Ceratonereis mirabilis Kinberg, 1865

Fig. 2A–G

Ceratonereis mirabilis Kinberg, 1865: 170; Hartman 1948: 71–72; Imajima & Hartman 1964: 141–142; Day 1967: 324, fig. 14.10a–g; Imajima 1972: 64–66, figs 13a–s, 17; Hartmann-Schröder 1979: 113–114, figs 184–187; Hartmann-Schröder 1980: 58; Perkins 1980: 4–11, figs 1–4; Hutchings & Turvey 1982: 98; Hartmann-Schröder 1985: 43, fig. 23; Imajima 2003: 170; Conde-Vela 2021: 305–309, figs 3–4.

Type locality. Brazil.

Material examined. WesternAustralia: Cowrie Creek, Bidyadanga, 18°32′23.82″S 121°46′09.91″E, 4November 2020, 2 specimens (WAM V11616). Cape Bosut, Bidyadanga, 18°42′4.99″S 121°37′34.11″E, 3 November 2020, 2 specimens (WAM V11617). Cape Keraudren, 19°57′52.62″S 119°46′54.44″E, 5 November 2020, 2 specimens (WAM V11618). Cemetery Beach, Port Hedland, 20°18′21.44″S 118°36′40.39″E, 2 November 2020, 1 specimen (WAM V11619). Five Finger Reef, Ningaloo, 23°11′24.36″S 113°46′24.35″E, 19 September 2020, 4 specimens (WAM V11620). Gnaraloo, 23°46′21.83″S 113°32′9.24″E, 22 September 2020, 2 specimens (WAM V11621). Coral Bay, Ningaloo, 23°9′16.27″S 113°46′4.40″E, 26 July 2016, 1 specimen (WAM V11622).

Description. Incomplete specimens with 15–61 chaetigers, posterior end missing, remaining body 3.0– 19.4 mm long and 0.6–1.0 mm wide; cream yellow or reddish brown in alcohol. Dark brown pigment present on prostomium and tentacular segments, thin dark brown bands present on few anterior chaetigers.

Prostomium wider than long, with antero-medial incision. Eyes two pairs, equal size, in trapezoidal arrangement. Palps one pair, palpophores tubular, palpostyles subconical. Antennae one pair, as long as palps. Tentacular cirri four pairs with basal articulation, longest ones extending to chaetiger 8–16. Pharyngeal jaws reddish brown or translucent in small specimens, curved at tips, with nine teeth on each jaw. Paragnaths reddish black, present on maxillary ring only, arranged as follows: Area I= 0, Area II= 6–13 cones in an oblique oval, Area III= 8–14 cones in a circle, Area IV= 12–24 cones in a circle, Area V= 0, Area VI= 0 (1 rounded papilla in some specimens), Areas VII–VIII= 0 (Fig. 2A–B).

Apodous segment as long as first chaetiger. First two chaetigers uniramous. Notopodia present with digitiform dorsal and ventral ligules, dorsal ligules about half as long as ventral ligules in middle chaetigers and much smaller in posterior chaetigers. Dorsal cirri cirriform, attached on middle of dorsal parapodia in anterior chaetigers, nearer to distal edge of dorsal parapodia in posterior chaetigers, about five times longer than ventral ligules, similar length throughout chaetigers. Neuropodia with digitiform ventral ligules, acicular ligules, and triangular postchaetal lobes extending to same level of acicular ligule tips. Ventral cirri cirriform, attached basally on ventral parapodia, slightly longer than ventral ligules, similar length throughout chaetigers (Fig. 2C).

Notochaetae present with homogomph spinigers in anterior chaetigers, sesquigomph falcigers from chaetiger 13–19 (Fig. 2D). Notopodial falcigerous blades long, slightly curved, bidentate (with a small distal tooth), with fine serrations, serrations longer towards tips.Neurochaetae present with heterogomph falcigers (Fig.2E) and homogomph spinigers (Fig. 2F) in dorsal fascicles; falcigerous blades long, slightly curved, bidentate with fine serrations, serrations longer towards tips. Neurochaetae also present with heterogomph spinigers (Fig. 2G) and falcigers (Fig. 2H) in ventral fascicles; falcigerous blades long, slightly curved, unidentate (without a small distal tooth), with fine serrations, serrations longer towards tips. All spinigerous blades long, with fine serrations. Acicula translucent.

Remarks. Our specimens differ from Ceratonereis mirabilis from South Australia, Mozambique, Madagascar, Japan, and Brazil. Ceratonereis mirabilis from South Australia has more elongate conical paragnaths in some specimens, digitiform prechaetal lobes in dorsal neuropodial ligules, and heterogomoph spinigers in the dorsal fascicles of the neuropodia (Hutchings & Turvey 1982). Ceratonereis mirabilis from Mozambique and Madagascar has minutely papillated dorsum in posterior segments (Day 1967). Ceratonereis mirabilis from Japan has unidentate falcigers in noto- and neuropodia of some specimens (Imajima 1972). Ceratonereis mirabilis from Brazil has fewer teeth on each jaw (7) and heterogomph spinigers in the dorsal fascicles of the neuropodia (Conde-Vela 2021).

The degree of variation in C. mirabilis is highly suggestive of a species complex. Assessing specimens using molecular and morphological evidence of atokes and epitokes across the oceans: Indian Ocean (Mozambique, Madagascar, and Western Australia), and Southern Ocean (South Australia), Pacific (Japan), and Atlantic (Brazil) will be required to establish the possible presence of additional species. Ceratonereis species from Western Australia, i.e., Ceratonereis (Ceratonereis) perkinsi Hartmann-Schröder, 1985; Ceratonereis singularis australis HartmannSchröder, 1985; Ceratonereis (Ceratonereis) longiceratophora Hartmann-Schröder, 1985; and Ceratonereis tentaculata Kinberg, 1865, differ from the present material. Ceratonereis perkinsi and C. singularis australis have unidentate falcigers in notopodia, instead of bidentate falcigers for C. mirabilis. Ceratonereis longiceratophora has only bidentate falcigers in ventral fascicles of neuropodia, instead of both unidentate and bidentate falcigers or only unidentate falcigers for C. mirabilis. Ceratonereis tentaculata has longer dorsal notopodial ligules than those of C. mirabilis.

Distribution. Indo-Pacific Ocean: Red Sea, Australia, Japan, Galapagos Islands; and the western Atlantic Ocean: Brazil, Gulf of Mexico (Table 2).

Habitat. Intertidal, subtidal, rocky shores (Table 2).