Squatinella bifurca (Bolton, 1884)
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Squatinella bifurca
Diagnosis:
- lorica oval with two distinct dorsal spines
- head shield large, often with two lateral indentations
- two large auricles below head shield
- length 122–182 µm
- two eyespots with lenses
- ventral shield absent
- foot with three segments
- a semicircular plate covering the first foot segment
- equal pair of slender, pointed toes
I have only found two specimens of Squatinella bifurca so far. Both specimens come from the Simmelried, in samples with decomposing plant masses. The species is very characteristic due to the two dorsal spines of different lengths, which are arranged one behind the other (s. figs. 1 a and 2 a). However, the second, smaller spine is easily overlooked because it is often covered by the dominant primary spine, which is about 100 µm long. In my specimens, the secondary spine was about 25 µm long.
The head shield is comparatively large for the body and two large, conically shaped auricles protrude below it. These may have a sensory function. In my specimens, the head shield had two slight lateral indentations, as drawn by Lucks (s. drawing 2, above). Squatinella bifurca is the only species within the genus Squatinella to have a dorsal, semicircular shield covering the first segment of the foot (s. fig. 2 a).
Fig. 1 a-b: Squatinella bifurca. L = 140 µm. Two focal planes of a slightly squashed specimen from dorsal. Note the primary dorsal spine (PDS) and secondary dorsal spine. The primary spine has a length of 98 µm and the secondary spine of 25 µm. AU = auricles, HS = head shield. Obj. 60 X.
Fig. 2 a-b: Squatinella bifurca. L = 149 µm. Two focal planes of a slightly squashed second specimen from dorsal. Note the semicircular foot plate (FP). 1–3 = three segments of the foot, AU = auricles, PDS = primary dorsal spine, SDS = secondary dorsal spine, TO = toes. Obj. 60 X.