Platynereis antipoda Hartman, 1954

Fig. 14A–G

Platynereis dumerilii antipoda Hartman, 1954: 35–36, figs 33–37; Hartmann-Schröder 1979: 118; Hutchings & Rainer 1979: 757–758; Hartmann-Schröder 1980: 60; Hutchings & Turvey 1982: 141; Wilson 1985: 136–137; Hutchings & Reid 1991: 55–56.

Platynereis antipoda .— Bakken & Wilson 2005: 533–534.

Type locality. Southern Australia .

Material examined. Western Australia: Horrock, 28°23′23.32″S 114°25′48.98″E, 18 November 2020, 1 specimen (WAM V11668). Coronation Beach, 28°33′16.88″S 114°33′48.66″E, 19 November 2020, 1 specimen (WAM V11669). Glenfield Beach, 28°41′01.32″S 114°36′21.65″E, 17 November 2020, 1 specimen (WAM V11670) . Shag Rock Beach, Nambung, 30°35′40.00″S 115°06′11.00″E, 31 December 2020, 2 specimens (WAM V11671) . Yanchep Beach, 31°33′02.36″S 115°37′24.86″E, 14 January 2021, 1 specimen (WAM V11672) . Yanchep Beach, 31°33′02.36″S 115°37′24.86″E, 14 January 2021, female epitoke, 1 specimen (WAM V11673) . Beaumaris Beach, 31°44′23.57″S 115°43′17.82″E, 18 January 2021, 5 specimens (WAM V11674) . Avalon Point, Mandurah, 32°35′40.25″S 115°38′00.16″E, 13 January 2021, 3 specimens (WAM V11675) . Gnarabup, 33°59′33.73″S 114°59′20.16″E, 16 December 2020, 1 specimen (WAM V11676) . Foul Bay Beach, 34°13′56.54″S 115°01′55.97″E, 15 December 2020, 1 specimen (WAM V11677) . Hunters Beach, Green Head, 30° 4′27.54″S 114°58′11.46″E, 29 July 2016, 1 specimen (WAM V11678) . Cape Peron, 32°15′59.14″S 115°41′06.74″E, 26 July 2016, 3 specimens (WAM V11679) . Ellensbrook Beach, 33°54′25.59″S 114°59′16.29″E, 24 July 2016, 1 specimen (WAM V11680) .

Description. Complete specimens with 34–77 chaetigers, body 5.4–26.8 mm long and 0.4–1.8 mm wide; cream yellow in alcohol. Incomplete specimens with 42–53 chaetigers, posterior end missing, remaining body 18.7–32.5 mm long and 2.2–2.3 mm wide; cream yellow in alcohol.

Prostomium as long as wide. Eyes black, two pairs, outer eyes slightly larger than inner ones, in trapezoidal arrangement. Palps one pair, palpophores globose, palpostyles conical. Antennae one pair, slightly shorter than palps. Tentacular cirri four pairs with basal articulation, longest one extending to chaetiger 7–12. Pharyngeal jaws reddish brown, curved at tips, with seven teeth on each jaw. Paragnaths reddish brown, pectinate bars, present on maxillary and oral rings, arranged as follows: Area I= 0, Area II= 0, Area III= 2–3 transverse rows, Area IV= four curved rows, outside ones shorter, Area V= 0, Area VI= two transverse rows, Areas VII–VIII= 5 patches in one row in lateral, two rows in ventral (Fig. 14A–B).

Apodous segment longer than first chaetiger. First two chaetigers uniramous. Notopodia present with subconical dorsal and ventral ligules, dorsal ligules enlarged in posterior chaetigers. Dorsal cirri cirriform, attached on middle of dorsal parapodia, about four times longer than ventral ligules, similar length throughout chaetigers. Neuropodia with subconical ventral ligules, acicular ligules, and triangular postchaetal lobes extending well beyond acicular ligule tips. Ventral cirri cirriform, attached basally on ventral parapodia, slightly shorter than inferior ligules (Fig. 14C).

Notochaetae present with homogomph spinigers in anterior chaetigers, homogomph spinigers (Fig. 14D) and falcigers (Fig. 14E) from chaetiger 21–30 or chaetiger 13 in small specimens. Notopodial falcigerous blades long, curved, with fine serrations and a hooked tip connected to blade. Neurochaetae present with homogomph spinigers and heterogomph falcigers (Fig. 14F) in dorsal fascicles, heterogomph spinigers (Fig. 14G) and falcigers in ventral fascicles. Neuropodial falcigerous blades medium size, slightly curved at tips, with fine serrations and a hooked tip connected to blade. All spinigerous blades long, with fine serrations. Acicula translucent. Pygidium with anus on dorsal side, anal cirri cirriform, as long as last four to six chaetigers.

A complete, female epitokous specimen with 62 chaetigers, body 17.7 mm long and 1.5 mm wide; cream yellow in alcohol. Body divided into 16 pre-natatory chaetigers, 34 natatory chaetigers, and 12 post-natatory chaetigers. Neuropodial postchaetal lobes modified into large, flat lamella in natatory chaetigers. Dorsal and ventral cirri swollen basally, unmodified in natatory chaetigers.

Remarks. The species is considered a full species in this study, following Bakken & Wilson (2005) who found obvious differences between Australian specimens of Platynereis antipoda and northern European specimens of Platynereis dumerilii . They could not justify the subspecies based on this information, and thus P. antipoda is assigned as a valid species.

Pectinate bars on Area IV can also be arranged in 3–4 triangular rows (Hutchings & Turvey 1982). Pre-natatory chaetigers of our female specimens were fewer than those of female P. antipoda from Port Hedland, Western Australia (21) (Hartmann-Schröder 1979), Port Jackson, New South Wales (21) (Hartman 1954), and South Australia (18) (Hutchings & Turvey 1982), suggesting that they are probably sympatric species. Morphological examination of both male and female epitokes of P. antipoda across Australian waters will better establish the limits of species. Read (2007) has described sympatric species of Platynereis from New Zealand based on both epitokous male and female specimens.

Hutchings & Rainer (1979) found that P. antipoda from Careel Bay, New South Wales has dark brown acicula and no notopodial falcigers. Those characteristics look similar to a closely-related species, P. australis (Schmarda, 1861), which has black acicula (Imajima 1972) and lacks notopodial falcigers in adults (Hutchings & Reid 1991).

Distribution. Southern Australia: South-West Australia, South Australia, Victoria (Table 2).

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