Chrysochromulina tenuispina is a haptophyte microalga in the family Prymnesiaceae, distinguished by slender spines (tenuispina: Latin, thin-spined) projecting from the surface scales. These fine spine-like extensions are visible under transmission electron microscopy and provide a key feature distinguishing this species from other spine-bearing Chrysochromulina species. Cells are biflagellate with a haptonema and are enclosed in a coat of organic scales produced in the Golgi apparatus. C. tenuispina is a marine nanoplankton organism found primarily in coastal and shelf waters of temperate and subarctic seas, where it participates in primary production and the microbial food web. The genus Chrysochromulina thrives in physically mixed and nutrient-enriched waters, and many species exhibit plasticity in their nutritional strategies, supplementing photosynthesis with bacterial ingestion under low-light or nutrient-limited conditions. The slender spine structure may function in anti-grazing defense, reducing palatability or accessibility to protozoan predators. C. tenuispina has not been assessed for conservation status by the IUCN and is categorized as Not Evaluated. Its ecology and genetic diversity are incompletely characterized.