Breviolum

Breviolum is a genus of single-celled dinoflagellates in the family Symbiodiniaceae. Members are endosymbiotic algae that inhabit the tissues of marine invertebrates, most notably reef-building corals, and contribute to the host's nutrition through photosynthesis. The genus was established during a molecular-based revision of the former genus Symbiodinium, with several species reassigned to Breviolum and related genera.

Breviolum species are photoautotrophic dinoflagellates that reside within host cells in a stable symbiotic relationship. They possess chloroplasts with photosynthetic pigments and translocate photosynthates to the host. They can be acquired horizontally from the environment or vertically through parental transmission, depending on the host species. They are found in tropical and subtropical reef environments and are common in association with scleractinian corals, but also occur in other invertebrates such as sea anemones.

The symbiotic relationship is central to coral nutrition and energy budgets, especially in oligotrophic waters. The composition of Breviolum lineages within a coral holobiont can influence ecological responses, including tolerance to heat stress. Under elevated temperatures or other stressors, the mutualism can break down, contributing to coral bleaching as the host expels the symbiont.

The genus comprises several species, including Breviolum minutum, which has been cited in multiple studies as a representative of the group. Breviolum remains an active area of research as molecular phylogenetics continues to refine its taxonomy and ecological role in coral symbioses.