Biology of Dicyemid Mesozoans

  title={Biology of Dicyemid Mesozoans},
  author={Hidetaka Furuya and Kazuhiko Tsuneki},
  booktitle={Zoological science},
Abstract 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… 

Diversity and Morphological Adaptation of Dicyemids in Japan

Dicyemid mesozoans (phylum Dicyemida) are the most common and characteristic endosymbionts found in the renal sac of benthic cephalopod mollusks, a unique environment in which they spend most of

Three New Species of Dicyemid Mesozoans (Phylum Dicyemida) from Amphioctopus fangsiao (Mollusca: Cephalopoda), with Comments on the Occurrence Patterns of Dicyemids

Three new species of dicyemid mesozoans are described from the renal appendages of Amphioctopus fangsiao, collected off Akashi, in Harima Nada, and from Osaka Bay, suggesting that dricemids infect each renal appendage independently.

Two New Dicyemids from Sepia longipes (MollUsca: Cephalopoda: Decapoda)

  • H. Furuya
  • Biology
    The Journal of parasitology
  • 2009
Abstract Two new species of dicyemid mesozoan are described from Sepia longipes, Sasaki, 1913, collected from Tosa Bay in Japan. Dicyema oxycephalum n. sp. is a medium-sized species that is about

Distinction of Cell Types in Dicyema japonicum (Phylum Dicyemida) by Expression Patterns of 16 Genes

In certain genes, regional specific expression patterns were observed among somatic cells of vermiform stages and infusoriform larvae of dicyemids, and it was revealed that the Ets domain-containing protein and Rad18 are molecular markers for agametes.

Dicyemida and Orthonectida: Two Stories of Body Plan Simplification

Dramatic simplification of body plans in dicyemids and orthonectids, as well as their intricate life cycles that combine metagenesis and heterogony, evolved independently in these two lineages.

Phylogenetic Analysis of Dicyemid Mesozoans (Phylum Dicyemida) From Innexin Amino Acid Sequences: Dicyemids Are Not Related to Platyhelminthes

The Bayesian and maximum likelihood trees based on the innexin amino acid sequences suggested dicyemids to be more closely related to the higher lophotrochozoans than to the flatworms.


  • H. Furuya
  • Biology
    The Journal of parasitology
  • 2007
Two species of dicyemid mesozoan are redescribed from Rossia pacifica Berry, 1911, collected off Iwase in Toyama Bay, Honshu, Japan. Dicyemennea brevicephaloides Bogolepova-Dobrokhotova, 1962, is a

Three New Species of Dicyema (Dicyemida: Dicyemidae) from Octopus kagoshimensis (Mollusca: Cephalopoda: Octopodidae)

Three new species of dicyemid mesozoan are described from OctQpus kagoshimensis Ortmann, 1888 eollected ofi' Irino in Tosa Bay. sourthern Shikoku, Japan. Diqyema tosaense sp, nov. is a small species

Molecular contributions to species boundaries in dicyemid parasites from eastern Pacific cephalopods

The addition of DNA sequences to understanding dicyemid diversity clarifies species boundaries in a lineage that is difficult to define in nearly every aspect.

A New Dicyemidfrom Sepiella japonica (Mollusca: Cephalopoda: Decapoda)

  • H. Furuya
  • Biology
    The Journal of parasitology
  • 2008
A new species of dicyemid mesozoan is described from Sepiella japonica Sasaki, 1929, collected from the eastern area of Inland Sea, Osaka Bay, and Kii Strait in Japan. Dicyema sepiellae n. sp. is a



Fine structure of dicyemid mesozoans, with special reference to cell junctions

Ciliary rootlet systems at vermiform stages and in infusoriform embryos were unique in structure compared with those of other primitive multicellular animals.

Phylogenetic position of the dicyemid mesozoa inferred from 18S rDNA sequences.

The present results favor the hypothesis that the dicyemids do not represent an early divergent metazoan group, but rather a group degenerated from a triploblastic ancestor.

Development of the Infusoriform Embryo of Dicyema japonicum (Mesozoa: Dicyemidae).

The cleavage pattern and cell lineage of the infusoriform embryo of the dicyemid mesozoan Dicyema japonicum were studied in fixed material with the aid of a light microscope and the cell lineage appears to be invariant among embryos, apart from the derivation of the lateral cells.

Developmental Patterns and Cell Lineages of Vermiform Embryos in Dicyemid Mesozoans

Early developmental processes are almost identical in the vermiform embryos of all four dicyemid genera, and the cell lineages appear to be invariant among embryos and are highly conserved among species.

Calotte morphology in the phylum Dicyemida: niche separation and convergence

In the dicyemids, calotte morphology seems to result from adaptation to the structure of host renal tissues and helps to facilitate niche separation of coexisting species.


Two new species of dicyemids are described from 2 species of deep benthic cephalopods, Graneledone antarctica and G. macrotyla, collected in the Southern Ocean south of the Antarctic Convergence.

Reproductive traits in dicyemids

Several characters involved in the life cycle in dicyemids were examined to understand reproductive strategy and adaptations to cephalopod hosts and an inverse proportional relationship was found between the number of infusorigens and the gametes, suggesting a trade-off between them.

The Development of the Vermiform Embryos of Two Mesozoans,Dicyema acuticephalum and Dicyema japonicum

The pattern of cell division and the cell lineage of the vermiform embryos of dicyemid mesozoans were studied under the light microscope using fixed and stained specimens of two species, namely,

Evolution: Dicyemids are higher animals

It is concluded that dicyemids are lophotrochozoans that have secondarily lost many morphological characters, so the simplicity of their body plan is not a primitive condition.

The Life-History and Systematic Relations of the Mesozoa

Although Hyman noted that most zoologists regard the Mesozoa as degenerate flatworms, she designated the group as a phylum, lower than the sponges in taxonomic status.