Horn and Angel Sharks: Unusual Predators on the Seabed - Owlcation - Education
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Horn and Angel Sharks: Unusual Predators on the Seabed

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

A crested horn shark (or crested bullhead shark) feeding on the egg of another species in its genus

A crested horn shark (or crested bullhead shark) feeding on the egg of another species in its genus

Unusual Fish

Many people think of sharks as ferocious killing machines that swim at high speed as they hunt for prey. This image is often inaccurate, however. First, research is showing that far from being "machines", at least some sharks are surprisingly intelligent. Secondly, not all sharks move fast or swim through the open ocean. Some, including the horn shark and the angel shark, live and feed on the seabed.

Horn sharks have a raised ridge above each eye. The ridges look like little horns and may have given the animals their name. The fish also have a blunt snout that resembles the snout of a bull. Horn sharks often hunt for food by "walking" over objects with their strong pectoral fins. They swim quite slowly compared to most other sharks.

Angel sharks have a wide, flattened body and wing-like pectoral fins. They hide in the sediments on the seabed with just their eyes above the ground They burst out of their hiding place in order to capture passing prey.

External anatomy and fins of a typical shark

External anatomy and fins of a typical shark

Divers can often get close to California horn sharks. This is often—but not always—safe.

Divers can often get close to California horn sharks. This is often—but not always—safe.

Bullhead sharks belong to the genus Heterodontus. The genus name is derived from two Greek words: heteros, which means "different", and odont, which means "teeth". The name refers to the two types of teeth in the mouth of the animals.

Features of Bullhead Sharks

Horn sharks are members of an order of fish known as bullhead sharks (Heterodontiformes). There are nine known species in this order, all belonging to the genus Heterodontus. The term "horn shark" is applied to three of the species—the California horn shark, the Mexican horn shark, and the crested horn shark.

The snout of a bullhead shark is blunt. There is a round opening on each side of the snout known as an oronasal groove. Each of these openings is surrounded by a fleshy ring of tissue.

The animal's teeth are adapted for grasping and grinding hard foods gathered from the seabed, such as sea urchins and crabs. The front teeth are pointed to enable efficient biting, and the back teeth are flattened for crushing,

Bullhead sharks have a crest over each eye and a spine in front of each of their two dorsal fins (the fins on the animal's back). Some reports say that the fin spines gave the horn sharks their name rather than the crest over their eyes. The pectoral fin on each side of the body is large and muscular and enables the fish to move with a walking motion over the ocean bottom.

Bullhead sharks generally aren't dangerous to humans, although they may bite or chase when threatened. They shouldn't be confused with bull sharks, which are aggressive.

The California Horn Shark

The California horn shark (Heterodontus francisci) lives on the west coast of North America. Its range extends from slightly north of San Francisco down to and into the Gulf of California. It's an attractive fish with a brown or grey surface that has darker spots. It reaches a maximum length of four feet. Most individuals are shorter than this, however.

The fish is usually nocturnal. During the day, it hides in caves or crevices, under ledges, or in thick beds of seaweed. Starting at dusk, it hunts for animals on or close to the seabed, including crabs, snails, squid, shrimp, sea urchins, sea stars (starfish), and occasionally other fish.

The shark is able to remove animals attached to a substrate by using its teeth like a chisel. Suction helps draw the prey into the shark's mouth. The fish may also pry animals off a surface with its mouth by bracing itself with its pectoral fins, moving into a vertical position, and then rapidly moving its body downwards. In effect, it uses its body as a lever.

About 43 percent of sharks and rays—including skates, most cat sharks, and the nine species of horn shark—lay eggs rather than give birth to live young.

— Julie Leibach, Science Friday (A public radio station show)

Reproduction

Fertilization is internal in all sharks. Fish have a pelvic fin on each side of their body behind the pectoral fins. A male shark has a tubular organ called a clasper on the inner side of each of his pelvic fins. Claspers insert sperm into the female's reproductive tract.

