Chaetonotus (Chaetonotus) furculatus Schwank, 1990

Schwank, Peter & Kånneby, Tobias, 2014, Contribution to the freshwater gastrotrich fauna of wetland areas of southwestern Ontario (Canada) with redescriptions of seven species and a check-list for North America, Zootaxa 3811 (4), pp. 463-490 : 475-477

Chaetonotus (Chaetonotus) furculatus Schwank, 1990

( Fig. 7 )

Type locality. In mud and mosses in ponds near Galt Creek, Puslinch district, Ontario, Canada. Type material. Drawing of one specimen. Lectotype, SMNH Type-8553 deposited at the Swedish Museum of Natural History, Stockholm, Sweden.

Other material. 7 specimens that are no longer extant.

Etymology. The species name is derived from the shape of the caudal furca.

Diagnosis. Small and slender species, 100–140 µm in total body length. Head three-lobed with one pair of sensory ciliary tufts. Two pairs of dorsal sensory bristles. Furca 20–25 µm in length with adhesive tubes 15–20 µm in length. Adhesive tubes pointing outwards at their distal ends. Dorsal surface covered by 8–9 columns of arrowhead-shaped scales with a simple spine distributed in approximately 30 rows. Pharynx cylindrical, 23–25 µm in length.

Description. Small species with slender, elongated body 100–140 µm in total body length. Head three-lobed with well developed cephalion, 9 µm in diameter, and pleuria. One pair of sensory ciliary tufts.

Body width 13–14 µm at the head (U08), 11–12 µm at the neck (U12), 17–18 µm at the trunk (U47) and 9–10 µm at the base of the furca (U85). Head only slightly delimited from trunk by neck constriction. Furca 20–25 µm in length, conspicuously elongated with adhesive tubes contributing to 15–20 µm of the total furca length. Base of furcal branches naked, adhesive tubes pointing outward at their distal end. Two pairs of dorsal sensory bristles present, anterior pair anchored at U20 and posterior pair anchored at U73. Dorsal surface covered by 8–9 columns, each with approximately 30 small arrowhead-shaped scales. Scales bear a simple, curved spine, 2–5 µm in length. Spines only marginally increase in length from anterior to posterior end.

The ventral surface could not be observed.

Mouth relatively large, 5–6 µm in diameter. Pharynx cylindrical, 23–25 µm in length, and widens slightly towards the PhIJ at U23.

Taxonomic remarks. C. (C.) furculatus can be differentiated from many species within the C. ( Chaetonotus ) complex based on its three-lobed head with only one pair of sensory ciliary tufts. It can be separated by the nature of its furca and the scales from the similar Chaetonotus (C.) formosus Stokes, 1887 . Chaetonotus (C.) africanus Schwank, 1990 bears spines that are much longer than the furcal branches. The head of Chaetonotus (C.) greuteri is wider than its trunk and additionally the spines increase significantly in length from 7 µm on the head to 17–19 µm in the posterior trunk region; in C. (C.) furculatus the spines are up to 5 µm only. Chaetonotus (C.) corderoi Schwank, 1990 has a broad, rounded head and much longer spines than C. (C.) furculatus .

Figures

FIGURE 7. Schematic drawing of Chaetonotus (Chaetonotus) furculatus. A) Dorsal view. B) Lateral view of head. C) Spined scale of the trunk region. D) Lateral view of posterior end of body.