Phaeophyta, Order: Sphacelariales. In some publications, the Stypocaulon appears under two names and is related to two different families: (Sphacelariaceae) or Stypocaulaceae.

Etymology

The previous scientific name of the genus, Halopteris, means ‘sea feather’. The genus’ current scientific name, Stypocaulon, refers to the thallus shape that resembles a broom. The name of the species, scoparia, means ‘broom’ or ‘multi-branched’.

Description

The Stypocaulon is a small and dense bush-like alga. Its thallus is comprised of many branches that emanate from a common point. The branches are rigid and dichotomously feathered. The holdfast is comprised of a cluster of rhizoids, which attach the alga to the substrate.

Size

Most individuals attain a length of up to 5 cm. Sometimes individuals can be found measuring 15 cm. The width of each feather is 1 cm, and the width of the shoots is less than a millimetre.

Colour

The Stypocaulon scoparium is brown, sometimes tending towards dark brownish-black.

Special features

From a distance, the Stypocaulon resembles dense, brown clusters. To examine the feathered structure, a branch must be separated from the bush.

Habitat

The Stypocaulon can be found in abundance in the subtidal zone, upon rocks facing the open sea. The Stypocaulon can also be found in potholes upon abrasion platforms. Sometimes, a single bush may be seen, and sometimes a larger group.

Biology and reproduction

The branches grow in a vertex manner; at the edge of each branch a vertex apical cell is located, evident thanks to its large size and its dark colour, compared to the other cells.

Seasonality and distribution

The Stypocaulon appears in waves, although it is evident nearly the whole year. The Stypocaulon is common in the Mediterranean and parts of the Atlantic Ocean.

Additional species

Two or three species of Halopteris (currently called Stypocaulon) are known to exist in the Mediterranean. In the eastern basin, only one species apparently exists - the Stypocaulon (Halopteris) scoparium. Edelstein describes Halopteris filicina (Grateloup)  Kutzing , which has been reported in Egypt, in deeper water and described as a smaller species. This species is now commonly referred to as Cladophora retroflexa.