Nuclearia Key – Microworld

Genus Nuclearia Cienkowsky, 1865

Diagnosis: Cell amoeboid, normally spherical to subspherical, with sharply pointed fine radiating pseudopodia; actively moving form varies in shape; cell readily adopt a flattened form without severe compression being applied; branching of pseudopodia occurs; with or without a mucous envelop; with one or many nuclei.

Ecology: Fresh water. Feeding by either ingestion of food particles or penetration of eukaryotic algal filaments.

Key to the species.

Note: the weak point of this key is that it is very difficult to detect any nucleus in a Nuclearia-species (Key after Patterson, 1984).

1	Organisms not adopting a rounded form when free from compression	2
–	Organisms readily adopting a spherical form when uncompressed	9
2	Organisms typically with 1, occasionally 2, nuclei	3
–	Organisms typically with more than 2 nuclei. The nucleoli appear spherical and smooth. Body diameter typically 30 – 60 µm. No cysts reported. Polymorphic, adopting either a spherical or flattened body form, and with or without a mucus sheath. Food includes filamentous blue-green algae.	*N. delicatula*
3	Nucleus without evident nucleolus. Body typically about 16 µm in diameter. A spherical and a flattened form have been described, but cysts and enveloping mucus sheath have not.	*N. polypodia*
–	Nuclei with evident nucleolus	4
4	Body typically 10 µm or less in length. The nucleoli appear spherical and smooth. A spherical form has not been described, nor have cysts nor an enveloping mucus sheath.	*N. leuckarti*
–	Body typically 15 µm or more in length	5
5	Body enveloped by mucus sheath through which radiating pseudopodia can protrude	6
–	Mucus sheath not evident	7
6	Mucus sheath in 2 layers. Cells typically 30 µm in diameter, having one nucleus with a smooth spherical nucleolus	*N. rubra*
–	Mucus sheath single.	see note below
7	No cysts evident	8
–	Cysts produced	See note below
8	Body typically 15 µm in length. Only a flattened form has been described. The nucleolus is spherical and smooth. No cysts nor spherical form of the body have yet been described.	*N. moebiusi*
–	Body typically 30 µm in diameter. Two organisms, N. rubra and N. simplex satisfy this diagnosis	See note below
9	With evident enveloping mucus sheath	10
–	Without any evident mucus sheath	16
10	Sheath double	*N. rubra*
–	Sheath single	11
11	Nuclei without any evident nucleoli	12
–	Nuclei with nucleoli	13
12	Cell body diameter typically about 15 µm	*N. polypodia*
–	Cell body diameter typically about 30 µm. Only a spherical form with a single-layered mucus sheath has been described. No report of a flattened form nor of a cyst.	*N. flavescens*
13	Nucleolus tends to spherical but has a folded appearance. The cell body is typically about 30 µm in diameter. The normal body form is spherical with a single-layered mucus sheath. A flattened form can be adopted under severe compression. Relatively immobile.	*N. radians*
–	Nucleolus spherical and smooth in appearance	14
14	With more than 2 nuclei	*N. delicatula*
–	With 1, occasionally 2, nuclei.	15
15	Filopodia sometimes with knobs	*N. thermophila*
–	Filopodia never with knobs; two polymorphic species satisfy this diagnosis, and can only be distinguished on the basis of appearance of other cells in the population	See note below
16	With more than 2 nuclei	*N. delicatula*
–	Uninucleate, or occasionally with 2 nuclei	17
17	Cysts also present. Could be 1 or 2 species	N. simplex or N. rubra
–	No cysts seen. Organisms satisfying this diagnosis could belong to 1 of 3 taxa	*N. rubra* or N. flavocapsulata or N. simplex