(12-07-10) Coralline world hides some of the most beautiful and delicate forms of life on Earth. Incredible multicoloured designs and forms characterize their inhabitants, real living jewels.

    Coral reefs are among the richest ecosystems on Earth, only comparable to virgin forests. There, the biodiversity reaches one of the peaks of the planet regarding forms of life and number of specimens. There are more species in a small area that many of the most famous parks and reserves. Given this explosion of life, it is very frequent to see only “goldfish”. I mean, given the abundance we don’t know where to see and our brains, stunned, cannot   process all the information it receives.

    We are going to describe briefly some of the most characteristic groups of the coralline ecosystem. This way we will enjoy the dives more and will understand better this fascinating and also delicate universe in which we all have to assume our responsibility to preserve it.

A dangerous beauty

    Coralline world is a complex structure that may remind the jungle, as Cousteau said. Different species of hard and soft corals create different landscapes with many habitats that allow a wide variety of interlinked species. Many of them act like real icons of this tropical paradise we all sometimes think of. Brilliant colours in spectacular designs appear in most of the families, creating creatures undoubtedly beauty and smart. Beauty and rareness that has turned against them, unfortunately.

    Besides the ecosystem is threatened by pollution, global warming and so on, there is another threat. Most of coralline fish are very difficult to reproduce in captivity because of their habitat and especially their feeding. Because of this, to meet the growing demand for existing aquariums, they proceed to the capture wild specimens. In most of the cases it is done using totally destructive means for reef and fish (for example cyanide). A lot of them die both when they are caught and during the transport.

Angelic elegance

    Angel fish probably are one of the most beautiful and sophisticated inhabitants in oceans. They live in all coralline areas in the planet. We can distinguish them by their big size, about 40 cm the biggest, although there are also small ones, such as pygmy angels (Centropyge). Their bodies are high and compressed, and rounded. They have a visible thorn in the bottom of the gill operculum. Dorsal fin is continuous, clearly surrounding the animal body.

    They use to appear alone, swimming over corals. They are very territorial and do not doubt to attack anyone approaching them. This explains one of the most surprising characteristics of their biology. We are talking about the colour change experienced by individuals in their change from juvenile to adult. This is so incredible that in the past they were thought to be different species.

    This can be seen clearly in the emperor angelfish (Pomacantus imperator). When it is young it is blue with rounded white strips and a rounded body. When adult, the body gets longer and blue and yellow strips and a dark mask on the eye appear. The explanation has to do with the territoriality: young fish can develop without being attacked by adults.

    There are more than 80 species, so it is very difficult to highlight one, each person will prefer one. But I am sure that emperor, queen, French or Arabian angelfish will be in that list.

Fluttering the reef

    Few names are as appropriate as the one of this family, since anyone who has seen them evokes the image of undulating flight of butterflies. They live in all reefs, bus especially in the Red Sea and surroundings. They are small, no longer than 15 cm, with a disk-shaped body that has a continuous dorsal fin and spectacular coloured designs in which yellow predominates. The position of the fins and their anatomical design allows a great mobility and manoeuvrability in the intricate world of coral branches, even swimming backward.

    Unlike the angelfish, some species of butterflies form large groups that are a delight to behold. At the other extreme, it has also been shown that some species form stable partners for life.

    The design of them has generated different explanations. There are some species with black dots, very conspicuous in the tail, and numerous bands scattered throughout the body. Some theories explain this as if it was a false eye, thus an attack would not damage a vital part of the animal; or maybe being stripped hinders the perfect vision of the attacker. Another characteristic of them is the great food specialization: some species feed on only one type of polyp. This also causes anatomical adaptations in their mouths, with longer snouts to reach the food of the reef.

 

    Some well known members of the family of butterfly fish are called bannerfish (Heniochus). Their main characteristic is that the fourth bone in the dorsal fin is longer. Although it is similar in its fin to Moorish idol (Zanclus cornutus), it has nothing to do with this family, but with surgeons. As a curiosity, let’s say that it is symbol of good luck to Arabian fishermen, who always release them if they are caught accidentally.

Coral crushers

    Parrotfish, a very adequate name for these fish also. They have teeth fused in sheets, which makes their mouths look like beaks. Most of them are green and blue, so, along with the beak, are the reason for their name. They all are this way, from the smallest to the giant green humphead parrotfish (Bulbometopon muricatus), which can be up to 1.5 m long and 80 kg weight. They are difficult to differentiate regarding species, but it is easy for a diver to know that is seeing a parrotfish.

