INDUCED TRIPLOIDY IN THE CHILEAN BLUE MUSSEL, MYTILUS-CHILENSIS (HUPE, 1854), AND PERFORMANCE OF TRIPLOID LARVAE

Triploidy in embryos of the Chilean blue mussel, Mytilus chilensis, wa s induced with heat shock using 32 degrees C applied for 10 min, 10 an d 40 min post insemination (blocking meiosis I and meiosis II respecti vely) in zygotes incubated at 18 degrees C. Four separate experiments in time were carried out using different stocks of progenitors. Ploidy levels were assessed by chromosome counting in embryos at 20 hrs. The diploid number (2N) for M. chilensis was found to be 28 and therefore triploids (3N) presented 42 pairs of chromosomes. The highest percent of triploids was obtained in embryos treated 10 min post egg activati on (51%) in experiment 4. Low percentages of triploids were obtained ( ranging 15 to 51%), in relation with results using heat shock reported in the literature. Low survival in the cultures was observed, caused mainly by the high proportion of aneuploids that did not reach the D-s tage larvae. We observed a significant difference for growth in shell length between controls and treated larvae after 15 days of culture.