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Zoomorphology

, Volume 130, Issue 4, pp 273–282 | Cite as

Spermatogenesis and the structure of the testes in Nemertodermatida

  • Mieke Boone
  • Wim Bert
  • Myriam Claeys
  • Wouter Houthoofd
  • Tom Artois
Original Paper

Abstract

The ultrastructure of the testes in two representatives of the enigmatic taxon Nemertodermatida was studied using transmission electron microscopy. Nemertoderma westbladi has paired testes, which are delineated by lining cells. Within each testis, different follicles, each surrounded by a membrane-like structure, are found. Flagellophora apelti has genuinely follicular testes, consisting of several follicles, each containing a certain stage of spermatogenesis. As the gametes are not enclosed by a structure that can be called a true gonad, the structure of the testes differs from most bilaterian animals, but resembles the organization of gametogenic areas of ctenophores. Each stage of spermatogenesis in F. apelti is described, enabling the inference of the origin of the structures seen in mature spermatozoa. The overall structure of the mature spermatozoa is similar in all nemertodermatids and unique within the Metazoa: an elongated head containing the nucleus; a middle piece containing an axoneme, mitochondrial derivatives and in F. apelti granular derivatives; and a flagellar tail.

Keywords

Nemertodermatida Acoelomorpha Spermatogenesis Ultrastructure Germline Bilateria 

Notes

Acknowledgments

The authors wish to thank the Flemish Marine Institute (VLIZ) for the use of the research vessel “Zeeleeuw” and the assistance of its crew for the collection of F. apelti. We acknowledge Prof. Dr. Ulf Jondelius for the assistance during the collection of N. westbladi, and thank the crew at the Sven Lovén Centre for Marine Sciences (Kristineberg). We thank Prof. Dr. Ernest Schockaert for useful discussions and Dr. Nikki Watson (Australia) for linguistic corrections. This research was funded by an aspirant grant to MB provided by the Research Foundation Flanders (FWO-Vlaanderen), the samplings were carried out in the framework of project G.08.208, also financed by the Research Foundation Flanders (FWO-Vlaanderen). We gratefully acknowledge the reviewers for their valuable comments, which helped us to improve this paper.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Mieke Boone
    • 1
  • Wim Bert
    • 1
  • Myriam Claeys
    • 1
  • Wouter Houthoofd
    • 1
  • Tom Artois
    • 2
  1. 1.Nematology Unit, Department of BiologyGhent UniversityGhentBelgium
  2. 2.Centre for Environmental Sciences, Research Group Zoology: Biodiversity and ToxicologyHasselt UniversityDiepenbeekBelgium

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