Acta Parasitologica

, Volume 63, Issue 1, pp 1–14 | Cite as

Ultrastructure of digenean trematode eggs (Platyhelminthes: Neoophora): A review emphasizing new comparative data on four European Microphalloidea

  • David Bruce ConnEmail author
  • Zdzisław Świderski
  • Jordi Miquel
Invited Paper


Despite their tremendous diversity and their medical and veterinary importance, details of egg ultrastructure among the digenean trematodes has been studied rather little. The available literature is spread over several decades and several species, but has not been adequately reviewed to reveal patterns of similarity and divergence. We present this review to synthesize and analyse what is known from the available literature reporting studies using both transmission electron microscopy (TEM) and scanning electron microscopy (SEM). To support our general review of existing literature, we also have synthesized our own previously published descriptions, and present herein our new previously unpublished data. From these new electron micrographs, we provide a comparative analysis of the intrauterine eggs of four digenean species, representing four genera and three families of the superfamily Microphalloidea, collected from four different host wildlife species in four European countries: 1) Mediogonimus jourdanei (Prosthogonimidae) from Myodes glareolus (Mammalia: Rodentia), collected in France; 2) Maritrema feliui (Microphallidae) from Crocidura russula (Mammalia: Soricimorpha), collected in Spain; 3) Brandesia turgida (Pleurogenidae) from Pelophylax ridibundus (Amphibia: Anura: Ranidae), collected in Russia; and 4) Prosotocus confusus (Pleurogenidae) from Rana lessonae (Amphibia: Anura: Ranidae), collected in Belarus. All were studied by preparing whole worms by various techniques for TEM, so that eggs could be studied in situ within the uterus of the parent worm. Based on the literature review and the new data presented here, we describe basic similarities in patterns of embryogenesis and egg formation among all trematode species, but substantial variations in timing of larvigenesis, sculpturing of egg shell surfaces, and some other features, especially including accessory cocoon coverings outside the egg shells of B. turgida and P. confusus. In the future, many more studies are needed to explore egg ultrastructure in other digenean taxa, to explore potential phylogenetic patterns in egg development and structure, and to correlate structure with function in the life cycle.


Development embryo larva reproduction ultrastructure vitellocyte 


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Copyright information

© Witold Stefański Institute of Parasitology, Polish Academy of Sciences 2018

Authors and Affiliations

  • David Bruce Conn
    • 1
    • 2
    Email author
  • Zdzisław Świderski
    • 3
  • Jordi Miquel
    • 4
    • 5
  1. 1.Department of Biology and One Health CenterBerry CollegeMount BerryUSA
  2. 2.Department of Invertebrate Zoology, Museum of Comparative ZoologyHarvard UniversityCambridgeUSA
  3. 3.W. Stefański Institute of ParasitologyPolish Academy of SciencesWarsawPoland
  4. 4.Secció de Parasitologia, Departament de Biologia, Sanitat i Medi Ambient, Facultat de Farmàcia i Ciències de l’AlimentacióUniversitat de BarcelonaBarcelonaSpain
  5. 5.Institut de Recerca de la Biodiversitat, Facultat de BiologiaUniversitat de BarcelonaBarcelonaSpain

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