Order: Anguilliformes
Family: Murenidae

Currently, there are about 200 species of moray eels divided into 16 genera. They belong to the two subfamilies Muraeninae and Uropterygiinae, which can be distinguished by the location of the fins on their body. In Muraeninae, the dorsal fin starts at the height of the gill slits, runs down the dorsum and joins the caudal fin, while the anal fin is behind the anus. In Uropterygiinnae, both the dorsal and anal fins are at the tip of the tail.

Moray eels are almost exclusively marine fish. Only a few species are regularly observed in brackish waters, in mangroves or in rivers, among them, for example, Gymnothorax polyuranodon. Moray eels occur in tropical and subtropical waters, with the greatest diversity found in tropical waters of the Indo-Pacific. Only a few species occur in the temperate zone, incl. the Californian moray (Gymnothorax mordax) and the Yellow moray (Gymnothorax prasinus). Many moray species inhabit shallow waters with bottoms covered in rocks or coral reefs, where they hide in holes and crevices. Others live on sandy or silty bottoms up to 500 meters deep. Many species are active at night and spend the day in hiding places.

These animals reach a length of 20 cm to almost 3.75 m, although most of them have a total length of just over 1 m. The largest species reach a weight of up to 30 kg. The body of moray eels is elongated, muscular, laterally flattened and devoid of scales, and their smooth skin is covered with protective mucus. Additionally, the lack of pectoral and abdominal fins (in most species) gives them the appearance of a snake. Moray eels have a thicker skin than other eel species, which, combined with the high density of goblet cells (mucus-producing cells), allows mucus to be produced faster. This is important for sand-dwelling moray eels, because the mucilage makes the sand granules stick to the walls of the burrows and they are more durable. This makes it easier for the moray eel to breathe freely, which is not easy considering the size and location of the gill opening.

Moray eels exhibit a stunning variety of color patterns, from solid brown or green to complex patterns of spots, stripes, mesh, and rosettes, ranging in colors from red to yellow and green and brown to white. In some species, the inside of the mouth is also patterned. Their jaws are wide and surround a protruding snout. Most of them have large, pointed teeth that are used for tearing meat apart or grabbing slippery food. A relatively small number of species, such as the Snowy moray (Echidna nebulosa) and Zebra moray (Gymnomuraena zebra), feed mainly on crustaceans and other hard-shelled animals and have blunt, molar-like crushing teeth. Their large jaws are set wide open, usually just beyond the back of the eye, which is well developed. Due to the fact that the eyes are small, moray eels rely mainly on their highly developed sense of smell. Moray eels have two pairs of nostrils. The front nostrils are tubular in shape and are located near the tip of the mouth. The posterior nostrils lie below or above the eye and look like a tube or dimple. The combination of a raised head profile, the position of the posterior nostril, the absence of pectoral fins, and a reduced lateral line is not found in any other fish family.

Moray eels are nocturnal predators that hunt crabs, prawns, cuttlefish, squid, octopus, and fish. They can also feed on carrion. Few predators prey on moray eels, incl. barracudas and sea snakes, which is why many moray eels, especially the larger ones, are the apex predators in their ecosystems. They are dioecious animals, although in some species all juveniles are male and only change sex over time. Fertilization is external and the eggs and larvae are pelagic. Moray eels have a leptocephalus stage, which is characterized by a glassy, ​​laterally flattened, high and elongated ribbon-like body. It is somewhat reminiscent of a willow leaf. Since leptocephalus has neither red blood cells nor hemoglobin in their blood, their body is translucent.

Several species of moray eels are popular with aquarists for their hardiness and flexible diet. The most popular are the Snow moray, Zebra moray, and Goldtail moray (Gymnothorax miliaris). In addition, they are eaten in many parts of the world, but there are risks.

Ingestion of moray eels weighing more than 4 kg can lead to ciguatera toxin poisoning, which is sometimes fatal.

The Giant moray (Gymnothorax javanicus) and Yellow-bank moray (G. flavimarginatus) are known to accumulate large amounts of ciguatoxins, which are mainly concentrated in the liver. A special case was the poisoning of 57 people who ate the head and half of the body of the cooked yellow-bank moray. It took place in the Northern Mariana Islands. Ciguatoxin poisoning is characterized by neurological, digestive and circulatory problems. Therefore, these fish are not recommended for consumption.

Given the great variety and variability among moray eels, they are difficult to identify. Identification is made on the basis of many features, including fin positions, tail length, anus position, nostril profile, jaws and dentition, and color pattern. Both the color pattern and dentition can change significantly as an animal grows, and the presence of fins is sometimes difficult to determine.

Moray eel – the prototype of the ‘Alien’?

