The spotted ratfish (''Hydrolagus colliei'') is a
chimaera
Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to B ...
found in the north-eastern
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...
. Often seen by divers at night in the
Pacific Northwest
The Pacific Northwest (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 no official boundary exists, the most common ...
, this
cartilaginous fish
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeleto ...
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'' (bandicoo ...
-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 (biology), family Chimaeridae found in the Atlantic Ocean, Atlantic, Indian Ocean, Indian and Pacific Oceans.Weigmann, S. (2016)Annotated checklist of the living sharks, batoids and chimaeras (Chond ...
'', 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 Solitary animal, solitarily or in pairs. They nest in slight depressions called forms, and their young are precociality, able to fend for themselves ...
,
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 on ...
, 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

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
A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
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), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...
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. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...
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 cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...
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 modern sharks ( division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by h ...
, the upper jaw of the
chimaera
Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to B ...
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 (Sometimes spelled Holocephala; Romanization of Greek, Greek for "complete head" in reference to the fusion of Palatoquadrate, upper jaw with the rest of the skull) is a Subclass (biology), subclass of Chondrichthyes, cartilaginous fi ...
, 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 ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
to
Baja California
Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
, with an isolated population in the
Gulf of California
The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...
.
[ They are abundant in much of their range.][ They be found most commonly off the ]Pacific Northwest
The Pacific Northwest (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 no official boundary exists, the most common ...
. 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.[ 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 (meaning "short tailed" in Greek), which typically have a very short projecting tail-like abdomen, usually hidden entirely under the thorax. Their exoskeleton is often thickened and ha ...
and clams
Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...
. 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 sharks, 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 ...
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 the definition, to Antarctica in the south, and is bounded by the continen ...
, pinniped
Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant taxon, extant families Odobenidae (whose onl ...
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 reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...
. Their spawning
Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...
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 section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...
process can last 18–30 hours and the actual laying can last another 4–6 days. The egg sack 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 ...
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 describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...
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 vertebrates is the passageway from an ovary. In human females, this is more usually known as the fallopian tube. The eggs travel along the oviduct. These eggs will either be fertilized by spermatozoa to become a zygote, or will dege ...
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 ...
(tentaculum) is a unique, club-like organ not found in any other vertebrate. The cephalic clasper is located on the head of the fish, just anterior
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...
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 sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
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 helix, helical path, approximately maintaining its original direction. It is sometimes describe ...
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 reddish pink or blue eyes. Individuals with the condition are referred to as albinos.
Varied use and interpretation of ...
Puget Sound
Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...
ratfish was discovered near Whidbey Island
Whidbey Island (historical spellings Whidby, Whitbey, or Whitby) is the largest of the islands composing Island County, Washington, Island County, Washington (state), Washington, in the United States, and the largest island in Washington stat ...
, Washington
Washington most commonly refers to:
* George Washington (1732–1799), the first president of the United States
* Washington (state), a state in the Pacific Northwest of the United States
* Washington, D.C., the capital of the United States
** A ...
. It is the only pure albino among the 7.2 million specimens in the University of Washington
The University of Washington (UW and informally U-Dub or U Dub) is a public research university in Seattle, Washington, United States. Founded in 1861, the University of Washington is one of the oldest universities on the West Coast of the Uni ...
's fish
A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
collection.
References
External links
*
*
*
*
Hydrolagus Colleie
- #ScanAllFish Database - CT scans,12/16/2016, K. Newton M. Kolmann A. Summers
{{Taxonbar, from=Q1262285
spotted ratfish
Western North American coastal fauna
spotted ratfish