Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Ultrastructure of the male reproductive organs in the interstitial annelid Sphaerosyllis hermaphrodita (”Polychaeta”, Syllidae)


 The reproductive organs of the simultaneous hermaphrodite Sphaerosyllis hermaphrodita (Syllidae, Exogoninae) were examined by TEM and reconstructed from ultrathin serial sections. Oocytes are produced in the 11–13th chaetigerous segments and then attached to the outer body surface. The male organs comprise a seminal vesicle, testes, sperm ducts and copulatory chaetae. The unpaired seminal vesicle is an uncompartmented cavity above the gut and within the chaetigerous segments 8–10. Its interior is lined with a layer of gland cells that degenerate as spermatogenesis in the vesicle proceeds. The testes are situated ventrolaterally, close to the seminal vesicle in the 9th chaetigerous segment. They contain cells at early stages of spermatogenesis, which are connected to one another by zonulae collares. The testes and seminal vesicle are enclosed in epithelia. Paired sperm ducts run ventrally from about the midline of the body under the seminal vesicle and into the parapodia of the 9th chaetigerous segment. There they open, together with the protonephridia of this segment, to the outside next to the stout copulatory chaeta. Each sperm duct consists of six cells, the luminal surface of which bears microvilli but no cilia. Only in animals with fully differentiated sperm does the small opening of the proximal duct cell in each duct give access to the seminal vesicle. The mode of sperm transfer is discussed.

This is a preview of subscription content, log in to check access.

Author information

Additional information

Accepted: 9 December 1996

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Kuper, M., Westheide, W. Ultrastructure of the male reproductive organs in the interstitial annelid Sphaerosyllis hermaphrodita (”Polychaeta”, Syllidae). Zoomorphology 117, 13–22 (1997).

Download citation


  • Luminal
  • Seminal Vesicle
  • Reproductive Organ
  • Duct Cell
  • Gland Cell