Contrôle de la ploidie par imagerie numérique dans des expériences d'induction de la triploidie chez les mollusques bivalves

Individual determination of ploidy level in experimentally induced triploid bivalve molluscs using image cytometry. The sexual maturation in bivalve molluscs causes decreased growth and sometimes increased mortalities. These drawbacks can be avoided by genetic sterilization (triploidy). Triploïdy induction require a egg treatment and a ploidy control at each generation. The ploidy level is usually determined by counting the chromosomes, a technique which is relatively easy for the trochophora stage and for juveniles measuring from 5 mm to 3 cm only. ln order to be able to follow up the evolution of the ploidy rate during any stage of animallife, we have developed an estimation method based on image cytometry. Individual DNA content is determined by integrated optical density of Feulgen-stained nuclei. The technique can be used for routine examination. The reaction is stoechiometric and the reading is quantitative. If compared to chromosome counting, image cytometry is more reliable. Moreover, it is simpler than flow cytometry.