Coral Biology
Plant or animal?
Although many species of corals look like plants, they belong to the animal kingdom. Corals are mostly modular organisms that form colonies. A coral colony consists of many small “individuals” called polyps, which look similar to a sea anemone. In fact, corals belong to the same group as sea anemones and jellyfishes, the phylum cnidaria.
Plant or animal?
Although many species of corals look like plants, they belong to the animal kingdom. Corals are mostly modular organisms that form colonies. A coral colony consists of many small “individuals” called polyps, which look similar to a sea anemone. In fact, corals belong to the same group as sea anemones and jellyfishes, the phylum cnidaria.
The coral polyp – a close-up
A single coral polyp can be viewed as a sac that has a central mouth surrounded by tentacles armed with stinging cells called nematocysts. The polyps are interconnected and exchange nutrients with each other via stem canals. When one part of the coral feeds – it does so by capturing small prey from the water with its tentacles or by nourishment provided by the symbiotic algae living in their tissues that photosynthesize – it can share the nutrients with the rest of the colony.
What appears to us as a coral at first sight, is actually the coral’s skeleton. It is created by the coral itself and provides the organism protection.
A single coral polyp can be viewed as a sac that has a central mouth surrounded by tentacles armed with stinging cells called nematocysts. The polyps are interconnected and exchange nutrients with each other via stem canals. When one part of the coral feeds – it does so by capturing small prey from the water with its tentacles or by nourishment provided by the symbiotic algae living in their tissues that photosynthesize – it can share the nutrients with the rest of the colony.
What appears to us as a coral at first sight, is actually the coral’s skeleton. It is created by the coral itself and provides the organism protection.
How does a coral grow?
Corals grow by asexual duplication of the polyps, replicating themselves repeatedly to form a colony. This occurs through a budding process in which a parent polyp produces a new polyp. One parent polyp can simply divide into two or more polyps (intratentacular budding), or it can bud off a part of itself to form a daughter polyp (extra-tentacular budding). As the colony grows, it keeps producing the calcareous substance that forms the skeleton, providing support and allowing for further growth.
How does a coral grow?
Corals grow by asexual duplication of the polyps, replicating themselves repeatedly to form a colony. This occurs through a budding process in which a parent polyp produces a new polyp. One parent polyp can simply divide into two or more polyps (intratentacular budding), or it can bud off a part of itself to form a daughter polyp (extra-tentacular budding). As the colony grows, it keeps producing the calcareous substance that forms the skeleton, providing support and allowing for further growth.
How does a coral reproduce?
Sexual reproduction in corals involves the production of gametes (egg and sperm cells), fertilization and embryo development into a larva.
In general, we know very little about sexual reproduction of temperate and cold-water corals. This is a fundamental part of our research, which is extremely important to ensure the survival of the species.
Sexual reproduction in corals occurs in one of two forms:
1) broadcast spawning, in which species release egg and sperm cells into the water over one or a few days. They then fertilize each other in the water (i.e. external fertilization) and grow into small coral larva;
2) brooding, in which only the sperm cells are expelled and carried through the water to another coral. There they encounter egg cells and fertilize them. The coral larva develops in or on the maternal coral colony and is then released into the water.
The small larvae move entirely free and are carried out to a new place by the ocean currents. Through environmental stimuli, when the larvae are carried over suitable substrate, it is capable of finding a good spot to settle onto. Once settled, it starts the metamorphosis into the coral polyp stage, which will then bud new polyps to form a colony. After reaching a certain size, the coral becomes sexually mature.
The larva is effectively the only free-living life stage of a coral that disperses.
This cycle of sexual reproduction is generally repeated on an annual basis, especially in temperate and cold-water coral species like those occurring in Europe. Unlike most reef building tropical corals that are hermaphrodites (a single polyp produces both egg and sperm cells), the colonies of our corals have separate sexes.
How does a coral reproduce?
Sexual reproduction in corals involves the production of gametes (egg and sperm cells), fertilization and embryo development into a larva.
In general, we know very little about sexual reproduction of temperate and cold-water corals. This is a fundamental part of our research, which is extremely important to ensure the survival of the species.Sexual reproduction in corals occurs in one of two forms:
1) broadcast spawning, in which species release egg and sperm cells into the water over one or a few days. They then fertilize each other in the water (i.e. external fertilization) and grow into small coral larva;
2) brooding, in which only the sperm cells are expelled and carried through the water to another coral. There they encounter egg cells and fertilize them. The coral larva develops in or on the maternal coral colony and is then released into the water.
The small larvae move entirely free and are carried out to a new place by the ocean currents. Through environmental stimuli, when the larvae are carried over suitable substrate, it is capable of finding a good spot to settle onto. Once settled, it starts the metamorphosis into the coral polyp stage, which will then bud new polyps to form a colony. After reaching a certain size, the coral becomes sexually mature.
The larva is effectively the only free-living life stage of a coral that disperses.
This cycle of sexual reproduction is generally repeated on an annual basis, especially in temperate and cold-water coral species like those occurring in Europe. Unlike most reef building tropical corals that are hermaphrodites (a single polyp produces both egg and sperm cells), the colonies of our corals have separate sexes.
What does this have to do with our project?
Corals, and especially those living in the deep sea, have very slow growth rates (a few mm to cm of linear growth per year). It takes a long time for them to reach sexual maturity, and as such many corals are very old. Our project is crucial because we rescue and transplant corals that are generally sexually mature and that can continue reproducing. In this way, we can reforest coral gardens manually while also promoting natural recovery by sexual reproduction.
What does this have to do with our project?
Corals, and especially those living in the deep sea, have very slow growth rates (a few mm to cm of linear growth per year). It takes a long time for them to reach sexual maturity, and as such many corals are very old. Our project is crucial because we rescue and transplant corals that are generally sexually mature and that can continue reproducing. In this way, we can reforest coral gardens manually while also promoting natural recovery by sexual reproduction.
PLANT A CORAL
save our coral gardens
PLANT A CORAL
save our coral gardens