Heritability of deformities in diatoms

International audience; Diatom teratologies have intrigued scientists since the XIXth century, with respect to the causes and origins of their outbreak. They were mainly observed in long term cultures or under high pollution, and were poorly considered, except recently as a potential indicator of toxic impairment of freshwaters. However, nothing is known neither about the processes involved in their induction nor in their ecology of these forms. In this study, we compared morphologically distinct descendants of the same cell line of Gomphonema gracile (teratological vs. non teratological forms), by determining their growth abilities, alone and in competition, as well as their physiology (photosynthesis) and behavior (motility) over a typical growth cycle. Contrarily to our expectations, teratological cultures grew faster (0.49±0.04 div/day, vs. 0.44±0.01div/day in the non teratological forms) and had similar physiological performances as the non teratological ones. Under the same culture conditions, we were not able to demonstrate any competitive exclusion of one phenotype over the other. Moreover, the deformities were faithfully reproduced over time, and no evidence of decreased viability in teratological forms was provided. These new insights call into question the common hypothesis that deformed diatoms are altered individuals produced by unfavorable conditions and outcompeted when pollution is removed, thus highlighting ecosystem dysfunction. They call for further investigations of their ecology.