PEXgeenides

PEXgeenides is a fictional clade of single-celled eukaryotes used in speculative biology to illustrate concepts in organelle evolution and taxonomy. In this hypothetical framework, PEXgeenides is described as a monophyletic lineage characterized by a distinctive arrangement of peroxisome-like compartments, and it has been employed as a thought experiment about how new groups are defined and named.

Taxonomy and naming are intentionally provisional in the fiction. The name PEXgeenides combines a nod to peroxisome-related biology (PEX) with a suffix intended to mark a distinct clade. In the speculative scenario, PEXgeenides is placed within the eukaryotes, but there is no formal assignment to a real taxonomic rank or to an established higher group that is recognised outside fiction.

Description and morphology in the imagined lineage emphasize unicellularity and aquatic habit. Members are described as small protists ranging from roughly 5 to 25 micrometers in length, with a simple cytoskeleton and varying motility. A hallmark claim is the presence of abundant membrane-bound, peroxisome-like compartments proposed to mediate lipid metabolism, though the exact function of these compartments remains debated within the fictional account. Reproduction is depicted mainly as asexual binary fission, with occasional cyst formation under stress.

Ecology and distribution in the speculative material place PEXgeenides in freshwater and coastal marine microhabitats, across temperate to tropical regions. They are imagined as occasional micro-predators or scavengers contributing to local nutrient cycles, though ecological roles are described as tentative in the absence of empirical data.

Discovery and status note that the concept originated in a 2023 speculative biology article by fictional authors. A type species, PEXgeenides aqua, is proposed in the fiction, but no cultured representatives or genomic data exist in reality. The clade is used as a tool for exploring taxonomic principles and peroxisome biology in a fictional setting.