Manayunkia brasiliensis Banse, 1956

(Figure 12)

Manayunkia brasiliensis Banse 1956: 420–422, fig. 4.

Material examined. Paratypes: Brazil, Canaea between Santos and Curityba, coll. 1954, 5 incomplete specimens (USNM 40710) .

Description (based on the description of Banse (1956) and own observations). Total length of specimens, including radiolar crown, between 1.7 and 2.0 mm, (paratypes without radiolar crown only about 1.2–1.3 mm); width about 0.15 mm (paratypes 0.10–0.14 mm) (Fig. 12A); length of radiolar crown about 0.3 mm (radiolar crown of paratypes about 0.15 mm long); ratio between length of radiolar crown and body length, without radiolar crown, between 0.18 and 0.21 (not determinable in paratypes). Body slender, posteriorly oval or tapered. Radiolar crown with three pairs of radioles and one pair of unbranched vascularized ventral filamentous appendages; dorsal radioles unbranched, median radioles with 3 and ventral radioles with 4 branches (see Figure 4a, b in Banse (1956)); ventral filamentous appendages and branches of the radioles end at about the same height.

Peristomium longer than first chaetiger, with longer anterior and shorter posterior rings; anterior margin of anterior peristomial ring as membranous collar ventrally, indented laterally, narrowly separated mid-dorsally; border between anterior and posterior peristomial rings clearly visible; one pair of black peristomial eyes. First chaetiger distinctly shorter than peristomium and second chaetiger, chaetigers 2–4 successively longer (Fig. 12B), chaetiger 5 slightly shorter than chaetiger 4, chaetigers 6 and 7 significantly longer, chaetiger 8 shorter again; first 5 thoracic chaetigers wider than long, last 3 thoracic chaetigers distinctly longer than wide; borders between thoracic chaetigers clear visible (Fig. 12A, B); abdominal chaetigers short, borders between these chaetigers indistinct; abdomen, including pygidium, in total about as long as chaetiger 8; pygidium about same length as chaetiger 10 (Fig. 12C); pygidial eyes absent.

First chaetiger with about 2–3 short, and 3–5 elongate, narrowly hooded notochaetae, neuropodial uncini absent; notopodia of chaetigers 2–5 superiorly with 4–5 elongate, narrowly hooded chaetae, 120–150 µm long, and inferiorly with 2–3 pseudo-spatulate chaetae, 75–90 µm long; notopodia of chaetigers 6–8 superiorly with 3–4 elongate, narrowly hooded and 2 short, narrowly hooded chaetae; neuropodia of chaetigers 2–8 with 5–7 (sometimes 8) uncini, 40–45 µm long, with main fang and apical with about 4 rows of progressively smaller teeth; abdominal neuropodia with 2–3 elongate chaetae, 120–130 µm long, and 1–2 short narrowly hooded chaetae; abdominal notopodia with about 20 uncini on chaetiger 9, 18 on chaetiger 10, and 15 on chaetiger 11; abdominal uncini, 20–22 µm long, with about 3–4 rows of equal-sized teeth, about 6 teeth per row; dentate region about 4 µm long; manubrium about four times as long as dentate region.

Females with brood chamber on chaetigers 6 and 7, formed by wing-like protrusions of the integument of these chaetigers, boundaries of these chaetigers still visible (Fig. 12A, C).

Fixed specimens usually without colour and translucent, only anterior peristomial ring sometimes slightly pigmented.

Pygidium dorsoventrally flattened, posterior margin oval or tapered (in paratypes) (Fig. 12C).Anterior chaetigers darkly pigmented, blood greenish.

Remarks. We examined five incomplete paratypes, three specimens (one slightly broken) without radiolar crown, one specimen with remnant of a radiolar crown and one anterior end with radiolar crown, from the polychaete collection of the Smithsonian National Museum of Natural History. However, these specimens were not in good condition. They were dark brown in colour (Fig. 12A–C). This indicates that they may have dried out in the past. One incomplete specimen has a radiolar crown, the chaetae of all specimens are mostly broken off. It is not certain whether these relatively small individuals are actually juveniles or whether they have shrunk due to drying out.

We have also made attempts to examine the holotype of this species, which is believed to be in the collection of the Zoological Museum in Kiel, Germany. However, these specimens were not found there.

The presence of a brood chamber in females was not mentioned in the original description. But the wing-like protrusions on chaetigers 6 and 7 were clearly visible in one paratype (see Fig. 12A, C). Due to the relatively poor state of conservation of paratypes, it is not possible to say with certainty whether transitional chaetae or transitional uncini are present in females. They were not mentioned in the original description. However, transitional uncini or transitional chaetae have often been overlooked in other species in the past (see Atkinson et al. 2020 and Bick et al. 2024, for example).

The radiolar crown of juveniles has slightly fewer branches on the middle and ventral radioles. Median radioles have 2 and ventral radioles 3 branches (Banse 1956).

Geographic distribution. Known only from the type locality, south Brazilian coast between Santos and Curitiba.

Biology. Eggs were found in chaetiger 4 in females.

Ecology. Manayunkia brasiliensis lives on mud in coastal mangrove habitat. Hutchings et al. (1981) suggested that this species may be exposed to hyper-marine salinity in the interstitial water at low tide.