Starfish Fungus

Aseroe rubra is one of the earliest fungi to be formally described from Australia and remains among the most striking. Where most stinkhorns are either columns or cages, this species builds a flattened radiating disc perched on a short stalk, with each ray splitting into two slender tips so the whole resembles a sea anemone or starfish.

The genus Aseroe sits in the family Phallaceae. Its defining feature is precisely this disc-plus-rays construction, with the gleba concentrated in a central depression rather than spread over the arms.

Native to Australia, New Zealand and neighbouring Pacific regions, it has been carried around the world in mulch and nursery stock and is now reported from the southeastern United States, Hawaii, parts of Europe, South Africa and Asia — usually in landscaped ground rather than native forest.

Stalk

A short, hollow, spongy stalk 3–8 cm tall and 1–3 cm thick, whitish to pale pink, rising from a whitish to brownish, sac-like volva with a white cord below. The stalk is round in cross section and chambered like foam.

Disc and arms

The stalk flares at the top into a flattened, radially arranged disc 3–10 cm across, bright red to orange-red. From the disc margin arise five to ten arms, each of which forks near its base into two tapering, tentacle-like tips, so a specimen with seven rays may present fourteen points. The arms are usually red, sometimes fading paler, and often curve down toward the ground.

Gleba and flesh

Dark olive-brown to blackish spore slime fills the central depression of the disc, forming a glistening dark eye at the centre of the red star. The flesh is soft, wet and honeycombed throughout, and the entire fruiting body collapses within about a day. The egg stage is a whitish to pale brown ball 2–4 cm across, gelatinous within.

It is at home in wood chip mulch, bark beds, sawdust, garden borders, lawns over buried woody debris and the litter of eucalypt, pine and mixed forest. Landscaping mulch is the classic substrate outside its native range, and fruitings are often in loose troops where the rhizomorph network is dense.

Fruiting occurs from late spring through autumn in temperate areas, and more or less year-round in warm humid climates, always following rain. Its native range spans eastern Australia, Tasmania, New Zealand and Pacific islands, with introduced populations now scattered across several continents.

The Starfish Fungus is saprobic, decomposing bark, wood chips and other plant litter through white to pale rhizomorphs that thread the substrate and terminate in eggs.

Its flattened disc and outspread arms provide a broad, low landing platform, and the central pool of fetid gleba puts the spore mass exactly where alighting flies will walk. Insects feeding there pick up spores on their legs and mouthparts and ingest others, and dispersal follows their movement, entirely replacing wind-borne spore release.

Clathrus archeri has similarly red, outspread arms but they are unforked, arise directly from a very short base with no expanded disc, and carry the gleba in blotches along their inner surfaces rather than in a central pool. Pseudocolus fusiformis has three or four tapering arms that stay joined at the apex, forming a cage rather than a flat star.

Lysurus species keep their arms short and clustered at the top of a distinct stalk. Where only the egg stage is found, a vertical section shows the folded red disc and gelatinous layer, unlike the uniformly firm interior of a young puffball.