After fertilization, the female horn shark reproduces by laying eggs. She produces two eggs at a time, starting in the late winter or early spring. There is a gap of eleven to fourteen days between egg-laying sessions. Eggs are produced for as long as four months.

The egg case has a spiral shape. It's soft when it's laid and gradually hardens over time. The female wedges each egg into a rock crevice to protect it from predators. The embryo takes a long time to develop. Pups aren't born until six to eight months after the eggs are laid. The typical lifespan of California horn sharks isn't known for certain, but they have lived for twelve years in captivity. Some reports say that they can live for as long as twenty-five years.

Heterodontus galeatus lives off the coast of Australia. It's known as the crested horn shark or the crested bullhead shark.

Population Status of the California Horn Shark

The IUCN (International Union for Conservation of Nature) classifies animal species according to their nearness to extinction. The California horn shark has been placed in the Data Deficient category. This means that the size of its population isn't known. The last population assessment was performed in 2014.

The fish generally isn't caught for food, but it is sometimes caught for its long fin spines. The spines are used in jewelry. Today the main problem for the animal seems to be that it forms part of the bycatch in the fishing industry. "Bycatch" is defined as an animal that is accidentally trapped when another type of animal is being caught. Luckily, the horn shark seems to be a hardy creature. When it's returned to the ocean after being trapped in fishing gear, it often survives. Unfortunately, it's sometimes injured and dies.

An angel shark blending in with its background

An angel shark blending in with its background

Angel Sharks

Angel sharks belong to the order Squatiniformes and the genus Squatina. Many species have been recognized. They live in oceans around the world. The front section of an angel shark's body is flattened, including its head. The fish has greatly enlarged pectoral fins that are flat and extend outwards. Its smaller pelvic fins also extend out from its body. The pectoral fins often look like wings and make the fish look quite like a ray. In skates and rays, however, the fins are attached to the side of the head. In angel sharks, they aren't.

The rear section of an angel shark's body isn't flattened and looks more like that of a typical shark. The lower lobe of the tail is longer than the upper lobe, however. In other sharks, the upper lobe is longer than the lower lobe.

Like horn sharks, angel ones are bottom feeders. Instead of actively patrolling the ocean bottom, they use an ambush technique to catch their prey. They cover themselves with a thin layer of sediment on the seabed so that just their eyes show. Then they patiently wait. When they detect a suitable prey animal, they pounce. The fish have powerful jaws and sharp teeth, which make them very successful predators.

Angel sharks are generally not dangerous to humans. If a person gets too close to the jaws, though, they may get a nasty wound. It should never be assumed that a totally still angel shark is dead because it almost certainly isn't.

Unlike some sharks that must swim continually to force water over their gills, angel sharks (and horn sharks) have muscles that pump water over their gills. Therefore, they can remain motionless and still survive.

The Pacific Angel Shark

The Pacific angel shark (Squatina californica) lives in the eastern part of the Pacific Ocean. Its range extends from Alaska down into South America. The fish reaches a maximum length of about five feet but is usually shorter than this. In California, it's sometimes known as the California angel shark.

The animal is brown or grey with dark spots. The mottled surface appearance is very useful for camouflaging the fish against the ocean bottom. The pectoral and pelvic fins are noticeably angular and pointed. The fish also has barbels around its mouth. Barbels are slender sensory organs that are sensitive to both taste and touch.

Catching Prey

Like the California horn shark, the Pacific angel shark is more active during the night than the day. It feeds mainly on fish and squid. Research suggests that sight is the most important factor in the animal's detection of food. Scientists say that when it hunts at night, bioluminescence created by planktonic organisms may help the animal to see its prey.

Another very interesting discovery has been made by means of high speed videography. The researchers who conducted this experiment found that the sharks caught their prey in about one tenth of a second.

Egg Production and Lifespan

Angel sharks have internal fertilization and give birth to live young. Eggs are produced, but they hatch inside their mother's body. The pups feed on yolk stored in a yolk sac until they are born. The fish is said to be ovoviviparous due to this method of producing offspring. The "ovo" part of the description means that the fish produces eggs, and the "viviparous" part means that it gives birth to live young.

