Chionoecetes opilio
Encyclopedia
Chionoecetes opilio is a predominantly epifaunal crustacean
found at shelf depths
in the northwest Atlantic Ocean
and north Pacific Ocean
. It is a well-known commercial species of Chionoecetes
, often caught with traps or by trawling
. Male C. opilio with a total length above 95 millimetres (3.7 in) long are the most commonly trapped, especially around Canada and Newfoundland. This crab genus is found all across both the Atlantic and Pacific oceans. There are seven species in the genus Chionoecetes, all of which bear the name "snow crab." Chionoecetes opilio is also related to Chionoecetes tanneri, commonly known as the tanner crab, and other crab species found in the cold, northern oceans.
s, or protective shell-coverings, over their bodies. Their tubercle
s, or the bodily projections on their shell, are moderately enclosed in calcium deposits, and they boast hooked seta
e, which are rigid, yet springy, hair-like organs on their claws. Snow crabs have a horizontal rostrum
at the front of the carapace; the rostrum is basically just an extension of the hard, shell covering of the carapace and it boasts two flat horns separated by a gap. They have triangular spines and well-defined gastric and branchial regions internally. Snow crabs also have little granules along the border of their bodies, except their intestinal region. Concerning their walking legs, their first three are compressed; their chelipeds, or pincers, are usually smaller, shorter, or equal to their walking legs. Snow crab are iridescent and range in color from brown to light red on top and from yellow to white on the bottom, and are bright white on the sides of their feet.
. This crab species is also found across the North Pacific area, in areas ranging from Alaska to northern Siberia, and through the Bering Strait to the Aleutian Islands, Japan, and Korea.
Snow crab are often found in the ocean's benthic shelf and upper slope, in the sandy and muddy bottoms, and in depths as shallow as 20 m (65.6 ft) and as deep as 1200 m (3,937 ft). The most snow crab can be found at 70 metre in the Atlantic waters. There are interesting differences in where male and female snow crab are found in the ocean depths: Small adult and senescent adult males occur mainly at intermediate depths over much of the year, while large and hardy adult males are found mostly at depths greater than 80 m (262.5 ft). Adult females are gregarious and congregate at depths of 60 metre.
s, bivalves, brittle star
s, polychaete
s, and even phytobenthos and foraminiferans. Snow crabs are also scavenger eaters, and aside from preying on other benthic shelf invertebrates, they also prey on annelid worms and mollusks. Males typically prove to be better predators than mature females, and prey type depends upon predator size, with the smallest crabs feeding mainly on amphipods and ophiuroids, while the largest crabs feed mainly on annelids, crustacean decapods and fish. Cannibalism
is also practiced at times among snow crabs, most frequently by intermediate sized females.
Off the coast of Newfoundland, two amphipod species – Ischyrocerus commensalis and Gammaropsis inaequistylis – have been found to live on the carapace
of the snow crab.
Adult snow crabs usually live between five and six years; before their deaths, they usually molt, mate a final time, and then die. New snow crab offspring hatch along with the late spring phytoplankton boom, so that they have an ample food source to take advantage of upon hatching. When they hatch, the snow crabs are in the zoeal stage, meaning that they are developing larva that can swim on their own. Then, they morph into the megalops stage and settle to the ocean floor among the phytodetritus; the megalops stage is the advanced larval stage that the crab develops into before becoming a true adult.
in 1780, under the name Cancer phalangium, a name which was invalid due to Johan Christian Fabricius
having used it previously for the species now known as Inachus phalangium
. The first valid scientific name was provided by Otto Fabricius in 1788, when he redescribed the species as Cancer opilio. The type locality is Greenland
.
As the genus Cancer
was divided up, the species C. opilio was transferred to a new genus, Chionoecetes
by Henrik Nikolai Krøyer in 1838. Chionoecetes opilio was the only species in the genus at first, and is therefore the type species
.
