Haltidytes pseudosquamosus Minowa & Garraffoni, 2017

Minowa, Axell K. & Garraffoni, André R. S., 2022, New data on Brazilian semiplanktonic gastrotrichs (Gastrotricha: Chaetonotida), Zootaxa 5209 (1), pp. 45-68 : 54

Haltidytes pseudosquamosus Minowa & Garraffoni, 2017

(figs. 5–6)

Haltidytes with 93–109 μm body length, 117–199 μm (spines included) (figs. 5, 6). Four groups of long and strongly curved spines along the trunk (ta–td) (fig. 5B), with blade-like structure and ventral insertion ending in a pointed apex (figs. 5B, E, 6A, C, E), but only the posteriormost saltatorial group (td) is barbed (fig. 5E). Four pairs of spines are inserted dorso-laterally (ta1–3, tb1), and five pairs are ventrolateral (tb1, tb2, tc2 and td) (fig. 5B). Saltatorial spines (td) intersect with each other posteriorly to spines tb2 and tc2 (figs. 5A, B, E, 6A) (fig. 5B). The dorsal posterior portion of the trunk is covered by smooth scales with different sizes, and without overlapping.

Cephalic ciliature consists of lateral tuft adjacent to the mouth (U6), mediolateral tuft (U13), and posterior pair of conspicuous lateral transverse bands (U21) (fig. 6B, D). A pair of dorsal sensory bristles inserted on the posterior neck (U47) (fig. 6C).

Remarks: Specimens found in the new locality show practically all morphological traits reported in the original description ( Minowa & Garraffoni, 2017). A characteristic not reported in the description of Minowa & Garraffoni (2017) is the presence of paired sets of filaments in the trunk, parallel to the midgut, which we interpret as protonephridia (fig. 5C, D: nf). The present specimen of H. pseudosquamosus has a pair of elongated and laterally compressed structures lateral to the intestine, rather dorsally disposed. Each “protonephridium” extends for a large portion of the body (U53 to U77), with meandering loops (fig. 5C, D), covering 12 µm maximum width (fortunately the animal’s body was not compressed by coverslip, as frequently occurs in soft-bodied invertebrates). It is important to note that we could not perform ultrastructure studies, such as transmission electron microscopy, because the organism was lost during the light microscopy study; so we inferred protonephridium and canal cells according to comparisons of other studies with light photomicrographs of these structures supported by TEM analyses (e.g. Kieneke & Hochberg 2010).