Fitness of teratological morphotypes and heritability of deformities in the diatom Gomphonema gracile

Type Article
Date 2019-11
Language English
Author(s) Coquillé Nathalie1, 2, 3, 4, Morin Soizic1
Affiliation(s) 1 : Irstea, UR EABX, 50 avenue de Verdun, 33612 Cestas Cedex, France
2 : Ifremer, Laboratoire d’écotoxicologie, rue de l’île d’Yeu, BP 21105, 44311 Nantes Cedex 03, France
3 : Université de Bordeaux, UMR EPOC 5805 CNRS, LPTC, 351 Cours de la Libération, CS 10004, 33405 Talence Cedex, France
4 : CNRS, UMR 5805, EPOC, LPTC, 351 Cours de la Libération, CS 10004, 33405 Talence Cedex, France
Source Ecological Indicators (1470-160X) (Elsevier BV), 2019-11 , Vol. 106 , P. 105442 (11p.)
DOI 10.1016/j.ecolind.2019.105442
WOS© Times Cited 7
Keyword(s) Gomphonema gracile, Morphology-based assessment, Teratology, Transmissibility of morphological characters, Phenotypic variability, Fitness

Diatom teratologies have intrigued scientists since the XIXth century, with respect to their causes and origins. These deformities, mainly observed in long-term cultures or under high levels of pollution, were poorly considered, until they were recently found to be potential indicators of toxic impairment of freshwaters. However, very little is known about their ecology.

In this study, the growth and fitness of morphologically distinct descendants of the same cell line of Gomphonema gracile (teratological vs. non teratological forms) were compared over a typical growth cycle. Contrary to expectations, teratological populations grew slightly faster, at a rate of 0.47 ± 0.03−1, versus 0.41 ± 0.04 for the normal morphotype. They had similar physiological performances as non-teratological forms. They did not differ in their movement velocities, but the trajectory of teratological forms was more linear, likely as a consequence of their elongated outline. Under the same culture conditions, no competitive exclusion of one phenotype over the other was demonstrated on the time scale of an exponential growth cycle (9 days). 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 thus highlight ecosystem dysfunction. They call for further investigations of their ecology.

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