Mollusca: Gastropoda)
McDonald, Kathryn A., Rachel Collin, Maryna P. Lesoway
2014 Invertebrate Biology

4- The development of viable and nutritive embryos in the direct developing gastropod Crepidula navicella
Lesoway, Maryna P., Ehab Abouheif, Rachel Collin
2014 The International Journal of Developmental Biology