Echinoids (sea urchins) are divided into twomajor groups – cidaroids (a ‘primitive’group)andeuechinoids (a ‘derived’group).Thecidaroidsarea promisingmodelspecies for understanding theancestral developmental mechanisms in echinoids, but little is known about the molecular mechanisms of cidaroid development. In euechinoids, skeletogenic mesenchyme cell specification is regulated by the double-neg...

The class Echinoidea assumed prominence in the field ofcomparative biochemistry when it was shown by Needham, Needham, Baldwin & Yudkin (1932) that the jaw muscles of Strongylocentrotus lividus contained both phosphocreatine and phosphoarginine. Further work by Baldwin & Needham (1937) showed that extracts of the jaw muscles of two other echinoids, Paracentrotus lividu,s and Sphaerechinus granu...

Resolving evolutionary relationships in groups that underwent fast radiation in deep time is a problem for molecular phylogeny, as the scant phylogenetic signal that characterises short internal branches is generally swamped by more recent substitutions. We implement an approach, that maps how the support for rival phylogenies changes when analysing subsets of sites with either faster and more ...

Introduction: Echinoids (sea urchins) provide shelter for a variety of facultative or obligatory ectosymbionts. Objective: To evaluate the hypothesis that decapods and fishes prefer to associate with echinoid individuals species have longer spines. Methods: We visually studied frequency decapod crustaceans associated echinoids in shallow water (< 4 m) deeper (5-20 at Los Cabos, Baja Californ...

The performance requirements of ciliary band feeding explain the convoluted forms of many marine invertebrate larvae. Convolutions increase surface area and therefore feeding rates per unit body volume. We review recent advances in morphology, neural development, and behavior at settlement of the echinoid Lytechinus pictus and provide new ultrastructural and expression data on larvae of its con...