The Australian ghostshark (''Callorhinchus milii'') is a cartilaginous fish (
Chondrichthyes
Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue. ...
) belonging to the subclass
Holocephali
Holocephali ("complete heads"), sometimes given the term Euchondrocephali, is a subclass of cartilaginous fish in the class Chondrichthyes. The earliest fossils are of teeth and come from the Devonian period. Little is known about these primiti ...
(
chimaera
Chimaeras are cartilaginous fish in the order Chimaeriformes , known informally as ghost sharks, rat fish, spookfish, or rabbit fish; the last three names are not to be confused with rattails, Opisthoproctidae, or Siganidae, respectively.
At ...
). Sharks, rays and skates are the other members of the cartilaginous fish group and are grouped under the subclass
Elasmobranchii
Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of gil ...
. Alternative names include elephant shark, ''makorepe'' (in
Māori
Māori or Maori can refer to:
Relating to the Māori people
* Māori people of New Zealand, or members of that group
* Māori language, the language of the Māori people of New Zealand
* Māori culture
* Cook Islanders, the Māori people of the C ...
), whitefish, plough-nose chimaera, or elephant fish. It is found off southern
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, including
Tasmania
)
, nickname =
, image_map = Tasmania in Australia.svg
, map_caption = Location of Tasmania in AustraliaCoordinates:
, subdivision_type = Country
, subdi ...
, and south of
East Cape
East Cape is the easternmost point of the main islands of New Zealand. It is located at the northern end of the Gisborne District of New Zealand's North Island. It can also refer to the broader Gisborne cape.
East Cape was originally named "C ...
and
Kaipara Harbour
Kaipara Harbour is a large enclosed harbour estuary complex on the north western side of the North Island of New Zealand. The northern part of the harbour is administered by the Kaipara District and the southern part is administered by the Auckl ...
in
New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, at depths of .
Morphology and biology
The fish is silvery in colour with iridescent reflections and dark, variable markings on the sides.
Males mature at and females at , and the maximum length head to tail is .
It has an elongated body, smooth and torpedo shaped with two widely separated, triangular dorsal fins.
They use their hoe-shaped snouts to probe the ocean bottom for invertebrates and small fishes.
From spring to autumn, adults migrate inshore to estuaries and bays and females lay their eggs on sandy or muddy substrates. The eggs are contained in large yellowish capsules. The egg partially opens enabling seawater to flow in to the egg capsules after a few months and juveniles emerge from the capsule after six to eight months as about in length.
Maximum age is estimated to be 15 years.
This fish has three
cone
A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex.
A cone is formed by a set of line segments, half-lines, or lines con ...
pigments for
colour vision
Color vision, a feature of visual perception, is an ability to perceive differences between light composed of different wavelengths (i.e., different spectral power distributions) independently of light intensity. Color perception is a part of ...
(like humans); its
dorsal fin
A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...
has a very sharp spine. The spine has been reputed to be venomous, but no serious injuries have yet been reported.
Distribution
At present this species is regarded as being known from southern Australian and New Zealand waters.
However it has been hypothesised with some supporting evidence that the New Zealand population may differ from the population found in Australian waters.
Fishing
In South Australia, they are caught by some recreational fishers in inshore waters during autumn and winter, typically from surf beaches or sheltered beaches.
In New Zealand, Australian ghostsharks are exploited commercially, particularly during spring and summer when they migrate into shallow coastal waters.
In Australia, they are caught by southern shark
gillnet
Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...
fishery, particularly in
Bass Strait
Bass Strait () is a strait separating the island state of Tasmania from the Australian mainland (more specifically the coast of Victoria, with the exception of the land border across Boundary Islet). The strait provides the most direct waterwa ...
and south-east Tasmania, though this fishery targets the
gummy shark
The gummy shark (''Mustelus antarcticus''), also known as the Australian smooth hound, flake, sweet william or smooth dog-shark, is a shark in the family Triakidae. These small to medium-sized bottom-dwelling sharks are found mostly in, but are ...
, ''Mustelus antarcticus,'' and will sometimes discard ghostsharks due to the considerably lower price they fetch at market. They are also a popular target of
recreational fishers in
Westernport Bay
Western Port, (Boonwurrung: ''Warn Marin'') commonly but unofficially known as Western Port Bay, is a large tidal bay in southern Victoria, Australia, opening into Bass Strait. It is the second largest bay in the state. Geographically, it is ...
