Biology of Dicyemid Mesozoans

We reviewed recent advances of some aspects on the biology of dicyemid mesozoans. To date 42 species of dicyemids have been found in 19 species of cephalopod molluscs from Japanese waters. The body of dicyemids consists of 10–40 cells and is organized in a very simple fashion. There are three basic...

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Bibliographic Details
Published inZoological Science Vol. 20; no. 5; pp. 519 - 532
Main Authors Furuya, Hidetaka, Tsuneki, Kazuhiko
Format Journal Article
LanguageEnglish
Japanese
Published Japan Zoological Society of Japan 01.05.2003
UniBio Press
Subjects
Adaptation, Physiological
Animals
cell junctions
cell lineages
Conocyema
Dicyema
dicyemid mesozoans
Dicyemida
Invertebrates - anatomy & histology
Invertebrates - classification
Invertebrates - cytology
Japan
life history traits
Marine Biology
Microcyema
morphological adaptation
Pseudicyema
Review
Japan
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Summary:We reviewed recent advances of some aspects on the biology of dicyemid mesozoans. To date 42 species of dicyemids have been found in 19 species of cephalopod molluscs from Japanese waters. The body of dicyemids consists of 10–40 cells and is organized in a very simple fashion. There are three basic types of cell junction, septate junction, adherens junction, and gap junction. The presence of these junctions suggests not only cell-to-cell attachment, but also cell-to-cell communication. In the development of dicyemids, early stages and cell lineages are identical in vermiform embryos of four genera, Conocyema, Dicyema, Microcyema, and Pseudicyema. Species-specific differences appear during later stages of embryogenesis. In the process of postembryonic growth in some species, the shape of the calotte changes from conical to cap-shaped and discoidal. This calotte morphology appears to result from adaptation to the structure of host renal tissues and help to facilitate niche separation of coexisting species. In most dicyemids distinctly small numbers of sperms are produced in a hermaphroditic gonad (infusorigen). The number of eggs and sperms are roughly equal. An inverse proportional relationship exists between the number of infusorigens and that of gametes, suggesting a trade-off between them. Recent phylogenetic studies suggest dicyemids are a member of the Lophotrochozoa.
Bibliography:ObjectType-Article-2
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ISSN:0289-0003
DOI:10.2108/zsj.20.519