Achiralems

Achiralems is a small genus of filamentous organisms discovered in the late 20th century. The name derives from the Greek akhiralos, meaning “without chirality,” reflecting the unique lack of handedness in its cellular arrangement. Classified within the domain Eukarya, kingdom Plantae, phylum Chlorophyta, class Chlorophyceae, and order Chaetocerotales, Achiralems is closely related to the genera Chaetoceros and Thalassiosira.

Members of the genus appear as unbranched, cylindrical filaments approximately 5 to 12 µm in diameter. Each cell contains a single, centrally placed chloroplast with a palisade arrangement of thylakoid stacks. Unlike most diatoms, Achiralems cells lack the typical left–right asymmetry of the silica frustule, giving the filaments a mirror‑symmetric appearance. The filaments usually grow in loose sheets or loose rosettes, and individual cells are separated by thin cytoplasmic bridges.

Achiralems is found in coastal seas worldwide, most frequently in temperate to subtropical regions such as the Gulf of Mexico, the Baltic Sea, and the Tasmanian coast. The species thrives in nutrient‑rich, low‑salinity waters and forms part of the early phytoplankton community during spring blooms. While the ecology of Achiralems is not yet thoroughly understood, it is thought to play a role in carbon fixation and as a food source for small zooplankton.

Because of its atypical symmetry, Achiralems has become a model for studies of cellular symmetry and developmental genetics in blue‑green algae. Genome sequencing projects have revealed genes that differ from those of related diatoms, providing insights into the evolution of frustule morphology. Several research groups have used Achiralems as a test system for studying the impact of climate change on photosynthetic efficiency.