Valonia (alga)

''Valonia'' (C. Agardh, 1823) is a genus of green algae in the Valoniaceae family. The genus ''Ventricaria'' is now regarded as a synonym of ''Valonia''.

Taxonomy and nomenclature

The genus ''Valonia'' belongs to the order Cladophorales and class Valoiaceae. It comprises several taxonomically acceptable species based from available data and literatures.

Below is a list of common species of ''Valonia'' found throughout the tropics:

* ''Valonia fastigiata'' Harvey ex J. Agardh 1823
* Valonia ventricosa J.Agardh 1887
* ''Valonia utricularis'' (Roth) Agardh 1823
* ''Valonia aegagropila'' C. Agardh 1823
* ''Valonia macrophysa'' Kützing 1843
* ''Valonia ovalis'' C.Agardh 1822
* ''Valonia chlorocladus'' Hauck 1886
* ''Valonia cespitula'' Zanardini ex Kützing
*''Valonia pachynema'' (G. Martens) Børgesen
*''Valonia barbadensis'' W.R.Taylor, 1969
*''Valonia nutrix'' (Kraft & A.J.K.Millar) Kraft, 2007
*''Valonia oblongata'' J.Agardh, 1887
*''Valonia trabeculata'' Egerod, 1952

General morphological description

Thalli

The succulent thallus of ''Valonia'' exhibits various shapes and form depending on species: vesicular or tubular cells forming either irregular cushions or hemispherical domes of intermediate sizes. Thalli color can be green to dark green, olive-green, and brownish-green in some species.

Vesicles and rhizoid systems

The vesicles can be subspherical, subclavate, elongate, or deformed. The branching of vesicles begins at the lenticular cells, which can be terminal and subdichotomous, or lateral and irregular. Seaweeds are attached to the substratum by short rhizoid system to basal rhizoidal cells.

Life history

The life history of the genus ''Valonia'' is indistinguishable with the other Siphonocladales family members, particularly genus ''Boergesenia.'' Similar in several seaweeds, they exhibit a diplohaplontic life cycle, meaning an alternation between haploid (gametophytic) and diploid (sporophytic) free-living forms completes the cycle.

Specifically in ''Valonia'', production of three-types of quadriflagellate zoospores (diploid) were observed and recorded in the species ''Valonia fastigiata'' and ''Valonia utricularis.'' These are mitozoospores (diploid) and meiozoospores (haploid) produced from the sporophytic phase, and mitozoospores (haploid) produced by the gametophytes. Eventually, meiozoospores will give rise to the gametophytes, while the mitozoospores produces the sporophytes thus completing the life cycle.

Distribution and ecology

The genus ''Valonia'' is widely distributed throughout the tropical region, and some extends to the warm temperate areas. They are mainly found in coastal shallow waters from low intertidal to upper intertidal areas, typically deep, inhabiting sheltered or wave exposed rocky substrates and pools.

Previous study have shown that the Mediterranean Sea ecotype - ''Valonia utricularis'' can extend its biogeographic distribution to warm temperate regions. This is attributed to the seaweed's chloroplast to function as a thermal acclimation organelle in response to exposure of varying temperature levels. It is achieved by controlling the number of pigments thereby decreasing light attainment while increasing the capacity for zeaxanthin-induced energy dissipation. However, ecotypes from the Indian Ocean display photoinhibition when exposed to colder temperatures.

In addition, ''Valonia ulticularis'', along with other intertidal seaweeds (''Gelidium corneum'', ''Osmundea pinnatifida'', and ''Caulacanthus ustulatus'') where found to influence the vertical distribution of peracarid crustaceans at the lower intertidal zones. Highest peak of peracarids were found to coincide with the highest seasonal growth of the associated macroalgae (around April–August). However, there are also some important ecological factors such as weather conditions, competitions, and predation which may also influence distribution patterns.

Economic Use/ Natural Products

The genus ''Valonia,'' specifically ''Valonia aegagropila'' is utilized for human consumption as food. It contains numerous natural products/ secondary metabolites, such as, Pigments (carotene, chlorophyll ''a'', chlorophyll ''b'', lutein, siphonaxanthin, zeaxanthin, siphonein), Polysaccharide (starch), as well as Minerals (heavy metals).

''Valonia ventricosa'' which compose similar natural products is often studied for the crystalline-structure of its cellulose to promote applications on accurate physical measurements.

The crystal-structure of ''Valonia'' cellulose Iβ was studied by Finkenstadt and Millane (1998). Using X-ray fiber diffraction analysis, it resolves the ambiguities in the cellulose structure that has been baffling for years. The crystalline structures were shown to be in parallel- up arrangements. The packing of the cellulose sheets of ''Valonia'' is similar to the ramie cellulose (ramie fiber) found in other macroalgae and higher plant taxa. Application in fabric production can be explored due to the fact that ramie fiber is specifically used in that industry.

Production of levulinic acid from ''Valonia aegagropila'' and another Cladophorales, ''Chaetomorpha linum'', were also explored and developed in recent years. Using an acid-catalyzed conversion, ''Valonia aegagropila'' were studied as a potential source for levulinic acid. The results were promising, achieving 16 wt% from ''V. aegagropila'', calculated with respect to the initial dried biomass. This supports the potential use of the macroalgae as starting feedstocks for renewable biofuels that addresses natural resource and environmental issues.

Amino acids such as alanine, glutamine, methionine, proline, asparagine among others, as well as minerals such as calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and chlorine (Cl), were also found in ''Valonia'', specifically ''Valonia fastigiata.''

Furthermore, unsaturated fatty acids where shown to be high of concentration in ''Valonia aegagropila'', together with other macroalgae (''Agarophyton tenuistipitatum'', and brown seaweeds (Pheaophyta). Unsaturated fatty acids are healthy fats that can be utilized for medicinal applications, e.g. improving cholesterol levels, reduce inflammations, and stabilize heart rhythms among others.

References

*See the NCBIbr>webpage on Valonia
Data extracted from the

External links

{{Taxonbar, from=Q2086405

Cladophorales
Cladophorales genera