Paramoeba and Neoparamoeba


Paramoeba and Neoparamoeba are genera of small, naked amoebae with lobose (more or less fingerlike) pseudopodia. The six described species have been found in temperate marine environments in the northern and southern hemispheres. Some species are free-living, feeding on bacteria and protists. Others are pathogens in finfish, crustacea and echinoderms, including commercially-valuable species such as salmon, turbot, blue crabs, Atlantic clawed lobster, and green sea urchins. Many of the pathogens can persist as free-living amoebae, consuming bacteria.

Paramoeba and Neoparamoeba amoebae can usually be recognized by the presence of a "parasome". "Parasome" is derived from Greek words meaning "secondary body"; it is also called "Nebenkörper" (German for "secondary body"), "paranucleus", or "secondary nucleus". The structure is about the same size as the cell nucleus, and it contains DNA. Each amoebal cell usually has one or more of these parasomes.

Hollande (1980) thought that the parasome was an endocommensal kinetoplastid protist, which he named "Perkinsiella amoebae". Recent molecular evidence supports this interpretation, and indicates that the "parasome" is closely related to Ichthyobodo, a genus of fish parasites (Dykova et al. 2003). It is found elsewhere only in the single, parasitic species of the genus Janickina, which was originally described as a Paramoeba; its relationship to Paramoeba and Neoparamoeba remains uncertain.

Paramoeba and Neoparamoeba are closely related to other amoebae with naked cell bodies, lobose pseudopodia, tubular mitochondrial cristae and no flagellate cells in the life history; together with some other smaller amoebae of similar appearance but without parasomes (Korotnevella, Vexillifera pro parte), it forms a separate and distinct amoebal clade (Peglar et al. 2003). Its more distant relatives include Amoeba itself and Acanthamoeba, a facultative pathogen of humans (especially associated with certain diseases of the eye), that has been the subject of evolutionary genetics research.

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