Creatures of Iriomote Island - Sea

Hello everyone! Iriomote Island, called the Galapagos of the East, is home to a wide variety of creatures. On land, there are many endemic species such as Iriomote wild cat and Kammuriwa that can be seen only here. There are also diverse ecosystems in the sea. One of the reasons for this is the largest coral reef in Japan. There are hundreds of species of corals alone, and the marine life inhabiting there is too diverse to count. This article introduces the wide variety of marine life in Iriomote Island.

A wide variety of Iriomote Island's sea creatures

(1) Sea turtles

 

After all, the tropical sea, including Iriomote Island, is associated with sea turtles. Speaking of sea turtles, they are often depicted on T-shirts in Hawaii, and can often be seen in the warm sea.
Nowadays, sea turtles swim gracefully in the sea, but in fact, their ancestors spent their lives on land. This is a surprise.

Yes, sea turtles are turtles that lived on land and then moved into the sea! During the evolutionary process, in order to swim faster in the sea, their hands were modified to resemble fins, and their carapace was modified to be more streamlined so as to be less subject to water resistance. This evolution has resulted in the bones of the carapace having more spaces and becoming very light, allowing the turtle to swim faster.

It is said that there are eight species of sea turtles in the entire world. Of these, six species are said to live in Japan: the loggerhead, green, hawksbill, leatherback, leatherback, and black sea turtles. However, it is rare to confirm the presence of the leatherback, green, and black turtles in Japan, and it is said that the three species often observed in Japan are the loggerhead, green, and taimai turtles. These species can be seen during snorkeling in Iriomote Island.

manta ray

The manta ray is said to have originated from the Spanish word manta, which refers to the pectoral fins that spread out like a cape.

When manta rays are born, they are said to be about 1 m long and weigh about 50 kg. When they grow up and are large, they are 6 to 7 meters across, weigh 2 tons, and have a known lifespan of about 40 years, making them one of the longest-lived fish species.

Although they look like this, they are members of the shark family and feed on plankton. The fact that they eat large amounts of small plankton is similar to the feeding habits of baleen whales.

There are two main types of manta rays: the manta ray and the Japanese manta ray.

You can easily distinguish them by looking at their mouths. A black mouth is a manta ray and a white mouth is a manta ray.

The manta rays seen at "Manta Scramble" and "Manta City," which are diving spots where manta rays can be observed in Iriomote Island, are mainly Nanyo-umantas.

(iii) Southern spotted boxfish

The southern spotted puffer is a member of the boxfish family and lives in warm waters south of Wakayama. Although it looks very similar to the boxfish that Sakana-kun wears on his head, the southern boxfish can be distinguished from the other two by the small black spots on the head and caudal fins of adult fish, and the black spots on the body of juvenile fish as large as the eye diameter.

Adults are approximately 35 cm in length and are known to be omnivorous, feeding on sponges, algae, and benthic animals. They are found in coral reefs and rocky reefs at depths shallower than 50 meters, and can be seen while snorkeling and diving.

Its bright colors make it a popular ornamental fish, but it releases mucus toxin from its skin when it senses danger, so care should be taken when keeping it as an ornamental fish or observing it in the ocean.

4) Clownfish (Chlamydoselachus anguineus)

Many of you probably know the bearfish. This fish, which is also the motif for the main character in the Disney movie Finding Nemo, has a cute orange, white, and black appearance. They live symbiotically with sea anemones, and there are six known species of fish in the genus Clownfish in Japan.

They are distinguished by the distinctive white transverse bands on the head and body, and by the fact that males have yellow caudal fins and females have whitish ones!

Popular as an ornamental fish, it is hardy, easy to keep, and long-lived.

Because of their strong personalities, they sometimes peck at your mask when you approach them while snorkeling, but that is just to intimidate you, not to be friendly.

(5) Coral

At first glance, some people may think that corals are a type of plant or mineral because they do not move at all, but there is no doubt that corals are animals in their own right. In fact, corals are members of a group of animals called cnidarians, the same as sea anemones and jellyfish.

Corals are composed of a body part called a polyp and a calcareous skeleton. Polyps are so small that they are not easily seen at a glance, but if you look closely, you can see them moving. The polyp has a mouth surrounded by tentacles through which it feeds, excretes, and spawns. Inside the cells are symbiotic zooxanthellae.

(vi) unicornfish

Like the bearfish, the blue tang is a fish that was used as a motif for the main character in Finding Nemo. In the film, they are introduced as forgetful characters, but it is not that they have a particularly poor memory. This point was probably added for the sake of character development.

Now, to return to the description of the elasmobranch, the body color is bright blue, and the dorsal and anal fins are blue with black margins. The pectoral fins have yellow areas at their tips and the caudal fins are yellow with their upper and lower edges black.

The blue tang has this distinctive coloration from the time it is a juvenile fish, and has long been popular as an ornamental fish because of its unique coloration.

Although the coloration of the blue tang varies somewhat depending on its habitat and the food it eats, it is believed to be the only one of its kind found at this stage.

seven-spot red snapper (Lutjanus bohar)

Scarabaeus is about 5 cm long and has a translucent body, with the posterior end of the caudal fin black with a transparent margin. Only the rostrum is dark, and males have a yellow line in the middle of the anterior half of the body, while females do not.

They are widely found on coral reefs and inner bay reefs, and are known to form large schools. When light hits the translucent bodies of these large schools, they reflect and glisten silver, making them look very beautiful.

They feed on small crustaceans and zooplankton.

(viii) Gonzui

Gonzui look like eels or loaches at a glance and have four pairs of whiskers. It has four pairs of whiskers. They have two longitudinal lines on their body and large, poisonous spines on their pectoral and dorsal fins.

