Swimming crabs are characterized by the flattening of the fifth pair of legs into broad paddles, which are used for swimming. This ability, together with their strong, sharp claws, allows many species to be fast and aggressive predators.
"While these organised structures might look like the work of an artist, they’re actually just the remnants left behind where a sand bubbler crab’s been snacking.
During low tide they exit their burrows (as seen in the top pic) to scour the sand for tiny bits of organic debris in a radial motion. While eating, the crabs ball the excess sand on their heads, then discard it when it gets too big for them to see over, leaving behind a remarkable-looking reminder which helps them keep from searching for food in the same sand twice.
Each time High Tide returns, the small structures crumble and are washed away, all while leaving behind more food particles to fuel the tiny crab’s next accidentally artistic pursuits.”
The giant spider crab is the largest known species of crab and may live up to 100 years. The Japanese name for this species is taka-ashi-gani literally translating to “tall legs crab.” Their armored exoskeletons help protect them from larger predators such as octopi, but giant spider crabs also use camouflage. The crab’s bumpy carapace blends into the rocky ocean floor. To further the illusion, a spider crab will adorn its shell with sponges and other animals.
CONSERVATION The spider crabs are considered a prized delicacy in many parts of Japan. They are caught using small trawling nets. Harvesting of the crab is forbidden during the spring, when crabs move to shallower water to reproduce. Populations of this species of crab have diminished over recent years and there are many efforts to protect them.
Unlike us humans, the skeleton of crustaceans are found on the outside, serving as both structural support and protection for the animal.
However, having a rigid exoskeleton means crustaceans cannot grow little-by-little over time, the way we do.
In order to grow, these creatures must first shed their old, tough exoskeleton, in a process called ‘molting’. They emerge with a new exoskeleton, which remains relatively soft after a molt. Crustaceans must then quickly expand their exoskeleton while in this pliant state, before it hardens once more.
In addition to growth, molting is exhibited when crustaceans need to regenerate lost limbs. Some species of spider crab, like the one shown here, have been known to grow back nearly 50% of a totally severed limb after a single molt, and over 70% after a second molt.
Going somewhere? Juvenile cancer crabs hitch rides on sea nettles, dropping off as jellies get closer to shore. It’s the beach or bust for these travelers! Thanks to Instagrammer @reesies87 for this fun video!