In 48 hours it will have developed into a trochophore larva. These feed on small phytoplankton cells and soon begin to develop the larval shell which has a very distinct D shape. They are now called veliger larvae, because they have a velum, and are very active. The velum has cilia with which the larva swims and captures food. Growth to the pediveliger stage, at a size of about 0.4 mm, takes 4-5 weeks at 15 C. As it approaches this size, the larva develops a foot, with which it can crawl very effectively.
Gills also begin to develop.
The larva is now ready to metamorphose. It slowly settles to the sea floor, extending the foot and withdrawing the velum. If the bottom is not suitable, the larva swims off again. When the pediveliger finds a suitable place to settle, such as rough or filamentous surfaces, it will secrete byssus threads and anchor itself in place. This setting habit can be exploited by growers wishing to capture wild scallop larvae.