Rhodophyta, Red Algae
Chondroclonium acicularis (Roth) Fredericq
Rhodophyta, Order: Gigartinales; Family: Gigartinaceae. Formerly, the genus was ascribed to Gigartina, and that is how it appears in most literature. At present, however, Gigartina acicularis has been defined as belonging to the Chondroclonium genus, which is the name we adhere to.
The former scientific name, Gigartina, means ‘grape seed’, due to its wine-like colour. Acicularis refers to the sharp branches and means ‘needle’. The new name of the genus is Chondroclonium, and refers to the characteristic cartilaginous texture of the genus and to the shape of the colony the plant creates. Freely translated, it means ‘cartilaginous colony’.
The Chondroclonium acicularis is a cylindricly shaped alga, branched with bow-like, rounded branches that intertwine. The Chondroclonium acicularis spreads a net-like covering over small areas in the intertidal zone. The intertwined branches are sometimes dichotomous and usually irregular. The branches are cartilaginous and slightly sharpened at their edges. In hot water, the thallus disintegrates and turns into a sticky substance.
A microscopic cross-section reveals several lines of small, elongated and irregular cells on the outer layer (the cortex). The inner layer (medulla) contains larger cells that have a thicker wall and no pigment.
The branches are 1 mm in diameter and sometimes more. They become thinner towards the edge. Lengths change. The plant is several centimetres in diameter and no taller than 5 cm.
The branches are a shade of crimson, tending towards green. The algal colour depends to a large extent on light in the habitat. Dark and bright stains may be seen on the same individual. Lighter stains appear where the alga is covered, usually by the Chondroclonium acicularis’s branches or by other species.
The species is easily identified, based on the general shape of the bush, which resembles a hill or small cushion, as well as the bowed tangled branches. The sporangia are visible as small spots along the thallus, and can help in identifying this species.
The Chondroclonium acicularis is to be found in the intertidal zone, upon abrasion platforms and at the top (usually) of potholes. It is sometimes found deeper, in the subtidal zone accompanied by coralline.
Biology and reproduction
Probably all Chondroclonium species undergo a three-stage life cycle (among some of the species, proof of sexual reproduction has not yet been found). The algal sporangium is dark and globular, 1 mm in diameter, and spread along the whole alga’s thallus.
Seasonality and distribution:
The Chondroclonium acicularis can be found most months of the year, but it is more common in spring and winter. Its geographic distribution is very wide and includes the Mediterranean Sea, the Black Sea, the Canary Islands, Brazil and the Indian Ocean.
An additional species of Chondroclonium found in the region is Chondroclonium teedii = Gigartina teedii. This species is rarer and has two types of branches: central and peripheral. These are short and sharp, and hold the reproductive organs. The species resembles the Hypnea and used to be quite common, but at present may have disappeared. Another explanation for its rarity might also be the fact that there are fewer people who are able to identify it.
Three additional species mentioned in various publications are listed below, some whose names have been altered, according to Professor G. Giaccone, they are not Mediterranean species, and should be re-examined:
Gigartina mamillosa (Goodenough and Woodward) J. Agardh
Gigartina pistillata (S. G. Gmelin) Stackhouse
Gigartina tepida Hollenberg.