Mastocarpus
stellatus
Mastocarpus
stellatus: a lower-shore plant growing with Himanthalia elongata.
[Gigartina stellata; Gigartina mammilosa]
Description:
Cartilaginous, purplish brown fronds, often in dense tufts, arising from a discoid
holdfast, to 200 mm high. Narrow compressed stipe expands into strap-like blade,
usually inrolled to form a channel, with thickened margins. Repeatedly dichotomously
branched, axils acute. Upper part of frond with
papillae to 10 mm or more long on surfaces and margins on female plants. Male
plants lack papillae but are generally rare. Tetrasporophyte a purplish-black
crust. (see Petrocelis-phase)
Habitat:
On rocks in lower intertidal, often in large continuous mats, widespread and
abundant.
Petrocelis-phase of Mastocarpus stellatus
Description
:
Blackish, glossy crusts, to 1 mm thick, up to 120 mm diam.; without surface
markings.
Key characteristics :
Almost completely black colour and absence of surface markings; association
with Mastocarpus stellatus in the lower intertidal.
Habitat :
On rock, lower intertidal, widely distributed, common. Generally associated
with Mastocarpus stellatus , of which it is the tetrasporophyte, in the lower
interntidal and shallow subtidal. Commonest on southern and western coasts.
Similar species: Cruoria pellita (Lyngbye) Fries is more gelatinous and
is found only on the lowest of tides and in the shallow subtidal; expert opinion
is required for identification of it and Haemescharia hennedyi (Harvey)
Wilce et Maggs, is less common and is a similar, darkly coloured lower-shore
crust.
(In: Seaweed Site - ©Michael D. Guiry - http://seaweed.ucg.ie/descriptions/Petcru.html)
