Swellshark
Encyclopedia
The swellshark, Cephaloscyllium ventriosum, is a catshark
of the family
Scyliorhinidae. It is found in the subtropical eastern Pacific Ocean
between latitude
s 40° N
and 37° S
, from the surface to 460 m.
It grows to about 100 centimetres (39.4 in) in length, and can expand its body to about double its regular size to prevent its predators such as seals
and larger sharks from pulling it out from rocky reefs, under ledges, and in crevices. The swellshark's appearance resembles that of the leopard shark
in that it has spots. Younger swellsharks are lighter in color than the older ones. Swellsharks are nocturnal, sleeping in reef crevices and caves during the day. Sometimes, these sharks will grab onto their tail with their mouth in a ring shape to prevent other fish to attack. During the night they hunt molluscs
, crustaceans and bony fishes. The swellshark is oviparous, and the females lay two flattened egg sacks which contain the embryo
which is attached by two tendril
s to a reef
. Swellsharks are commonly found in aquariums and are completely harmless to humans, usually staying completely motionless when encountered by divers. The World Conservation Union
has assessed this species as a least concern species
worldwide, as it is usually not fished by divers and fishermen due to its poor flesh quality. However the odd swellshark gets killed by fishermen and this along with its low egg production put the species at risk.
word kephale which means skylla was used for the term Cephaloscyllium while ventriosum which means large belly was used to describe the shark's ability to suck in water.
coast, the Gulf of California
and the southern tip of Mexico
. Swellsharks have been as far south as Chile
but it is believed that it is a totally different species of shark. It can be found resting over continental shelves and subtropical waters and can be seen as deep as 457 metres (1,499.3 ft) or as close as five meters below the surface. Swellsharks prefer to make their homes in algae covered rock bottoms. In the California area it shares the same habitat as the Horn shark
and unlike that shark, the swellshark is more tolerant of water temperatures below 20 °C (70°F).
area. Another fin is located in the anal area. The fins are light brown with dark patches and are covered along with the rest of its body with black dots. Usually the younger sharks are lighter in color than the adults. Its spotted coloration closely resembles that of the leopard shark
. The gills of a swellshark are usually very small and tight. Swellshark eyes are large and gold and the lower eyelid is nictitating. The largest swellsharks can be up to 110 centimetres (43.3 in) but are usually around 90 centimetres (35.4 in) in length. Every swellshark has around 55–60 teeth, which contains mostly small teeth.
and crustaceans. When hunting the swellshark will either lie on the bottom of the ocean, and wait until their prey is a few centimeters (inches) away before it attacks. Another hunting tactic used by the swellshark is to lie on the bottom of the ocean with its mouth open, waiting for a fish to swim into its mouth. Swellsharks also enter lobster trap
s to get an easier meal. Swellsharks are nocturnal and sleep in reef
crevices during the day. When the shark feels threatened, it will bend its body into a U–shape, grab its tail fin with its mouth, and suck in water. Doing so makes it more difficult for predators to remove it from rocky crevices, allows the shark to double in size, and makes it harder for larger sharks and seals
to eat it. During the time when the air is in its stomach the swellshark floats upward to the water surface. When letting the air out, the swellshark makes a dog–like bark. The swellshark is very sociable with other sharks, and are commonly seen sleeping next to or on top of one another..
The swellshark is oviparous and they lay two green or amber flattened eggs which are attached to the reef with tendril
s. After a study, it was determined that the length of the tendrils depends on the amount surf action the region is under. The egg case which contains the embryo
and is approximately 2.5 centimetre (0.984251968503937 in)–5.1 centimetres (2 in)
by 7.6 centimetres (3 in)–13 centimetres (5.1 in)
. The embryos will feed solely on yolk before they hatch. The hatching time for swellshark eggs solely depend on water temperature but usually will hatch between 7.5–12 months. When born after this period of time in the egg, the swellshark pup will immediately begin feeding on molluscs and crustaceans.
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When confronted by a human
in the water, the swellshark will become motionless. However, if they are threatened, they will swell up to double their regular size. The swellshark is common in public aquarium
s because it can live for several years in captivity.
It is usually not caught purposely but, if it is, usually it will be released because its flesh is of poor quality. Since the swellshark often enters lobster traps to find food, it will sometimes get caught incidentally and killed when brought to the surface. This accidental catching threatens the species mainly because of its age at maturity and the low number of eggs it produces. Despite this, the swellshark is listed as Least Concern
by the World Conservation Union
.
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....
of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Scyliorhinidae. It is found in the subtropical eastern Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
between latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
s 40° N
40th parallel north
The 40th parallel north is a circle of latitude that is 40 degrees north of the Earth's equatorial plane. It crosses Europe, the Mediterranean Sea, Asia, the Pacific Ocean, North America, and the Atlantic Ocean....
and 37° S
37th parallel south
The 37th parallel south is a circle of latitude that is 37 degrees south of the Earth's equatorial plane. It crosses the Atlantic Ocean, the Indian Ocean, Australasia, the Pacific Ocean and South America....
, from the surface to 460 m.