Moray eels have well-developed pharyngeal jaws, which are deeper in the body of the fish and resemble the jaws of the mouth. However, they have much smaller teeth. While feeding, the moray eels extend these jaws into the mouth, where they grab the victim and transport it to the esophagus. They are the only animals known to use the throat jaws to actively capture and restrain prey in this way. In the Californian moray, the teeth are able to fold as the victim shifts backward, thus preventing the teeth from breaking and keeping the victim during transport to the throat. Moreover, in order to avoid the escape of the captured victim, the moray eel’s mouth extends far into the head. Thanks to this, when throwing at the prey, the water flows out of the back of the mouth and does not displace the prey.

Order: Tetraodontiformes

family: Ostraciidae

Lactoria cornuta

The order of Tetraodontiformes also includes such families as: Tetraodontidae, Diodontidae (porcupinefish), Balistidae (triggerfish), Monacanthidae (filefish) and Molidae (sunfish).

While Tetraodontiformes use many different defense mechanisms, Ostraciidae are characterized by armor composed of polygonal bone plates, which gives them a characteristic box-like shape. Due to its rigidity, it hinders the velocity of move, but protects them from predators.

The Longhorn cowfish is found near the Indo-Pacific coral reefs, from South Africa through Indonesia, the Marquesas Islands to southern Japan. It occurs at a depth of 1 to 100 meters. This fish survives over a dozen years and reaches a length of 40 cm, although it can grow up to 50 cm. Its diet is mainly composed of bottom invertebrates. Adults are loners, while adolescents form small groups. They have a yellow or olive body covered with turquoise spots. The caudal fin grows throughout their life, sometimes reaching as much as 2/3 of the body length, but it does not have a drive function, but rather acts as a rudder.

By moving the pectoral and anal fins, these fish create vortices around its body, which results in a specific self-correcting swimming movement.

The characteristic feature of the Longhorn cowfish is four horns. Two grow out of the head and are directed forward, while the other two grow near the anal fin and are directed backwards. Supposedly, the horns are an additional defense mechanism discouraging predators from swallowing it. This can be confirmed by the fact that broken horns have an ability to regenerate, they grow back in a few months. In addition, when the fish is hurt or feels threatened, it releases a toxin (ostracitoxin) which repels predators. In such a case, if any animals are found in a limited space, it is deadly for them, including the fish itself.

Order: Myliobatiformes
family: Whiptail stingray

Taeniura lymma

The Bluespotted ribbontail ray, a representative of cartilaginous fish, is common in the Indo-Pacific from southern Africa to the Solomon Islands, including the Red Sea. This is the most common stingray among coral reefs. Interestingly, adults and adolescents live in different habitats. Adult stingrays occur in deeper reefs (up to 20 meters deep), while young prefer warm, shallow waters with a bottom covered with seagrass, mangroves or covered with rocks, where they find shelter from predators. The Bluespotted ribbontail ray grows up to 70 cm in length with its tail being half of this length. The maximum width of her body is 30 cm. Its main food are annelids, small molluscs, crustaceans and cephalopods, which it finds by combing the sandy bottom. In this way, it plays an important ecological role as a bioturbator by modeling bottom morphology, and also determines the density patterns and distribution of benthic infauna (organisms living in bottom sediments). It hunts mainly at night, and spends the day still.
T. lymma has a characteristic blue dots on the back, and the tail is distinguished by blue stripes on both sides. At the end of the tail are two sharp venom spines that are used for defense. They are remnants of skin teeth that covered the body of stingrays. Lost spikes grow back and the wounds inflicted by them are very painful. It is a ovoviviparous species. During courtship the male bites the female. Pregnancy can last from 4 to 11 months depending on many external factors. Such a long pregnancy makes them more susceptible to the collapse of the population. Fortunately, these rays are able to breed in captivity.

Atractosteus spatula

The Aligator gar looks like something between a pike and a crocodile: a lengthened trunk with three fins in the tail part refers to a pike, and long, toothed jaws are associated with a crocodile. The Aligator gars do not take care of their offspring. They are the largest freshwater fish in North America and may exceed the length of 3 m and the weight of 100 kg. They hunt for large prey, not only for other fish, but also for lizards, snakes and turtles.

It is one of the most primitive and the largest freshwater fish species in the world. Fossils from the Cretaceous period (145-66 million years ago) have been found in America, Europe and Asia. Currently, their natural environment are lakes, rivers and reservoirs in central and northern America, however, their number is constantly decreasing due to overfishing and dams, which prevent reproduction. They reach huge sizes, grow up to 200 cm on average and the largest specimen caught was 305 cm in length and weighed 166 kg. They can live up to 50 years. From time to time, the fish is observed to swim under the surface of water to get extra air, which makes it easier to survive in a low oxygen environment. It is possible thanks to the vascularized bladder connected to the pharynx. Female may deposit 138,000 eggs at a time. The eggs are bright orange and unfit for consumption, as they are poisonous. The Alligator gar has two rows of teeth and the internal row is longer. This feature allows to catch and effectively hold the victim in the mortal grip of strong jaws.

order: Perciformes

family: Acanthuridae

Paracanthurus hepatus

The only representative of the genus Paracanthurus.