Mary J. Rathbun described a subspecies, C. opilio elongatus in 1924. This is now generally recognised as a full species, Chionoecetes elongatus.
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
found at shelf depths
Continental shelf
The continental shelf is the extended perimeter of each continent and associated coastal plain. Much of the shelf was exposed during glacial periods, but is now submerged under relatively shallow seas and gulfs, and was similarly submerged during other interglacial periods. The continental margin,...
in the northwest Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
and north Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. It is a well-known commercial species of Chionoecetes
Chionoecetes
Chionoecetes is a genus of crabs that live in the northern Pacific and Atlantic Oceans.Other names for crabs in this genus include "queen crab" and "spider crab" – they are known by different names in different areas of the world....
, often caught with traps or by trawling
Trawling
Trawling is a method of fishing that involves pulling a fishing net through the water behind one or more boats. The net that is used for trawling is called a trawl....
. Male C. opilio with a total length above 95 millimetres (3.7 in) long are the most commonly trapped, especially around Canada and Newfoundland. This crab genus is found all across both the Atlantic and Pacific oceans. There are seven species in the genus Chionoecetes, all of which bear the name "snow crab." Chionoecetes opilio is also related to Chionoecetes tanneri, commonly known as the tanner crab, and other crab species found in the cold, northern oceans.
Anatomy
Snow crabs have equally long and wide carapaceCarapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
s, or protective shell-coverings, over their bodies. Their tubercle
Tubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
s, or the bodily projections on their shell, are moderately enclosed in calcium deposits, and they boast hooked seta
Seta
Seta is a biological term derived from the Latin word for "bristle". It refers to a number of different bristle- or hair-like structures on living organisms.-Animal setae:In zoology, most "setae" occur in invertebrates....
e, which are rigid, yet springy, hair-like organs on their claws. Snow crabs have a horizontal rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
at the front of the carapace; the rostrum is basically just an extension of the hard, shell covering of the carapace and it boasts two flat horns separated by a gap. They have triangular spines and well-defined gastric and branchial regions internally. Snow crabs also have little granules along the border of their bodies, except their intestinal region. Concerning their walking legs, their first three are compressed; their chelipeds, or pincers, are usually smaller, shorter, or equal to their walking legs. Snow crab are iridescent and range in color from brown to light red on top and from yellow to white on the bottom, and are bright white on the sides of their feet.
Distribution and habitat
Snow crab are very abundant in the Atlantic Ocean region. More specifically, they are found in the Western Atlantic area near countries such as Greenland, Newfoundland, and in the Gulf of MaineGulf of Maine
The Gulf of Maine is a large gulf of the Atlantic Ocean on the east coast of North America.It is delineated by Cape Cod at the eastern tip of Massachusetts in the southwest and Cape Sable at the southern tip of Nova Scotia in the northeast. It includes the entire coastlines of the U.S...
. This crab species is also found across the North Pacific area, in areas ranging from Alaska to northern Siberia, and through the Bering Strait to the Aleutian Islands, Japan, and Korea.
Snow crab are often found in the ocean's benthic shelf and upper slope, in the sandy and muddy bottoms, and in depths as shallow as 20 m (65.6 ft) and as deep as 1200 m (3,937 ft). The most snow crab can be found at 70 metre in the Atlantic waters. There are interesting differences in where male and female snow crab are found in the ocean depths: Small adult and senescent adult males occur mainly at intermediate depths over much of the year, while large and hardy adult males are found mostly at depths greater than 80 m (262.5 ft). Adult females are gregarious and congregate at depths of 60 metre.
