Slinger wrasse: a fish with a retractable jaw, variable coloration and hermaphroditism

Have you ever seen a fish that can extend its jaw half the length of its body? Such a fish exists, and it's called the sling-jaw wrasse (sling-jaw wrasse). It is one of the most unusual and amazing fish in the world, possessing unique adaptations to its habitat and lifestyle. In this article, we will tell you all about the sling-jaw wrasse: what it looks like, where it lives, how it hunts, reproduces, and interacts with other fish and humans.

 

Description of the Sling-jaw Wrasse

The sling-jaw wrasse (Epibulus insidiator) belongs to the Labridae family, which also includes parrotfish, wrasses, roosters, and other colorful fish. It is widespread in the tropical and subtropical waters of the Indo-Pacific region, from Africa to Polynesia.

The sling-jaw wrasse has an elongated body that reaches 35 cm in length. Female individuals are smaller in size than males. Some males can reach 54 cm in length.

The body coloration depends on the age, sex, and habitat of the fish. Young individuals are white with dark spots and stripes that help them camouflage among corals. Adult males are grayish-brown with an orange back, a yellowish transverse stripe on the side, and a pale gray head marked by a thin black stripe running through the eye. Females can be bright yellow or dark brown. A feature of the sling-jaw wrasse is its scales, which have protruding edges and create a mosaic effect on the fish's body.

But the most amazing feature of the sling-jaw wrasse is its jaw, which can extend into a long tube. This adaptation allows the fish to capture its prey at a distance without swimming too close to it.

The jaw of the sling-jaw wrasse consists of two parts: upper and lower. The upper part is attached to the skull with a joint that allows it to rotate up and down. The lower part is attached to the upper part with another joint that allows it to extend forward and retract back. When the sling-jaw wrasse hunts, it quickly extends its jaw and opens its mouth, creating a vacuum that sucks the prey inside. Then it quickly closes its mouth and retracts its jaw, chewing and swallowing the prey. You can see this unusual process in a short video at the end of this article.

Interesting fact

The sling-jaw wrasse has the largest jaw protrusion among fish. Its extendable jaw can increase to half the length of the body, forming a tubular shape.

The sling-jaw wrasse also has the ability to change its coloration depending on the situation. It can become brighter or darker, showing its mood, health status, or sexual identity. For example, when the sling-jaw wrasse encounters another male of its species, it can become darker and show its scales, demonstrating its strength and readiness to fight. When the sling-jaw wrasse is ready to reproduce, it can become brighter and show its stripes, attracting the attention of females. When the sling-jaw wrasse experiences stress or illness, it can become paler and lose its patterns, showing its weakness or malaise.

 

Habitat and Lifestyle of the Sling-jaw Wrasse

The sling-jaw wrasse prefers to live in coastal waters where there are many corals, sponges, algae, and other hiding places. It inhabits depths from 1 to 30 meters but is most commonly found at depths of 5 to 15 meters. It likes warm and clean water, with temperatures from 24 to 28 degrees Celsius. It avoids strong currents and waves that can interfere with its hunting and communication.

The sling-jaw wrasse leads a solitary lifestyle, although it can sometimes form small groups of several individuals. It is very territorial and defends its area from other fish, especially its own kind. It marks its territory with sounds, color signals, and pheromones that it releases from its gills. It can also attack or chase intruders using its protruding jaws.

The sling-jaw wrasse communicates with other fish using sounds it makes by clicking its teeth. It also uses its coloration, posture, and movements to convey different messages. For example, when it wants to show its friendliness or submission, it may lower its fins and become lighter. When it wants to show its aggression or dominance, it may raise its fins and become darker.

The sling-jaw wrasse is a predator that feeds on small fish, shrimp, crabs, mollusks, and other invertebrates. It hunts using its protruding jaw, which allows it to capture prey at a distance without getting too close. It can also use its coloration to camouflage itself among corals or sand, or, conversely, to deter or attract other fish. The sling-jaw wrasse mainly hunts during the day when its prey is active. At night, it hides in shelters where it sleeps and regains its strength.

 

Reproduction Features of the Sling-jaw Wrasse

The sling-jaw wrasse reaches sexual maturity at about two years of age. It is a hermaphrodite, meaning it can change its sex during its lifetime. In most cases, the sling-jaw wrasse is born as a female and then transforms into a male when it reaches a certain size or age. However, sometimes it can remain a female all its life or switch from male to female if there is a shortage of females in its group. This allows the sling-jaw wrasse to maintain an optimal sex ratio in its population.

The mating season for the sling-jaw wrasse falls in spring and summer when the water is warm enough and fertile. At this time, males become brighter and more aggressive, trying to attract the attention of females and ward off competitors. They also display their scales, fins, and jaws, making various movements and dances. Females choose a male based on his appearance, sounds, and behavior. When a female finds a suitable partner, she swims up to him and lets him know she is ready to mate.

The spawning process takes place in open water, where the male and female rise up, wrapping around each other. They simultaneously release their eggs and sperm, which mix in the water. A single female can produce up to 200,000 eggs at a time. The eggs and sperm have no protection and are subject to currents, predators, and other factors. The sling-jaw wrasse does not care for its offspring and does not protect them from dangers.

The eggs of the sling-jaw wrasse hatch within a few days, and larvae emerge, feeding on plankton and drifting in the water. The larvae have transparent bodies with large eyes and fins. They are very vulnerable to predators and can die from many causes. Only a small portion of the larvae survive and reach the fry stage, when they begin to resemble adult fish. The fry descend to the bottom and seek shelter among corals and other objects. They grow and develop, changing their coloration and body shape. They also change their sex if necessary for the balance in the population.

 

The Importance of the Sling-jaw Wrasse for the Ecosystem and Humans

The sling-jaw wrasse plays an important role in the ecosystem as it affects the populations of other fish and invertebrates that are its prey or competitors. It also serves as prey for other predators such as sharks, barracudas, rays, and other large fish. The sling-jaw wrasse helps maintain biodiversity and balance in its habitat.

This fish is not of great significance to humans, as it is not a target of commercial or sport fishing. The sling-jaw wrasse is also not considered edible, as its flesh can be toxic due to the presence of cyanobacteria it consumes along with other food.

However, the sling-jaw wrasse may be of interest to scuba diving and photography enthusiasts, as it has a beautiful and unusual appearance and behavior. It can also be kept in an aquarium, but this requires special conditions and care, as it is very sensitive to changes in temperature, water quality, and diet. It can also attack other fish in the aquarium if it does not feel comfortable or does not have enough space. Overall, the sling-jaw wrasse is rarely found in aquariums, probably due to its large size.

The sling-jaw wrasse is not under threat of extinction, as it has a wide distribution and high numbers. However, it can suffer from the destruction and pollution of its habitat, as well as from overfishing of other fish that are its prey or breeding partners. Therefore, it is necessary to preserve and protect its natural environment, as well as to observe the rules and standards of fishing and aquarium keeping.