Crab Kingdom Photos
Crabs use chemical (pheromone) and visual signals to attract a mate. Mating usually takes place soon after a female has moulted and the fertilised eggs are stored on her abdomen until they hatch into minute planktonic larvae.
This winter Kinosaki Onsen’s Crab Kingdom will open and welcome guests to enjoy a variety of snow crab dishes as well as relax in its seven outdoor hot springs!
The heaviest living arthropod, the Japanese spider crab (Carinectes sapidus), has a leg span of more than 12 feet (3.76 m) and a body size of up to 44 pounds (20 kg). Fully grown, its carapace can be as wide as 15 inches (38 cm).
Despite their ferocious appearance, these crabs have a gentle disposition. They spend most of their time crawling on the sea floor in search of food. Their omnivorous diet includes shellfish, dead fish, algae, and aquatic plants.
Crabs display significant sexual dimorphism, with males usually having one greatly enlarged claw that is used for communication. Mating occurs as soon as the crab completes a molt. Fertilization is internal and takes place on the female’s pleon, which is wider than the males to accommodate the brooding egg mass until it hatches into minute planktonic larvae.
The green shore crab (Carcinus maenas) is a small, darkly patterned crustacean that lives in rock pools. It spends much of its time buried in mud and sand, only emerging to feed during high tide on bivalves, fish and algae. The crab’s camouflage is primarily driven by its colour, with disruptive markings that break up the body outline. Its natural predators are highly visually guided, being mainly birds (such as corvids and gulls, plausibly tetrachromatic), but also include numerous species of fish, catsharks and cephalopods, which are generally di- or tri-chromatic.
We tested how a variation in crab phenotype affected participants’ ability to form search images by asking them to sort crabs into distinct categories based on their colour and patterning. We found that, on average, participants took longer to capture a novel crab that had poor colour match or low chromatic edge disruption than one they had previously encountered. This effect was most pronounced for colour matching.
Known for its striking appearance, the Japanese spider crab is one of the largest arthropods. Fully grown, it has a leg span of more than 12 feet (3.7 m) and a carapace width of 15 inches (38 cm). Males are larger than females.
The body of this omnivorous crustacean is covered with a tan-colored carapace that is triangular in shape and has a row of nine low spines running down the center. Its gills are protected by short tubercles.
A defining characteristic of crabs is their ability to shed and replace their shells, a process called molting. When this occurs, the old shell breaks away from the body and a new shell forms underneath. The gill and eye stalk coverings also remain with the new shell.
The thorax of females has a broader shape than that of males to provide space for brooding fertilized eggs until they hatch into planktonic larvae. The claws of males are enlarged to impress potential mates during mating.
Crabs are omnivorous, and as such, they eat a balance of animal and plant matter. They use chemoreceptors to detect chemical emissions from potential prey, allowing them to hunt efficiently despite their lackluster vision.
These crabs also have a variety of feeding practices, such as deposit-feeding, predation, cannibalism and scavenging. They can be found on sandy beaches worldwide, where they are able to leverage different food resources to meet their nutritional needs.
Researchers studied the feeding practices of Ocypode gaudichaudii at two sandy beaches, Culebra Beach (CB) and Playa Venao (PV). The crabs’ dietary and foraging behavior were observed using two separate manipulative in situ experiments. In one, the washed sediment was seeded with low or high densities of diatoms and rove beetles. The results of the experiment showed that the crabs were able to adapt their foraging behaviors according to the density of the supplemented food. The crabs on the plates with diatoms tended to deposit-feed more frequently, while those on the plate with beetles scavenged the beetles.