Rhizopoda By: Seth Rudd

Radiolarians Mostly marine forms with glassy shells that differ in shape from each species Have skeletons most commonly made of silica. When they die their skeletons accumulate at sea bottom and form ooze Have a segregated soft anatomy into the central capsule containing the endoplasm, and the surrounding ectoplasm

Foraminiferans Almost all marine, most species live in the sand or attach themselves to rocks and algae, but some are also abundant in plankton Single celled protists with shells also called tests. Shells are commonly divided into chambers which are added during growth Foraminiferan fossils, caused by their calcium carbonate shells, are excellent markers for correlating the ages of sedimentary rocks in different parts of the world

Heliozoans Mainly freshwater protists with stiff axopodia used for feeding Roughly spherical amoeboids with many stiff, microtubule supported projections called axopods Similar to radiolarians but they are distinguished from them by lacking central capsules and other complex skeletal elements

Amoeba All unicellular and use pseudopodia to move and feed. Cytoskeleton consists of microtubules and microfilaments that help in amoeboid movement Has simple contractile vacuole to maintain osmotic equilibrium Reproduce asexually by various mechanisms of cell division, mitosis, and cytokenesis. Spindle fibers form but all stages of mitosis aren’t apparent

Three Facts Some Rhizopodians are important parasites. Entamoeba histolytica causes amebic dysentary and other Entamoeba is a common symbiont in the human mouth where it feeds on bacteria and human macrophages Some Rhizopodians are among the largest protists known. For example, Pelomyxa palustrus, easily reaches 5mm in length Amoebas obtain their food through phagocytosis