Bristled
Crayweed

Seirococcus axillaris, commonly known as Bristled Crayweed, is a large brown seaweed that can grow up to 2 metres long. It is typically medium to dark olive-brown in colour, with a tough, leathery texture.

The plant has a short, rounded stalk that develops into long, flattened, ribbon-like branches. These branches grow alternately along the main stem, spreading out in a single plane, and may be straight or slightly curved. A pale, flattened central rib runs along the length of the larger branches.

The plant attaches to rocks through a large holdfast with several branching, root-like structures. Unlike some other brown seaweeds, it does not produce air-filled floats.

One of its most useful identifying features is the presence of numerous tiny, bead-like reproductive structures, known as receptacles, which develop along the edges of the flattened branches. These may form short, bristly fringes but are only visible when the plant is reproductive.

Seirococcus axillaris can be confused with Scytothalia dorycarpa, which has a similar overall appearance but generally has more open branching and larger, beak-like reproductive structures. Without these reproductive features, the two species can be difficult to distinguish reliably.

Seirococcus axillaris Identification 2 Seirococcus axillaris Identification 1 Seirococcus axillaris Identification 3 Seirococcus axillaris Identification 4