The spotted ratfish (''Hydrolagus colliei'') is a
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 ...
found in the north-eastern
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
. Often seen by divers at night in the
Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
, this
cartilaginous fish
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 ...
gets its characteristic name from a pointed
rat
Rats are various medium-sized, long-tailed rodents. Species of rats are found throughout the order Rodentia, but stereotypical rats are found in the genus ''Rattus''. Other rat genera include ''Neotoma'' ( pack rats), ''Bandicota'' (bandicoot ...
-like tail. The ratfish lays leathery
egg cases on the bottom of muddy or sandy areas, which are often mistaken by divers as something inanimate. While mainly a deep-water species, it occurs at shallower depths in the northern part of its range. The generic name, ''
Hydrolagus
''Hydrolagus'' is a genus of fish in the family Chimaeridae found in the Atlantic, Indian and Pacific Oceans.Weigmann, S. (2016)Annotated checklist of the living sharks, batoids and chimaeras (Chondrichthyes) of the world, with a focus on biogeog ...
'', comes from the Greek words ὕδωρ, meaning water,
[Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie.'' Oxford: Clarendon Press.] and λαγώς/λαγῶς, meaning
hare
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores, and live solitarily or in pairs. They nest in slight depressions called forms, and their young are able to fend for themselves shortly after birth. The ge ...
,
and the specific name honors
Alexander Collie
Dr Alexander Collie (2 June 1793 – 8 November 1835) was a Scottish surgeon and botanist who journeyed to Western Australia in 1829, where he was an explorer and Colonial Surgeon.
Early life
Collie was born in Insch in Aberdeenshire, Scotland ...
, who was a ship surgeon and early naturalist. The spotted ratfish is common in much of its range, not typically eaten by humans, and is not commercially caught.
Description
![Hydrolagus colliei 03](https://upload.wikimedia.org/wikipedia/commons/7/79/Hydrolagus_colliei_03.jpg)
The spotted ratfish has a very distinct appearance compared to unrelated fish species. The female is up to long, much bigger than the male. These
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
have a smooth and scaleless skin that is a silvery-bronze color, often with sparkling shades of gold, blue, and green. The speckled white spots along their backs contribute to their name. Dark edges outline both the caudal and dorsal fins, whereas the pectoral fins have a transparent outline. Their pectoral fins are large and triangular, and extend straight out from the sides of their bodies like airplane wings. They have a
venomous
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
spine located at the leading edge of their dorsal fin, which is used in defense. It does not present a serious danger to humans, but can cause painful wounds and has been known to kill
harbor seal
The harbor (or harbour) seal (''Phoca vitulina''), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared sea ...
s that ate spotted ratfish (caused by the spine penetrating vital tissue in the stomach or
esophagus
The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...
after the ratfish was swallowed). The tail of the ratfish constitutes almost half of its overall length and closely resembles a pointed, rat-like tail. The body of this fish is supported by
cartilage
Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...
rather than bone. It has a duckbill-shaped snout and a rabbit-like face. The mouth is small and contains one pair of forward-directed, incisor-shaped teeth in the bottom jaw and two pairs in the top jaw. Unlike
shark
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...
s, which have sharp teeth that are easily replaceable, spotted ratfish teeth are plate-shaped, mineralized, and permanent, which assist them in grinding their prey. Like many bony fishes, but unlike its sister group, the
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 ...
, the upper jaw of the
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 ...
is fused with the skull. Although their jaws are soft and mouths are relatively small, they have the largest
biting force and jaw leverage found within the
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 ...
, which supports their ability to consume large prey. One of their most mesmerizing features is their large, emerald green eyes, which are able to reflect light, similar to the eyes of a cat.
Distribution and habitat
The spotted ratfish can be found in the northeastern Pacific Ocean, ranging from
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...
to
Baja California
Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
, with an isolated population in the
Gulf of California
The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...
.
[ They are abundant in much of their range.][ They be found most commonly off the ]Pacific Northwest
The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...
. The range of depths in which this fish is found extends from below sea level, but it is most common between .[ Spotted ratfish typically live closer to the shore in the northern part of their range than in the southern, but it is also found as shallow as off California.] Spotted ratfish tend to move closer to shallow water during the spring and autumn, then to deeper water in summer and winter. For most of the year, they prefer temperatures between , but seasonally they do move into slightly warmer water. They can most commonly be found living near the sea floor in sandy, muddy, or rocky reef environments. Unlike most of its relatives, which are entirely restricted to deep waters, the spotted ratfish has been held in public aquaria
A public aquarium (plural: ''public aquaria'' or ''public Water Zoo'') is the aquatic counterpart of a zoo, which houses living aquatic animal and plant specimens for public viewing. Most public aquariums feature tanks larger than those kept b ...
.[ It has also been bred in such aquaria, where two of the main issues are the requirements of low light and low temperature (generally kept at ).][
]
Diet
The spotted ratfish swims slowly above the seafloor in search of food. Location of food is done by smell. Their usual hunting period is at night, when they move to shallow water to feed. They are particularly drawn to crunchy foods such as crabs
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
and clams
Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two shel ...
