Neogossea acanthocolla Kisielewski, 1991

Minowa, Axell K. & Garraffoni, André R. S., 2022, New data on Brazilian semiplanktonic gastrotrichs (Gastrotricha: Chaetonotida), Zootaxa 5209 (1), pp. 45-68 : 54-58

Neogossea acanthocolla Kisielewski, 1991

( Fig. 7 . Table 2 )

Measurements based on a mature specimen from the northeast location: Neogossea with elongated body, 102 μm long (caudal spines excluded), 131 μm (spines included) (fig. 7). Cone-shaped head, slightly narrower than the trunk, with a pair of cephalic tentacles projected anterolaterally, 14 μm long, 2 μm thick basally, and 2.6 μm distally (fig. 7A). Terminal mouth ring, 5 μm long and 8 μm wide (fig. 7A). Pharynx is 28 μm long, with two bulbs separated by two weak constrictions, the posterior one much stronger than the other (fig. 7B). Neck weakly constricted. Posterior end truncated and provided laterally with a pair of small projections (fig. 7A).

Cephalic ciliation consists of an anterior tuft inserted laterally adjacent to the mouth ring (fig. 7A, B), followed by two pairs of interrupted transverse lateral bands that extend from ventral side to dorsum, with a median interruption, each cilium is 10 μm long. Each band is provided with four series of cilia (fig. 7B). Trunk ciliation distributed in two paired ventral tufts, anterior one inserted at middle trunk (U60) and posterior one at caudal end (U95), ventrally adjacent to caudal protuberance (fig. 7A).

Cuticular armature with spined scales covering the whole dorsal and ventral trunk, except for the insertion of each ciliary tuft (fig. 7D). A variation in the length and curvature of the spines is visible along the body, with short strongly bended spines on the head portion, and being longer at the middle trunk, with much smoothless curvature and thicker base, followed by shorter thick spines at posterior end. A characteristic “brush” of spines, densely packed on a small area on the dorsal neck, with 15 simple, 15 μm long spines, thicker basally (fig. 7C, E). A ventral medial group of short spines at posterior end between the caudal protuberances (fig. 7A).

Remarks: The morphometry and morphological traits are in accordance with the original description, except for the cuticular armature. Neogossea acanthocolla have been reported in four separated localities: Belém (Pará, Northern Amazon) ( Kisielewski, 1991), Corumbá (Mato Grosso do Sul, West-Central Pantanal wetlands) ( Kisielewski, 1991), Teresina (Piauí, Northeastern Cerrado) (present study), and KwaZulu-Natal ( South Africa, iSimangaliso wetland) ( Todaro et al., 2013). Kisielewski (1991) reported rhomboid pedunculated scales that extend from dorsal head to posterior trunk on specimens from Corumbá. In contrast to this, the armature of specimens from Belém consists of partially pedunculated and spined scales, with the dorsal head covered by pedunculated rhomboid scales, followed posteriorly by simple spined scales with concave posterior end. Todaro et at. (2013) reported two individuals from South Africa, with dorsal body covered by simple spined scales. Even though we only found a single specimen from Teresina, we can notice its similarity with the representatives from South Africa, with simple spined scales. It is therefore possible to recognize two morphological patterns in Neogossea acanthocolla , one with presence of rhomboid pedunculated scale (Corumbá and Belém specimens) and another only with rounded simple spined scales with concave posterior edges (Teresina and South Africa). The unusual brush of densely packed spines seems to have less variability between these four localities, with around 15 to 23 straight, thick, and long spines (Belém form with highest spine number of 23), with length between 12 to 15 μm.

Figures

FIGURE 7. Neogossea acanthocolla differential interference contrast photomicrographs.A–B: dorsal view, C–E: Lateral view, F–G: Dorsal view. ac: anterior constriction; at: anterior cilia tuft; br: neck brush spines; cs: cephalic short spines; db: dorsal cilia band; mv: median ciliary tuft; pb: posterior bulb; ts: trunk scales.