Antarctic king crabs (Neolithodes yaldwyni) warming up to invade continental shelf, threatening unique marine community
Stephen Tung (special to Mongabay)
Dangerous and disruptive king crabs lurk in a deep pocket of the Antarctic continental shelf, clamoring to escape their cold-water prison to reach and permanently change the shallower, prehistoric paradise above.
The marine communities on the underwater shelf above Palmer Deep are unique, Aronson said. “It’s much more reminiscent of the Paleozoic era before all those shell-crushing crabs and bony fish and bottom-feeding sharks and rays evolved,” he said. “The bottom communities in Antarctica are anachronisms. They’re a window to the past. They’re going to get modernized when these crabs show up.”
Spotted Porcelain Crab (Neopetrolisthes maculatus) with eggs
The (oh-so-cuddly) Teddy Bear Crab
© Ivan Choong
This charismatic crab is much sought after by underwater photographers. Note the small anemones attached to claws for feeding and defense.
Mosaic Boxer Crab or Pom Pom Crab
Notice the two pom-poms (boxing gloves) it is holding, these are a type of anemone (one of three kinds) used to protect itself and collect food at the same time. By using a boxers style approach of steady jabs, this true crab stings and collects micro organism munchies from the water column, then wiping the food into its mouth to feed.
If one anemone is lost it will split the other and it will continue to grow and if both are lost it will start over.
A hands-on approach to symbioses!
And you thought crabs weren’t “cute and fluffy”! Meet the Hairy Crab (Pilumnidae sp.).
Its body and limbs are covered with long, silky hairs. These trap sediments allowing the crab to blend perfectly with its surroundings. In the water, its hairs ‘fluff up’ breaking up its body outline. It also moves slowly and thus overlooked as some bit of drifting rubbish. It has large claws, some with thick black fingers.
** I miss the rock pooling activities from my last job! **
About 5mm worth of the soft coral crab Hoplophrys oatesii
© John Forsyth
Boxer Crab or Pom-pom Crab (Lybia tesselata)
They are notable for their mutualism with sea anemones, which grow on their claws for defense. In return, the anemones find new places to eat and mate. It rarely puts the anemones down and totes them through life.This is how the crab got its name. As it walks along, it looks as if it is carrying boxing gloves or pom-poms. The bonding with the anemone is not required for survival, however, and boxer crabs have frequently been known to live without them, sometimes substituting other organisms such as sponges and corals.
I was lucky enough to see a few of these whilst I was in Malapascua (known for Thresher Sharks but amazing macro around the island). They are truly mesmerizing!
Found from Japan to south-west Australia these beautiful little crabs Zebra crabs Zebrida spp. are commensal on various species of Sea Urchins and although not rare, are not always easy to find.
They appear to be a dependant associate of their hosts and are not found to live anywhere else. Females appear to be larger than males (sexual dimorphism) and there is generally a male and female present. The ends of their back legs are hooked so they can cling onto the Sea Urchins spines.
Hermit Crab by Suzy Walker
Hermit Crabs are the super Family Paguroidea, not ‘true’ crabs. They have a soft abdomen, only the front legs are covered in an exoskeleton, hence the use of mollusk shells for protection.