Gametogenesis, spawning, and fertilization in bivalves and other protostomes

Ryusaku Deguchi, Makoto Osada

Research output: Chapter in Book/Report/Conference proceedingChapter

2 Citations (Scopus)


The diversity of protostomes is demonstrated by the classification of these animals into more than 20 phyla and 1,000,000 species. Many species of aquatic protostomes are considered valuable for basic studies of reproduction as well as for fishery resources. The aim of this chapter is to provide a brief overview of the process and mechanism of fertilization in three protostome groups, the mollusks, annelids, and arthropods, in which various modes of sexual reproduction have evolved. Regarding the series of interactions between oocytes and sperm at fertilization, we have described the structural changes in gametes and the regulatory mechanisms of polyspermy block and increases in intracellular Ca2+, which enable the successful fertilization of oocytes. Prior to fertilization, oocytes and sperm are produced and matured in gonads and released at the optimal time. The second half of the article focuses on gonial cell multiplication, oocyte growth, and spawning (oocyte release and sperm release) in bivalve mollusks, in which these processes are precisely regulated by endocrine systems. Although bivalves share many endocrine regulatory molecules with vertebrates, they also employ unique mechanisms such as the use of the neurohormone serotonin (5-hydroxytryptamine, 5-HT), which acts directly on oocytes and sperm to induce oocyte maturation, sperm activation, and spawning.

Original languageEnglish
Title of host publicationReproduction in Aquatic Animals
Subtitle of host publicationFrom Basic Biology to Aquaculture Technology
PublisherSpringer Singapore
Number of pages53
ISBN (Electronic)9789811522901
ISBN (Print)9789811522895
Publication statusPublished - 2020 Jan 1


  • Annelid
  • Arthropod
  • Bivalve
  • Ca2+ rise
  • Endocrine control
  • Gonial multiplication
  • Mollusk
  • Oocyte maturation
  • Polyspermy block
  • Spawning
  • Sperm motility
  • Vitellogenesis

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)


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