Sea Fan

The sea fan belongs to the genus named Gorgonia. It is a genus consisting of all the marine invertebrate animals of the Holaxonia suborder, Cnidarian phylum, and Anthozoa class. These corals are of many varieties and are made up of polyps or attached cylindrical forms which form a fan-like pattern while growing together. Eight tentacles are present in each polyp of a particular colony. Gorgonin is the internal central skeleton made up of horny and flexible scleroprotein. A layer is formed by the living tissues covering the entire surface, while the skeleton supports all the colony branches. Most of the tissues have beautiful hues of colour over them like yellow, purple, orange, and red. They can reproduce both asexually and sexually where they release all the sperms and eggs in the current of water. Sea fans are often dried up and collected as souvenirs due to their brilliant colour and shapes. They love being admired by humans.

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Common Characteristics of Sea Fans

A marine organism catching net is formed when the sea fan spreads its polyps along with the tentacles. The ability of the fan-shaped colonies to ensnare prey subsequently increases in most cases when they tend to grow across or along with the current. Most of them grow about two feet in height or around 65 cm. Gorgonia has approximately more than 500 species with different colours, separate branching, and marking patterns. In all oceans, pink sea fans are mostly found in shallow waters. Along the coasts of the Atlantic belt like Bermuda, Florida, and the West Indies, they are extremely abundant.

Ciliated microscopic larvae or planulae are formed from the eggs which have been fertilized during the reproduction of the organism. The next stage is its metamorphosis into adulthood but before that each larva is dispersed and separated from the parent colony. After that through asexual budding, the newly metamorphosed adult polyp transforms into a giant colony of sea fan. Now, we will try to look into some interesting facts about sea fans.

Sea Fans and their Expanse

There are various types of sea fans such as red sea fan, black sea fan coral, and more. But there are certain interesting facts about sea fans which will turn you into their fans. They are found almost in all the seas of the world as they have a huge variety of species and are abundant. They are found in shallow coral beds and especially near the Caribbean belt. It is also found in tropical regions mostly. Sea fans cover huge areas of the seabed where there are stronger currents. If you are lucky enough, you can also find sea fan forests with them occupying places in the sea wall.  

Sea fans are not found individually. Small coral polyps form a colony that expands to form each fan. We love the branching structure of the red sea fan. It is very delicate and formed by the joining of several polyps which are only a few millimetres in size. These polyps have connecting tissues which help them share nutrients amongst themselves and work together.

Feeding Characteristics of Sea Fans

The black sea fan coral or any other species have polyps with tentacles in the form of a pennate. From the main tentacle, the rest of it branches out like a feather. They can easily contract into the main tissue of the coral. They usually trap bacteria and tiny marine animals or food particles using these polyps. The sea fans want the water current to flow over their tentacles so that they can easily catch food particles. Fleshy tissues connect the polyps. A digestive cavity is present in each polyp which is connected via tubular structure present in the tissues. 

Just like a trunk of a huge tree or stem of a plant, the pink sea fan and other species have a central axis supporting the entire sea fan. The protein which makes up this stem is known as Gorgon. It is only because of this structure that the sea fan looks like a plant though it is an animal. Some of the gorgonian fan coral consists of dinoflagellates, zooxanthellate which helps in conducting photosynthesis. Many nutrients are produced during the process and the gorgonian symbiotically extracts benefits from it. It is usually a passive carnivorous feeder. Sea fans usually feed during the night on zooplankton. 

Reproduction of Sea Fans 

Most species of sea fans like white sea fan do not move around but stay attached to hard rock or any other surfaces. Its interaction and behaviour with other species are very limited. The common species of sea fans reproduce both asexually and sexually. The reproduction is interesting as it can take place in different ways. They tend to release huge quantities of sperms and eggs on columns of water. These sperm and eggs are openly released into the sea and not protected by the parents. There is a huge chance that these young ones can get separated from the rest and form new sea fan colonies far off from where their parents were. Sometimes they even reproduce asexually when from a fragment of coral an entire new colony forms.

Physical Appearance of the Sea Fan

The shape of the organism highly depends on the area they occupy to live as because they are generally fixed to a particular point. They are usually in the shape of a fan that allows them to be flexible with the flow of current. They become more rigid, taller, and thinner in deep waters. They can be up to 1 meter in height as well. These gorgonian fan coral are usually soft and fleshy, unlike the hard rocklike reef corals. They do not have thick skeletons.

During the nighttime, the sea fans spread their polyps which consist of stinging tentacles to catch their prey which is usually small seafood particles. The entire fan’s breadth, tentacles, branched structures makes the entire thing look like a huge mesh or net ready to capture its prey. One of the main reasons for the underwater world being extremely colourful is due to the sea fans. They are available in extraordinary hues of pink, red, yellow, purple, orange, white, and black. Each polyp has living algae in its flesh due to which it gets such marvellous and spectacular colours. A polyp tissue’s centimetre square area consists of almost a million algae or more. The polyps even perform photosynthesis using sunlight. They even produce a good amount of nutrients and oxygen which the polyps can easily use. 

Hosting Characteristics of Sea Fans

Living within the various branching structures of sea fans, you can also find a close community of plenty of other tiny creatures. These creatures monopolize their position on the sea fan to catch their food in the water currents. Organisms like molluscs, brittle stars, algae, basket stars, sponges, fish, and many more find their home in the fans. The tiny organism known as pygmy seahorse can also be found on the branches, tightly holding onto the mesh with its tail. The seahorse body has a structure looking exactly like polyps known as knobby protrusion. They have a similar colour to that of the host body depicting a great camouflage. It has two colour shades, one yellow and another pink shade. 

Chemical Defensive Techniques

Be it a white sea fan or purple fan coral, whatever the sea fan species it might be, they always have a defence strategy. Most animals would prevent themselves from eating a sea fan because they are full of foul taste and poisonous chemicals. But sea snails and butterflyfish have evolved and can get around this. A small snail or a flamingo will eat only a small portion of the sea fan as they are pretty creative in dining. They would allow the recovery of the original colony before moving onto the next portion. The flamingo after eating the poisonous chemical repurposes the thing into its flesh to stop being eaten himself. 

These chemicals might have some medical use in the case of human beings and marine biologists are continuing to research on the topic. Dolphins make use of the antibacterial nature of the chemicals from the fan by rubbing their bodies against the sea fans. 

Use of Sea Fans as Souvenirs

Sea fans are undoubtedly one of the most beautiful underwater creatures and due to their beautiful hues and striking fan shape, they are often sold as decorations. Generally collected and dried sea fans are sold at high prices for home décor and sometimes even turned into jewellery. It’s almost like wearing fur because sea fans are animals. They are used in aquariums by harvesting them or using a dried sea fan itself. Scallops are also feeding on sea fans continuously across the sea for seafood. 

Conclusion

Many organizations have tried to conserve these species as now they are threatened by continuous exploitation. Imprisonment or high fines are imposed if anyone is found to smuggle harvested sea fans across the border as many countries have banned the exploitation of sea fans. One of the vulnerable species of sea fans is the pink sea fan living near the UK coastline. Snorkelling is the best option to experience sea fans in the wild. Never touch a sea fan as they are poisonous and always maintain a safe distance. These creatures are extremely delicate, fragile and get dismantled easily. 

Did You Know?

• Though sea fans are animals, they can prepare their food through photosynthesis.

• Sea fan compounds are used to prepare antibiotics.

• Sea fans love attention and you can enjoy interacting with them while snorkelling.

• Ecotourism considers sea fans as an important showcase souvenir and they are often harvested or dried to store as decorations.