Chaetonotus italicus
(Balsamo & Todaro, 1995)
Most likely ID: n.a.
Synonym: n.a.
Sampling location: Simmelried
Phylogenetic tree: Chaetonotus italicus
Diagnosis:
- body short and stocky, shoe-shaped
- length 90–110 µm
- head five-lobed
- ventral a trapezoid hypostomium
- dorsal 7 rows of trilobed, keeled scales (6.2–7.0 µm) with simple spines (3.2–9.7 µm)
- dorsal spines thick and straight
- two pairs of dorsal, tactile bristles
- at the dorsal base of furca three elongated keeled scales arranged around a rounded scale with two parallel keels
- ventral side with two rows of roundish or rectangular scales, 1.2 µm
- ventral scales become larger (2.8–4.0) µm) toward posterior end
- ventrally two oval, keeled terminal scales (6.4–6.8 µm)
Chaetonotus italicus was first described by Balsamo and Todaro in 1995 and has so far only been recorded in Italy. I found a specimen in the Simmelried in September 2023 in the uppermost layer of mud, among rotting plants. As it is quite small at around 100 µm, I may have overlooked it earlier. My specimen was 95 µm long.
I can essentially confirm the description by Balsamo and Todaro. The three-lobed dorsal scales bear a straight spine, which is slightly keeled. In the last quarter there are two special scales with two keels (s. figs. 3 b and 5). I was also able to recognize the two rows of smooth ventral scales, although I had to focus from the dorsal side (s. fig. 6). The two enlarged terminal scales on my specimen had a distal incision and were not completely oval (s. fig. 6). I could not recognize the trapezoidal hypostomium described by Balsamo and Todaro, although I have only been able to examine one specimen so far.
Fig. 1: Chaetonotus italicus. L = 95 µm. A slightly squashed specimen from dorsal with focal plane on the pharynx (PH) and the intestine (Int). Obj. 100 X.
Fig. 2 a-b: Chaetonotus italicus. L = 95 µm. A slightly squashed specimen from dorsal with focal plane on the straight spines and the dorsal scales. Obj. 100 X.
Fig. 3 a-b: Chaetonotus italicus. L = 95 µm. The same specimen as shown in fig. 2 a-b but stronger squashed. Note the double keeled scales (DKS) in the posterior fourth. Obj. 100 X.
Fig. 4: Chaetonotus italicus. The trilobed dorsal scales in detail. Obj. 100 X.
Fig. 5: Chaetonotus italicus. The arrangement of the dorsal scales near the base of the furca. Obj. 100 X.
Fig. 6: Chaetonotus italicus. Focal plane on the ventral scales from the dorsal side. Note the two rows of rectangular ventral scales (VS) and the two keeled terminal scales (TS). Obj. 100 X.