HORMONAL CONTROL OF OOCYTE MATURATION IN ARENICOLA MARINA L. (ANNELIDA, POLYCHAETA) I. MORPHOLOGICAL STUDY OF OOCYTE MATURATION

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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 reach the 1st metaphase at which they remain arrested until fertilization. The meiosis reinitiating substance induces numerous morphological changes in the oocytes: general (shape), cortical (microvilli retraction, plasma membrane flattening), cytoplasmic (cortical granules repartition) and nuclear modifications (germinal vesicle breakdown, chromosome condensation, formation of a meiotic maturation spindle). A kinetic study of these morphological modifications was performed.