Lepidodermella forficulata 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 : 471

Lepidodermella forficulata Schwank, 1990

( Fig. 5 )

Type locality. Among Lemna spp. in ponds near Galt Creek, Puslinch district.

Type material. Drawing of one specimen. Lectotype, SMNH Type-8551 deposited at the Swedish Museum of Natural History, Stockholm, Sweden.

Other material. 4 specimens that are no longer extant.

Etymology. Species name derived from the forcipate furca.

Diagnosis. Small tenpin-shaped species, 120–125 µm in total body length. Cephalion present, pleuria absent. Hypostomion present. Furca forcipate, 30 µm in length with thin adhesive tubes that are terminally knobbed. Proximal parts of furcal branches covered by round smooth scales. Dorsal surface covered by 5–7 columns of smooth scales. One pair of parafurcal spines present and reach halfway down the length of the furcal branches. Ventrolateral scales with short simple spine distributed in 2–3 columns on either side of the body. Ventral interciliary area apparently naked or with poorly developed keels. A pair of ventral terminal scales present. Pharynx with slight terminal swellings, 30–32 µm in length.

Description. A small species, 120–125 µm in total body length. Body tenpin-shaped. Head rounded with large cephalion, 12 µm in diameter. Pleuria absent. Hypostomion present and similar to a clasp or a buckle. One pair of cephalic ciliary tufts. Two pairs of dorsal sensory bristles present, anterior pair anchored by papillae at U27 and posterior pair anchored by papillae at U74.

Body width 20–25 µm at the head (U06–07), 18–21 µm at the neck (U22), 25–30 µm at the trunk (U52) and 17–20 µm at the base of the furca (U74). The forcipate furca is 30 µm in length, adhesive tubes curved inwards, thin and terminally knobbed, 20–22 µm in length. The proximal parts of the furcal branches are completely covered by round, smooth scales. One pair of simple parafurcal spines 10–15 µm long, and reach approximately halfway down the forcipate furca. The head is covered by 7 columns of smooth scales (6–7 x 6–7 µm in length and width respectively). The trunk is covered by 5 columns of larger smooth scales, maximum 12 x 9 µm. Scales of neck and trunk region overlap. The scales are posteriorly hollowed out like a spoon ( Fig. 5 C, D), their proximal rim is thickened.

There are 2–3 ventrolateral rows on either side with small, keeled scales that bear short simple spines ( Fig. 5 E). The ventral interciliary area is apparently naked or with only slight developed keels. Ventral plates or scales could not be observed in the pharynx or intestinal region. A pair of ventral terminal scales present.

Mouth subterminal, 4–6 µm in diameter. Pharynx with weak terminal swellings, 30–32 µm in length. PhIJ at U30.

Only parthenogenetic individuals were observed.

Taxonomic remarks. L. forficulata can be separated from most species within the genus based on the forcipate furca, the parafurcal spines, and the ventrolateral short-spined scales. There are only three species within Lepidodermella that possess parafurcal spines, Lepidodermella intermedia Kånneby, Todaro & Jondelius, 2012 , Lepidodermella minor chaetifer Kisielewski, 1991 and Lepidodermella spinifera Tretjakova, 1991 . L. intermedia and L. minor chaetifer also have spined ventrolateral scales, but possess a pharyngeal tooth as well as differently shaped dorsal scales, and have at least the posterior part of the interciliary area covered by scales. L. spinifera possesses a somewhat forcipate furca, but in all other aspects, including shape and distribution of scales, it is very different from L. forficulata .

Figures

FIGURE 5. Schematic drawing of Lepidodermella forficulata. A) Dorsal view. B) Lateral view. C) Dorsal scale. D) Lateral view of dorsal scale. E) Ventrolateral spined scale.