 

    They are herbivorous and spend the whole day, as a cow, eating. They feed on small living algae that exist on corals. The fish cannot separate them mechanically from the calcareous mass to which they are attached, and the solution is to eat everything: algae and coral. The nutritional content is minimal, so that the manoeuvre is lasts all day. Thanks to their strong teeth they can pull out corals, and thanks to some small teeth in the pharynx they crushed calcium carbonate, just taking advantage of algae. They produce a distinctive sound that is perfectly heard during the dive.

    Now, what happens to the crushed coral? A typical image in any reef is to see parrotfish continuously evacuating sand, in a kind of fine rain that falls on the bottom. It is estimated that a single specimen can produce up to five tonnes of sand per year, making them a key element in creating beaches and in the dynamics of the reef.

    This relentless activity is interrupted at sunset, when parrotfish fall into a deep sleep. Crouched in caves, they sleep so soundly that it is even possible to touch them with photographic systems. To mitigate somehow this vulnerability to its enemies they coated themselves with protective mucus that appears to limit their scent to avoid being discovered by predators. 

 

A tail with scalpel

    Other classic family of reef fish is surgeonfish. They are named after some cutting blades on the caudal peduncle that they activate when they want to defense themselves or attack. These weapons use to be highlighted with brilliant colours (yellow, white, etc.) to warn other fish of their power. In some species they are strengthen by poison. It is a very distinctive characteristic. They have a compressed structure with an oval and lightly elongated body, with continuous dorsal and anal fins, and a small mouth.

    With more than 75 species, they are represented in all reefs, many times in the form of colourful shoals composed of individuals of different species. I want to stress the family of unicorn fish. The male has a horn-shaped prominence in the face.

 

 

Fish of William Tell

    Like the Swiss legendary hero, coralline world has own archers. They are animals with a peculiar aspect: high and laterally compressed body that many times reminds a trapezium. Their head is big: covers more than one third of the body and their eyes are separated from mouth and can move independently. Teeth are small and prominent and are fused. Their design evokes cubism because of these details that give them a little weird appearance. A species (Rhinecanthus assai), has been named Picasso triggerfish.

    The characteristic of the group is the first dorsal bone, where Nature has created a complex defense system. This fin is retracted usually, having no role in swimming fish. In case of danger, a second bone “shoots”, propping and locking the first one without the possibility of folding. This way the fish has a sting not appetizing for a predator, and it can fit into caves and crevices from where it is very difficult or impossible to take out.

    He feeds on crustacean and molluscs, mainly sea urchins, which have become a real plague in many places. These fish have a jaw and special design of the eyes written above. As they are very separated from the mouth is very difficult that they prick themselves with their quills.

    Another feature of this genre is the great territoriality they show during the laying of eggs. These are deposited by the female in a small depression in the ground, and they are defended at all costs by the male, which do not hesitate to attack not only other fish, but even a diver, who can prove their strong bites.

Coralline lions

    One of the most spectacular inhabitants in reefs are lionfish, also named scorpionfish, firefish, turkeyfish, dragonfish, and stingfish. They had been seen only in the Indo-Pacific, including the Red Sea. Recently, due to indiscriminate releases we don’t know the consequences; they have been seen in the Caribbean Sea. 

    Their appearance is unique and distinct. They are adorned by long radios in the fins. They have feathery terminations in some species. Their head is large and prickly, with different crests and appendages over the eyes. Red and white tones predominate, showing their toxicity to the rest of inhabitants in the reef. They use to be near the bottom on in small caves lying in wait of preys, not getting scared by the presence of divers.

    Like the rest of scorpaenidae, their bones have a powerful poison, but, unlike the stonefish it is not fatal for a healthy person. The sensation is a heavy pain and a great swelling in the affected area, which drops in a few days. We have to be aware of the place we put our hands because accidents are always passively and these animals are not aggressive at all to human beings.

    With this arsenal the lionfish has few natural enemies. On the contrary, its design does not let them swim fast, so crustacean, their main prey, is able to corner them with their fins radios extended and, when they are close to them, eat them with their large mouth.