The last drifting larval stage of a crab, with adult eyes and claws on a body still built to swim.
A small transparent animal that reads as a crab from the front — stalked eyes, a pair of claws, walking legs folded beneath — and as a shrimp from the side, because the abdomen is still extended behind rather than tucked under. Many carry fine colour, orange or red spots on an otherwise clear body. This entry is pitched at the infraorder because a megalopa cannot be taken to family, let alone species, from a photograph.
It is the stage between the zoea, the spiny larva that hatches from the egg, and the first true crab. The megalopa swims with the abdominal appendages, feeds on small plankton, and is looking for somewhere to settle; at the next moult the abdomen folds under, the swimming appendages are lost, and the animal is a miniature crab. Most crab species pass through this stage, so a megalopa in the water column may become anything from a porcelain crab to a swimming crab.
Megalopae are commonly found riding other animals — jellyfish, salps, comb jellies and floating debris — which gives both transport and shelter, and a photograph that includes the host is generally the more useful record.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
