Phenotypic plasticity in diatoms: Janus cells in four Gomphonema taxa

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Diatom Research


We observed four Gomphonema taxa with a high abundance of Janus cells, which are cells that have valves of two different morphologies, also termed heterovalvar cells. The specimens were collected from a habitat with periodic drying, alternating with standing water. A high proportion of Gomphonema Janus cells (up to 20% of the frustules for each taxon) were found. Heterovalvy within a frustule is based on stria count, and two types of heterovalvy were observed. Cells produced either coarsely or finely striated valves with discontinuous phenotypic plasticity or highly variable stria density within a frustule along a continuous phenotypic gradient. In our study, we measured stria density in complete frustules and single valves. Other features of the frustules showed no noticeable variation. Variable stria density was found in frustules and single valves, although it is not possible to determine whether the single valves were part of Janus cells or homomorphic frustules. Therefore, our conclusions are based on the measurements of complete frustules only. We propose that Janus cells result from two ecophenotypic responses (reaction norm and polyphenism) of these taxa to one or more environmental factors. As such, Gomphonema taxa that produce Janus cells may be model organisms for deciphering the genetic basis of developmental plasticity in diatoms.


Biological and Environmental Sciences

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