Dicranochaete – an enigmatic green alga with surprising adaptive capabilities

Abstract:

Dicranochaete is a green coccoid alga with a spiny cap and a long branched seta that was described more than 100 yr ago from field samples. Although Dicranochaete has been repeatedly reported to be found on Sphagnum ‘leaves’ in peat bogs, our knowledge about its development is still fragmentary, and its phylogenetic affiliation remained controversial. To advance knowledge about this lesser-known alga, I used two Dicranochaete strains, grew them in a medium that mimics chemical properties of peat bogs and studied their life history and development. Furthermore, phylogenetic analyses using rDNA sequence comparisons were performed. My studies resulted in the following key observations: (1) Dicranochaete possesses a unique development that together with its characteristic morphology likely represents adaptations to the specific environment of peat bogs: the spiny cap, especially in early stages of algal development, presumably serves as a defence against predators. The seta provides an additional surface area to aid the uptake of nutrients, in particular phosphate. (2) Phylogenetic analyses identified Dicranochaete as a member of the Chaetopeltidales (Chlorophyceae). Moreover, a new species of Dicranochaete, Dicranochaete variabilis sp. nov., was erected, and the genus Dicranochaete Hieronymus (1890) was emended. In conclusion, this study provides new insights into the life history, developmental processes and phylogenetic position of Dicranochaete and provides insights into adaptation of epiphyllous microalgae to nutrient-poor environments (i.e. peat bogs).

Key Words::

• Adaptation
• Chaetopeltidales
• Chlorophyta
• Coccoid alga
• Dicranochaete variabilis sp. nov.
• Dicranochaetaceae
• Nutrient uptake
• Peat bogs
• Seta
• Spiny cap

ACKNOWLEDGEMENTS

I thank Karl-Heinz Linne von Berg for help in sample preparations for SEM and Michael Melkonian for fruitful discussions and access to his work group's resources. This study was supported by the University of Cologne.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/15-135.1.s1.