Solukarikoiden

Solukarikoiden are a proposed clade of eukaryotic microorganisms that include unicellular species and small colonial forms. They are defined by a membrane-bound nucleus and internal organelles, exhibiting cellular complexity intermediate between prokaryotes and multicellular eukaryotes. The term appears in some taxonomic discussions and educational contexts to illustrate early-eukaryote features in aquatic environments.

Key characteristics include eukaryotic cells with nuclei, mitochondria-like organelles, and a cytoskeleton. Most solukarikoiden are microscopic, typically 2–20 micrometers in diameter, though some colonial forms are larger. Metabolic strategies are diverse: phototrophic, heterotrophic, and mixotrophic modes exist, with nutrition sometimes shifting with light, nutrients, and habitat. Reproduction is mainly asexual via mitosis; rare sexual events have been reported.

Habitat and distribution: solukarikoiden occur in freshwater and marine systems, including plankton, sediments, and biofilms. They have a cosmopolitan distribution, with higher diversity in nutrient-rich coastal areas and temperate freshwater bodies. They are often more abundant in the upper photic zone.

Taxonomy and phylogeny: the monophyly of solukarikoiden is debated. Molecular data place various members in different positions among eukaryotic lineages, leading many researchers to treat solukarikoiden as an informal grouping rather than a formal, monophyletic clade.

Ecology: solukarikoiden contribute to primary production in photosynthetic members and to nutrient cycling and microbial food webs in non-photosynthetic ones. They serve as prey for microzooplankton and participate in carbon cycling in aquatic ecosystems.

Research and applications: they are used to study early eukaryotic evolution and cell biology, with potential biotechnological applications in enzymes and bioactive compounds.