Chaetonotus (Primochaetus) heteracanthus Remane 1927

Chaetonotus (Primochaetus) heteracanthus Remane, 1927

(Fig. 19)

Localities: Skaftö, Bohuslän (N 58º 14’ 39’’; E 11º 27’ 16’’), July 24, 2009. Material: 2 specimens.

TL, 190–192 µm; FL, 30–32 µm; AL, 21–22 µm; PhL, 39–40 µm; MD, 8 µm; CW, ~17 µm; TNC, 12–13; DC, 6–7; DR, 20–22; VLC, 6; HS, 3– 5 x 4–5 µm; NS, 5 x 5 µm; DS, 10– 12 x 10–11 µm; HSp, 7–9 µm; NSp, 9–11 µm; DSp, 20–30 µm; VC, 18–19; VR, ~55–60.

Head five-lobed with two pairs of cephalic sensory ciliary tufts. Epi- and hypopleurae well developed. Hypostomium developed as a weak gently curved plate. Two pairs of dorsal sensory bristles, posterior pair inserted at U82. Furca tong-shaped with adhesive tubes constituting 2/3 of the total furca length. Dorsal surface of head- and neck region covered by smaller crescent-shaped to rounded scales. Most of dorsal trunk surface covered by large rounded to slightly heart-shaped scales with curved simple spines. Spines abruptly end approximately 2/3–3/ 4 down the trunk region. Scales posterior to this boundary are of different shape: the anteriormost are similar to the spined scales but only possess a keel, which does not reach the anterior end of the scale. Further down towards the caudal incision scales get smaller and more elongated and the keel can extend from the posterior to the anterior part of the scale. Scales of the one or two posteriormost rows with spines, which can be observed dorsally between the furcal appendages. Additionally, two pairs of parafurcal spines present.

Scales of the ventrolateral area are similar to those of the dorsal surface. Ventral interciliary area covered by numerous elliptical partly keeled scales. The scales in the posteriormost row of the interciliary area have fine short spines that can be seen ventrally between the furcal appendages.

Mouth subterminal. Pharynx short and relatively wide. PhIJ at U24–25. Intestine straight with anus at U83–84.

The Swedish specimens were in parthenogenetic phase and conformed to literature data.

Previously reported from Germany (Remane, 1927), Great Britain (Martin, 1981), Poland (e.g. Kisielewski, 1974), Romania (Rudescu 1967) and Brazil (Kisielewski 1991).