Chaetonotus (Hystricochaetonotus) macrochaetus Zelinka, 1889

Kånneby, Tobias, 2013, New species and records of freshwater Chaetonotus (Gastrotricha: Chaetonotidae) from Sweden, Zootaxa 3701 (5), pp. 551-588 : 571-572

Chaetonotus (Hystricochaetonotus) macrochaetus Zelinka, 1889

( Fig. 14A )

Localities: Bird bath, Swedish Museum of Natural History, Stockholm (N 59º 22’ 06’’; E 18º 03’ 23’’), April 7, 2009; Small lake, Highway E10, Lapland (N 68º 20’ 53’’; E 19º 02’ 16’’), July 6, 2010.

Material: 2 specimens.

TL, 114–134 µm; FL, 15–18 µm; AL, 8–10 µm; PhL, 32–40 µm; MD, 5–6 µm; TNC, 12–14; DC, 8; DR, 16– 17; VLC, 4–6; HS, 3– 4 x 2–5 µm; NS, 4– 5 x 5 µm; DS, 7– 10 x 6–8 µm; HSp, 4–6 µm; NSp, 6–10 µm; DSp, 15–22 µm; VC, 5–6; VTS, 6– 8 x 2 µm.

Head rounded to weakly five-lobed with two pairs of cephalic sensory ciliary tufts. Cephalion and pleurae weakly developed. Hypostomium present. Two pairs of dorsal sensory brsitles, posterior pair emerging from specialized sub-triangular double-keeled scales at U72. Furca straight with adhesive tubes constituting approximately half of the total furca length. Dorsal surface covered by three-lobed scales with barbed spines. In the mid-trunk region both scales and spines suddenly increase in length. Posterior trunk region with three-lobed scales that lack spines. Three pairs of elongated almost rectangular three-lobed scales at the base of the furcal appendages.

Ventrolateral scales and spines similar to those of dorsal surface but smaller in size. A pair of keeled ventral terminal scales with short spines present. Interciliary area covered by rounded usually keeled scales. Ventral ciliation in two separate longitudinal bands.

Mouth terminal to subterminal. Pharynx with weak terminal swellings. PhIJ at U30–32. Intestine straight with anus at U81.

The Swedish specimens were adults in parthenogenetic phase and fell within the ranges previously reported in the literature. C. (H.) macrochaetus is a very variable species according to Schwank (1990). It can be separated from: (i) C. (H.) euhystrix in that the trunk spines are significantly shorter and do not overshoot the furca, and moreover scales are less widely spaced; (ii) from C. (H.) persetosus in that the ventrolateral spines do not possess lamellae and are all barbed. C. (H.) macrochaetus also has a larger number of large scales and spines in the trunk region (25–29 vs. 15–22). The sudden increase in length of the trunk spines may be a misleading character since this feature is also more or less true for C. (H.) persetosus ; and (iii) from C. (H.) hystrix in that it lacks the doublekeeled scales at the base of each furcal branch and that spines are substantially longer.

Previously reported from Austria (Zelinka 1889), Bulgaria (Konsuloff 1913), Denmark (Grilli et al. 2010), Estonia (Järvekülg 1961), Germany (Schwank 1990), Great Britain (Matin 1990), Hungary (Varga 1949), Italy (e. g. Balsamo 1983), Poland (e.g. Kisielewski 1981), Romania (Rudescu 1967), Russia (Preobrajenskaja 1926), Switzerland (Greuter 1917), Sweden (Hofsten 1923), Ukraine (Jakubski 1919), Brazil (Kisielewski 1991), Canada (Schwank 1990), Israel (Kisielewski 1999) and USA (Robbins 1973).

Figures

FIGURE 14. A, Chaetonotus (H.) macrochaetus. B and C, Chaetonotus (H.) persetosus. A) Habitus. Note the sudden increase in spine length in the anterior trunk region. B) Ventral view of anterior body showing ventral ciliation and mouth. Note the spines with lamellae (arrow). C) Dorsal view of posterior body showing distribution of scales and spines. Note the “ not so sudden ” increase in spine length. Scale bars: A, 25 µm; B and C, 10 µm.