It would be normal that when we think of the word coral the image of the animals of the Great Barrier Reef comes to mind, because without these animals capable of forming calcareous exoskeletons, there would be no reefs, essential for life in the ocean. There are several types of corals, including types of soft corals. But do you know how many types of corals there are? We tell you about it, along with other curiosities about corals, in this article on our site.
Characteristics of corals
Corals belong to the phylum Cnidaria, like jellyfish. Most corals are classified in the Anthozoa class, although there are some within the Hydrozoa class. They are hydrozoans that generate a calcareous skeleton, called fire corals because their bite is dangerous. They are part of the coral reefs
There are many types of marine corals and around 6,000 species We can find types of hard corals, which are those with a calcareous exoskeleton, others have a flexible horny skeleton and others do not form a skeleton itself, but have spicules immersed in the dermal tissue, which protects them. Many corals live in symbiosis with zooxanthellae (symbiotic photosynthetic algae) that provide most of their food.
Some of these animals live in large colonies and others solitary. They have tentacles around their mouths that allow them to catch food floating in the water. Like a stomach, they have a cavity with a tissue called gastrodermis, which can be septate or with nematocysts (stinging cells, like jellyfish) and a pharynx that communicates with the stomach.
Many species of corals form reefs, they are those that present symbiosis with zooxanthellae and are known as hermatypic corals. Non-reef forming corals are of the ahermatypic type. This is the classification that we will use to know the different types of corals. Corals can reproduce asexually by various mechanisms, but they also reproduce sexually.
Hermatypic corals and examples
The hermatypic corals are the types of hard corals, they have a stony exoskeleton formed by calcium carbonate. This type of coral is dangerously threatened by what is called "coral bleaching". The color of these corals comes from their symbiotic relationship with zooxanthellae.
These microalgae, the corals' main source of energy, are being threatened by rising ocean temperatures as a result of climate change, excess sunlight and certain diseases. When the zooxanthellae die, the corals bleach and die, for this reason hundreds of coral reefs have disappeared.
Some examples of hard corals are:
Genus Acropora or staghorn corals:
- Acropora cervicornis
- Acropora palmata
- Acropora prolifera
Genus Agaricia or flat corals:
- Agaricia undata
- Agaricia fragilis
- Agaricia tenuifolia
Brain corals, of various genera:
- Diploria Clivosa
- Colpophyllia natans
- Diploria labyrinthiformis
Hydrozoan corals or fire corals:
- Millepora alcicornis
- Stylaster roseus
- Millepora squarrosa
Ahermatypic corals and examples
The main characteristic of ahermatypic corals is that they do not have a calcareous skeleton, although they can establish a symbiotic relationship with zooxanthellae. Therefore, they do not form coral reefs either, however, they can be colonial.
Very important in this group are the gorgonians whose skeleton is made up of a protein substance that they secrete themselves. In addition, within its fleshy tissue are the spicules, which act as support and protection.
Some species of gorgonians are:
- Ellisella elongata
- Iridigorgia sp.
- Acanella sp.
In the Mediterranean Sea and the Atlantic Ocean we can find another type of soft coral, in this case of the subclass Octocorallia, the hand of dead (Alcyonium palmatum). A small soft coral that sits on rocks. Other soft corals, such as those of the Capnella genus, have an arboreal conformation, branching from a main foot.
