Chaetonotus (Hystricochaetonotus) persetosus Zelinka, 1889

Kånneby, Tobias, 2013, New species and records of freshwater Chaetonotus (Gastrotricha: Chaetonotidae) from Sweden, Zootaxa 3701 (5), pp. 551-588 : 572-573

Chaetonotus (Hystricochaetonotus) persetosus Zelinka, 1889

( Fig. 14 B, C)

Localities: Askö, Södermanland (N 58º 49’ 23’’; E 17º 38’ 32’’), May 14, 2009.

Material: 1 specimen.

TL, 120 µm; FL, 18 µm; AL, 9 µm; PhL, 30 µm; MD, 4 µm; TNC, ~13; DC, 9; DR, 15; VLC, 2–3; HS, 3– 4 x 2–3 µm; NS, 4 x 4 µm; DS, 9 x 8 µm; HSp, 2–3 µm; NSp, 3–4 µm; DSp, 12–22 µm; VC, 5–6; VTS, 7 x 2 µm.

Head five-lobed with two pairs of cephalic sensory ciliary tufts. Cephalion and pleurae thin. Hypostomium absent. Two pairs of dorsal sensory bristles; anterior pair in posterior pharynx region and posterior pair emerging from specialized sub-triangular double-keeled scales at U78. Furca straight with adhesive tubes constituting half of the total furca length. Dorsal surface covered by three-lobed scales that increase in size from anterior to posterior. Scales with barbed spines, which are short at the anterior end but suddenly increase in length approximately half way down the length of the body. The total number of long spines in the trunk region is 22–23 in Swedish specimens and in the medial portion of the trunk they are distributed in 6 rows. The posteriormost medial spine is the longest and can be seen between the furcal branches. The posterior trunk region also holds three-lobed scales without spines as well as three pairs of elongated, almost rectangular, three-lobed scales at the base of the furcal appendages. Double-keeled scales at the base of each furcal branch are absent in the nominal species (Zelinka 1889; Schwank 1990).

Ventrolateral scales are similar in shape to those of the dorsal surface but smaller. Most ventrolateral scales have barbed spines but there are also simple spined scales with lamellae. Ventral interciliary area with smooth rounded to hexagonal scales; posteriormost rows of scales sometimes keeled. A pair of keeled ventral terminal scales with short thin simple spines present in the posterior interciliary area. Ventral ciliation in two longitudinal bands that further divide and merge in the head region.

Mouth subterminal. Pharynx with weak swellings. PhIJ at U28. Intestine straight with anus at U83.

The Swedish specimen, an adult in parthenogenetic phase, agrees well with morphological and numerical data previously reported for the species.

Previously reported from Bulgaria (Valkanov 1937), Denmark (Grilli et al. 2010), France (d’Hondt 1971), Germany (Schwank 1990), Great Britain (Martin 1981), Italy (Balsamo 1983), Poland (Kisielewski & Kisielewska 1986), Romania (Rudescu 1967), Russia (Preobrajenskaja 1926), Brazil (Kisielewski 1991), Japan (Saito 1937), Korea (Lee & Chang 2000).

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.