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Walking and Epaulette Sharks: Intriguing Fish With Muscular Fins

Linda Crampton is a writer and teacher with an honors degree in biology. She loves to study nature and write about living things.

An epaulette shark (Hemiscyllium ocellatum)

An epaulette shark (Hemiscyllium ocellatum)

Unusual and Interesting Fish

Walking sharks are unusual fish with an elongated shape and muscular fins on the lower part of their body. The fins enable the fish to "walk" along the ocean floor. In the case of at least one species, they enable the animal to move over land as well. The body of walking sharks is decorated with spots, blotches, or stripes. The animals belong to the genus Hemiscyllium. Researchers have recently announced the existence of four new species of walking sharks, bringing the total number to nine.

Though most people probably think of sharks as fierce and fast-moving predators that are occasionally dangerous for humans, many more benign species (from our point of view) exist. Walking sharks are one example. When the fish are "walking", the front part of their body resembles that of a moving salamander. They aren't believed to be closely related to the amphibian, however. In this article, I highlight the epaulette shark, which is the best known species in its genus and the one known to leave the water and travel over land.

The genus Hemiscyllium belongs to the family Hemiscylliidae. This family is also known as the longtail carpet shark family. Carpet sharks (or carpetsharks) are named for the fact that the pattern on their body surface resembles that of an ornate carpet.

Fins and Features of a Walking Shark

The illustration above shows the type of shark that is probably most familiar for many people. The fish has:

  • two dorsal fins on its back
  • a pectoral fin on each side near the gills
  • a pelvic fin on each side underneath the body and towards the rear end
  • an unpaired anal fin behind the pelvic fins
  • a caudal fin, which forms the tail; the upper lobe of this fin is larger than the bottom one

The body shape of a walking shark is different from that of the torpedo-shaped animal shown above. A walking shark is long and slender. It has a long "tail" or caudal peduncle behind the last dorsal fin. The caudal peduncle is the narrow area in front of the caudal fin of a fish.

Walking sharks have the same fins as the classical shark. The pectoral and pelvic fins are muscular and paddle-shaped, however. In addition, the caudal fin has only one lobe. The dorsal fins are located far back on the body and the anal fin is located near the caudal one.

The new announcement that nine species of walking sharks exist is based on a twelve-year study. Researchers suspect that more fish belonging to the genus Hemiscyllium will be discovered. The known species live in warm water on the coast of Australia, New Guinea, and Indonesia.

The Epaulette Shark

The epaulette shark lives in water around Australia and New Guinea. Unconfirmed reports suggest that it also lives in other areas nearby. The fish is light grey or brown in colour and has darker spots. Its name comes from a large black spot encircled with white that is located on each side of its body just behind the pectoral fin. The spot reminded earlier biologists of military epaulettes. It's thought that it may act as a distraction for predators. It looks like a large eye from a distance. It's easy to imagine that the "eye" belongs to a bigger animal than the shark. The animal's real eye is much smaller.

The adult fish is generally no longer than a metre. It has the long caudal peduncle that is typical of its genus. Its snout is noticeably rounded and has barbels at its tip. Barbels are fleshy extensions that are believed to act as sense organs and to play a role in detecting food.

An opening called a spiracle is located under and behind each eye. The spiracle absorbs water and sends it to the gills. The blood vessels in the gills absorb oxygen from the water. They also send carbon dioxide waste made by the shark's body into the water. The water then returns to the ocean through the gill slits on the side of the animal.

An epaulette shark in a public aquarium

An epaulette shark in a public aquarium

Surviving on Land

The epaulette shark is usually found in shallow water. It swims through the water and walks on the ocean floor and on land. Though walking sharks don't walk in the way that we do, their muscular fins have a wide range of motion and are a useful aid to propulsion on a solid surface. The walking movement of the epaulette shark is thought to resemble that of the first four-legged animals that appeared on land.

The shark can survive for an amazingly long time with a low oxygen level in its body. This means that it can exploit habitats that other fish are unable to reach. It can reportedly stay out of water for up to an hour. Some researchers claim that the time is even longer. The features that enable the fish to survive under these conditions are still being studied. It seems to have multiple adaptations that enable it to live on land, including the ones listed below.

