Taxonomy  Order: Corallinales; Family: Corallinaceae.

Etymology

Amphiroa, is Portuguese for ‘rock-hugging’, describing the  algal habitat. Rigida, means ‘hard’ or ‘rigid’, and refers to  the character of the calcified thallus.

Description

The Amphiroa rigida is a hard, calcified alga, articulated,  irregular and dichotomously branched. The dichotomous  branching often occurs in the midst of a joint or at its edge.  The joints are solid and maintain their shape, even after the  alga has dehydrated.

Size

The alga sometimes reaches several centimeters in length,  usually 3 cm. The joints are 0.5 mm to 1 mm wide and double  to five times that in length.

Colour

Various shades of pink ranging from gentle to vivid. When  dry, the alga turns white.

Special features

The alga is characterized by its pink colour and its coral-like  shape. It is less tangled and populous than its neighbouring  alga, corallina. In contrast to the Jania, its branches are  jointed. They are also elongated and straight, as opposed  to the triangular joints of the Corallina elongata.

Habitat

The alga grows in deep water at depths of up to 80 m. It is  usually found in the subtidal zone or in potholes. The  Amphiroa rigida is mostly solitary and not found in large  colonies. It does not come in contact with air. Individuals  have been found in Egypt growing upon snail shells.

Biology and reproduction

The sexual reproductive organs and spores are arranged in  special sex pods that are spread along the joints and