Appearance
It grows from a discoid holdfast stipe, and the fronds are channeled unlike those of "Chondrus crispus," which are flat. It grows to a height of 10–20 cm and branches dichotomously. The frond is cartilaginous and reddish-brown in colour, with a greenish or purplish tinge. The mature algae show reproductive structures which develop on erect filaments up to 1 mm in diameter, these make it readily distinguishable from "Chondrus crispus". In colour it is reddish brown, purple or bleached.
Distribution
"M. stellatus" occurs commonly on rocks in the mid and lower-intertidal. It is generally found on all coasts of Ireland and Britain, except perhaps for parts of the east of England: Lincoln, Norfolk and Suffolk. Other recorded locations include: Iceland, Faeroes, North Russia to Rio de Oro, Canada to U.S.. "Mastocarpus stellatus" is able to coexist with "C. crispus" on the northern New England coast despite being a competitive inferior to "C. crispus". A greater tolerance for freezing allows it to exist above "C. crispus" in northern environments where freezing stresses are significant. "M. stellatus" is rarely found south of Cape Cod on the United States Atlantic coast because it is out competed by "C. crispus" when the freezing tolerances are lower.References:
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