Nereis longdongensis, Hsueh, 2020

Hsueh, Pan-Wen, 2020, New species of Nereis (Annelida, Polychaeta, Nereididae) from Taiwanese waters, Zootaxa 4802 (1), pp. 1-31 : 6-10

Nereis longdongensis n. sp.

Figs 3A–I, 4A–F

Material examined. Holotype ( NMNS 8174-002 ), Longdong (25°06.04´N 121°55.12´E), New Taipei City, Taiwan, rocky shallow subtidal hard bottom, 3 June 1996.

Description. Holotype (NMNS 8174-002), complete, body length 37.0 mm with 72 chaetigers, maximum width 1.8 mm at chaetiger 6, excluding parapodia; beige in alcohol (Fig. 3A). Prostomium wider than long, lateral antennae antero-lateral; palpophores massive, palpostyles conical, four pairs of tentacular cirri, longest one reaching chaetiger 1 (Fig. 3B). Two pairs of eyes, in trapezoidal arrangement, anterior eyes slightly larger than posterior ones. Apodous anterior segment about 1.4 times as long as chaetiger 1. Pharynx with dark brown jaws, each with 6 teeth; I=2, in a longitudinal line; II=25 (left), 16 (right), in 2–3 oblique rows; III=15, in 3 transverse rows; IV=21 (left), 18 (right), in a cluster; V=0; VI=6 (left), 6 (right), in a cluster; VII/VIII=about 261, with 8 large cone in a row anteriorly, numerous minute cones in a broad band posteriorly (Fig. 3C, D).

Notopodial dorsal ligules conical with a rounded tip on anterior chaetigers, narrow triangular with a pointed tip on mid-body to posterior chaetigers (Fig. 3E–H). Notopodial prechaetal lobe absent. Dorsal cirri basally attached to dorsal ligules throughout, about 2.0 times as long as dorsal ligules on anterior and mid-body chaetigers, about 2.0–2.3 times as long as dorsal ligules on posterior chaetigers (Fig. 3E–I). Notopodial ventral ligules conical on anterior chaetigers, narrow triangular with pointed tip on mid-body to posterior chaetigers (Fig. 3E–H). Neuropodial ventral ligules lobe conical on anterior to mid-body chaetigers, narrow triangular with pointed tip on posterior chaetigers; neuropodial postchaetal lobes absent (Fig. 3E–H). Ventral cirri basally attached to ventral edge of parapodia throughout, about as long as ventral ligules throughout (Fig. 3E–H).

Notochaetae present from chaetiger 3 to posterior end, homogomph spinigers present on anterior chaetigers (Fig. 4A), homogomph falcigers present from chaetiger 25 to posterior end, blade bent subdistally, blunt-tipped, base with minute serrations (Fig. 4B). Neurochaetae upper fascicle: homogomph spinigers present (Fig. 4C), heterogomph falcigers with serrated short-blade (Fig. 4D). Neurochaetae ventral fascicle: heterogomph spinigers present (Fig. 4E), heterogomph falcigers with serrated short-blade (Fig. 4F). Pygidium round, one pair of filamentous anal cirri attached ventrally, about as long as last 3 chaetigers (Fig. 3I).

FIG. 3. N ereis longdongensis n. sp. (NMNS 8174-002): A, whole animal; B, anterior body; C–D, paragnaths (arrows point to Areas VI, VII/VIII paragnaths); E, chaetiger 10, left parapodium, posterior view; F, same, left parapodium, anterior view; G, chaetiger 34, left parapodium, posterior view; H, same, left parapodium, anterior view; I, posterior segments of the animal. (Abbreviations: AC, anal cirri; DC, dorsal cirrus; NeVL, neuropodial ventral ligule; NoDL, notopodial dorsal ligule; NoVL, notopodial ventral ligule; VC, ventral cirrus). Scale: A, 2.5 mm; B, 1.0 mm; C, D, 0.5 mm; E–H, 0.25 mm; I, 1.0 mm.

FIG. 4. N ereis longdongensis n. sp. (NMNS 8174-002): A, chaetiger 11, notochaetal homogomph spiniger; B, chaetiger 27, notochaetal homogomph falciger; C, chaetiger 12, neurochaetal upper fascicle, homogomph spiniger; D, same, neurochaetal, upper fascicle, short-bladed heterogomph falciger; E, chaetiger 10, neurochaetal ventral fascicle, heterogomph spiniger; F, same, neurochaetal ventral fascicle, short-bladed heterogomph falciger. Scale: A–C, E, 0.025 mm; D, F, 0.01 mm.

Etymology. The name is derived from the name of location, Longdong, where the worm was collected.

Type locality. Longdong , New Taipei City, Taiwan .

Distribution. Only known from type locality.

Remarks. Of the 36 species reported from East Asia and the present study, five species share a feature of having Areas VII & VIII with 1 row of large teeth anteriorly and 4 or more rows of small teeth posteriorly, and these species are: N. longdongensis n. sp., N. multignatha Imajima & Hartman, 1964 , N. multignatha paraneanthes Khlebovich, 1996 , N. paporae n. sp., and N. wuchiensis n. sp. (see the Key provided in the present study). Of these five species, the morphology of N. longdongensis n. sp. is similar to that of N. multignatha and N. multignatha paraneanthes . Paragnath patterns on the pharynx of N. longdongensis n. sp. are mostly within the range of the latter two species ( Imajima & Hartman 1964: 148; Imajima 1996: 156; Khlebovich 1996: 130; Table 2). Moreover, parapodia of N. longdongensis n. sp. are similar to those of the latter two species, which all have conical dorsal and ventral notopodial ligules on anterior chaetigers and become narrow triangular with a pointed tip on the mid-body to posterior chaetiger ( Imajima 1996: 156, fig, 122d – f; Khlebovich 1996: 130, pl. XXXII, fig.4–6; Fig. 3E–I). All three species have short-bladed neuropodial heterogomph falcigers ( Imajima 1996: 156, fig. 122j; Khlebovich 1996: 130, pl. XXXII, fig.8; Fig. 4D, F, Table 2). However, several morphological differences between N. longdongensis n. sp. and N. multignatha were observed: 1) the length of the longest tentacular cirri of N. longdongensis n. sp. reaching chaetiger 1 (versus reaching chaetiger 5); 2) dorsal cirri on posterior chaetigers of N. longdongensis n. sp. is 2.0–2.3 times longer than dorsal ligules (versus 3.0–5.0 times longer); 3) blades of notopodial homogomph falcigers of N. longdongensis n. sp. are blunt and exposed for about one-fourth their length (versus pointed and exposed for about half their length); and 4) the number of paragnaths on Areas III & IV of N. longdongensis n. sp. are 15 and 18–21 (versus 20 and 33–36), respectively ( Imajima 1996: 156, fig. 122a – f, h; Figs 3B, 3E–H, 4B, Table 2). N ereis longdongensis n. sp. differs from N. multignatha paraneanthes by lacking of paragnaths on Area V (versus 3–7) ( Khlebovich 1996: 130; Table 2).

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TABLE 2. (Continued)