vesikulids

Vesikulids are a proposed group of unicellular eukaryotes characterised by abundant intracellular vesicles that give the cytoplasm a vesiculated appearance. They occur in a variety of aquatic habitats, including freshwater, brackish, and marine environments, as well as moist terrestrial soils.

Morphology and physiology vary among vesikulids but most are small to medium-sized, typically a few to several tens of micrometres in length, with a flexible pellicle and a rounded to elongated form. The cell interior contains vesicles of varying sizes that are implicated in osmoregulation, secretion, and digestion. Some species possess a rudimentary contractile vacuole system for water balance, while others rely on alternative mechanisms for maintaining osmotic stability.

Taxonomy and phylogeny in vesikulids are unsettled. They have been allied with multiple major protist lineages, and molecular data are limited. As a result, many researchers view vesikulids as a potentially polyphyletic assemblage rather than a single, coherent clade. Ongoing genetic and ultrastructural studies aim to clarify their relationships to better understand protist diversity.

Ecology and life cycle extend across diverse trophic modes. Vesikulids are primarily bacterivores or mixotrophs, feeding on bacteria and small eukaryotes. Reproduction is commonly asexual via binary fission, with some lineages showing limited sexual processes or cyst formation under adverse conditions.

Significance and research attention often focus on vesicle biology. The prominent vesicles in vesikulids make them useful models for studying vesicle trafficking and membrane dynamics in protists, contributing to broader insights into microbial ecology and evolution. The name derives from vesicle-like cytoplasmic structures and should not be confused with viral taxa sharing similar-sounding names.