Settlement of a Chthamalus larva

Here, a Chthamalus barnacle larva (1) finds a patch of unsuitable substrate for settlement, (2) desists to settle, (3) re- enters the water column and then (4) finds a patch of suitable substrate, where it settles. It then (5) metamorphoses into a young barnacle. 

Note that the metamorphosis from cyprid to spat takes from a few hours to up to 4 days. Metamorphosis appears to be modulated by immersion time (e.g. cyprids stop metamorphosis when the "tide" recedes) and water temperature (metamorphosis is slower in colder waters). See photos of attached cyprids and young barnacles here.

The larva that decided not to test  the substrates is a Pollicipes cyprid.

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