Séminaire Ecobio - Emma Lavaut (Ecobio)

During this seminar, I will present some of my thesis work, which explores the complexities of reproduction in the red alga Gracilaria gracilis, and I will give a brief (5 min) presentation of my future work at ECOBIO.
Red algae have a complex life cycle with alternating haploid and diploid phases, involving three types of individual: diploid tetrasporophytes and haploid male and female gametophytes. The particularities of their reproduction are that: male gametes do not have a flagellum, female gametes are not released and after fertilisation the zygote develops on the
female into a structure called a cystocarp. Without a flagellum, the transport of spermatia to the female gametes depends, a priori, on water movements. A study of the interaction with the isopod Idotea balthica, a frequent mimic on the algal fronds, revealed animal-mediated fertilisation, similar to pollination in plants. This suggests that this phenomenon, unknown until now in red algae, may have originated earlier than the colonisation of the terrestrial
environment by plants, or may have evolved in parallel in aquatic and terrestrial environments. Furthermore, my work has shown that the opportunity for sexual selection is present in G. gracilis, a species where sexual dimorphism is absent. One possibility would be to explore traits linked to pollinator attraction, such as reproductive phenology and mucilage
production. Finally, my work looked at the consequences of this cycle on the demography of G. gracilis, by means of long-term monitoring of this alga. The results show a high survival rate of individuals, some of which are still present 25 years after the first surveys, and low demographic growth.