Pseudonereis trimaculata Horst, 1924

Yousefi, Shetav, Rahimian, Hasan, Nabavi, Seid Mohammad Bagher & Glasby, Christopher, 2011, Nereididae (Annelida: Polychaeta) from intertidal habitats in the Gulf of Oman, Iran, Zootaxa 3013, pp. 48-64 : 61

Pseudonereis trimaculata Horst, 1924

( Figs 2 E, 8A–G)

Nereis (Pseudonereis) trimaculata Horst, 1924: 187 –188, pl. XXXVI, figs 8, 9. Pseudonereis rottnestiana forma costatodentata Hartmann-Schröder, 1979: 119, figs 220–222. Pseudonereis trimaculata . — Bakken, 2007: 166, fig. 13.

Material examined. Iran, Gulf of Oman, Ramin, 6 specimens ( ZUTC Ann. 1104), 1( NTM W23743).

Description. Material examined 50–57 mm long, 97–135 chaetigers, 3.5–3.8mm wide at chaetiger 10 (excluding parapodia), prostomium with entire anterior margin. Colour in alcohol is light brown, with darker brown pigment on dorsal surface of prostomium and anterior segments ( Fig. 2 E). Longest tentacular cirri extending to chaetiger 4–6. Paragnaths on maxillary ring arranged as follows: I = 1 conical paragnath, II = 12–22 p-bar paragnaths in 4 rows arranged in regular comb-like rows, III = 12–45 p-bars in 3 rows arranged in comb-like rows, IV = 65–78 p-bars and smooth bars (near jaws) in 5 rows. Paragnaths on oral ring arranged as follows: V = 1 conical paragnath with sharp tip, VI = 1 large shield-shaped paragnath, VII–VIII = 23–25 large conical paragnaths and two rows of p-bars ( Fig. 8 A, B). In anterior chaetigers, notopodia have two distally rounded, digitiform ligules equal in length to neuropodial ligules ( Fig. 8 C). Dorsal cirrus 2–3 times longer than dorsal ligule, basally attached in anterior chaetigers, terminally attached to dorsal ligule in posterior chaetigers, although vestige of dorsal notopodial lobe still visible ( Fig. 8 E). Mid-body parapodia having intermediate form ( Fig. 8 D). Posterior notopodial ligules larger and longer than anterior ones ( Fig. 8 E). In anterior neuropodia, ventral cirrus is similar in length to ventral ligule ( Fig. 8 C). Ventral neuropodial ligules distally rounded in all parapodia ( Fig. 8 C–D). Notochaetae all homogomph spinigers. Neurochaetae are heterogomph falcigers and homogomph and heterogomph spinigers (throughout body) ( Fig. 8 F, G).

Remarks. Horst (1924) described Pseudonereis trimaculata briefly, and he referred to a black spot on the parapodia that he used to distinguish his new taxon from other described Pseudonereis taxa. These spots are actually parapodial glands that occur on the dorsal edge of parapodia of many nereidids ( Bakken, 2007). Although their colour may be diagnostic at the species level, the present specimens and those of Bakken (2007) lacked the black pigment. Bakken (2007) revised the genus Pseudonereis , and showed that most Pseudonereis species are similar morphologically. The material described in the present study is very similar to P. trimaculata from eastern Indonesia and north-west Australia described by Bakken (2007), but differs in a few pharyngeal and parapodial features. Bakken’s material has 1–3 paragnaths in Area V compared to the present material which has only one paragnath; Bakken’s specimens have 51–69 paragnaths in Area III while the material in present study has 12–45 paragnaths; and the dorsal cirri of the present material, while terminally attached in posterior parapodia, are offset slightly as a result of the presence of vestigial dorsal notopodial lobe. Although these differences may be taxonomically significant, the possibility that they could be size-related needs to be investigated before a new species could be erected (all of the present specimens are larger than Bakken’s specimens). Finally, the paragnaths in Area IV of the present specimens, and those of other Pseudonereis species (CJG pers. obs.), comprise p-bars and nearer to the jaws, smooth parallel bars. Bakken refers to the ones near the jaws as cones, but they are elongate and closer in form to bars. Both in terms of their shape and position, they seem to be homologous to the smooth bars in Area IV of other nereidid genera.

Regional distribution. Rocky shores of Gulf of Oman (Ramin) ( Table 2 ).

World distribution. Geser, Indonesia (type locality); north-west Australia ( Bakken, 2007).

Figures

FIGURE 2. Dorsal views of anterior end of selected nereidid species collected from the intertidal of Gulf of Oman, A, Nereis coutieri, body width about 1 mm; B, Perinereis heterodonta, body width about 2.5 mm; C, Perinereis horsti, pharynx everted, body width about 2 mm; D, Perinereis nuntia, pharynx everted, body width about 3 mm; E, Pseudonereis trimaculata, pharynx everted; body width about 2 mm.

FIGURE 8. Pseudonereis trimaculata, A, anterior end, dorsal view showing everted proboscis; B, ventral view of same; C, anterior parapodium; D, mid-body parapodium; E, posterior parapodium; F, neuropodial heterogomph falciger, anterior parapodium; G, neuropodial homogomph spiniger, posterior body.