Silver Coin Dendrogyra Cylindricus 2011 Proof Tuvalu

RAZITKO_POSTOVNE_ZDARMA_NENI

Coral Protection series

This exclusive silver coin issued in Tuvalu in 2011 from the Coral Protection series features the beautifully wet-dyed coral Dendrogyra Cylindricus on its reverse (a unique dyeing technique that provides amazingly realistic colours), along with the inscriptions "DENDROGYRA CYLINDRICUS", "CORAL PROTECTION" and the year of issue. The obverse shows a portrait of Queen Elizabeth II and the face value.

The coin comes in a blue gift box with grey and silver trim along with a numbered certificate of authenticity in a limited edition of only 1000 pieces for the entire world!

Coral

Coral is the name given to some sea urchins in the class Coralline (Anthozoa). They are characterized by suppressed metagenesis, which means that they remain in the polyp stage. All of the 6000 or so species live sessile in the seas, usually in colonies. Corals include the well-known coral reef-dwellers of tropical seas, which secrete calcium carbonate to form their hard outer shells. Over millions of years, these shells layer up and sometimes form an island. Hexacoralia group corals are mainly involved in coral building, but in addition to these, pinworms, molluscs, algae (especially calcite encrusted red algae) are also involved.

One "branch" of a coral is not, contrary to the general view, just one individual, but millions of genetically identical polyps. A distinction is made between animal corals (tree-branching), as organisms hidden inside the coral tube and e.g. by means of water-filtering fans on one side, and plant stromatolites, which are not hidden in any way but live on the surface of their own mineral deposits, thus forming spherical colonies.

Although corals may feed on plankton, most of their food is provided by symbiotic algae, zooxanthellae. Therefore, corals usually grow in sunny seas (up to 60 m) to provide enough light for the algae. However, it is sometimes possible to find strange corals without endosymbionts at depths of 3,000 m and even in the Arctic Aleutians. Corals with endosymbionts are referred to as hermatypic, those without as ahermatypic. Ahermatypic corals have to feed on their own, but can penetrate into different places than hermatypic corals.

Coral symbionts are armored corals that can make up to three-quarters of the coral biomass. Corals obtain up to 90% of their organic matter from their endosymbiont, allowing rich coral communities to form even in nutrient-poor tropical waters.

The death of the bryozoans is the cause of a phenomenon known as coral bleaching, which is the whitening of the coral. Coral without endosymbionts is severely weakened, does not grow and is in danger of dying, resulting in the destruction of the entire reef. The most common reasons for coral death are increased water temperature, pollution or pathogen infection.