Geographic Range
Pseudocarcharias kamoharai
(Crocodile sharks) can be found in nearly all subtropical and tropical oceans of
the world (Compagno 1984).
- Biogeographic Regions
- palearctic
- ethiopian
- neotropical
- australian
- oceanic islands
- indian ocean
- atlantic ocean
- pacific ocean
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).
- Habitat Regions
- tropical
- saltwater or marine
- Aquatic Biomes
- pelagic
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).
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
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).
- Development - Life Cycle
- indeterminate growth
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).
- Key Reproductive Features
- iteroparous
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- ovoviviparous
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
-
provisioning
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).
- Key Behaviors
- natatorial
- nocturnal
- motile
- solitary
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.
- Other Communication Modes
- photic/bioluminescent
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.
- Primary Diet
- carnivore
- 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.
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).
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).
- 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.
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.
Additional Links
Contributors
Tanya Dewey (editor), Animal Diversity Web.
Nitin Sharma (author), University of Michigan-Ann Arbor, Kevin Wehrly (editor, instructor), University of Michigan-Ann Arbor.
- Palearctic
-
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Australian
-
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- pelagic
-
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
- 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.
- 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.
- indeterminate growth
-
Animals with indeterminate growth continue to grow throughout their lives.
- 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).
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- 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.
- natatorial
-
specialized for swimming
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- solitary
-
lives alone
- visual
-
uses sight to communicate
- electric
-
uses electric signals to communicate
- photic/bioluminescent
-
generates and uses light to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- electric
-
uses electric signals to communicate
- carnivore
-
an animal that mainly eats meat
- piscivore
-
an animal that mainly eats fish
- molluscivore
-
eats mollusks, members of Phylum Mollusca
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 .