Chaetonotus novenarius (Greuter, 1917)
Most likely ID: n.a.
Sampling location: Simmelried
Phylogenetic tree: Chaetonotus novenarius
- head five-lobed, cephalion and pleurae strongly developed
- four very long ciliate tufts, anterior ones with setolae
- length 106–193 µm, width 11–39 µm
- anteriorly four long tufts of cilia
- two pairs of dorsal setolae, posterior ones on special scales
- head with 7 longitudinal rows of scales, 12 rows on trunk
- the first two rows of scales on head are prominent with simple, elongated spines
- scales on trunk delicate and variable in shape, basis shape is trilobed
- 7–9 long spines with one or two secondary spines arise in a field above midbody
- the long spines inserted in a vase-shaped basis
- ventrolateral spines are simple and curved
- at posterior end on dorsal side a field of elongated, keeled scales
- ventral side with 4–6 rows of oval, keeld scales and two elongated terminal scales with 2 short spines each
I find Chaetonotus novenarius rarely, but regularly. All finds come from the Simmelried. It is striking that all finds were made in the summer months between May and August. This fits in with the description by Schwank (1990) that this species has a maximum in summer.
Chaetonotus novenarius has a conspicuous bundle of 8-9 long spines, which originate just above mid-body and can reach up to the toes. In my population all specimens had 9 of the long spines. At low magnification, Chaetonotus novenarius can be confused with other species with dorsal long spines, such as Chaetonotus aemilianus. However, Chaetonotus novenarius has a characteristic “crown” of thickened scales at the front end of the head (s. figs. 3 b, 5 and 6) and the long spines are inserted in a vase-shaped basis (s. fig. 8). The long spines may have 1 or 2 secondary spines. In my population, all the specimens examined had 2 secondary spines (s. fig. 7), as drawn by Balsamo (s. drawing 2, above). The other body scales are very thin and delicate and are hard to contrasting in DIC. The body scales are triangular and three-lobed, with a short, simple spine. At the posterior end there is a field of elongated oval scales with a keel (s. fig. 9).
Fig. 1 a-b: Chaetonotus novenarius. L = 172 µm. Two focal planes of a freely swimming specimen. Obj. 60 X.
Fig. 2 a-b: Chaetonotus novenarius. L = 187 µm. Lateral view from left of a freely swimming specimen. Obj. 40 X.
Fig. 3 a-b: Chaetonotus novenarius. L = 112 µm. Dorsal view of a slightly squashed specimen. Note the “crown” of strong apical scales (AS) and the prominent main spines (MS) arising above midbody. 60 X.
Fig. 4 a-c: Chaetonotus novenarius. L = 130 µm. A second, slightly squashed specimen from dorsal. Obj. 100 X.
Fig. 5: Chaetonotus novenarius. The enlarged and strongly developed scales in the front of the head (AS). They have a curved and simple spine. Obj. 100 X.
Fig. 6: Chaetonotus novenarius. The apical scales in a strongly squashed specimen. The scales are trilobed with a curved spine (arrows). Obj. 100 X.
Fig. 7: Chaetonotus novenarius. The group of 9 main spines (1–9) arising slightly above midbody. The main spines have two secondary spines (SS) each near the distal end. Obj. 100 X.
Fig. 8: Chaetonotus novenarius. the long, dorsal main spines (SP) are inserted in a vase-shaped basis (VB). Obj. 100 X.
Fig. 9: Chaetonotus novenarius. The field of elongated and keeled scales (KS) at the posterior end of the dorsal side. Obj. 100 X.