Chaetonotus aff. acanthocephalus Valkanov, 1937

Garraffoni, Axell Kou Minowa and André Rinaldo Senna, 2025, Expanding the knowledge of Brazilian Gastrotrich biodiversity: Freshwater Paucitubulatina (Gastrotricha: Chaetonotida) from Northeastern Brazil, Zoologia (e 24025) 42, pp. 1-17 : 5

Chaetonotus aff. acanthocephalus Valkanov, 1937

Fig. 1F

Locality: PT 09, 10 (Fig. 1).

Examined Material: 6 specimens. TL 107–120 Μm; FL 20–22 Μm; AL 17–18 Μm; PhL 30–32 Μm; MD 6–10 Μm; DR 23; TSl 4–5 Μm; TSw 7–8 Μm; TSp 11–16 Μm; DC 5; DSL 19–23 Μm .

Remarks: Small, compact fusiform habitus. Head three-lobed with very small conical shaped cephalion, and large lateral epipleura and hypopleura, hypostomium unseen. Mouth subterminal, cylindrical pharynx with narrow pharyngo-intestinal junction. Cephalic ciliature consists of one sub-oral tuft of tactile cilia and locomotory ciliar tufts are discreet. Head followed by subtle neck constriction with almost the same width, and trunk slightly wider. Posterior end bears a very short V-shaped furca with long thick adhesive tubes, no sensory bristles were seen. The dorsal surface is covered by 5 intercalated columns with several simple spined scales with various shapes and sizes. A set of five long anteriormost keeled scales on the head, with conspicuous spiny process posteriorly adjacent to the cephalion. Followed by several simple spined scales smaller on head and neck than the trunk. Two pairs of dorsolateral scales with longer scales strongly curved posteriorly on the mid-neck. Two pairs of lateral scales with very long and stronger spines on the posterior end of the trunk. Interciliary cuticles were unobservable. The specimens share the general morphology with Chaetonotus acanthocephalus with the presence of the set of anteriormost keeled cephalic dorsal scales, and sparse strong simple-spined scales with various shapes and sizes along the longitudinal axis. However, they differ in the presence of smooth scales on the dorsal head and neck region, and presence of spined scales on ventral pharyngeal region, and longer and thinner spines on the ventrolateral row.

Distribution: Brazil: Delmiro Gouveia (AL; present study).