Phaeophyta,  Order: Scytosiphonales; Family: Scytosiphonaceae.

Etymology

Colpomenia refers to an object with volume (like a purse, for example), and refers to the Colpomenia’s bloated shape. Sinuosa means “winding” (twisting, as in sinus).

Description

The Colpomenia sinuosa is a ball-shaped, hollow alga, rigid and smooth. The thallus is often covered with a shiny mucousy layer. The alga is usually full of gasses, the product of photosynthesis. At its onset, the Colpomenia is small and round, and with time its surface becomes folded and wrinkled. The Colpomenia occurs as a solitary individual or in large groups. Microscopic examination reveals the thallus to be constructed of two or three layers of cells. The upper layer has small cells, each of which contains a single flat chloroplast. The inner cells have no chloroplast.

Size

The algal diameter changes with age and environment. Large individuals reach 10 cm. The thallus’ width ranges between 1-3 mm.

Colour

The Colpomenia sinuosa is coloured tobacco brown.

Special features

The Colpomenia genus is easily identified by its shape: a bloated mass covered with wrinkles anddepressions . It is more difficult to differentiate between the species. One species, Colpomenia peregrina, is rarer and more delicate. There are differences also in seasonal activities between the species.

Habitat

The Colpomenia sinuosa grows in the subtidal zone, and sometimes higher - in the intertidal zone. Its endurance to exposure is very low, individuals exposed to the air become singed and rot. The Colpomenia can also be found as an epiphyte upon other species; however, it usually grows directly on rocks.

Biology and reproduction

The reproductive organs usually develop among the tiny depressions, where several sterile hairs may be found. The reproductive cells are biflagellate and mobile. The Colpomenia sinuosa has been observed reproducing, especially during spring. Following photosynthetic activity, the body of the alga fills with gas, enabling it to float. The alga, as it disconnects from the substrate, possesses a low specific weight, and this probably provides a good distribution mechanism, although many individuals float ashore and dehydrate.

Seasonality and distribution

During the growing season, the Colpomenia sinuosa can be found on all Eastern Mediterranean coasts. It seems that the reproductive activities peak during winter and spring, at which season the species makes its appearance amongst the waves. The Colpomenia’s main global distribution focuses on warm seas, tropical and sub-tropical areas and the Red Sea.

Additional species

Two species are common in the world, distinguished by the width of the thallus and the size of the spores containing the reproductive organs. Colpomenia peregrina (Sauvageau) Hamel and Colpomenia sinuosa. The Colpomenia peregrina is found mostly in temperate places, where it grows in winter and spring. It was first reported in the British Isles at the end of the nineteenth century and in Denmark and Norway in recent decades. Migration north is not understood, though this development may be either the result of climatic change or some other unknown reason, as is the disappearance of a herbivore of some rival species.

Colpomenia -general view of the thallus. The Colpomenia sinuosa is popularly referred to as ‘Sea tomato’, and it appears under that name in several publications. Research undertaken in various countries has found the Colpomenia sinuosa to contain antibiotic materials that are active against bacteria and fungus.