ABSTRACT
During the exotrophic phase, the larvae of echinoids pass through several morphological stages characterized by the development of new appendages near or outside the circumoral area. Formation of new larval arms near the mouth increases the area of the ciliated band which collects the food particles. One may suppose that increasing the length of the ciliated circumoral band would result in a greatest efficiences of particle ingestion. Variations in the ingestion rate, by larvae of the sea urchin Para-centrotus lividus (Lamarck) fed of one of two Haptophyceae Hymenomonas elongata (Droop) Braarud and Mono-crysis lutheri (Droop) Braarud, are studied. Measurements of ingestion are made on plutei at times corresponding to different stages of the larval development: plutei with two pairs of anterolateral and postoral arms, development of poste-rodorsal arms, preoral arms, epau-lettes, pedicellars and the adult rudiment.