The Blue surgeonfish is found in the coastal waters of the Indo-Pacific Ocean, from the coasts of East Africa to Oceania, excluding the Red Sea. It has a wide extent of occurrence, but is not common. We can meet it, among others, on the coral reefs of the Philippines, Indonesia, Japan, Australia, New Caledonia, Samoa, as well as Sri Lanka. It is associated with coral reefs, it lives mainly near their outer parts, where sea currents are stronger. The extent of occurance is related to its love of swimming. It inhabits coastal waters with a bottom covered with vegetation. It can be observed at depths from 1 to 40 meters. Its maximum length is 31 cm, but they usually grow up to 20 cm. It can live up to 30 years in the wild, and 8 to 20 years in captivity. Its food is comprised mainly of zooplankton and algae. Juveniles feed exclusively on plankton. It is a very important inhabitant of the reefs, because he cleanses corals of algae growing on them, thus keeping them in good condition. Most often, this species lives in pairs or form small groups of 8 to 14 animals.

Its characteristic feature is its coloration, blue body with black back and yellow fins. The attractive colors makes it a popular aquarium fish. Until recently, all individuals that we could admire in aquariums were caught directly from their natural environment. Currently, this species is successfully propagated in laboratory conditions, but not on a global scale. The larvae differ significantly in color from adults. Their body is almost transparent and silvery. It gradually turns blue, yellow pigmentation appears at the very end of development. At night its blue color pales, presumably avoiding the attack of nocturnal predators. Another characteristic feature of the Blue surgeonfish is the presence of sharp, poisonous spikes located on the tail, one on each side, which are used for defense. It is not of great commercial importance, but it can account for a significant proportion of inshore fisheries.

Its meat has an unpleasant smell and is poisonous. After ingesting it, the symptoms of food poisoning may occur.

This surgeonfish does not produce a toxin (ciguatoxin) by itself. It is accumulated in its body along with the consumed algae that produce toxin.

Why is it blue?

The fish do not have blue pigment in their skin. The blue color that we can see is nothing but a light phenomenon. Isidophores, i.e. pigment cells that reflect light, are responsible for this phenomenon. In the light they create iridescent colors, but by proper orientation of the schematochromes (prism-like structures, refracting and dispersing visible light to the surroundings,) and using biochromes (biological pigments) as a filter, they create a blue color.

order: Tetraodontiformes
family: tetraodontidae

Canthigaster solandri

This species is found in the Indo-Pacific, from East Africa east to the Tuamotu Archipelago, north to the Ryukyu Islands, and south to New Caledonia and Tonga. Its presence has also been reported in Hawaii, but is not numerous. Populations from the Philippines, Indonesia, New Guinea, Queensland and Belau differ slightly in coloration. Species from the Pacific seem to be slightly darker compared to those in the Indian Ocean. Puffer inhabits a variety of habitats, including open sea areas, vegetated areas, lagoons, coral reefs and artificial reefs. Its depth range is 10 to 36 meters. Like the other representatives of the genus Canthigaster, it is rather small, it only grows up to 12 cm in length. It feeds mainly on thread-like algae, but also sponges, corals, tunicates, molluscs, echinoderms, polychaetes and crustaceans. It uses its four impressive, strong teeth for nutrition. Teeth grow all their lives, and to grate them, the Spotted sharpnose eats hard food. It is often seen in pairs, sometimes in small groups. It is an optional monogamist, which means that the male is forced to associate with one female due to the limited number of individuals. They are oviparous. Females build nests to lay their eggs in and look after them. This fish has an interesting coloration. Its body is greenish brown and is covered with many light blue spots and lines. Bright colors inform predators about its toxicity. It makes characteristic noises.

How does the puffer defend against predators?

The Spotted sharpnose creates a symbiotic relationship with the bacteria Pseudoalteromonas tetraodonis, which produce tetradotoxin – a potent neurotoxin. Fish accumulates the toxin in the skin, gonads and liver. The degree of animal toxicity depends on the geographical area and the season of the year. When it is stressed or dies, it releases a toxin into the water. Despite its toxicity, it is consumed by people, but it must be prepared in certified restaurants. Inappropriate preparation of the fish may result in the death of the person who consumed it. Another form of defense against predators is to increase in body size. When it feels threatened, it pumps water into its stomach, thereby increasing its volume, which in most cases discourages a predator which is unable to swallow it. An additional form of protection is the presence of a ‘false eye’ located at the dorsal fin. Its task is to confuse predators about the actual location of the fish head.