Nereis yuedensis Hadiyanto 2023, n. sp.

Nereis yuedensis n. sp.

Fig. 11A–J

Nereis cf. jacksoni Hartmann-Schröder, 1982: 78. Not Kinberg, 1865.

Material examined. Holotype. Western Australia: Dynamite Bay, Green Head, 30°04′15.62″S 114°57′44.93″E, 28 December 2020, 1specimen (WAM V11661). Paratypes: Dynamite Bay, Green Head, 30°04′15.62″S 114°57′44.93″E, 28 December 2020, 9 specimens (WAM V11662). Dynamite Bay, Green Head, 30°04′15.62″S 114°57′44.93″E, 28 December 2020, male epitoke, 1 specimen (WAM V11663).

Description. A holotype specimen incomplete, posterior end missing, with 45 chaetigers, remaining body 9.9 mm long and 0.6 mm wide; cream yellow in alcohol.

Prostomium as long as wide. Eyes black, two pairs, equal sizes, in rectangular arrangement. Palps one pair, palpophores globose, palpostyles conical. Antennae one pair, shorter than palps. Tentacular cirri four pairs with basal articulation, longest one extending to chaetiger 3. Pharyngeal jaws reddish brown, curved at tips, with seven teeth on each jaw. Paragnaths small, translucent to reddish, conical, present on maxillary and oral rings, arranged as follows: Area I= 0, Area II= 1 on left and 2 on right, Area III= 0, Area IV= 3 on left and 6 on right, in one curved row each side, Area V= 0, Area VI= 0, Areas VII–VIII= 10 in one row (Fig. 11A–B).

Apodous segment as long as first chaetiger. First two chaetigers uniramous. Notopodia present with strongly reduced dorsal ligules from first chaetiger and conical ventral ligules. Dorsal cirri digitiform, attached on middle of dorsal parapodia, about twice longer than ventral ligules, similar length throughout chaetigers. Neuropodia with conical ventral ligules, acicular ligules, and triangular postchaetal lobes extending to same level of acicular ligule tips. Ventral cirri cirriform, attached basally on ventral parapodia, as long as ventral ligules, similar length throughout chaetigers (Fig. 11C–E).

Notochaetae present with homogomph falcigers from chaetiger 3, one for each notopodia.Notopodial falcigerous blades short, with terminal and three large lateral teeth in anterior chaetigers (Fig. 11F), two large lateral teeth and two smaller teeth basally in posterior chaetigers (Fig. 11G). Neurochaetae present with heterogomph falcigers and homogomph spinigers (Fig. 11H) in dorsal fascicles, heterogomph spinigers (Fig. 11I) and falcigers (Fig. 11J) in ventral fascicles. Neuropodial falcigerous and spinigerous blades short, with fine serrations. Acicula reddish brown to black.

Variations in paratypes. Complete specimens present with 32–44 chaetigers, body 3.9–6.8 mm long and 0.3–0.4 mm wide; cream yellow in alcohol. Incomplete specimens present with 35–38 chaetigers, posterior end missing, remaining body 4.7–9.3 mm long and 0.4–0.5 mm wide; cream yellow in alcohol. An incomplete, male epitokous specimen present with 51 chaetigers, anal cirri missing, body 10.2 mm long and 0.6 mm wide; cream yellow in alcohol.

Longest tentacular cirri extending to chaetiger 1–3. Area VI present with 2–3 cones, Areas VII–VIII present with 8–10 cones in one row, other Areas difficult to see. Notopodial falcigerous blades short, with terminal and two large lateral teeth and one smaller tooth basally. Pygidium present with anus on dorsal side, anal cirri cirriform, as long as last three chaetigers.

A male epitokous specimen present with black, enlarged, overlapping paired eyes. Body divided into 11 prenatatory chaetigers, 23 natatory chaetigers, and 17 post-natatory chaetigers. Parapodia elongated, neuropodial postchaetal lobes modified into large, flat lamella in natatory chaetigers. Dorsal cirri swollen basally with elongated lateral papillae in first seven pre-natatory chaetigers, slender and longer with shorter and more papillae in natatory chaetigers, unmodified in post-natatory chaetigers. Ventral cirri swollen basally with lateral papillae in first four pre-natatory chaetigers, slender and longer in natatory chaetigers, unmodified in post-natatory chaetigers. Paddleshaped notochaetae present in natatory chaetigers.

Remarks. The number and arrangement of paragnaths were evaluated based on the holotype and two paratype specimens (including an epitokous specimen). Other paratype specimens had retracted pharynx and were too small to dissect ventrally. Nevertheless, important taxonomic characters, including parapodia and chaetae, were consistent with those of the holotype and paratype specimens with everted pharynx.

Nereis yuedensis n. sp. resembles those Nereis species having one row of paragnaths on Areas VII–VIII and notopodial homogomph falcigers with at least one large lateral tooth, including N. bifida Hutchings & Turvey, 1982; N. denhamensis Augener, 1913; N. falcaria (Willey, 1905); N. heirissonensis Augener, 1913; N. panamensis Fauchald, 1977; N. spinigera Hutchings & Turvey, 1982; N. taitungensis Hsueh, 2020; N. taiwanensis Hsueh, 2020; and N. usticensis Cantone, Catalono & Badalamenti, 2003. However, notopodial homogomph falcigers of the latter species often begin after chaetiger 10 or from median chaetigers. Nereis yuedensis n. sp. also differs in the distinct arrangement of lateral teeth of the notopodial falcigers, the absence of notopodial dorsal ligules, and the arrangement of paragnaths (Table 3).

Nereis yuedensis n. sp. differs from N. cockburnensis. The first notopodial homogomph falcigers of both species appear at chaetiger 3, but those of the latter species are present with serrated lateral teeth and the remaining falcigers are present with a long terminal tooth and much smaller teeth basally. In addition, N. cockburnensis has more paragnaths on both maxillary and oral rings and well-developed dorsal notopodial ligules throughout chaetigers.

Hartmann-Schröder (1982) assigned a nereidid specimen having notopodial homogomph falcigers at least from chaetiger 5 with 3–4 teeth from Jurien Bay (about 25 km from the type locality of N. yuedensis n. sp.) to Nereis cf. jacksoni, yet the arrangement of paragnaths of the specimen was not described. The characteristics of notopodial homogomph falcigers of that specimen is similar to those of N. yuedensis n. sp, and thus they are probably same species.

Etymology. The species is named in honour of the Aboriginal people of the Dynamite Bay area, the Yued (Yued is also the name of the region and dialect group), who are part of the broader group of Noongar Aboriginal Australians who have lived in the southwest corner of Western Australia for approximately 40,000 years. The Yued name for the bay is Cuencandjaa, meaning ‘mouthful of sand’.

Distribution. Dynamite Bay, Green Head, Western Australia. Although records are limited, at this stage the new species is possibly endemic to temperate Australia realm (Table 2).

Habitat. Rocky shores, intertidal (Table 2).