Fucus

Fucus is a genus of brown algae found in the intertidal zones of rocky seashores almost throughout the world. The thallus is perennial with an irregular or disc-shaped holdfast or with haptera. The erect portion of the thallus is dichotomous or subpinnately branched, flattened and with a distinct midrib. Gas-filled pneumatocysts (air-vesicles) are present in pairs in some species, one on either side of the midrib. The erect portion of the thallus bears cryptostomata and caecostomata (sterile surface cavities). The base of the thallus is stipe-like due to abrasion of the tissue lateral to the midrib and it is attached to the rock by a holdfast. The gametangia develop in conceptacles embedded in receptacles in the apices of the final branches. They may be monoecious or dioecious. These algae have a relatively simple life cycle and produce only one type of thallus which grows to a maximum size of 2 m. Fertile cavities, the conceptacles, containing the reproductive cells are immersed in the receptacles near the ends of the branches. After meiosis oogonia and antheridia are produced and released, fertilisation follows and the zygote develops directly into the diploid plant. It may be considered to be analogous to the life cycle of the flowering plant, but in algae the oogonia are released and fertilised in the sea while in flowering plants the ovules are fertilised while attached to the parent plant and then released as a seed. Species of Fucus are recorded almost worldwide. They are dominant on the shores of the British Isles, the northeastern coast of North America and California. In the British Isles these larger brown algae occur on sheltered shores in fairly well defined zones along the shore from high-water mark to below low water mark. On the more exposed shores not all of these species can be found and on very exposed shores few, if any, occur. Pelvetia canaliculata forms a zone at the top of the shore. Just below this Fucus spiralis, Fucus vesiculosus and Fucus serratus and Laminaria form clear zones, one below the other, along the shore down to low water mark. On sheltered shores Ascophyllum nodosum usually forms a broad and dominating zone along the shore at the mid-littoral. On very exposed shores few if, any plants, of these species can be found. Other brown algae can be found at the low-littoral such as Himanthalia, Laminaria saxatilis and Alaria esculenta. Small green and red algae and animals occur, protected under these large brown algae. In Scotland and Norway, up until the mid-19th century, several seaweed species from Fucus and other genera were harvested, dried, burned to ash, and further processed to become 'kelp', which was a type of soda ash that was less costly in Britain than the barilla imported from Spain. It has an alkali content of about 2.5%–5% that was mainly sodium carbonate (Na2CO3); alkali is essential to soapmaking, glassmaking, and other industries. The seaweed was also used as fertilizer for crop land in the same areas in which it was harvested. The purest barilla had a sodium carbonate concentration of about 30%. Fucus species can also be used for thalassotherapy, along with other species such as Turkish towel (Chondracanthus exasperatus), feather boa (Egregia menziesii), and finger kelp (Laminaria digitata). In 2005, it was announced that bacteria grown on Fucus have the ability to attack and kill the MRSA superbacterium.