Chaetonotus aemilianus (Balsamo, 1978)

Most likely ID: n.a.


Synonym: Hystricochaetonotus aemilianus


Sampling location: Simmelried, Purren pond


Phylogenetic tree: Chaetonotus aemilianus



  • body short and stocky
  • length 80–100 µm, width 31–37 µm
  • head weakly five-lobed
  • cephalion very thin
  • 4 anterior ciliary tufts, variable in length
  • 4 dorsal setolae, posterior pair always on special scales
  • 7–11 longitudinal rows of small, finely spined scales
  • scales three-lobed, about 2–6 µm long
  • 7–9 large spines with distal secondary spines distributed in 3–4 transverse rows
  • the large spines are straight, 18 – 26 µm long
  • between the large spines there are 7–13 trilobed keel plates lacking a spine
Chaetonotus aemilianus
Chaetonotus aemilianus

I have found Chaetonotus aemilianus so far in Simmelried as well as in Purren pond. In the samples it is a conspicuously small gastrotrich (mostly 90–100 µm), bearing few dorsal spines in the mid-body. The spines have only one secondary spine. Chaetonotus aemilianus belongs to the very variable species. The dorsal scales are basically trilobate, but often different in shape (s. drawings from Balsamo and Kitchener of 4 shape variants above). A constant character, however, are the long spines, which are mostly straight and of which 7–9 are present. In my populations there were always 8 long spines.


Fig. 1 a-d: Chaetonotus aemilianus. L = 95 µm. Dorsal view of a freely swimming specimen. Obj. 40 X.


Fig. 2 a-b: Chaetonotus aemilianus. L = 98 µm. A slightly squashed (a) and strongly squashed specimen (b) for visualisation of the dorsal scales. Obj. 100 X.


Fig. 3: Chaetonotus aemilianus. Detail of the dorsal scales in mid-body and the posterior end. Obj. 100 X.

Chaetonotus aemilianus

Fig. 4: Chaetonotus aemilianus. L = 95 µm. A strongly squashed specimen for visualisation of the long and straight dorsal spines. This specimen has 8 of these long spines. Obj. 100 X.


Fig. 5: Chaetonotus aemilianus. The ventral scales at the posterior end in detail. Note the pair of keeled terminal ventral scales (TVS). Obj. 100 X.