  • The breathing rate decreases.
  • The heart rate also decreases.
  • Blood flow to the heart increases.
  • Blood vessels going to some parts of the brain dilate, allowing more oxygen to reach the organ. Blood flow to less vital areas of the brain is decreased, however.
  • Nerves continue to function in a low-oxygen environment.

On land, the fish sometimes dampens its body as it travels through tide pools and into puddles in the coral reef. It also moves over dry sand, however, which would seem to be a less hospitable environment. Its survival abilities are impressive.

Diet of an Epaulette Shark

Epaulette sharks are mainly bottom feeders and feed mostly on invertebrates, such as crabs, shrimp, and polychaete worms. They also eat small fish, including ones trapped in tide pools. By coming onto land as well as feeding in the ocean, epaulette sharks are able to find food items that are unavailable to most other fish. They sometimes chew their prey before swallowing it, which is an unusual behaviour for a shark.

Researchers have discovered that the sharks are active at any time during the day or night but are most active during crepuscular (dawn or dusk) conditions. They detect their prey by using their sense of smell or by detecting the weak electric currents produced by the muscles of the animals. Sharks have electroreceptors that contain tubes filled with jelly and connect to the outer world via pores in the animal's skin. The receptors are known as the ampullae of Lorenzini.

Behaviour on Land

It might be thought that by coming onto land the epaulette sharks expose themselves to terrestrial predators. If this is the case, it doesn't seem to be hurting their population size. It's known that the sharks sometimes come into conflict with other fish when they are on land. The epaulette shark is not the only species to leave the ocean and survive. Some species of moray eels occasionally come onto land, for example.

Epaulette sharks sometimes travel over sand to reach desirable feeding areas. They may pause and become stationary on the sand for a while. This appears to be the case for the animal in the photo above. The fish face the prevailing air current when they pause. The behaviour is known as rheotaxis. It's not known for certain why epaulette sharks perform this behaviour. Suggestions include improvement of respiration or a way to detect predators.

Egg and fetus of Scyliorhinus canicula (a type of catshark)

Egg and fetus of Scyliorhinus canicula (a type of catshark)

The beautiful photo above shows a typical egg case of a shark and the developing animal inside it. Epaulette shark egg cases and the moving youngsters inside them are shown in the video below.

Reproduction

In their natural environment, epaulette sharks breed from July or August to December. Fertilization is internal, as in other sharks. The male inserts sperm into the female's body with his claspers. A clasper is an elongated structure under each pelvic fin. It can be seen in the illustration of shark fins shown above. Sperm leaves the male's body, travels along a groove in a clasper, and enters the female's cloaca.

Epaulette sharks lay eggs and are therefore said to be oviparous. Two eggs are generally laid for every mating incident, which sometimes happens as often as every two weeks. The female ignores the eggs after they are released. She may lay as many as fifty eggs in total during the breeding season, though there is some debate about this number.

Each egg is enclosed in a case that is sometimes known as a mermaid's purse. Fibrous extensions on the case help to attach it to the surroundings. Gestation lasts for around 120 days. The young sharks that emerge from the cases are decorated with black and white bands. These break up into spots as the fish mature. The animals may live for twenty years or more.

Population Status

Thankfully, the epaulette shark population appears to be doing well. The fish is not of much interest to commercial fisheries. It's captured for the aquarium trade, however, and is sometimes collected by local people who need food.

Some people pick up the fish for amusement when they find it. This is potentially harmful for two reasons. The fish is sometimes injured when it's handled. In addition, it's not advisable to pick up any shark, no matter how docile it seems to be. Although the epaulette shark is often said to be harmless to humans, it may bite when it's frightened. In Australia, some of the animal's habitat is located in marine reserves, which is probably helpful for its numbers.

The IUCN (International Union for Conservation of Nature) classifies the shark in its Least Concern category and says that its population is stable. The assessment is based on data obtained in 2015. It's good to know that the fish seems to be safe at the moment.

The epaulette shark has some fascinating features. More research is needed to clarify some of the facts about the fish and to solve the puzzles linked to its life. Hopefully more information about the animal and more discoveries about walking sharks in general will soon appear.

