Callorhincus milii, also known as elephant fishes, elephant sharks, ghost sharks, or whitefish, have a fairly selective range. Found in the South Pacific, they prefer the continental shelves of temperate waters. They are primarily found along the southern coast of Australia, and in the waters surrounding Tasmania and New Zealand. There are a few reports of them in the rivers of South Africa and Tasmania, and along the southwestern coast of South America. (Allen, 1999; Last and Stevens, 2009)
Although mostly found in shallow waters 30 to 200 m in depth, elephant fishes have also been found at depths of greater than 600 m. C. milii primarily live on coastal continental shelves, but females seasonally move to shallower waters to lay eggs. (Allen, 1999; Ferrari and Ferrari, 2002; Reardon, et al., 2003)
chimaera, a cartilaginous fish related to sharks and rays. Other characteristics include an elongate body, presence of an anal fin, an arched caudal fin, and two widely spaced dorsal fins. The first fin has a serrated spine at its front, and the second is relatively tall with a short base compared to other chimaera species. Mature males exhibit a unique head clasper, an erupted tenaculum on a pre-pelvic clasper, and large calcified pelvic claspers.are silver in color, and often have irregular dark blotches on the sides and fins. They have a distinctive flexible, trunk-like projection at the tip of the snout. This “trunk” has earned them the name elephant fishes or elephant sharks despite the fact that they neither true fish nor shark. is a type of
A feature unique to elephant fishes (Callorhincidae) that should be noted is that unlike all other chimaera species, they have a very well developed rectal gland. The rectal gland is crucial in regulating osmotic conditions in the body of the fish. It is thought that since elephant fishes migrate for mating and may encounter water with varying salinity, they developed a rectal gland superior to that of other chimaeras. While all other chimera species are found in deep water habitats, this adaptation may allow elephant fishes to successfully inhabit more shallow coastal waters. (Ferrari and Ferrari, 2002; Francis, 1997; Last and Stevens, 2009)
Embryonic development is divided into 36 stages followed by hatching. These stages are determined by assessment of morphological characteristics including but not limited to length, amount of pigmentation, eye development, and head flexure. Rostral bulb size is used primarily when classifying embryos from stages 17-29 while tail length, gill filament size, and snout development are used to identify more mature embryo specimens. While early characteristics are more notable from one stage to the next, later stage assignment is often made more complex by less distinction between the characteristics of each stage. Hatchlings are fully developed and look just like miniature adults upon emergence from the egg case.
From the time they hatch at about 10 cm until they reach a length of approximately 50 cm, elephant fishes grow in a linear fashion. At this length males are mature. However, the female growth then accelerates to about twice the rate of males until they reach sexual maturity at about 70 cm in length. Maturity is reached in males at about 3 years of age and in females at 4 to 5 years of age. (Didier, et al., 1998; Francis, 1997; Sullivan, 1977)
Males have a pair of retractable head claspers, pre-pelvic claspers, and calcified claspers to help hold the female during copulation. The head and pre-pelvic claspers are unique to Chondrichthyes>. Females have a “sperm pouch” to store spermatic material. Actual mating behavior remains undocumented. (Hamlett, et al., 2002; Last and Stevens, 2009)and are not found in other species of
Maximum recorded age in the wild is fifteen years from a tag return, but dorsal fin spine growth increments indicate maximum size to occur at about nine years. No age data has been recorded for (Reardon, et al., 2003)in captivity.
Behavior has not been extensively observed in elephant fishes since they live in a less accessible habitat, but seasonal migration for mating has been well documented in the shallow coastal areas that are more populated by people. Elephant fishes are not known to be a social species. However, fishermen report separate catches of males and females in the same areas suggesting the sexes segregate in the wild when not reproducing. (Hyodo, et al., 2007; Reardon, et al., 2003)
Evidence of territorial behavior or the size of the home range has not been documented in.
Elephant fishes have large eyes, and also use their unique “trunk” for perception. It is covered with sensory pores that can detect movements and small electrical impulses. This allows the animal to find prey hidden in the substrate. Social communication between individuals has yet to be investigated. (Last and Stevens, 2009)
Callorhincus milli is a carnivorous species. Elephant fishes probe the substrate with the plow-shaped protrusion on their snout to find food. They primarily feed on mollusks and shellfish including the clam species Maorimactra ordinaria. (Anonymous, 2014)
Elephant fishes are secondary consumers that help may affect the populations of primary consumers through predation. Although they are predators, they provide a food source for tertiary consumers as well. Elephant fishes thus play an intermediate role in the food web linking small organisms like filter feeders to large apex predators.
Elephant fishes are caught both commercially and recreationally and are often marketed as "whitefish." They are often used as the fish in “fish and chips” meals in Australia and New Zealand. Recently humans are also using (Mullo, 2013; Reardon, et al., 2003; Vankatesh, et al., 2014)in genetic research as model organisms to learn more about the evolution of cartilaginous fishes and the early ancestors of all vertebrates.
Elephant fishes very little threat to humans. The dorsal spine may cause injury to fisherman, but otherwise there are no known adverse effects of (Bester, 2010)on humans.
is relatively abundant throughout the waters of southern Australia and New Zealand and was listed as a species of Least Concern by the IUCN Red List of Threatened Species in 2003, the last date of review. Commercial fishing reports showed that catch rates remained stable for roughly 20 years prior to that reivew. A total allowable catch (TAC) has been imposed on in both Australia and New Zealand to limit catch numbers. Subsequent work found that some stocks in Australia were being overfished, in part due to previously undocumented recreational fishing taking breeding females near shore (Bracchini et al., 2008).
Some elephant fishes may also take refuge in marine protected areas that are closed to fishing. ("Evaluation of effects of targeting breeding elephant fish by recreational fishers in Western Port.", 2008; Reardon, et al., 2003)
Kayla Boyes (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne.
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.
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.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
fertilization takes place within the female's body
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
mainly lives in oceans, seas, or other bodies of salt water.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
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