They inhabit coastal reefs and sandy bottoms, and juvenile fish form dense schools, also known as "gonzui balls," like the scalloped hammerhead sea bream introduced earlier. The main difference between this species and the Gonzui is that Gonzui form a dense school rather than a school.

They are omnivorous and feed mainly on benthic animals, but juveniles may also clean other fish.

(ix) jawfish

The jawfish is a very cute fish with its adorable appearance and ecology. Jawfish have been known to peek out of their burrows, and along with clownfish, they are very popular among females.

Because they are easy to keep, many saltwater fish lovers have been keeping them in recent years.

Despite its lovely appearance, it is one of the easiest saltwater fish to keep because it is highly resistant to pathogens that tend to accumulate in the sand and has virtually no susceptibility to disease, which is considered a weakness of saltwater fish.

It is not as easy as the Squirrel Sparrowfish or the Silycyrrhini Sparrowfish, but it is a step down in difficulty from the Clownfish.

(10) Hub jellyfish

One thing to be especially wary of in Okinawa's summer waters would be the habu jellyfish.

Habu jellyfish belongs to the genus Habu jellyfish of the family Nettaiidon jellyfish. The umbrella is 10-12 cm in diameter, and each of its four legs has eight tentacles, each about 1.5 m long.

The venom of the habu jellyfish is so powerful that a sting is instantly painful. The venom is so strong that the site where its tentacles become entangled can develop worm sores, blisters, and cell necrosis, and severe injuries can cause respiratory distress and cardiopulmonary arrest due to shock symptoms, even death.

Although the habu jellyfish is such a highly ranked dangerous creature, its body is a transparent bluish color and it is difficult to dispatch it unless one wears underwater glasses. In addition, while jellyfish generally have almost no swimming ability, the habu jellyfish has very high swimming ability and is said to move as fast as a person can walk. It is possible to be stung by a jellyfish that is right in front of you when you notice it, so you need to be very careful.

crown-of-thorns starfish (Acanthaster planci)

The starfish is a member of the family of starfish in the order Acanthuroidea. Starfish are echinoderms like sea urchins and sea cucumbers, and the starfish is a large starfish that likes to eat coral. Some of the largest starfish are said to be nearly 60 cm in length, and they have 10 to 20 arms and their body surfaces are covered with numerous spines.

The spiny thorns covering the starfish's body surface are highly neurotoxic, and accidental bites cause severe pain and swelling. In addition to pain and swelling, symptoms such as itchy throat, nausea, and low blood pressure may also occur.

There was a temporary problem of coral mortality caused by a massive outbreak of crown-of-thorns starfish. During the extermination work, many people inadvertently came into contact with the starfish and were stung by them.

It is said that a second sting from a wasp can cause "anaphylactic shock" and lead to death, and the same can be said for starfish.

Since this is a life-threatening situation, it is important to learn how to properly treat a sting if you are stung. The following two operations can be performed as first aid, so be quick about it.

(1) Get out of the water as soon as possible.

(2) Remove the spike from the affected area and squeeze the poison out of the body while applying pressure to the affected area.

⑫⑫Hebi

Sea snakes are venomous snakes of the cobra family that have adapted to life in the sea. It is also surprising that a sea snake is a member of the cobra family.

It is said that there are nine species of sea snakes living in the seas around Japan: the elabid sea snake, the black-bellied sea snake, the white-tailed sea snake, the seguro sea snake, and the blue-bellied sea snake.

Sea snakes have many different characteristics. The common sea snake is known for its small head and mild-mannered nature. However, they are full-bodied snakes with scales all over their bodies. Some of them have neurotoxins that can kill people. If you see one in the ocean, do not provoke it unnecessarily, as you could get into serious trouble.

A bonito fish (Sphyrna tiburo, species of hammerhead shark found in the eastern Pacific Ocean from southern Mexico to northern Peru)

Bryozoans are cnidarians belonging to the order Cnidaria. Although it is a jellyfish, it is technically not a jellyfish at all, but a member of a group of organisms called hydrothecae.

The vesicular body, which looks like a crow's nest and is about 10 cm in size, has a clear blue color. The vesicular body is said to extend from about 10 to 50 meters below the sea surface. Their very long tentacles possess a strong neurotoxin that is said to be lethal to humans in some cases.

Despite their small appearance, they are quite aggressive creatures.

red lionfish (Pterois volitans)

Minnow scorpionfish inhabit many fields, from shallow coastal waters to slightly deeper waters, reef areas, and sandy bottoms mixed with rocky areas.

The thirteen spines on the dorsal fin are venomous, and the sting is irritating. They are not fatal, but may cause swelling. They prey on small fish, shrimp, and other crustaceans, and they lay their eggs protected in agar egg sacs.

It is caught by fixed nets, gill nets, trawl nets, and fishing, and is often eaten because of its delicious white flesh.

(xv) square octopus (Octopus vulgaris)

The leopard octopus is a very small octopus, about 10 cm in length. When stimulated, the leopard octopus displays a bright lapis lazuli-colored ring pattern on its body. This pattern looks like a leopard print, hence the name "leopard octopus.

Although the leopard octopus looks cute, it actually has a fearsome side.

The saliva of the leopard octopus contains tetrodotoxin, a neurotoxin similar to pufferfish poison.

A single bite can cause paralysis leading to difficulty breathing and even cardiac arrest due to lack of oxygen. In fact, several deaths have been reported, so be very careful.

in the end

We have introduced the marine life of Iriomote Island. How was it?

There were various sea creatures of Iriomote Island, such as the famous sea turtles, bear fleas, and manta rays. Some of them had neurotoxins that could kill people, such as sea snakes and leopard octopus. Be well informed about this, how to avoid them, and be prepared for the worst. Remember that you are always next to danger in the sea, so enjoy observing living creatures!

Thank you for reading to the end.