Effects of delayed metamorphosis and food rations on the perimetamorphic events in the echinoid Paracentrotus lividus (Lamarck, 1816) (Echinodermata)

Abstract

Effect of delayed metamorphosis and food ration on late (competent) larvae and postlarvae of Paracentrotus lividus were investigated. Metamorphosis of competent larvae was either not delayed or delayed from 1 up to 4 days. Larvae were starved or submitted to two different food rations of the algal species Phaeodactylum tricornutum. Larvae during the prolonged competence period and the resulting postlarvae were characterised by: (1) the size of the larval body, (2) the size of the rudiment, (3) the rate of metamorphosis, (4) the size of postlarvae 24 h after metamorphosis, (5) the rate of opening of mouth and anus, (6) the rate of survival, and (7) the growth rate of early postmetamorphic individuals. Both the width of the larval body and the diameter of the echinus rudiment grew in competent larvae that were fed. Unfed larvae did not grow. There was no significant difference in growth between the two food rations. The rate of metamorphosis was higher with larvae that metamorphosed soon after they became competent. Lower capacity of larvae to metamorphose during the delay period was associated with treatments yielding a greater larval width and rudiment diameter during the same period. Postlarval development was affected by a delayed metamorphosis treatment inflicted on competent larvae before metamorphosis. Acquisition of exotrophy happened earlier in postlarvae issued from prolonged competent larvae whatever the larval food rations. The delay treatment negatively affected the development of the digestive tract though it positively affected the growth of early postmetamorphic individuals during the first 6 days following metamorphosis. However, selective mortality occurred afterwards as bigger individuals died preferentially.