Chaetonotus

Kånneby, Tobias, 2013, New species and records of freshwater Chaetonotus (Gastrotricha: Chaetonotidae) from Sweden, Zootaxa 3701 (5), pp. 551-588 : 584-585

Chaetonotus (Z.) succinctus Voigt, 1902

( Fig. 24 )

Localities: Artificial pond, Nybro, Småland (N 56º 44’ 89’’; E 15º 54’ 27’’), June 28, 2008.

Material: 1 specimen.

TL, 192 µm; FL, 40 µm; AL, 27 µm; PhL, 43 µm; MD, ~6 µm; CW, 18 µm; TNC, 16–18; DC, 8–9; DR, 24– 26; VLC, 8–9; HS, 4 x 3 µm; NS, 5– 6 x NA µm; DS, 6– 8 x 4–5 µm; DSp, 12–20 µm; Gsp, 63–66 µm; VC, ~20.

Head clearly five-lobed with two pairs of cephalic sensory ciliary tufts; the posterior pair with longer cilia than the anterior pair. Cephalion and pleurae well developed. Hypostomium absent. Two pairs of dorsal sensory bristles (Schwank 1990), posterior pair emerging from sub-triangular double-keeled scales at U79. Furca straight to weakly tong-shaped with adhesive tubes constituting almost 3/4 of the total furca length. Anterior dorsal surface covered by small polygonal keeled scales with a very short simple spine. A little less than halfway down the body (U45), 9 long simple spines anchored by small polygonal scales form a transversal girdle. Posterior dorsal trunk surface covered by rounded to oval or weakly three-lobed keeled scales, which decrease in size at the base of the furca. A pair of long (43 µm) simple lateral spines inserted at U71. A pair of long (58 µm) simple parafurcal spines that greatly overshoot the furca, inserted at U82. Five short simple spines can be seen between the furcal branches, the outer pair originates from ventral scales.

The ventral surface of the pharynx region covered with approximately 14 transverse scale plates. The rest of the ventral interciliary area covered by numerous small oval keeled scales. Ventral ciliation in two separate longitudinal bands that divide on the head.

Mouth subterminal. Pharynx muscular with large posterior swelling. PhIJ at U26. Intestine straight with anus at U76.

The Swedish specimen was an adult in parthenogenetic phase. It agrees well with diagnostic characters presented in the literature. One exception is that the scales in the trunk region are smaller than previously reported, and they apparently do not overlap. Moreover, the anterior pair of dorsal sensory cilia could not be seen in the Swedish specimen.

Previously reported from Bulgaria (Valkanov 1937), Germany (Voigt 1902), Norway (Schwank 1990), Poland (Roszczak 1968), Romania (Rudescu 1967), Russia (Preobrajenskaja 1926), Brazil (Kisielewski 1991), Japan (Saito 1937), Korea (Lee & Chang 2000), USA (Weiss 2001).

Figures

FIGURE 24. Chaetonotus (Z.) succinctus. A) Habitus. B) Dorsal view of posterior body showing girdle and lateral spines. C) Ventral view of anterior body showing scales of the interciliary area. Scale bars: A, 25 µm; B and C, 10 µm.