Thalassiophyllum clathrus

Spiral sieve kelp

Authority: (S.G.Gmelin) Postels & Ruprecht

Thallus of this unique kelp is brown with a branched holdfast (haptera) and a woody stipe that is spirally twisted due to meristematic growth from which new blades unfurl. The blade can grow up to at least 50 cm (20 in) long and has somewhat regular perforations. Reproductive patches (sori) develop on the older portions of the blade.

Habitat

This perennial kelp is found on rock in the very low intertidal and shallow subtidal and prefers semi-exposed habitats. It is also found in tidepools.