References

© 2020 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on February 25, 2020:

Thank you, Paula. I appreciate your visit and comment very much.

Suzie from Carson City on February 25, 2020:

Linda/Alicia.....Well, my dear, looks like you are bound & determined to make all your readers, highly-informed/knowledgeable individuals! Thanks for this fascinating read. Your research and efforts are much appreciated.

Linda Crampton (author) from British Columbia, Canada on February 24, 2020:

Hi, Genna. I think all sharks are interesting, though I agree that the smaller species look less intimidating! Thank you for the visit.

Genna East from Massachusetts, USA on February 24, 2020:

Hi Linda. the smaller variety of these critters look so cute. But sharks still scare me -- walking or not. :-) This is such an interesting article; it's amazing to learn how various species adapt in order to survive oin their environment.

Linda Crampton (author) from British Columbia, Canada on February 16, 2020:

Hi, Flourish. The fish do have an interesting method of reproduction! Thank you for the comment.

FlourishAnyway from USA on February 16, 2020:

Very interesting and the name “mermaid purse” is so cute. Laying eggs every two weeks during breeding season sounds exhausting! But I guess since it’s only two at a time and you don’t have to raise them that may me okay.

Linda Crampton (author) from British Columbia, Canada on February 08, 2020:

Hi, Kari. I'd like to visit Cape Cod. It has always sounded like an interesting place to me.

Kari Poulsen from Ohio on February 08, 2020:

Thanks for all the good information! I think I used to see "mermaid purses" on the beach while vacationing in Cape Cod.

Linda Crampton (author) from British Columbia, Canada on February 06, 2020:

Thank you very much, Denise. Blessings to you as well.

Denise McGill from Fresno CA on February 06, 2020:

I believe I've heard of this shark before but didn't pay much attention. This is great information. Thanks.

Blessings,

Denise

Linda Crampton (author) from British Columbia, Canada on February 05, 2020:

Hi, Bill. I think the shark is a fascinating creature, too, as well as any other fish that can survive on land. Thank you very much for the visit and the comment.

Bill De Giulio from Massachusetts on February 05, 2020:

What a fascinating creature, Linda. I was remotely aware of some fish and shark species that could travel on land, but have never heard of the epaulette shark. You continue to amaze me by introducing us to these amazing creature.

Linda Crampton (author) from British Columbia, Canada on February 05, 2020:

Thank you very much for the kind comment, Dora. I appreciate your visit.

Dora Weithers from The Caribbean on February 05, 2020:

Congratulations on your 2019 HubAward! Your articles always inform and educate us. As usual, it is fascinating to know about these different kinds of sharks and their habits.

Linda Crampton (author) from British Columbia, Canada on February 04, 2020:

Hi, Peggy. A fish walking on land is an interesting thought! Sharks have some surprising features. They're not as simple as some people believe.

Peggy Woods from Houston, Texas on February 04, 2020:

Thanks for introducing me to another interesting sea creature, Linda. It must be amazing to see such a creature walking on land!

Linda Crampton (author) from British Columbia, Canada on February 04, 2020:

Hi, Nithya. I think the sharks are amazing animals. I hope researchers learn more about them.

Linda Crampton (author) from British Columbia, Canada on February 04, 2020:

Hi, Rachelle. Thanks for the comment. I read lots of biology articles and enjoy exploring nature in real life. I often get ideas for writing topics when I do this.

Nithya Venkat from Dubai on February 04, 2020:

I did not know about the epaulette shark until I read this article. The photos are amazing. The adaptations of these sharks to survive out of the water for nearly an hour must be amazing. It is great that the population of these sharks is stable.

Rachelle Williams from Tempe, AZ on February 04, 2020:

A shark that leaves the water and travels to land areas... First and foremost, where in the world did you first learn about these creatures? Second, thank you for introducing me to these little baby monsters, because I'd never heard of them before and third, please let's hope the SyFy channel doesn't catch wind of them....

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Hi, Mary. I think they're interesting fish, too. They are kept in some commercial aquariums, though I don't know how much room they have to walk in their tanks in these facilities. I hope they have enough space to be reasonably comfortable.

