Kamchatka crab or Alaskan red king crab legs crab, is a species of king crab native to the Bering Sea and Gulf of Alaska. The red king crab is the largest species of king crab.

The red king crab is native to the Bering Sea, North Pacific Ocean, around the Kamchatka Peninsula and neighboring Alaskan waters. The red king crab is the most coveted of the commercially sold king crab species, and it is the most expensive per unit weight. It is most commonly caught in the Bering Sea and Norton Sound, Alaska, and is particularly difficult to catch, but is nonetheless one of the most preferred crabs for consumption. Red king crabs are experiencing a steady decline in numbers in their native far east coastal waters for unclear reasons, though several theories for the precipitous drop in the crab population have been proposed, including overfishing, warmer waters, and increased fish predation. In the 1960s, the Soviet Union transported red king crabs from the North Pacific Ocean to the Murmansk Fjord. They did not survive transport overland, so a batch was flown in, which survived, was released, and bred and spread in the wild. It was first found in Norway in 1977.

In the Barents Sea, it is an invasive species and its population is increasing tremendously. This is causing great concern to local environmentalists and local fishermen, as the crab eats everything it comes across and is spreading very rapidly, eating most seabed life and “creating a desert”. By the mid 1990s, the king crabs reached North Cape. 2013 that they have reached Sørøya and are breeding there. A few have been caught as far south as Tromsø.

A report on 8 June 2009 said that a red king crab had been caught off Skogsvåg at Sotra south of Bergen in south Norway. In the Norwegian Sea, some evidence indicates that the red king crabs eat the egg masses of the capelin, which is an important prey for the cod. In January 2022 fishermen in the United Kingdom started catching King crabs. The red king crab has a wide range of tolerance to temperature, but it affects their growth. Overall, red king crabs have a high adaptation capacity in changes of salinity level because the crabs retain their vital functions and their feeding activities.

A difference is seen, though, in the salinity tolerance between juvenile and adult red king crabs. The red king crab has five sets of gills used for respiration, which are in the bronchial chamber within the carapace. The carapace is a covering of sheets of exoskeleton that overhang the thorax vertically to fit over the base of the thoracic legs. The carapace encloses two branchial chambers that enclose the gills. To induce a current into the branchial chamber the crab uses back and forth movements of an appendage called the scaphognathite. Each gill has a main axis with many lateral filaments or lamellae that are vascularized.

The afferent channel transports blood from the gill axis into each filament through a fine afferent canal to the gill top. Blood returns by a minute efferent canal to the gill tip to the efferent channel and passes to the pericardial chamber, which contains the heart. Due to their respiratory system’s limited ability to deliver by diffusion, respiratory gases must be transported around the body. Paralithodes camtschaticus has an open circulatory system with a dorsal, ostiate heart. An open circulatory system has circulating fluid that passes somewhat freely among the tissues before being collected and recirculated.

They have a neurogenic heart, which has rhythmic depolarization that is responsible for initiating heartbeats. The cardiac ganglion, which consists of nine neurons, attaches to the dorsal wall of the heart. The anterior neurons innervate the heart, whereas the other posterior neurons make synaptic contact with those anterior neurons. The posterior neuron acts as the pacemaker but also functions as the cellular oscillator and the central pattern generator.

This mechanism is important as it allows the organism to match its output of blood with its input of blood. Because of the stretching between beats, the Frank-Starling mechanism allows the heart to then naturally contract more forcefully, allowing greater flow of blood, which results in the matched heart output to the increased blood received. The Frank-Starling mechanism is a little different in crustaceans, as it involves the cardiac ganglion as described previously. The stretching of the heart induces the ganglion to fire more regularly and powerfully. Red king crab blood contains leukocytes and the second-most common respiratory pigment called hemocyanin. Arthropod hemocyanin is a distinct variation specific to arthropods and is a metalloprotein that uses copper atoms that are bound to its structure. Two copper atoms are needed to bind one O2 molecule.

Because it is a large protein molecule, it is found in the blood plasma, but not in body tissues or muscles. King Crabs of the World: Biology and Fisheries Management. A meal to get your claws into”. Alaska King Crabs: Wildlife Notebook Series”. Alaska Department of Fish and Game.