Caulacanthus ustulatus (Turner) Kütz.
Phycol.General. 395 (1843)

Conservation Code: Not threatened
Naturalised Status: Native to Western Australia
Name Status: Current

Scientific Description
John Huisman & Cheryl Parker, Thursday 8 September 2016

Habit and structure. Thallus forming a tangled mat of decumbent axes attached to the substratum by clusters of multicellular rhizoids arising from outer cortical cells, with irregularly produced upright axes to 1.5–2.5 mm tall bearing sparse short lateral branches. Axes terete to slightly flattened, 100–350 µm in diameter, tapering to 60 µm in diameter just below the distinctly pointed apices. Central axis conspicuous, with cells 35–100 µm long and 12–20 µm in diameter when mature, each bearing a pair of di-trichotomously branching lateral filaments that traverse a small cavity before forming a pseudoparenchymatous cortex of 2–3 layers. Outer cortical cells angular in surface view, 5–12 µm broad.


Reproduction. Reproductive structures not seen.


Distribution. Widespread species along tropical and warm-temperate coasts. It has been recorded from most regions, with the exception of the western Atlantic and Central and South America.


Habitat. C. ustulatus grows on intertidal rock or is epiphytic on a variety of algae and mangroves.