Mary Norton from Ontario, Canada on February 03, 2020:

I have not seen these sharks. I have seen moray eels but not these. They are quite interesting. I would love to see one walk.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thank you very much, Suchismita. I appreciate your visit.

Suchismita Pradhan from India on February 03, 2020:

Loads of information on walking shark.A well researched article.Keep writing.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thanks for the visit and the comment, Heidi. I agree with you. I think a lot of people may not realize how many types of sharks exist. I hope you have a good week.

Heidi Thorne from Chicago Area on February 03, 2020:

Another cool animal friend indeed! I think people have no idea of the variety of sharks out there, big and small. Thank Jaws for that. ;)

I can't remember if I saw one when I visited our Shedd Aquarium. But it would be cool to see.

Happy Monday!

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thank you very much for the kind comment, Linda.

Linda Chechar from Arizona on February 03, 2020:

That epaulette shark is quite remarkable. I've never heard of these species. It is amazing that they can walk on the ocean floor, in shallow water and on land. I always enjoy your articles!

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thank you very much, Chuck. The shark has some fascinating features that are interesting to explore.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thanks for the comment, Liz. I think the way in which the fish move is very interesting. Life in the ocean seems to hold many surprises for us.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thanks for the comment, Pamela. I think that sharks are a fascinating group of animals that are worth exploring.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

I agree, Raymond! It is great to hear about a species that is doing well. The animal is extraordinary, as you say.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Hi, Manatita. I'm not sure what sound you're referring to. Life on Earth is certainly awesome. There's a lot of beauty to be found here. Thank you for the comment.

Chuck Nugent from Tucson, Arizona on February 03, 2020:

This is a great Hub about a fascinating creature. I had never heard of this type of shark before and enjoyed reading your article. You did a great job of researching and writing this.

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Hi, Louise. I think the ocean is fascinating to explore. As you say, it contains some lovely creatures!

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Hi, Bushra. I think it's a fascinating animal, too!

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Hi, Devika. Thanks for the comment. The epaulette shark has some very interesting features. I think it's worth studying.

Liz Westwood from UK on February 03, 2020:

This is a very detailed and informative article. I have learnt a lot from reading it. I had no idea about epaulette sharks before. Thank you for enlightening me about their existence. I shall keep an eye out for them in future when visiting aquariums. I was especially amazed at their ability to 'walk' and survive for short periods out of the water.

Pamela Oglesby from Sunny Florida on February 03, 2020:

I have never heard of a walking shark before and I didnot know there were so many types of sharks. I found the epaulette shark to be quite interesting. Thanks a wealth of new informaiton.

Raymond Philippe from The Netherlands on February 03, 2020:

Isn’t it great, for a change, to read a particular species is doing well instead of disappearing from the earth’s surface. What an extraordinary shark.

manatita44 from london on February 03, 2020:

Fascinating! This sound that I hear in the videos, is it their breathing? They leave me in awe and all the more reverential to the Higher Intelligence, which some call God. We live with so much beauty! Just a little more in human hearts and we will enjoy an amazing universe. Gratitude.

Louise Powles from Norfolk, England on February 03, 2020:

I've never seen a shark like this before, but I think it's really cute. It's amazing the amount of lovely creatures in the ocean.

Anya Ali from Rabwah, Pakistan on February 03, 2020:

What a fascinating animal! Thank you for posting this article here.

Devika Primic on February 03, 2020:

Hi Linda an amazing write up here on this fish. I had no idea of it and somehow you got to it and informed me of such an interesting and fascinating . Facts are intriguing and a thorough research into the life of this fish tells me you know it better than I

Linda Crampton (author) from British Columbia, Canada on February 03, 2020:

Thank you for the visit and the comment, Eman.

Eman Abdallah Kamel from Egypt on February 03, 2020:

It is really an unusual and interesting fish. I enjoyed reading this educational article.

Linda Crampton (author) from British Columbia, Canada on February 02, 2020:

Thank you, Umesh. I appreciate the comment.

Umesh Chandra Bhatt from Kharghar, Navi Mumbai, India on February 02, 2020:

Well researched and exhaustive. Nice work. Thanks.

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