HORMONAL CONTROL OF OOCYTE MATURATION IN ARENICOLA MARINA L. (ANNELIDA, POLYCHAETA) II. MATURATION AND FERTILIZATION

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Abstract
In A. marina the oocytes are arrested in the 1st prophase stage of meiosis until spawning. Oocyte maturation is under hormonal control; when incubated in vitro in a brain extract oocytes proceed to the 1st metaphase at which they remain arrested until fertilization. The prophase-arrested oocytes can neither be fertilized nor parthenogenetically activated by ionophore A23187 or 1 M glycerol. The metaphase-arrested oocytes can be fertilized and parthenogenetically activated. Fertilizability thus appears during maturation; it seems to be linked to microvilli retraction. A study of spermatozoa capacitation and oocyte fertilization or activation is reported. A scanning electron microscope study of early contact and penetration of spermatozoa is presented.