Sarcodina, the largest phylum (11,500 living species and 33,000 fossil species) of protozoans). It comprises the amebas and related organisms; which are all solitary cells that move and capture food by means of pseudopods, flowing temporary extensions of the cell. Most sarcodines are free living; others are parasitic. One of these parasites is the causative organism of amebic dysentery. With the exception of chloroplasts, sarcodines are identical to the ameboid members of the phylum Chrysophyta. Sarcodines may reproduce asexually by cell division, often without breakdown of the nuclear envelope that is typical in mitosis, or sexually by meiosis and the production of haploid gametes, followed by fusion of gametes and the formation of zygotes.
The sarcodines include the naked forms (amebas) and forms with perforated shells, or tests, through which pseudopods may be extended. Best known of the shelled forms are the foraminiferans, with calcium carbonate shells.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.