It grows to about 100 centimetres (39.4 in) in length, and can expand its body to about double its regular size to prevent its predators such as seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
and larger sharks from pulling it out from rocky reefs, under ledges, and in crevices. The swellshark's appearance resembles that of the leopard shark
Leopard shark
The leopard shark is a species of houndshark, family Triakidae, found along the Pacific coast of North America from the U.S. state of Oregon to Mazatlán in Mexico...
in that it has spots. Younger swellsharks are lighter in color than the older ones. Swellsharks are nocturnal, sleeping in reef crevices and caves during the day. Sometimes, these sharks will grab onto their tail with their mouth in a ring shape to prevent other fish to attack. During the night they hunt molluscs
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
, crustaceans and bony fishes. The swellshark is oviparous, and the females lay two flattened egg sacks which contain the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
which is attached by two tendril
Tendril
In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts. They do not have a lamina or blade, but they can photosynthesize...
s to a reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
. Swellsharks are commonly found in aquariums and are completely harmless to humans, usually staying completely motionless when encountered by divers. The World Conservation Union
World Conservation Union
The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...
has assessed this species as a least concern species
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
worldwide, as it is usually not fished by divers and fishermen due to its poor flesh quality. However the odd swellshark gets killed by fishermen and this along with its low egg production put the species at risk.
Taxonomy
When discovered in 1880, the swellshark was first described as Scyllium ventriosum however it was later changed to Cephaloscyllium ventriosum. The GreekGreek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word kephale which means skylla was used for the term Cephaloscyllium while ventriosum which means large belly was used to describe the shark's ability to suck in water.
Distribution and habitat
The swellshark can be found in the Eastern Pacific, the central CaliforniaCalifornia
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
coast, the Gulf of California
Gulf of California
The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...
and the southern tip of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Swellsharks have been as far south as Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
but it is believed that it is a totally different species of shark. It can be found resting over continental shelves and subtropical waters and can be seen as deep as 457 metres (1,499.3 ft) or as close as five meters below the surface. Swellsharks prefer to make their homes in algae covered rock bottoms. In the California area it shares the same habitat as the Horn shark
Horn shark
The horn shark is a species of bullhead shark, family Heterodontidae. It is endemic to the coastal waters off the western coast of North America, from California to the Gulf of California. Young sharks are segregated spatially from the adults, with the former preferring deeper sandy flats and the...
and unlike that shark, the swellshark is more tolerant of water temperatures below 20 °C (70°F).
Anatomy and appearance
Swellsharks have a rounded dorsal fin located in the pelvicPelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
area. Another fin is located in the anal area. The fins are light brown with dark patches and are covered along with the rest of its body with black dots. Usually the younger sharks are lighter in color than the adults. Its spotted coloration closely resembles that of the leopard shark
Leopard shark
The leopard shark is a species of houndshark, family Triakidae, found along the Pacific coast of North America from the U.S. state of Oregon to Mazatlán in Mexico...
. The gills of a swellshark are usually very small and tight. Swellshark eyes are large and gold and the lower eyelid is nictitating. The largest swellsharks can be up to 110 centimetres (43.3 in) but are usually around 90 centimetres (35.4 in) in length. Every swellshark has around 55–60 teeth, which contains mostly small teeth.
Diet and behavior
When hunting at night, the swellshark hunts for bony fish, molluscsMollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
and crustaceans. When hunting the swellshark will either lie on the bottom of the ocean, and wait until their prey is a few centimeters (inches) away before it attacks. Another hunting tactic used by the swellshark is to lie on the bottom of the ocean with its mouth open, waiting for a fish to swim into its mouth. Swellsharks also enter lobster trap
Lobster trap
Not to be confused with Lobster-tailed potA lobster trap or lobster pot is a portable trap that traps lobsters or crayfish and is used in lobster fishing. A lobster trap can hold several lobsters. Lobster traps are constructed of wire and wood. An opening permits the lobster to enter a tunnel of...
s to get an easier meal. Swellsharks are nocturnal and sleep in reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
crevices during the day. When the shark feels threatened, it will bend its body into a U–shape, grab its tail fin with its mouth, and suck in water. Doing so makes it more difficult for predators to remove it from rocky crevices, allows the shark to double in size, and makes it harder for larger sharks and seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
to eat it. During the time when the air is in its stomach the swellshark floats upward to the water surface. When letting the air out, the swellshark makes a dog–like bark. The swellshark is very sociable with other sharks, and are commonly seen sleeping next to or on top of one another..
Reproduction
Tendril
In botany, a tendril is a specialized stem, leaf or petiole with a threadlike shape that is used by climbing plants for support, attachment and cellular invasion by parasitic plants, generally by twining around suitable hosts. They do not have a lamina or blade, but they can photosynthesize...
s. After a study, it was determined that the length of the tendrils depends on the amount surf action the region is under. The egg case which contains the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
and is approximately 2.5 centimetre (0.984251968503937 in)–5.1 centimetres (2 in)
by 7.6 centimetres (3 in)–13 centimetres (5.1 in)
. The embryos will feed solely on yolk before they hatch. The hatching time for swellshark eggs solely depend on water temperature but usually will hatch between 7.5–12 months. When born after this period of time in the egg, the swellshark pup will immediately begin feeding on molluscs and crustaceans.
Relationship to humans
Human
Humans are the only living species in the Homo genus...
in the water, the swellshark will become motionless. However, if they are threatened, they will swell up to double their regular size. The swellshark is common in public aquarium
Public aquarium
A public aquarium is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquariums feature tanks larger than those kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-19th century, they have become popular...
s because it can live for several years in captivity.
It is usually not caught purposely but, if it is, usually it will be released because its flesh is of poor quality. Since the swellshark often enters lobster traps to find food, it will sometimes get caught incidentally and killed when brought to the surface. This accidental catching threatens the species mainly because of its age at maturity and the low number of eggs it produces. Despite this, the swellshark is listed as Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
by the World Conservation Union
World Conservation Union
The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...
.