Spotted ratfish

Taxobox
name = Spotted ratfish
status = LC | status_system = IUCN3.1


image_width = 240px
regnum = Animalia
phylum = Chordata
classis = Holocephali
ordo = Chimaeriformes
familia = Chimaeridae
species = "H. colliei"
binomial = "Hydrolagus colliei"
binomial_authority = Lay & Bennett, 1839

The spotted ratfish, "Hydrolagus colliei", is a chimaera found in the Atlantic, Pacific, and Indian oceans.Often seen by divers at night in the Pacific Northwest and British Columbia, this unique shark relative gets its characteristic name from a pointed rat-like tail. The ratfish lays leathery egg cases on the bottom of sandy/mud areaswhich are often mistaken by divers as something inanimate. The bane of fishermen, a shallow water sighting of this fish often turns an uneventful muddy dive into an interesting encounter.

This unusual fish has smooth skin and large green eyes with a rabbit-like face. Ranging in depth from 40 - 3000 feet, these fish survive on a diet of shrimp, worms, small crustaceans, clams and small fish, which they grind and eat with a plate-like mouth very similar to that of a skate. They also have a venomous spine located on the front of their dorsal fin. It is also considered to be the missing link between the cartilaginous and bony fish, since the ratfish contains both. Other relatives of this interesting fish include the Australian ghost shark, or elephant fish ("Callorhinchus milii").

Physical Description

The spotted ratfish has a very distinct appearance compared to other fish. The average female is about three feet (38 inches) long, much bigger in comparison to the smaller male. These fish have a smooth and scaless skin that is a silvery-bronze color, often with sparkling shades of gold, blue, and green. The speckled white spots along their back contributes to their name. Dark edges outline both the caudal and dorsal fins; whereas, the pectoral fins have a transparent outline. The ratfish’s pectoral fins are large and triangular, which extend straight out from the sides like airplane wings. They have a venomous spine located at the leading edge of their dorsal fin. The tail of the ratfish constitutes for almost half of their overall length and closely resembles a pointed rat-like tail. The body of this fish is supported by cartilage rather than bone, making it go limp when removed from the water. It has a duckbill shaped snout and a rabbit like face. Their mouth is small and contains forward directed, incisor-shaped teeth, that act as plate-like grinding teeth. One of their most mesmerizing features is their large emerald green eyes which are able to reflect light, similar to eyes of a cat.

Habitat

The spotted ratfish can be found in the Atlantic, Pacific, and Indian Oceans. They can most commonly be found between the Pacific Northwest and the British Columbia. The range of depths in which this fish is found extends from 0 – 3,000 feet below sea level. Near 115° N. longitude and further north, the spotted ratfish lives close to the shore. On the southern end of their range, they live in deeper waters. Ratfish tend to move closer to shallow water during the spring and autumn, then to deeper water in summer and winter. Spotted ratfish can most commonly be found living near the bottom of sand, mud or rocky reefs of the ocean floor.

Diet

The spotted ratfish swims slowly above the seafloor in search for food. Location of food is done by the sense of smell. Spotted ratfish are particularly drawn to crunchy foods like crabs and clams. Besides crabs and clams, the spotted ratfish also feeds on shrimp, worms, small fish, small crustaceans, and sea stars. As the spotted ratfish is out hunting for prey, they must also keep a lookout so that they don’t become prey for other sea creatures such as: the soupfin sharks, dogfish sharks, pigeon guillemots, and Pacific halibut. Their usual hunting period is at nighttime, when they move to shallow water to feed.

Reproduction

Like some sharks, spotted ratfish are oviparous. Their spawning season peaks during the spring to autumn months. During this time, the female releases up to two fertilized eggs into sand or mud areas of the seabed every 10 to 14 days. The extrusion process can last anywhere from 18 to 30 hours and the actual laying can last another four to six days. The egg sack is leather-like, five inches long, and has a filament connected to it which is used to attach itself to the ocean floor when it is let go by the mother. It is not unheard of to see a female ratfish swimming around her newly laid eggs, in hopes to prevent predators from finding them. Development of the egg can take up to a year, which can be harmful because the eggs are sometimes mistaken as inanimate objects by divers. When the young finally hatch, they are about 5.5 inches in length and continue to grow, reaching 11.8 inches in length their first year.

Miscellaneous Information

-The root meaning of the ratfishes scientific name, Hydrolagus colliei, comes from the Greek words hydro, meaning water, and lagus, meaning hare. -The species name gives honors to Alexander Collie, who was a ship surgeon and early naturalist.

-Related animals to the spotted ratfish are sharks, skates, rays, Australian ghost shark (elephant fish), short nose chimaeras and many others.

-A behavior of the ratfish when around divers is that they prefer to maintain a safe distance and are usually not aggressive. However, if they feel their territory has been invaded, the ratfish is able to inflict a mildly toxic wound.

-The ratfish is not typically eaten by humans being as it is not commercially caught for human consumption.

-As they swim gracefully about the ocean, the ratfish can be seen doing barrel rolls and corkscrew turns, as if they were flying.

Sources

* http://en.wikipedia.org/wiki/Spotted_ratfish
* http://www.elasmodiver.com/spotted_ratfish.htm
* http://www.nmfs.noaa.gov/speciesid/fish_page/fish70a.html
* http://www.oregonlive.com/sharks/index.ssf?/sharks/spottedratfish.frame
* http://www.elasmo-research.org/education/shark_profiles/chimaera.htm
* http://www.mbayaq.org/efc/living_species/default.asp?hOri=1&inhab=196
* http://animals.jrank.org/pages/1952/Chimaeras-Sharks-Skates-Rays-Chondrichthyes-SPOTTED-RATFISH-Hydrolagus-colliei-SPECIES-ACCOUNTS.html
* http://www.flmnh.ufl.edu/fish/Gallery/Descript/SpottedRatfish/SpottedRatfish.html

Gallery

External links

* [http://zipcodezoo.com/Animals/H/Hydrolagus_colliei.asp Spotted Ratfish entry at Zipcode Zoo]
* [http://www.fishbase.org/Summary/SpeciesSummary.php?id=2589 Spotted Ratfish entry at FishBase]