The Pacific angel shark produces about six pups at a time. The gestation period may vary, but it seems to be about ten months. There are reports that the fish can live for as long as thirty-five years. This fact needs to be confirmed, however.

Population Status of the Pacific Angel Shark

The Pacific angel shark is classified in the IUCN's Near Threatened category. As in the case of the Heterodontus francisci, the last population assessment was performed in 2014. There was a period in the 1970s and 1980s when the animal was caught for food in large numbers in the United States, which had a very serious effect on its population.

New fishing regulations seem to have helped in some parts of the animal's United States range, but not everywhere. The effect of the Mexican shark fishery on the species is unknown. Unfortunately, the IUCN says that the overall population of the animal is decreasing, which is not a good sign.

A Diverse Group of Animals

Sharks form a large and diverse group of organisms. The big ones that are dangerous to humans are generally better known by the public than the smaller and the bottom-dwelling fish. This is a shame because small sharks and the ones that roam the seabed or hide in its sediments are interesting animals. Some have unusual and even impressive features. I think the animals are definitely worthy of our attention.

References

© 2014 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on June 23, 2014:

Thank you, Anita! I appreciate your comment and the vote.

Dream Lover from Zagreb on June 23, 2014:

Voted up. Very interesting hub and beautiful pictures :)

Linda Crampton (author) from British Columbia, Canada on April 24, 2014:

Thank you very much, VioletteRose! I appreciate your visit.

VioletteRose from Atlanta on April 24, 2014:

Great details about the horn shark and angel shark. As you mentioned, the picture of a shark in my mind was something that swims and hunts. Thanks for sharing !

Linda Crampton (author) from British Columbia, Canada on March 19, 2014:

Hi, ologsinquito. Yes, I think the horn shark is an attractive and interesting fish. Thanks for the visit.

ologsinquito from USA on March 19, 2014:

The California horn shark is very attractive. I don't remember seeing one, even though I've been to the Monterey aquarium numerous times.

Linda Crampton (author) from British Columbia, Canada on February 06, 2014:

Thanks for the comment, Deb! It's certainly a very sad thought that some fish are being killed so that their spines can be used to make jewelry.

Deb Hirt from Stillwater, OK on February 06, 2014:

Amazingly wonderful information on these animals. As far as jewelry goes, I think what these creators need is a little plastic, don't you?

Linda Crampton (author) from British Columbia, Canada on January 25, 2014:

Hi, Dianna. I live close to the ocean, too, but luckily no dangerous sharks live nearby. The number and variety of animals on Earth is certainly amazing!

Dianna Mendez on January 25, 2014:

Living so close to the ocean, we know the dangers of shark swimming close to the beach. It is not a daily threat, but one has to be aware of the potential. I learned lots about different types of sharks from your post. always come away amazed at the variety of animals.

Linda Crampton (author) from British Columbia, Canada on January 25, 2014:

Thank you very much for the comment and the vote, Eddy.

Eiddwen from Wales on January 25, 2014:

You sure have outdone yourself here Alicia.

Voted up.

Eddy.

Linda Crampton (author) from British Columbia, Canada on January 23, 2014:

Thank you very much for the lovely comment and all the votes. D.A.L.! I love learning about nature, too. It's a fascinating and very enjoyable activity.

Dave from Lancashire north west England on January 23, 2014:

Fantastic hub , thoroughly enjoyed reading and the pictures are amazing. As a naturalists I never tire of being taught about animals of the world. Here I have been educated well by this inspiring work. Thank you. Voted up,interesting and beautiful.

Linda Crampton (author) from British Columbia, Canada on January 23, 2014:

Thanks for the visit, Vellur! I appreciate your comment and vote.

Nithya Venkat from Dubai on January 23, 2014:

Interesting and informative hub about sharks, learned a lot about sharks after reading your hub. Thank you for sharing and voted up.

