Maturation-Inducing Substance in Starfishes

Abstract

Publisher Summary This chapter discusses the maturation-inducing substance in starfishes. It reviews the mechanism of reproductive phenomena in starfishes based on the physiological activities of two substances, a gonad-stimulating hormonal peptide of neural origin and a maturation-inducing substance produced in the gonad under the influence of the former. The mechanism of gamete release and oocyte maturation in starfishes, based on the action of gonad-stimulating substance (GSS) and maturation-inducing substance (MIS), I-methyladenine, is summarized in the chapter. These reproductive phenomena are effected under hormonal influence in starfishes. Once GSS is liberated from the nerves, it reaches the celomic cavity and enters the ovary, and the cells of the follicles around the oocytes respond to GSS by producing I-methyladenine. The starfish gonad contains a substance that suppresses cell division of Chaetopterus and Arbacia eggs and seems to block oocyte meiosis in starfishes. Starfish oocytes remain in the germinal vesicle stage until just before spawning occurs, whereas spermatogenesis proceeds all the way to the formation of spermatozoa long before the release of sperm. However, the localization in the ovary, chemical nature, and mechanism of action under physiological conditions of such a substance are still obscure.