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

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. La rvae were starved or submitted to two different food rations of the algal s pecies Phaeodactylum tricornutum. Larvae during the prolonged competence pe riod and the resulting postlarvae were characterised by: (1) the size of th e 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 openi ng 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 th e diameter of the echinus rudiment grew in competent larvae that were fed. Unfed larvae did not grow. There was no significant difference in growth be tween the two food rations. The rate of metamorphosis was higher with larva e that metamorphosed soon after they became competent. Lower capacity of la rvae to metamorphose during the delay period was associated with treatments yielding a greater larval width and rudiment diameter during the same peri od. Postlarval development was affected by a delayed metamorphosis treatmen t inflicted on competent larvae before metamorphosis. Acquisition of exotro phy happened earlier in postlarvae issued from prolonged competent larvae w hatever the larval food rations. The delay treatment negatively affected th e development of the digestive tract though it positively affected the grow th of early postmetamorphic individuals during the first 6 days following m etamorphosis. However, selective mortality occurred afterwards as bigger in dividuals died preferentially. (C) 2001 Elsevier Science B.V. All rights re served.