Alcyonacea

Alcyonacea is an order of marine cnidarians within the subclass Octocorallia, comprising the soft corals, sea fans, sea whips, and related colonial forms. Members are generally sessile and form colonies that resemble plants in shape, yet are composed of numerous polyps connected by shared tissue. Like other octocorals, they exhibit eightfold symmetry, with polyps bearing eight tentacles and eight mesenteries.

Skeleton and morphology: Many Alcyonacea have a flexible internal skeleton made of a protein called gorgonin, which may be reinforced by calcareous sclerites. Some groups possess a more solid or partially mineralized skeleton, while others are entirely soft and semi-transparent. The resulting forms range from delicate fan-like sea fans to sturdy, branching sea whips and tree-like colonies.

Distribution and habitat: Alcyonacea occur in warm and temperate seas worldwide, from shallow coastal zones to deeper waters. They are common on reefs, rocky substrates, and other substrate types where water flow supplies food particles for their filter-feeding polyps.

Ecology and biology: These corals feed by extending their polyps to capture plankton and detritus from the water. Reproduction includes sexual strategies such as broadcast spawning and asexual methods like budding or fragmentation. As habitat-forming organisms, they provide shelter and foraging grounds for a variety of marine species.

Taxonomy and conservation: Alcyonacea belongs to the class Anthozoa and the subclass Octocorallia; it includes families such as Alcyoniidae, Gorgonidae, Plexauridae, and Nephtheidae. They face threats from ocean warming, acidification, pollution, and physical disturbance, and are sometimes targeted for the aquarium trade.