Rhodophyta, Order Ceramiales; Family: Rhodomelaceae.

Etymology

Alsidium genus refers to its reddish tint. The species name,  corallinum, derives from its resemblance to coral.

Description

The Alsidium corallinum is an erect alga, cylindrical and  branched. Its branches are interleaved, and the central  branch sprouts smaller, straight, sharp branches measuring  no more than several millimeters. The branching begins at  the base of the plant and continues irregularly.

Size

The alga can stand up to 20 cm in height, but is often no  taller than 5 cm.

Colour

The Alsidium corallinum appears in various hues, ranging  from red to green. Colouring differs from one individual to  another, and depends upon lighting.

Special features

The Alsidium corallinum resembles the Hypnea in many  ways, and the two can be easily mistaken for one another.  However, the Alsidium corallinum is more delicate, uniform,  and its branches are not hook-like. Nor does it sprout starlike  bristles.

Habitat

The Alsidium corallinum can usually be found on abrasion  platforms, in potholes, especially on their upper part, and  sometimes also in the Weathring pits in the lower part of the  notch. Sightings have been reported at up to twenty and  sometimes thirty metres upon sandy and rocky sea bottoms.

Biology and reproduction

The cystocarp (a stage in the life cycle of some red algae, an  asexual structure that develops around fertilized eggs and  appears as a parasite upon the sexual generation), measure  less than 1 mm, are transparent, vase-like and found on a  pedicle, which may grow up to 1.5 mm. The reproductive  tetraspores are concentrated among the side branches and  resemble a necklace.

Top: Alsidium corallinum general  view.  Bottom: Alsidium corallinum microscopic  view.

Seasonality and distribution

The Alsidium corallinum can be found along the coast  during the summer and autumn months. Its global  distribution includes the Mediterranean Sea and the Indian  Ocean.

Additional species

A smaller species found along the coasts is Alsidium  helminthochorton (Schwendimann) K.tzing.

In some places throughout eastern Asia, Alsidium  helminthochorton is used to manufacture medication  against worms.