um, I think you're lost, little megalopae
a closer view of the little guys
The crabs, originally reported as krill, are 2-3 mm long with a carapace width of about 1 mm. They were first noticed in the afternoon last Friday (April 22, 2011). The Phuket Marine Biological Center (PMBC) has been sampling the little guys from Kata and Karon beaches, as the crab babies have yet to be identified to species. The director of PMBC, Wannakiat Thubthimsang, noted that they are definitely swimming crabs, evidenced by the modification of the last pair of their legs to paddles (like blue swimming crabs Portunus pelagicus). Note: they may be just that.
The scientists are looking into several causes, such as hypoxic water conditions, but some are attributing the presence of millions of crab babies to overfishing: normally fish will munch on these little guys, but with less fish comes less predation and greater planktonic crab survival. Others suggest that it may have just been a fluke: moms releasing their clutches at the wrong place and/or time.
A LOT of lost babies
The world may never know.