Biology
Plicopurpura pansa being 'milked' for dye © http://traditionsmexico.phanfare.com/2402728
The average size of P pansa has halved in the last thirty years - from 60mm to 30mm long. Before 1980, some snails grew to more than 100mm.
The snail lays egg capsules, which hatch into planktotrophic larvae - meaning they feed on plankton. The larvae can delay settlement for 6 months or more.
The snails can live for about 11 years.
