Sperm evolution across reproductive and fertilization modes

Main funder

Funder's project number: 314219

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Funding program

Project timetable

Project start date: 01/09/2017

Project end date: 31/03/2021

Summary

First observed 350 years ago, spermatozoa diversity was soon recognized to be an evolutionary conundrum. However, most studies addressing these questions have looked at taxonomic groups where the variation in sperm is but a fraction, mostly showing quantitative (relative component size) vs. qualitative (component type and presence/absence) interspecific difference. Not surprisingly, many questions remain unanswered. Tardigrada are uniquely suited taxonomic phylum to conduct such research, by having unparalleled diversity in sperm design but providing a view of reproductive evolutionary forces, less confounded by huge phylogenetic spread. I propose an ambitious, forward-looking, yet attainable program, that takes advantage of the exceptional opportunities the biology of this groups offers for present and future (evolutionary) research. Tardigrades are small, transparent animals, with diverse reproductive biology: there are hermaphroditic and bisexual species, the latter with or without sperm storage; both internal and external insemination occurs. They are found globally, and terrestrial taxa can survive extreme conditions by undergoing reversible cryptobiosis (ametabolic state). This project will use a combination of research methods to investigate sperm evolution by comparing sperm form and function across the wide range of selective forces: (i) run comparative analyses using both published (design) and new (function) sperm traits; (ii) conduct experimentally controlled sexual interactions to monitor of mating behaviour and genetically score paternity; (iii) use modern imaging techniques for in vivo and/or in toto monitoring of sperm function from the testis to the egg across the wide range of insemination/fertilization paths. This project offers high potential for immediate and significant contributions to some, so far fundamentally unanswerable, long-standing questions in reproductive evolution. Their peculiar appearance, their incredible biological feats (e.g. survive outer Space) and their consequent promising role in medical applications (x-ray resistance), make tardigrades the ultimate study organism for academic and societal impact purposes. This project will create their first research centre in Finland.

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