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Pseudocarcharias kamoharaiCrocodile shark(Also: Japanese ragged-tooth shark; Kamohara´s sand-shark; Water crocodile)

By Nitin Sharma

Geographic Range

Pseudocarcharias kamoharai (Crocodile sharks) can be found in nearly all subtropical and tropical oceans of the world (Compagno 1984). (Compagno, 1984)

Habitat

Crocodile sharks are mostly pelagic; however, there have been some incidences where crocodile sharks have been found inshore (Compagno 1984). The known depth range of crocodile sharks from the water surface can reach 590 m (Martin 2003). (Compagno, 1984; Martin, 2003)

  • Range depth
    590 (high) m
    1935.70 (high) ft

Physical Description

Crocodile sharks are clearly distinguishable by huge eyes that lack nictitating eyelids and long gill slits that extend to the top of the head. Crocodile sharks have a slender, spindle-shaped body with two small, spineless dorsal fins. The second dorsal fin is less than half the size of the first dorsal fin. The pelvic fins are distinctly broad and round (Compagno 1984). Like all Lamniformes, crocodile sharks have 5 gill slits and a mouth that extends behind the eyes (Martin 2003). The size of adult crocodile sharks is on average 89 to 110 cm in length and between 4 to 6 kg in weight. The color of crocodile sharks can range from light to dark grey to dark brown. White or transluscent margins may also be found around the fins (Martin 2003). Some specimens have been found with whitish blotches on either side of the head between the corner of jaw and the first gill slit (Compagno 1984). (Compagno, 1984; Martin, 2003)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    4 to 6 kg
    8.81 to 13.22 lb
  • Range length
    89 to 110 cm
    35.04 to 43.31 in
  • Average length
    105 cm
    41.34 in

Development

At birth, crocodile sharks are 41 cm in length (Compagno 1984). Males mature at a length of about 74 to 100 cm and females mature at a length of about 89 to 102 cm (Martin 2003). (Compagno, 1984; Martin, 2003)

Reproduction

Crocodile sharks reproduce sexually through internal fertilization. There is little information on the mating systems of P. kamoharai.

Crocodile sharks reproduce sexually through internal fertilization. Females are ovoviviparous; they retain the eggs of their offspring until they hatch (Martin 2003). Females exhibit aplacental viviparity; the developing embryos lack a connection to the mother and thus feed on the yolk sac and the other ova produced by the mother (oophagy)(Compagno 1984). The mother typically produces four pups per litter; the pups are miniature adults, capable of swimming and feeding (Martin 2003). (Compagno, 1984; Martin, 2003)

  • Range number of offspring
    2 to 4
  • Average number of offspring
    4

Like all sharks, the crocodile shark provides no parental care after birth.

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

There are no data on the lifespan/longevity of crocodile sharks.

Behavior

It is speculated that crocodile sharks exhibit a diel pattern of vertical migration. They remain deep in the ocean by day and ascend to the surface at night. This pattern of vertical migration is believed to run parallel with the feeding patterns of their prey (Martin 2003). Crocodile sharks are probably nocturnal (Compagno 2001). (Compagno, 1984; Compagno, 2001; Martin, 2003)

Home Range

There is little available information on the home range of crocodile sharks.

Communication and Perception

The large eyes of crocodile sharks suggest that it is a visual hunter, specializing in bioluminescent and light-refracting prey (Martin 2003). Additionally, the crocodile shark is electroreceptive; it can sense changes in the surrounding electrical field (Martin 2003). Sharks, in general, also have a keen sense of chemical perception. (Martin, 2003)

Food Habits

Crocodile sharks are carnivores; they eat small bony fish, squids, and shrimp (Compagno 1984). They have protrusible and muscular jaws that suggest they are capable of eating a wide variety of prey (Martin 2003). Beyond this, very little is known about the specific feeding habits of crocodile sharks. (Compagno, 1984; Martin, 2003)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Predation

Very little is known about any anti-predator adaptations that the crocodile shark may exhibit. However, when removed from water, the crocodile shark snaps its powerful jaw vigorously, almost like a "crocodile." This may serve as a defense mechanism to fight off predators (Martin 2003). There are no known predators of crocodile sharks. (Martin, 2003)

Ecosystem Roles

Very little is known about the role crocodile sharks play in the ecosystem to which they belong. However, sharks in general are usually important predators in aquatic ecosystems (Martin 2003). (Martin, 2003)

Economic Importance for Humans: Positive

Crocodile sharks do not provide many benefits to humans; their large, squalene-rich liver is a source of potential value (Martin 2003). However, crocodile sharks generally are discarded due to their small size and useless flesh (Compagno 1984). (Compagno, 1984; Martin, 2003)

  • Positive Impacts
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Crocodile sharks have never been implicated in attacks on humans and are deemed harmless (Martin 2003). Thus, there are no known adverse effects of crocodile sharks on humans. (Martin, 2003)

Conservation Status

Due to small size and wide range in habitat, very little information has been accumulated on crocodile sharks. The current population size is unknown, however, crocodile sharks are vulnerable to catching by long-line fisheries (Martin 2003). There is no information to indicate trends in population size, but due to bycatch a population decline is probable (Compagno 2002). As a result, the IUCN Red List of Threatened Species has labeled crocodile sharks at low risk for extinction. (Compagno, 2002; Martin, 2003)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Nitin Sharma (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

electric

uses electric signals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

photic/bioluminescent

generates and uses light to communicate

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Compagno, L. 2001. FAO species catalogue Vol. 2. Sharks of the world. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes, and Orectolobiformes). Rome: FAO Species Catalogue for Fishery Purposes..

Compagno, L. 2002. Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Vol. 2. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes).. Rome: FAO Species Catalogue for Fishery Purposes..

Compagno, L. 1984. "Species Summary- Pseudocarcharias kamoharai" (On-line). Fishbase. Accessed October 19, 2005 at http://www.fishbase.org/Summary/SpeciesSummary.php?genusname=Pseudocarcharias&speciesname=kamoharai.

Martin, R. 2003. "Biology of the Crocodile Shark" (On-line). Biology of Sharks and Rays. Accessed October 19, 2005 at http://www.elasmo-research.org/education/shark_profiles/pseudocarcharias.htm.

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