Oedignathus
Encyclopedia
Oedignathus inermis is a species
of king crab
found off the Pacific
coasts of the United States
and Canada
, from California
to Alaska
, and disjunctly
around the coasts of Japan
. It is the only species in the genus Oedignathus, and is sometimes called the granular claw crab, paxillose crab or tuberculate nestling lithode crab.
s on the only slightly flattened chelipeds and legs
, and by the paucity of spines, seta
e; other genera have flattened chelipeds covered in setae, and legs with several large spines.
which encrust the rocks around the low tide mark, and may be found at depths of 0–45 m (0–147.6 ). When in the littoral zone, O. inermis is associated with mussel
beds, but it spends more time in the sublittoral zone. Larva
e are released in January and February, at a similar time to other hermit crab
s, perhaps to coincide with seasonal blooms
of plankton
for the larvae to feed on.
O. inermis is preyed upon
by bird
s such as the American black oystercatcher
.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of king crab
King crab
King crabs, also called stone crabs, are a superfamily of crab-like decapod crustaceans chiefly found in cold seas. Because of their large size and the taste of their meat, many species are widely caught and sold as food, the most common being the red king crab, Paralithodes camtschaticus.King...
found off the Pacific
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...
coasts of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, from California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
to Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, and disjunctly
Disjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
around the coasts of Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. It is the only species in the genus Oedignathus, and is sometimes called the granular claw crab, paxillose crab or tuberculate nestling lithode crab.
Characteristics
Oedignathus is distinguished from other king crabs in the subfamily Hapalogastrinae by the presence of numerous tubercleTubercle
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 on the only slightly flattened chelipeds and legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
, and by the paucity of spines, 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; other genera have flattened chelipeds covered in setae, and legs with several large spines.
Ecology
O. inermis lives in pairs under the purplish coralline algaeCoralline algae
Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls...
which encrust the rocks around the low tide mark, and may be found at depths of 0–45 m (0–147.6 ). When in the littoral zone, O. inermis is associated with mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
beds, but it spends more time in the sublittoral zone. Larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e are released in January and February, at a similar time to other hermit crab
Hermit crab
Hermit crabs are decapod crustaceans of the superfamily Paguroidea. Most of the 1100 species possess an asymmetrical abdomen which is concealed in an empty gastropod shell that is carried around by the hermit crab.-Description:...
s, perhaps to coincide with seasonal blooms
Algal bloom
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...
of plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
for the larvae to feed on.
O. inermis is preyed upon
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
by bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s such as the American black oystercatcher
American Black Oystercatcher
The Black Oystercatcher, Haematopus bachmani, is a conspicuous black bird found on the shoreline of western North America. It ranges from the Aleutian Islands of Alaska to the coast of the Baja California peninsula....
.