Florideophytes

Florideophytes are a major lineage of red algae (Rhodophyta), comprising the class Florideophyceae and related orders. They represent the most diverse and ecologically important group within red algae, with thousands of described species found in marine ecosystems worldwide, from shallow tide pools to deep-sea habitats. Florideophytes include crustose coralline algae that contribute to reef structure and many large seaweeds used commercially.

Morphology and life cycles: Florideophytes are typically multicellular and highly varied in form, from filamentous to sheet-like to rigid crusts. A defining feature is their complex reproductive biology; most species exhibit a triphasic life cycle that includes a diploid tetrasporophyte, a dependent diploid carposporophyte on the female gametophyte after fertilization, and a haploid gametophyte. The carposporophyte produces carposporangia that release carpospores, which germinate into the tetrasporophyte, continuing the cycle.

Ecology and uses: They occupy many marine niches and include many important calcified forms such as crustose coralline algae that cement reef frameworks, as well as edible and industrial seaweeds. Species of Florideophytes provide habitat, food, and commercial products; agar and carrageenan are derived from various florideophyte genera, while others are harvested for food or aquaculture.

Taxonomy and evolution: Florideophytes form the largest clade of red algae and show substantial diversification since the early Paleozoic. Their groups range from simple filamentous lines to highly complex, thalloid forms, reflecting extensive ecological and morphological diversification.