Squatinella longispinata (Tatem, 1867)
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Squatinella longispinata
Diagnosis:
- lorica oval with a distinct dorsal spine (96–180 µm)
- head shield small, almost circular
- length 80–140 µm
- two eyespots with lenses
- two lateral, ventral shields present
- foot with three segments
- a spine on the third foot segment, directed dorsally
- equal pair of slender, pointed toes
Squatinella longispinata occurs only rarely in my sampling site Simmelried. So far I have only observed two specimens. The first in July 2009 and the second in October 2022. I have not yet been able to record this species in my other sampling sites.
The most striking feature of Squatinella longispinata is the very long dorsal spine, which can be longer than the entire body (s. figss 1 and 2 a). In my specimens it was about 110 µm long. It can be erected and reattached to the body.
The head shield of Squatinella longispinata is only rudimentary and almost circular (s. fig. 3 b). There is a short spine on the third segment of the foot, which is directed dorsally (s. figs. 1, 2 a and 4 b). If this short spine is not present, then it is the similar species Squatinella leydigi, which lacks this spine on the foot.
The very long dorsal spine makes it difficult to observe this “bulky” species under the coverslip, but offers an advantage for obtaining a lateral view. If the layer thickness is reduced, the specimens tilt to the side. By careful shifting of the coverslip, it is now possible to get the dorsal spine and the body together in the focal plane at the same time. Images shown in figs. 1 and 2 a-b were taken in this way.
More images and information on Squatinella longispinata: Michael Plewka-Freshwater life-Squatinella longispinata
Fig. 1: Squatinella longispinata. L = 120 µm. Lateral view of the specimen found in July 2009. The dorsal spine (DS) has a length of 112 µm. HS = head shield, FS spine on the third segment of the foot. Obj. 60 X.
Fig. 2 a-b: Squatinella longispinata. L = 117 µm. Two focal planes of the second specimen found in Oct. 2022 in lateral view. The dorsal spine has a length of 106 µm. VS = ventral shield. Obj. 60 X.
Fig. 3 a-b: Squatinella longispinata. L = 120 µm. Two focal planes from dorsal of the specimen as shown in fig. 1. DS = dorsal spine, FS = spine on the third segment of the foot, HS = head shield. Obj. 60 X
Fig. 4 a-c: Squatinella longispinata. L = 117 µm. Three focal planes from ventral of the specimen as shown in fig. 2 a-b. CO = corona, FS = spine on the third segment of the foot, HS = head shield, TR = trophi. Obj. 60 X