Penard Labs

The Fascinating World of Amoebae
Actinophryidae Dujardin 1841
Nonciliated cells with axonemal pseudopodia. Axonemes originate from an amorphous centrosome near nuclei. Single large central nucleus or several peripheral nuclei. Cysts covered with siliceous elements. Sometimes autogamy with subsequent fusion of two amoeboid gametes in cysts.

1. Actinophrys Ehrenberg 1830
Naked, uninucleate cell. Axonemes originate from amorphous centrosomes near a single large central nucleus.
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Actinophrys sol (Müller 1773) Ehrenberg 1830

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Actinophrys sol with symbiotic algae

2. Actinosphaerium Stein 1857
Axopodia originate from amorphous centrosomes near multiple peripheral nuclei.
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Actinosphaerium eichhornii (Ehrenberg 1840) Stein 1857

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A. eichhornii with several nuclei (light blue spots with a central black dot).

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Here multiple cells of starving Actinosphaerium eichhornii are fusing to form a syncytium. Maybe forming a syncytium allows Actinosphaerium to attack larger prey.