Blue Ecosystems יעוץ סביבתי, בהנהלת ד"ר רחלי עינב - Gracilaria_bursa-pastoris

 

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דף הבית >> Seaweeds of Eastern Mediterranean coast >> Rhodophyta >> Gracilaria_bursa-pastoris
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Rhodophyta | Chlorophyta | Rhodophyta
Gracilaria bursa-pastoris (S. G. Gmelin) Silva = Gracilaria compressa (C. Agardh) Greville











Taxonomy
Rhodophyta, Order: Gigartinales; Family: Gracilariaceae.
Etymology
The generic name means ‘thin’ or ‘graceful’, and refers to the algal ‘stalk’. In other languages, Japanese, for example, Gracilaria is called agonori which means “sea-noodle” referring to the alga’s economic value as a source for agar manufacture.
Description
The Gracilaria bursa-pastoris is an elongated cartilaginous alga with a cylindrical, slightly flattened and irregularly branched thallus. The side branches are usually large and about as long as the base branches. A lateral cross-section of the thallus reveals a layer of external cortex comprising two to six rows of small, crowded cells that are rich in pigments. The medulla, the inner layer, is made of larger cells (250 to 450 microns) with no pigments. Fertile individuals display reproductive cells on the inner side of the cortex. All individuals have microscopic hairs.
Size
The branches are between 1-3 mm (unless eaten) and are sharp at their base. The alga grows to a length of 20 cm, but most are between 5 to 15 cm long.
Colour
The colour ranges between light green and bright red, depending on the level of light. Different colours may be found on the same branch.
Special features
The taxonomy of species is difficult, since the same species appears in nature in several forms (high variability). Examination of reproductive cells is required for a definitive identification, and these are not always available upon the plant.
Habitat
The Gracilaria bursa-pastoris is to be found in tidal pools and potholes in the intertidal zone. The alga seems to have a preference for shaded corners. Individuals have been found up to 15 m deep.
Biology and reproduction
The sporangium is located on branches and resembles condensed cones. They and the reproductive spores are dark red. Spores grow in clusters under a layer of outer cells.
Seasonality and distribution
The Gracilaria bursa-pastoris can be found year round, usually with sporangium. Some individuals have been reported for several years in the same spot. This indicates a life-span longer than a year.
Additional species
As mentioned above, the Gigartinales order is difficult to define. Additional species have been reported in this region, in Egypt and in Turkey. In spite of its economic value, extensive coastal research has not yet been undertaken to learn about the species prevalent in the Eastern Mediterranean.
Gracilaria arcuata Zanardini Gracilaria armata (C. Agardh) J. Agardh Gracilaria conferta (Schoesboe) J. and G. Feldmann
Gracilaria dendroides Garguilo, De Masi et Tripodi
Gracilaria disticha (J. Agardh) J. Agardh
Gracilaria dura (C. Agardh) J. Agardh Gracilaria furcellata Harvey
Gracilaria verrucosa (Hadson) Papenfuss
=  Gracilaria confervoides (Linnaeus) Gr.ville.
 
Throughout the twentieth century, the Gracilaria displaced the Gelidium as an important source of agar. It is being grown in Chile, the Philippines, South Africa and Japan. In Israel, the Gracilaria is cultivated for research, food and agar. In Japan, it is used as a therapeutic plant, for burn therapy and against the common cold.
 

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