tetraspore

A tetraspore is a spore produced as part of a four-spore unit, or tetrad. The term is most commonly used in phycology to describe spores that arise from a single tetraspore structure known as a tetrasporangium, typically during meiosis. Each tetraspore within the tetrad is haploid, and the tetrad arrangement is a characteristic feature recognized in several red algae (Rhodophyta).

In the life cycle of many red algae, the diploid tetrasporophyte generates tetrasporangia. Within these structures, meiosis yields four haploid tetraspores that are released together as a tetrad and then develop into the haploid gametophytic generation. The tetraspore arrangement can be cruciate (cross-shaped) or occur in other patterns, depending on the species. Tetraspores are generally non-motile and rely on environmental conditions for germination and subsequent growth.

Beyond red algae, the concept of a four-spore unit appears in other contexts of spore formation, but the exact term tetraspore is most routinely applied to tetraspores in Rhodophyta. In those contexts, the tetrad arrangement provides a synchronous release mechanism and can have taxonomic significance, helping distinguish species or life-cycle types within groups that exhibit tetrasporic development.

Terminology related to tetraspore includes tetrasporangium, the sporangial structure that houses the four spores, and tetraspores themselves. While the essential idea—spores produced in fours—appears in multiple lineages, the explicit use of the term tetraspore is most strongly associated with red algae and their zygotic life cycles.