Astasia pygmaea (Skuja, 1939)
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Astasia pygmaea
Diagnosis:
- body pear-shaped, somewhat flattened
- anterior end rounded
- posterior end abruptly tapered and rounded
- length 9–16 µm, width 7–9 µm
- flagellum of body length
- low euglenoid movement
- nucleus in mid-body or below cell equator
- paramylon grains oval or rod-shaped
- tight striation of pellicle
So far I have only found Astasia pygmaea in the mud layer of the Simmelried. The species can be recognized by its small size and compact shape. The posterior end often tapers abruptly and then appears cone-shaped (s. fig. 2 b), making the body pear-shaped.
Astasia pygmaea can be confused with the similar species Astasia parvula and Astasia kathemerios. However, the shape of Astasia parvula is never pear-shaped (broadly rounded posterior end) and Astasia kathemerios is twice as large and also not pear-shaped.
Fig. 1 a-d: Astasia pygmaea. L = 18 µm. A freely swimming specimen. Obj. 100 X.
Fig. 2: Astasia pygmaea. L = 14 µm. A second, slightly squashed specimen. AG = posterior accumulation of small paramylon grains, F = flagellum, Nu = nucleus, PG = paramylon grains, SP = striation of the pellicle. Obj. 100 X.