. Besides these, the spotted ratfish also feeds on shrimp, worms, small fish, small crustaceans, and sea stars. Species known to prey on the spotted ratfish include soupfin shark
The school shark (''Galeorhinus galeus'') is a houndshark of the Family (biology), family Triakidae, and the only member of the genus ''Galeorhinus''. Common names also include tope, tope shark, snapper shark, and soupfin shark. It is found world ...
s, dogfish shark
Squalidae, more commonly known as dogfish, dog sharks, or spiny dogfish, are one of several families of sharks categorized under Squaliformes, making it the second largest order of sharks, numbering 119 species across 7 families. Having earned t ...
s, Pacific halibut
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...
, pinniped
Pinnipeds (pronounced ), commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae (whose only living member is the walru ...
s, and pigeon guillemot
The pigeon guillemot (''Cepphus columba'') () is a species of bird in the auk family, Alcidae. One of three species in the genus ''Cepphus'', it is most closely related to the spectacled guillemot. There are five subspecies of the pigeon guille ...
s.
Reproduction
Like some sharks, spotted ratfish are oviparous
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...
. Their spawning
Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of releasing the eggs and sperm, and the act of both sexes is called spawning. Most aquatic animals, except for aquati ...
season peaks during the spring to autumn. During this time, the female releases up to two fertilized eggs into sand or mud areas of the seabed every 10–14 days. The extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
process can last 18–30 hours and the actual laying can last another 4–6 days. The egg sack
Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species dive ...
is leather-like, long, and has a filament connected to it which is used to attach it to the ocean floor when it is let go by the mother. A female may be seen swimming around her newly laid eggs, in hopes of preventing predators from finding them. Development of the egg can take up to a year, which can be dangerous because the eggs are sometimes mistaken for inanimate objects by divers. When the young finally hatch, they are about in length and grow, reaching in length their first year.
Male spotted ratfish have multiple secondary sexual characteristics, which include paired pelvic clasper
In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating.
Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...
s, a single frontal tentaculum, and paired pelvic tentacula. The pelvic claspers are located on the ventral
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Th ...
side of the fish. They protrude out from the pelvic fins and are responsible for the movement of sperm to the oviduct
The oviduct in mammals, is the passageway from an ovary. In human females this is more usually known as the Fallopian tube or uterine tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, o ...
of the female. The interior of the pelvic clasper is supported by cartilage and separates into two branches, ultimately ending in a fleshy lobe on the posterior end.
The cephalic clasper
In biology, a clasper is a male anatomical structure found in some groups of animals, used in mating.
Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve to channel semen into the female's c ...
(tentaculum) is a unique, club-like organ not found in any other vertebrates. The cephalic clasper is located on the head of the fish, just anterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
to the eyes. The tip of the retractable organ is fleshy and lined with numerous small, sharp barbs. For the male to stay attached during courtship, the clasper has been observed to clamp down on the pectoral fin
Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...
of the female.[limley, A. P., & Oerding, S. (2013). ''Biology of Sharks and Rays''. Chicago: University of Chicago Press.][Carrier, J. C., Heithaus, M. R., & Musick, J. A. (2012). ''Biology of sharks and their relatives''. Boca Raton: CRC Press.] Additional evidence for this use has been found in the form of scars and scratches on the dorsal sides of females. The significantly smaller body size of males, which is a sexually dimorphic
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
characteristic, may be a contributing factor to this mating behavior.
Behaviour
The ratfish prefers to maintain a safe distance from divers, and are usually not aggressive. However, if they feel their territory has been invaded, they are able to inflict a mildly toxic wound with their dorsal fin spines. As they swim, they perform barrel roll
A barrel roll is an aerial maneuver in which an airplane makes a complete rotation on both its longitudinal and lateral axes, causing it to follow a helical path, approximately maintaining its original direction. It is sometimes described as a ...
s and corkscrew turns, as if they are flying. Ratfish swim using large pectoral fins, and this has often been termed aquatic flight given the resemblance to a bird.
Albino Puget Sound ratfish
A rare albino
Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino.
Varied use and interpretation of the term ...
Puget Sound
Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected ma ...
ratfish was discovered near Whidbey Island
Whidbey Island (historical spellings Whidby, Whitbey, or Whitby) is the largest of the islands composing Island County, Washington, in the United States, and the largest island in Washington State. (The other large island is Camano Island, ...
, Washington
Washington commonly refers to:
* Washington (state), United States
* Washington, D.C., the capital of the United States
** A metonym for the federal government of the United States
** Washington metropolitan area, the metropolitan area centered on ...
. It is the only pure albino among the 7.2 million specimens in the University of Washington
The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington.
Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...
's fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...
collection.
References
External links
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{{Taxonbar, from=Q1262285
spotted ratfish
The spotted ratfish (''Hydrolagus colliei'') is a chimaera found in the north-eastern Pacific Ocean. Often seen by divers at night in the Pacific Northwest, this cartilaginous fish gets its characteristic name from a pointed rat-like tail. Th ...
Western North American coastal fauna
spotted ratfish
The spotted ratfish (''Hydrolagus colliei'') is a chimaera found in the north-eastern Pacific Ocean. Often seen by divers at night in the Pacific Northwest, this cartilaginous fish gets its characteristic name from a pointed rat-like tail. Th ...