Diet
Chionoecetes opilio eat other invertebrates that reside in the benthic shelf, such as crustaceanCrustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, bivalves, brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...
s, polychaete
Polychaete
The Polychaeta or polychaetes are a class of annelid worms, generally marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Indeed, polychaetes are sometimes referred to as bristle worms. More than 10,000...
s, and even phytobenthos and foraminiferans. Snow crabs are also scavenger eaters, and aside from preying on other benthic shelf invertebrates, they also prey on annelid worms and mollusks. Males typically prove to be better predators than mature females, and prey type depends upon predator size, with the smallest crabs feeding mainly on amphipods and ophiuroids, while the largest crabs feed mainly on annelids, crustacean decapods and fish. Cannibalism
Cannibalism
Cannibalism is the act or practice of humans eating the flesh of other human beings. It is also called anthropophagy...
is also practiced at times among snow crabs, most frequently by intermediate sized females.
Size and population structure
The snow crab grows slowly and is structured according to its size, with at least 11 recognized stages of growth for male crabs. The male crabs are usually twice the size of the female crabs. Male snow crabs can grow to be up to 150 mm (5.9 in), while females can grow up to 90 mm (3.5 in). Male carapaces are usually around 70 mm (2.8 in) in width and length, with the female carapace usually at about 55 mm (2.2 in) in width and length.Off the coast of Newfoundland, two amphipod species – Ischyrocerus commensalis and Gammaropsis inaequistylis – have been found to live on the carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
of the snow crab.
Breeding patterns
Snow crab have a very high reproductive potential: each year, every single female carries eggs. Females are fertilized internally and can carry up to 150,000 eggs under their abdomens after mating. Females usually lay their eggs in very deep areas of the ocean, such as in deposits of phytodetritus. Males are also capable of mating at both immature and mature stages of their lives.Adult snow crabs usually live between five and six years; before their deaths, they usually molt, mate a final time, and then die. New snow crab offspring hatch along with the late spring phytoplankton boom, so that they have an ample food source to take advantage of upon hatching. When they hatch, the snow crabs are in the zoeal stage, meaning that they are developing larva that can swim on their own. Then, they morph into the megalops stage and settle to the ocean floor among the phytodetritus; the megalops stage is the advanced larval stage that the crab develops into before becoming a true adult.
Commercial importance
This species of crab was commonly caught by trappers in the 1980s, but trapping of this type of crab has decreased since then. Much of the trapping has been in Canada for commercial use, such as for edible purposes.Taxonomy
The species was first described by Otto FabriciusOtto Fabricius
Otto Fabricius was a Danish missionary, naturalist, ethnographer and explorer of Greenland. He was sent to Greenland 1768–1773 and during this brief period he made enormous amounts of observations and collections. The facilities at his command were primitive to the extreme...
in 1780, under the name Cancer phalangium, a name which was invalid due to Johan Christian Fabricius
Johan Christian Fabricius
Johan Christian Fabricius was a Danish zoologist, specialising in "Insecta", which at that time included all arthropods: insects, arachnids, crustaceans and others...
having used it previously for the species now known as Inachus phalangium
Inachus phalangium
Inachus phalangium, Leach's spider crab, is a species of crab from the north-eastern Atlantic Ocean and Mediterranean Sea. It is up to wide, and is very similar to other species in the genus Inachus.-Description:...
. The first valid scientific name was provided by Otto Fabricius in 1788, when he redescribed the species as Cancer opilio. The type locality is Greenland
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
.
As the genus Cancer
Cancer (genus)
Cancer is a genus of marine crabs in the family Cancridae. It includes 8 extant species and 3 extinct species, including familiar crabs of the littoral zone, such as the European edible crab , the Jonah crab and the red rock crab...
was divided up, the species C. opilio was transferred to a new genus, Chionoecetes
Chionoecetes
Chionoecetes is a genus of crabs that live in the northern Pacific and Atlantic Oceans.Other names for crabs in this genus include "queen crab" and "spider crab" – they are known by different names in different areas of the world....
by Henrik Nikolai Krøyer in 1838. Chionoecetes opilio was the only species in the genus at first, and is therefore the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
.
Mary J. Rathbun described a subspecies, C. opilio elongatus in 1924. This is now generally recognised as a full species, Chionoecetes elongatus.