Chaetonotus

Kånneby, Tobias, 2013, New species and records of freshwater Chaetonotus (Gastrotricha: Chaetonotidae) from Sweden, Zootaxa 3701 (5), pp. 551-588 : 584

Chaetonotus (Z.) bisacer Greuter, 1917

Synonyms: Chaetonotus guruguetoi Grosso, 1973 [syn. Schwank 1990, see also Kisielewski 1991]; Chaetonotus truncatus Saito, 1937 [syn. Kisielewski 1979]; Chaetonotus cfr. truncatus Balsamo 1981 [syn. Kisielewski 1991]

Localities: Lake Trösvattnet, Västmanland (N 59º 33’ 21’’; E 14º 29’ 23’’), December 1, 2007; Artificial pond, Nybro, Småland (N 56º 44’ 89’’; E 15º 54’ 27’’), June 28, 2008.

Material: 2 specimens (1 measured).

TL, 174 µm; FL, 31 µm; AL, 20 µm; PhL, 39 µm; MD, 5–6 µm; CW, 16 µm; TNC, 17–20; DC, 11–13; DR, 21–22; VLC, 6; HS, 4– 5 x 3 µm; NS, 5– 6 x ~3–4 µm; DS, 6– 7 x 3–4 µm; HSp, ~1 µm; NSp, 1–2 µm; DSp, 1–2 µm; GSp, 34–36 µm; VC, 13–15.

Head five-lobed with two pairs of cephalic sensory ciliary tufts. The posterior pair with longer cilia than anterior. Cephalion and pleurae well developed. Hypostomium developed as a concave transverse bar. Two pairs of dorsal sensory bristles; anterior pair inserted between scales at U23, posterior pair emerging from sub-triangular double-keeled scales at U81. Anterior to the spine girdle the dorsal surface is covered by elongated weakly threelobed scales with very short simple spines. The girdle consists of 8 spines, with furcated tips, anchored at U50. Posterior to the girdle, dorsal scales are keeled with a simple spine generally reduced or very short. Closer to the base of the furca, scales get smaller and farther spaced apart. The posteriormost dorsal scales with short simple spines that can be seen between the furca branches. A pair of longer (15 µm) lateral spines inserted at U72. Moreover, a pair of long (40–44 µm) parafurcal spines inserted at U85.

Interciliary field covered by small elongated keeled scales. Ventral ciliation in two separate longitudinal bands.

Mouth subterminal. Pharynx with anterior and posterior swellings, the posterior larger than the anterior. PhIJ at U26. Intestine straight with anus at U83.

The Swedish specimens were adults in parthenogenetic phase. They fall within the morphometric limits reported for C. (Z.) bisacer , a very variable species according to Schwank (1990).

Previously reported from Denmark (Grilli et al. 2010), Germany (Schwank 1990), Great Britain (Martin 1981), Italy (Balsamo 1983), Poland (Kisielewski 1979), Romania (Rudescu 1967), Russia (www.faunaeur.org), Switzerland (Greuter 1917), Argentina (Grosso 1973), Brazil (Kisielewski 1991), Canada (Schwank 1990), Japan (Saito 1937), Korea (Lee & Chang 2000), USA (Pfaltzgraff 1966; Weiss 2001).