Number and Gross Morphology of Chromosomes in the Pearl Oyster, Pinctada fucata (GOULD) : Collected from Two Regions of Japan

Abstract

The number and gross morphology of chromosomes in the pearl oyster, Pinctada fucata (GOULD), collected from two regions of Japan, Koshiki Island and Ago Bay, are reported. Eggs were prepared using the aceto-orcein squash method. Fourteen bivalents during meiosis and 28 chromosomes during mitosis were observed in the just fertilized or cleaving eggs. About four pairs may be classified as subtelocentrics and the others as meta- or submetacentrics in the tentative arrangements of colchicine-metaphase mitotic chromosomes. Though no difference in the chromosome number was observed between samples from the two local regions, it was impossible to determine whether or not differences in chromosomal morphology exist between them.