, Volume 102, Issue 2, pp 87–98 | Cite as

Fine structure of the apical plate in the larva of the freshwater bryozoan Plumatella fungosa (Pallas) (Bryozoa: Phylactolaemata)

  • Åke Franzén
  • Terry Sensenbaugh


The fertilized egg of the freshwater bryozoan Plumatella fungosa develops into an elongated ovoid larva, which after embryogenesis in the embryo sack is released into the surrounding water. During the short free-swimming stage the larva is characterized by the presence of several locomotive and attachment cell types. The ectodermal epithelial cells are provided with numerous cilia. The cytoplasm of the epithelial cells contains numerous mitochondria, Golgi bodies, and ribosomes. Gland cells containing vacuoles of flocculent, lightly staining secretion material were observed between the epithelial cells in the anterior pole of the larva. From a neural center beneath the epidermal cells in the anterior pole nerves emerge in a radial direction. These nerves may include up to 30 axons. Beneath the nerves are a lamella of collagenous fibers and a layer of muscle cells. Internally the larva possesses a coelomic cavity bounded by a squamous epithelium. At the anterior pole large, irregular cells rich in rough endoplasmic reticulum and lipid droplets are seen associated with the coelomic wall. It is concluded that the P. fungosa larva is a true planctonic larva, although highly modified and reduced. There is an acceleration of adult features with differentiation of functional zooids within the larval body. This acceleration may be an adaptation to life in freshwater.


Lipid Droplet Rough Endoplasmic Reticulum Squamous Epithelium Gland Cell Surrounding Water 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of Abbreviations




anterior pole




cytoplasmic fold






endoplasmic reticulum


Golgi body


lipid droplet




muscle cell layer


macrophage-like cell




nerve cell






posterior pole


secretory droplet


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Copyright information

© Springer-Verlag 1983

Authors and Affiliations

  • Åke Franzén
    • 1
  • Terry Sensenbaugh
    • 2
  1. 1.Section of Invertebrate ZoologySwedish Museum of Natural HistoryStockholmSweden
  2. 2.Institute of ZoologyUppsala UniversityUppsalaSweden

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