ABSTRACT
In terms of demographic structure, regular echinoids seem to be characterised by a rather variable size structure which may be caused by year-to-year fluctuation in recruitment to the population from their usually planktotrophic larvae. Furthermore, although peaks in frequencies might be recognised corresponding to a discrete annual recruitment, it has often proved difficult to track the growth of the resulting mode in size frequencies despite a growth strategy where early, pre-reproductive, stages grow very rapidly, growth rates seems to be highly variable from one individual to another. As a consequence, the resulting size frequencies are composed of individuals of a wide range in age. The alternative approach based on analysis of skeletal growth marks visible in the plates has a long history but until recently has lacked validation as annual growth markers.
