Diversity and Ecology of Marine Parmales

Marine Parmales, members of the class Bolidophyceae, are minute, unicellular phytoplankton characterised by their distinctive silicified cell walls or naked flagellate forms. Although they represent a minor fraction of global marine biomass, Parmales occupy a broad range of habitats from polar to tropical waters and contribute to silica and carbon cycling in the upper ocean. Phylogenetically, they are the sister lineage to diatoms and display a dual ecological strategy: phago-mixotrophy, whereby cells ingest particulate prey, and photoautotrophy, harnessing light energy via chloroplasts. Morphological diversity is reflected in multiple plate arrangements, with most species forming eight interlocking silica plates. Biogeographical surveys reveal clade-specific distributions, suggesting adaptation to distinct temperature, light and nutrient regimes. Their ability to regulate silicification under varying silicate concentrations and to switch between trophic modes under resource limitation underscores their ecological flexibility. Despite low relative abundances in plankton assemblages, Parmales serve as an important model for understanding early heterokont evolution and the ecological transitions that gave rise to modern diatom dominance.

Research from Nature Portfolio

Comparative genomic analyses of multiple Parmales species have shed light on the evolutionary divergence between parmaleans and diatoms. Genomes of eight parmalean taxa reveal the retention of genes for phagocytosis alongside phototrophic pathways, in contrast to diatoms, which have lost phagocytic machinery and show expansions in nutrient-uptake gene families, notably for iron and silica transport. These findings indicate that the transition from phago-mixotrophy to exclusive photoautotrophy was a pivotal event in diatom evolution, linked to specialisation of silicified cell walls and enhanced nutrient assimilation capabilities. Such genomic insights provide a framework for interpreting the ecological success of diatoms and the more cryptic lifestyle of Parmales in modern oceans.

Diversity and Ecology of Marine Parmales publication trend

The graph below shows the total number of articles in diversity and ecology of marine parmales across all publications each year (not limited to Nature Index journals).

Technical terms

Parmales: A group of pico-sized marine phytoplankton in class Bolidophyceae, some with silicified plates and others flagellated.

Phago-mixotrophy: A nutritional mode combining ingestion of particulate prey with photosynthetic carbon fixation.

Photoautotrophy: Energy acquisition exclusively through photosynthesis, using light to convert inorganic carbon into organic matter.

Amplicon Sequence Variant (ASV): A highly resolved DNA sequence variant recovered from environmental sequencing, used to infer taxonomic diversity.

Metabarcoding: A method for assessing biodiversity through mass sequencing of standardized genetic markers from environmental samples.

References

1. Genome analysis of Parmales, the sister group of diatoms, reveals the evolutionary specialization of diatoms from phago-mixotrophs to photoautotrophs. Communications Biology (2023).
2. Global Distribution and Diversity of Marine Parmales. Microbes and Environments (2024).
3. Effects of Silicon-Limitation on Growth and Morphology of Triparma laevis NIES-2565 (Parmales, Heterokontophyta). PLOS ONE (2014).
4. Bolidophyceae, a Sister Picoplanktonic Group of Diatoms – A Review. Frontiers in Marine Science (2018).