Bladder wrack

Appearance

The fronds of "F. vesiculosus" grow to 90 centimetres long and 2.5 centimetres wide and have a prominent midrib throughout. It is attached by a basal disc-shaped holdfast. It has almost spherical air bladders which are usually paired, one on either side of the mid-rib, but may be absent in young plants. The margin is smooth and the frond is dichotomously branched. It is sometimes confused with "Fucus spiralis" with which it hybridises and is similar to "Fucus serratus".

Distribution

"Fucus vesiculosus" is a common large alga on the shores of the British Isles. It has been recorded from the Atlantic shores of Europe, Northern Russia, the Baltic Sea, Greenland, Azores, Canary Islands, Morocco and Madeira. It is also found on the Atlantic coast of North America from Ellesmere Island, Hudson Bay to North Carolina.

Behavior

Plants of "F. vesiculosus" are dioecious. Gametes are generally released into the seawater under calm conditions and the eggs are fertilised externally to produce a zygote. Eggs are fertilised shortly after being released from the receptacle. A study on the coast of Maine showed that there was 100% fertilisation at both exposed and sheltered sites. Continuously submerged populations in the Baltic Sea are very responsive to turbulent conditions. High fertilisation success is achieved because the gametes are only released when water velocities are low.Individuals of "F. vesiculosus "from the North Sea colonized the Baltic Sea less than 8 000 years ago. Today, "F. vesiculosus" is found deep inside the Baltic Sea, including areas of strong hypo saline waters, such as the inner parts of the Gulf of Riga, the Gulf of Finland and the Bothnian Sea.

The colonization of the Baltic Sea is paralleled by a switch from what seems to be obligate sexual recruitment to facultative asexual recruitment. Asexual reproduction in Baltic Sea populations is accomplished by the production of adventitious branches that come loose and reattach to the bottom by the formation of rhizoids. Adventitious branches are present in thalli of "F. vesiculosus" also in other areas, but asexual formation of new thalli has never been reported outside the Baltic Sea.

Habitat

The species is especially common on sheltered shores from the middle littoral to lower intertidal levels. It is rare on exposed shores where any specimens may be short, stunted and without the air vesicles. "F. vesiculosus" supports few colonial organisms but provides a canopy and shelter for the tube worm "Spirorbis spirorbis", herbivorous isopods, such as "Idotea" and surface grazing snails such as "Littorina obtusata". Phlorotannins in "Fucus vesiculosus" act as chemical defences against the marine herbivorous snail "Littorina littorea". Nevertheless, galactolipids, rather than phlorotannins, act as herbivore deterrents in this species against the sea urchin "Arbacia punctulata". Methyl-jasmonate may induce the phlorotannins production. Fucophlorethol A is a type of phlorotannin found in "F. vesiculosus".

Uses

Recently the researchers found that an extract of "Fucus vesiculosus", promotes the contraction of fibroblast-populated collagen gels through increased expression of integrin molecules. In this study, they investigated the effects of topical application of an aqueous extract of this alga on the thickness and the mechanical properties of human skin. A gel formulation that included 1% of the extract was applied topically to human cheek skin twice daily for five weeks. A significant decrease in skin thickness measured by B-mode ultrasound was elicited, as was a significant improvement in elasticity measured with a Cutometer as compared with controls. In cheek skin, the thickness normally increases and the elasticity usually decreases with age. These results suggest that the "Fucus vesiculosus" extract possesses anti-aging activities and may be useful for a variety of cosmetics.