Erect fan weed anchors deeply into silty reef sand using a massive, bulbous holdfast of interwoven filaments that binds loose sediment together. The upright, paddle-shaped frond consists of a single multinucleate giant cell branching without internal walls, giving the alga remarkable structural flexibility in shifting lagoon currents. It serves as an essential microhabitat, offering shelter to small juvenile fishes and cryptic invertebrates while contributing to tropical sediment stability.
MarineMacroalgaReef-Dwelling
—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Key facts
Diet & prey
Photosynthetic (autotrophic)
Predators
Sea Urchins
Surgeonfish
Parrotfish
ThreatsCoastal development, siltation, and ocean warming
HabitatsShallow reef flats, sandy lagoons, and seagrass meadows
Life span1–3 years
Classification
FamilyDichotomosiphonaceae
SpeciesAvrainvillea erecta
Range & activity
Range data is not available yet.
Safe observation
Interaction riskLow
Low
Moderate
High
Very high
Why interaction risk is low
Safe to observe at a normal distance.
Responsible observation
Substrate Care: Tread lightly when wading in sandy flats to avoid crushing the buried root-like holdfasts.
Snorkeling Observation: Drift slowly during low tide to view the velvety surface filaments without stirring up sediment.
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