Chlorophyta, Green Algae

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Valonia utricularis (Roth) C. Agardh

 Chlorophyta, Order: Siphonocladales; Family: Valoniaceae.

Etymology

The scientific name of the genus, Valonia, is devoted to the Albanian city where it was apparently first reported. The name of the species, utricularis, describes an ascus or a purse, and is appropriate, considering the bloated shape of the thallus.

Description

Generally, the alga resembles a cluster of greenish vesicles that have combined into a mass, usually creating a dense surface. The vesicles of the Valonia connect to the substrate through vesicular holdfasts. When disconnected from the substrate, the form of a single vesicle becomes apparent, elongated and narrow at the base. Often, the vesicles grow upon other vesicles and do not connect directly to the

substrate. Microscopic examination reveals a thick layer of cytoplasmic peripheral cells.

Size

The vesicles measure several millimetres in width, usually less than half a centimetre, and their length reaches 2 cm.

Colour

The colour of a single vesicle of Valonia utricularis is light green, nearly transparent. The entire cluster is a darker shaded.

Special features

The Valonia is easily identified thanks to the irregular shape of the vesicles. Another vesicled species (with which it may be confused) is the Botryocladia botryoides. However, its vesicles are red and arranged in a bunch.

 

 

Habitat

The Valonia usually appears in shaded areas at the upper part of the intertidal zone, sometimes in the upper regions of potholes on the abrasion platform, and sometimes in the upper regions of a cliff facing the sea in an area not exposed to low tide. In open seas, small individuals have been found at depths of up to 50 m.

Biology and reproduction

Each vesicle is a single unit, without cell walls and multinuclear. The exposed to air for extended periods, the vesicles lose water and soften. A vesicle disconnected from its place cannot continue to subsist, but may produce spores that can reproduce. Within a day, so long as the alga remains submersed in seawater, the contents of the disconnected vesicles becomes spores, and these disperse in the sea. They can then settle and begin to develop a new colony of Valonias.

Seasonality and distribution

The Valonia can be found along the coast throughout the year, although it is not common. The global distribution includes the Mediterranean, the Atlantic Ocean and the Indian Ocean.

Additional species

Three species of Valonia are known to exist in the Mediterranean. Of these, only one has been reported along Israeli coasts - the Valonia utricularis. In Egypt, Valonia macrophysa  Kutzing  has been reported, which has larger vesicles, reaches 3 cm in length and grows at a depth of 30 m. Another species mentioned in literature is Valonia aegagropila C. Agardh, which has smaller vesicles. Some researchers believe that this is a synonym for Valonia utricularis, which has been mentioned in this book.

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