Squatinella mutica (Ehrenberg, 1832)
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Squatinella mutica
Diagnosis:
- lorica oval with round dorsal marigin
- head shield smooth and circular
- length 100–266 µm
- two eyespots with lenses
- ventral shield present
- foot with three segments
- spine on third segment of foot absent
- equal pair of slender, pointed toes
So far I have only found Squatinella mutica in the Simmelried, mainly between floating and decomposing plant masses. The lorica of this form is rounded at the posterior end and has no spines or appendages. Squatinella mutica also lacks the spine on the dorsal side of the third segment of the foot, as is typical of other Squatinella species (e.g. Squatinella rostrum).
In all species of the genus Squatinella, the dorsal anterior margin of the lorica is elongated and widened into an almost circular shield. The wheel organ is fan-shaped. This specialization allows Squatinella mutica to graze surfaces on the ventral surface in a gliding manner. Small algae and bacteria serve as food. Squatinella mutica can usually only be viewed from the dorsal side, as it immediately turns to the glass surface on the slide. However, Squatinella mutica also likes to settle on the floating coverslip and the specimens can then be observed from the ventral side.
Further images and information on Squatinella mutica: Michael Plewka-Freshwater liefe-Squatinella mutica
Fig. 1 a-b: Squatinella mutica. L = 142 µm (of lorica). Two focal planes of a slightly squashed specimen from dorsal. 1–3 = three segments of the foot, ES = eyespot with lens, HS = head shield, TO = toes. Obj. 100 X.
Fig. 2: Squatinella mutica. L = 155 µm. Dorsal view with focal plane on the rounded dorsal margin (DM) of the lorica. Obj. 100 X.
Fig. 3 a-c: Squatinella mutica. L = 155 µm. Lateral view of the specimen as shown in fig. 2. Note the ventral shield (VS) and the lateral cleft (LC) of the lorica. A spine on the third segment of the foot is absent. LA = lateral antenna. Obj. 40 X.