Whale Shark

The whale shark is the largest species of fish with some adult whale sharks growing to nearly 50ft long! The whale shark is thought to have developed around 60 million years ago making the whale shark one of the oldest species on Earth today. The whale shark spends it's life swimming through the open oceans in search of fish and squid. Unlike many other species of shark, the whale shark is known to feed on large shoals of tiny fish rather than hunting bigger fish and sea mammals. This makes the whale shark a filter feeder similar to whales and smaller sea animals.

The whale shark inhabits the warm, tropical waters around the equator and despite often being found close to coastlines, the whale shark is also known to dive to depths of up to 700 meters (that over 2,000ft deep). In this part of the ocean, food is more scarce and the whale shark will therefore only venture to such depths if hunting in the shallower waters is not possible. The whale shark is the perfect example of a so-called friendly shark and to date have posed no significant threat to humans (mainly divers).

The whale shark is most commonly spotted around the Gulf of Mexico and the Indonesian Islands where the whale sharks have been known to be almost playful towards humans. Female whale sharks incubate their eggs inside them rather than outside. This means that whale sharks effectively give birth to live young. Inside the female whale shark are hundreds of eggs but only a few actually turn into baby whale sharks. The remaining eggs are thought to be there so that when the whale shark pups hatch, they have something to eat.

The female whale shark gives birth to an average litter of 12 whale shark pups that are around 60 cm long. Whale sharks grow quickly during their first few years and soon the whale shark pups are extremely big and therefore less likely to be hunted by marine predators such as other shark species and killer whales. Whale sharks tend to live for around 60 to 80 years but have been known be more than 100 years old. Source

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Wrasse

The wrasse is a typically small species of fish, found in the coastal waters of the world's major oceans. The Cleaner wrasse is the most commonly known wrasse species as it is often seen alongside other marine animals, including sharks. There are more than 500 different species of Wrasse found in the shallower coastal waters and coral reefs, of the Pacific, Indian and Atlantic oceans. Wrasse most commonly inhabit areas that have an abundance of both food and places to hide, making coral reefs and rocky shores the perfect home for the wrasse.

Cleaner wrasse are the most well-known wrasse species as they are often seen going into the mouths of large marine animals in order remove the dead material inside. Cleaner wrasse feed on dead tissues, scales and parasites that lurk inside the mouth of the larger animal, and few are actually eaten by the predator that they are assisting. Wrasse come in a variety of colours and sizes depending on the species of wrasse. Wrasse tend to be relatively small in size, with many species of wrasse being less than 20 cm in length. One species of wrasse however is enormous in comparison, growing to more than 2 meters long.

Wrasse are carnivorous animals that have thick lips with a row of teeth that usually face outwards. The mouth of the wrasse is protractile which means that it is capable of extending forwards. Wrasse feeds on a number of small invertebrates, small fish and food particles in the water. Wrasse are also known to follow large predatory fish, eating the trail of left-overs that it leaves behind it. Due to their small size, wrasse have numerous predators in their natural environment including larger fish, such as lionfish, dogfish and barracuda and wrasse are even eaten by some smaller species of shark.

Wrasse are known to live for a relatively long-time particularly for their small size. Wrasse mate by releasing their eggs and sperm in to the water, which are fertilised and become part of the plankton until they are big enough to join the reef. Female wrasse lay thousands of eggs at at time so the wrasse population numbers are relatively high. Source

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X-Ray Tetra

The X-Ray Tetra is a small species of schooling Fish that is naturally found in the Amazon River's coastal waters in South America. The X-Ray Tetra is also known as the Golden Pristella Tetra and the Water Goldfinch due to the faint golden colouration of their translucent skin. They were first described by Ulrey in 1894 and have since become one of the most popular freshwater Fish kept in artificial aquariums today. Although the X-Ray Tetra is the only known species in it's genus, it is closely related to other small and colourful South American Fish, including the nearly 100 other Tetra species.

The most distinctive feature of the X-Ray Tetra is the translucent layer of skin that covers it's small body, allowing the Fish's backbone to be clearly seen. The scales of the X-Ray Tetra are a silvery-yellowish colour that is very faint, looking almost golden in some lights. The X-Ray Tetra also has a re-tipped tail and strikingly striped dorsal and anal fins that are yellow, black and white in colour. This is a relatively small species of Fish that actually has a bony internal structure known as the Weberian apparatus, which is used in picking up sound waves, and contributes to their acute sense of hearing (this bony structure is also found in many of their relatives).

Like many other small, colourful Fish, the X-Ray Tetra is a schooling species of Fish inhabiting the region between the bottom and middle of the water as a group. They are incredibly peaceful and are often tolerant of the other species that they share their habitats with. The X-Ray Tetra is one of the most adaptable species of Tetra as it is able to inhabit both fresh and brackish water happily, in both acidic and alkaline conditions. It is widely observed that those X-Ray Tetra that are kept in tanks, can change quickly from being peaceful to becoming skittish in the presence of larger, predatory Fish, with the same behaviour known to be displayed if the school size is not big enough.

During the rainy season. the X-Ray Tetra return to the flood-lands to spawn. Unlike many similar Fish who give birth to live young, the female X-Ray Tetra lays between 300 - 400 eggs by scattering them amongst the vegetation (when she is ready to spawn, the see-through skin means that her eggs can also be easily seen). X-Ray Tetra fry begin to hatch as early as 24 hours later, and become free swimming within a few days. Once able to swim, the small and dull white young, are able to find better food sources and soon develop their characteristic adult markings. X-Ray Tetra usually live for three or four years in the wild but can get to older ages in captivity. Source

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