Linda Crampton (author) from British Columbia, Canada on January 22, 2014:

Hi, Nell. Yes, sharks are definitely amazing creatures! Thank you very much for the comment, the vote and the share. I appreciate them all!

Nell Rose from England on January 22, 2014:

Hi Alicia, fascinating hub about the Sharks, they are the most amazing creatures, and I didn't realise that some sharks could stay stationary, I learned something new, great hub! voted up and shared, nell

Linda Crampton (author) from British Columbia, Canada on January 22, 2014:

Hi, b. Malin. Thanks for the comment and the votes. It will be very interesting to confirm that the angel shark can live that long! It's a fascinating animal. Luckily, the angel and the horn shark generally aren't aggressive towards humans.

b. Malin on January 22, 2014:

A Great SAFE way to learn about ALL these Sharks... They really are a Fascinating read, thanks to your enlightening Hub. Alicia. I didn't know anything about their reproduction, or how long they can live...Thirty-five years for some...Wow...what are the chances of an attack by one?

Voted UP & Interesting.

Linda Crampton (author) from British Columbia, Canada on January 21, 2014:

Thank you so much for the comment and for showing the hub to your girls, Robin! I'm very interested in sharks, too. They are important animals, as you say. I think that both the angel and the horn shark look cool!

Robin Edmondson from San Francisco on January 21, 2014:

I am a huge shark lover, and I always appreciate Hubs that educate people on their importance. Our oceans are such a fragile ecosystem and our destruction of the top of the food chain has a huge impact on us all.

I had never heard of the California Horned Shark before your Hub. What a cool looking animal. Will definitely be showing this Hub to my girls!

Linda Crampton (author) from British Columbia, Canada on January 21, 2014:

Thank you, DDE. These sharks are interesting!

Devika Primić from Dubrovnik, Croatia on January 21, 2014:

Horn and Angel Sharks - Predators on the Seabed are unique creatures and is most interestingly explained in this hub.

Linda Crampton (author) from British Columbia, Canada on January 20, 2014:

Thank you very much for the comment, the votes and the share, Faith! It's fascinating to study life in the oceans. There is so much to discover! Blessings to you, Faith.

Linda Crampton (author) from British Columbia, Canada on January 20, 2014:

Hi, Bill. I agree - the last video is amazing! It's sad too, although it wasn't sad for the angel shark. When I first watched the video I was so glad that the horn shark escaped, and then almost immediately the angel shark ate a different fish! Thank you very much for the vote and the share. I hope that your week is great, too.

Faith Reaper from southern USA on January 20, 2014:

Fascinating creatures, the Horn and Angel Sharks! Your hubs are always so very interesting. I, too, just love reading and learning about sea life. Great article.

Up and more and sharing

Blessings,

Faith Reaper

Bill De Giulio from Massachusetts on January 20, 2014:

Amazing creatures Linda. Thanks you for bringing them to us. That video of the Angel Shark trying to eat the Horn Shark is amazing. Have a great week. Voted up and shared.

Linda Crampton (author) from British Columbia, Canada on January 20, 2014:

Thanks, EGamboa. Life is very different under the ocean than on land!

Linda Crampton (author) from British Columbia, Canada on January 20, 2014:

Hi, Bill. Thanks for the comment and for sharing your experience with bullhead fish.

Eileen Gamboa from West Palm Beach on January 20, 2014:

Point of view from the ocean. Very interesting.

Bill Holland from Olympia, WA on January 20, 2014:

I've caught a few bullheads in my time. Not a pleasant experience. LOL I love hubs about the animal kingdom....and fish...and birds....and...and....

Thanks for an enjoyable read, Alicia.

Linda Crampton (author) from British Columbia, Canada on January 19, 2014:

Thanks for the comment and the vote, Jodah. I think that sea life is very interesting, too. There is so much to discover under the ocean surface!

John Hansen from Queensland Australia on January 19, 2014:

Very interesting. I find all sea creatures, especially the lesser known varieties intriguing. Good hub. Vote up.

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