, Victoria and in the inshore waters of south-east Tasmania. Their white flesh
fillet
Fillet may refer to:
*Annulet (architecture), part of a column capital, also called a fillet
*Fillet (aircraft), a fairing smoothing the airflow at a joint between two components
*Fillet (clothing), a headband
*Fillet (cut), a piece of meat
*Fille ...
s are very popular with
fish-and-chips
Fish and chips is a popular hot dish consisting of fried fish in crispy batter, served with chips. The dish originated in England, where these two components had been introduced from separate immigrant cultures; it is not known who created t ...
restaurants in New Zealand and is sold as 'flake' or 'whitefish' in Australia.
Genome study
In January 2014, ''
Nature
Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'' reported research into the Australian ghostshark
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
that showed they lack a single gene family that regulates the process of turning cartilage into bone, and indicates a
gene duplication
Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. ...
event gave rise to the transformation in bony
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s.
The Australian ghostshark was proposed as a model cartilaginous fish genome because of its relatively small genome size. Its genome is estimated to be 910
megabase
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
s long, which is the smallest among all the cartilaginous fishes and one-third the size of the
human genome
The human genome is a complete set of nucleic acid sequences for humans, encoded as DNA within the 23 chromosome pairs in cell nuclei and in a small DNA molecule found within individual mitochondria. These are usually treated separately as the n ...
(3000 Mb). Because cartilaginous fishes are the oldest living group of jawed
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s, the Australian ghostshark genome will serve as a useful reference genome for understanding the origin and
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
of vertebrate genomes including humans, which shared a common ancestor with the Australian ghostshark about 450 million years ago. Studies so far have shown the sequence and the gene order (
synteny
In genetics, the term synteny refers to two related concepts:
* In classical genetics, ''synteny'' describes the physical co-localization of genetic loci on the same chromosome within an individual or species.
* In current biology, ''synteny'' mo ...
) are more similar between human and elephant shark genomes than between human and
teleost
Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tel ...
fish genomes (
pufferfish
Tetraodontidae is a family of primarily marine and estuarine fish of the order Tetraodontiformes. The family includes many familiar species variously called pufferfish, puffers, balloonfish, blowfish, blowies, bubblefish, globefish, swellfis ...
and
zebrafish
The zebrafish (''Danio rerio'') is a freshwater fish belonging to the minnow family ( Cyprinidae) of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish, frequently sold under the trade name zebra danio (and thus often ...
), though humans are more closely related to teleost fishes than to the Australian ghostshark. The Elephant Shark Genome Project was launched with the aim to sequence the whole genome of the elephant shark.
Conservation status
The New Zealand
Department of Conservation
An environmental ministry is a national or subnational government agency politically responsible for the environment and/or natural resources. Various other names are commonly used to identify such agencies, such as Ministry of the Environment ...
has classified the Australian ghost shark as "Not Threatened" with the qualifier "Conservation Dependent, Increasing" under the
New Zealand Threat Classification System
The New Zealand Threat Classification System is used by the Department of Conservation to assess conservation priorities of species in New Zealand.
The system was developed because the IUCN Red List, a similar conservation status system, had some ...
.
References
*
* Tony Ayling & Geoffrey Cox, ''Collins Guide to the Sea Fishes of New Zealand'', (William Collins Publishers Ltd., Auckland, New Zealand 1982)
* Nelson, J. S. ''Fishes of the world'' (Wiley, New York 2006)
* P. R. Last and J. D. Stevens ''Sharks and Rays of Australia'' (Intl Specialized Book Service Inc. June 1991)
* Venkatesh B, Kirkness EF, Loh YH, Halpern AL, Lee AP, et al. (2007) Survey Sequencing and Comparative Analysis of the (Callorhinchus milii) Genome. PLoS Biol 5(4): e101
Sequencing projectat the
Institute of Molecular and Cell Biology (Singapore)
The Agency for Science, Technology and Research (A*STAR) is a Statutory boards of the Singapore Government, statutory board under the Ministry of Trade and Industry (Singapore), Ministry of Trade and Industry of Singapore.
The agency support ...
Bibliography
* Katsu, Y., Kohno, S., Oka, K., Lin, X., Otake, S., Pillai, N. E., ... & Baker, M. E. (2019).
Transcriptional activation of elephant shark mineralocorticoid receptor by corticosteroids, progesterone, and spironolactone'. Science Signaling, 12(584), eaar2668.
* Katsu, Y., Kohno, S., Oka, K., Lin, X., Otake, S., Pillai, N. E., ... & Baker, M. E. (2018)
Transcriptional Activation of Elephant Shark Mineralocorticoid Receptor by Corticosteroids, Progestins and Spironolactone BioRxiv, 265348.
External links
Species Description of Callorhinchus milii at www.shark-references.com*
Fishes of Australia : ''Callorhinchus milii''
{{DEFAULTSORT:Australian ghostshark
Australian ghostshark
Marine fish of Southern Australia
Marine fish of New Zealand
Australian ghostshark