Genus Corallomyxa Grell, 1966

 

Diagnosis: Multinucleate amoeba forming reticulate plasmodium with a net-like structure. Bidirectional streaming of cytoplasm. They are multinucleated and reproduce by budding, releasing multi-, bi-, or uninucleate buds that usually float. Some species have an ultrastructural feature, centriole-like bodies.

Ecology: Thus far only been reported from marine environments.

 

There are five described species in the genus:

  • C. mutabilis Grell, 1966,
  • C. chattoni Grell and Benwitz, 1978,
  • C. multipara Grell, 1988
  • C. nipponica Grell, 1991

 

Remarks: Studies by Grell and Benwitz (1978) and Grell (1988, 1991) indicate that species designations within Corallomyxa were mainly based on organization of the plasmodial network, characters associated with the formation of buds and the numbers of bud nuclei, the presence or absence of bacteria in the cytoplasm, and other ultrastructural characters including organization of the nucleolus, Golgi complex, and lysosomes. There is only limited  documentation of the morphology and no molecular data for the described species, making detailed comparisons of taxa within the genus difficult. 

These are marine amoeboid protists with relatively stiff and branched pseudopodia which also often anastomose. Trophozoite forms large net-like plasmodia which can grow unlimited. From these plasmodia arise tree-like structures, so called buds, which detach from the plasmodium and float into the water. These floating buds settle somewhere forming new plasmodia. Formation of buds seems to be triggered by starvation of the plasmodium.

Depending upon the species, buds can be multinucleate or mononucleate. Trophozoites are multinucleate. Each nucleus with a central nucleolus. A MTOC like structure or electron dense body is associated with the nucleolus, but this phenomenon has not been observed in all species.

All cells show bidirectional streaming of granules like forams. Plasmodia change slowly and show a network with many meshes. Plasmodia can break up or may fuse.

Food capture takes place by formation of a hyaline cup shaped pseudopodium. Observed food particles are pennate diatoms and cryptomonas (in culture, Grell).