The walking legs often grow back during the successive molts. Spider crabs can usually survive with up to 3 walking legs missing. This is because the limbs are long and poorly-jointed to the body of the organism, and tend to come off due to predators and nets. One study reported that nearly three quarters of these crabs are missing at least one limb, most often one of the first walking legs. The weak movable finger is small, taking up less than a quarter of the palm.Īlthough long, the legs are often weak. The merus (upper portion of the leg) is slightly longer than the palm (portion of the leg containing the unmoving part of the claw), but comparable in shape. Females, on the other hand, tend to possess chelipeds that are shorter than the other walking legs. In adult males the chelipeds are far longer than any of the walking legs, with the right and left chelipeds being of equal size. These assist the creature in climbing and hooking onto rock, but prevent it from picking up or grasping objects. The walking legs of Macrocheira kaempferi end simply in inwardly-curving dactyls (the movable part at the tip of a walking leg). Like the carapace, the legs are also orange, but may be blotchy and mottled with both orange and white. Spider crabs are known for having long, spindly legs. The carapace tends to stay the same size throughout adulthood, but the walking legs and chelipeds lengthen considerably as the crab ages. The base of the well-developed antennae is fused with the epistome (the area above the mouth). The rostrum (an extension of the carapace above the head) is shaped into two slender spines that jut out from between the eyes. It possesses no cryptic coloration and is unable to change color. Spiny and stubby tubercles (growths) cover the carapace, which ranges from dark orange to light tan in color. Females tend to have wider, although slightly smaller, abdomens than males. The carapace of Macrocheira kaempferi is sub-circular and pear-shaped (pyriform), narrower towards the head. The well-calcified carapace is only around 37 centimeters long, but adult specimens can be nearly 4 meters long from one tip of one cheliped (a claw-bearing leg) to the other when stretched apart. Range depth 50 to 600 m 164.04 to 1968.50 ftĪlthough not the heaviest, the Japanese giant spider crab is the largest known living arthropod.Younger crabs tend to live in shallower areas with warmer temperatures. In Suruga Bay, at depths of 300 meters, the temperature is around 10 degrees Celsius. During spawning season the crabs spend most of their time in shallower waters around 50 meters. They have, however been found at depths of 600 feet. Japanese spider crabs most often inhabit the sandy and rocky bottom of the continental shelf and slope at an average depth of 150-300 meters. This is most likely a one time event it is possible a fishing trawler or extreme weather may have carried this individual much further south than its home range. However, the crab has been found as far south as Su-ao, in Eastern Taiwan. They are found most often in the Sagami, Suruga, and Tosa bays, as well as off the coast of the Kii peninsula. The Japanese spider crab exemplifies the importance of conservation laws and sustainable seafood consumption to protect balanced aquatic ecosystems.The Japanese spider crab Macrocheira kaempferi is mostly limited to the Pacific side of the Japanese islands, Konshu and Kyushu, usually at a latitude between 30 and 40 degrees North. Accordingly, Japan has banned their harvesting during their spring mating season to defend against over-consumption. Japanese spider crabs do not usually perform this past adolescence as their size deters most predators.Īlthough not endangered, these crabs are considered a delicacy in Japan which leaves populations vulnerable. The term “decorator crabs” is used to describe this method of disguise. Seventy-five percent of spider crab species exhibit this behavior. It is an aquatic scavenger that uses its appendages to scan the seabed for decaying matter while defending itself from small predators.įor safety, younger crabs camouflage themselves by attaching sponges and algae to their back. In the aquarium’s Spineless exhibit, I found the world’s largest arthropod, the Japanese spider crab ( Macrocheira kaempferi). Loving the diversity of our oceans and in need of a seaside destination, I visited the Wildlife Conservation Society’s New York Aquarium. Invertebrates SeptemA Super Sea Creature - as seen by - Brian Carrera
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