Nereis nuwalianensis, Hsueh, 2020

Hsueh, Pan-Wen, 2020, New species of Nereis (Annelida, Polychaeta, Nereididae) from Taiwanese waters, Zootaxa 4802 (1), pp. 1-31 : 11-13

Nereis nuwalianensis n. sp.

Figs 5A–D, 6A–F

Material examined. Holotype ( NMNS 8174-003 ), Jihuei (23°06.86´N 121°24.17´E), Taitung County, Taiwan, intertidal unvegetated hard bottom, 27 September 2014.

FIG. 5. Nereis nuwalianensis n. sp.; holotype ( NMNS 8174-003): A, anterior body; B, paragnaths (arrow points to Area V paragnath); C, chaetiger 11, right parapodium, anterior view; D, chaetiger 49, right parapodium, anterior view. (Abbreviations: DC, dorsal cirrus; NeVL, neuropodial ventral ligule; NoDL, notopodial dorsal ligule; NoVL, notopodial ventral ligule; VC, ventral cirrus). Scale: A, B, 1.0 mm; C, D, 0.25 mm.

Description. Holotype (NMNS 8174-003), incomplete, ovigerous female, posterior end missing, remaining body length 26.5 mm with 55 chaetigers, maximum width 2.0 mm at chaetiger 10, excluding parapodia; beige in alcohol (Fig. 5A). Prostomium wider than long, lateral antennae antero-lateral; palpophores globose, palpostyles conical, four pairs of tentacular cirri, surface smooth, longest one reaching chaetiger 2 (Fig. 5A). Two pairs of eyes, in trapezoidal arrangement, anterior pair larger than posterior pair. Apodous anterior segment about 1.3 times as long as chaetiger 1. Pharynx with dark brown jaws, each with 4 teeth; I=1; II=21 (left), 17 (right), in 4 transverse rows; III=30, in 5 transverse rows; IV=39 (left), 38 (right), in 4 irregular rows; V=1; VI=4 (left), 5 (right), in 1 transverse row; VII/VIII=26, in 2 rows (Fig. 5B).

Notopodial dorsal ligules conical with a rounded tip on anterior chaetigers, becoming small triangular, acute, base slightly elongated, dorsally slightly expanded, along posterior chaetigers (Fig. 5C, D). Dorsal cirri basally attached to dorsal ligules, acute, about 4.0 times as long as dorsal ligules on anterior and posterior chaetigers. Notopodial prechaetal lobe absent. Notopodial ventral ligules conical with a rounded tip on anterior chaetigers, conical and slightly longer on posterior chaetigers (Fig. 5C, D). Neuropodial postchaetal lobe absent. Neuropodial ventral ligules conical on anterior chaetigers, conical and slightly longer on posterior chaetigers; ventral cirri mid-ventrally attached to ventral edge of parapodia, acute, about as long as ventral ligules (Fig. 5C, D).

Notochaetae present from chaetiger 3 to posterior segments, homogomph spinigers present only on a few anterior chaetigers (Fig. 6A), homogomph falcigers present from chaetiger 5 to posterior segments, blade rod-like, blunt-tipped, margin with many teeth (11 or 20) (Fig. 6B, C). Neurochaetae upper fascicle: homogomph spinigers present (Fig. 6D), heterogomph falcigers with serrated short-blade (Fig. 6E). Neurochaetae ventral fascicle: heterogomph spinigers absent, heterogomph falcigers with serrated short-blade (Fig. 6F).

FIG. 6. Nereis nuwalianensis n. sp.; holotype (NMNS 8174-003): A, chaetiger 6, notochaetal homogomph spiniger; B, same, notochaetal homogomph falciger; C, chaetiger 11, notochaetal homogomph falciger; D, chaetiger 6, neurochaetal upper fascicle, homogomph spiniger; E, same, neurochaetal upper fascicle, short-bladed heterogomph falciger; F, chaetiger 11, neurochaetal ventral fascicle, short-bladed heterogomph falciger. Scale: A, D, 0.025 mm; B, C, E, F, 0.01 mm.

Etymology. The name is derived from “Nuwalian”, the local Amis aboriginal language for the location of the sampling site, meaning “the most eastern point”.

Type locality. Jihuei , Taitung County, Taiwan .

Distribution. Only known from the type locality.

Remarks. Of the 36 species reported from East Asia and the present study, only N. guangdongensis Wu, Sun & Yang, 1981 and N. neoneanthes Hartman, 1948 have Area III with 20+ paragnaths and Area V with at least 1 paragnath as in N. nuwalianensis n. sp. However, N. nuwalianensis n. sp. differs from N. guangdongensis by having: 1) less paragnaths on Areas I and VII & VIII (1 and 26 versus 3–6, 150+, respectively) and more paragnaths on Areas III & IV (30 and 38–39 versus 20–25 and 18–26, respectively); 2) longest tentacular cirri reaching chaetiger 2 (versus chaetiger 5); 3) dorsal cirri 4.0 times as long as dorsal ligules on anterior to posterior chaetigers (versus 2.0 times), 4) blade of notopodial homogomph falcigers rod-like with more than 10 small teeth (versus sickle-shaped with 2 teeth); and 5) short-bladed neuropodial heterogomph falcigers (versus short and medium-sized blade) ( Wu et al. 1981: 111–113, fig. 69A–F, H, G; Figs 5C, D, 6B, C, E, F, Table 2). Nereis nuwalianensis n. sp. can readily distinguished from N. neoneanthes by the number of paragnaths on Area V. Nereis nuwalianensis n. sp. has only 1 paragnath on Area V, whereas the latter species have 2–18 (depending on body size), ( Hartman 1948: 27; Imajima 1972: 133; Wu et al. 1981: 91, fig. 62B; Sun & Yang 2004: 135–136, fig. 72B; Fig. 6B, C, Table 2). Moreover, N. nuwalianensis n. sp. has straight rod-like blade with more than 10 teeth on notopodial homogomph falcigers, but the latter species have sickle-shaped blades with serrations at base on notopodial homogomph falcigers ( Hartman 1948: 27, fig. 7C; Imajima 1972: 133, fig. 44h; Wu et al. 1981: 91, fig. 52I; Sun & Yang 2004: 135, fig. 72J; Fig. 4B).

FIG. 7. Nereis paporae n. sp.; holotype (NMNS 8174-004): A, whole animal; B, anterior body; C, paragnaths of the maxillary ring (arrows point to Areas VI paragnaths); D, right parapodium, anterior view, chaetiger 10; E, left parapodium, posterior view, chaetiger 45. (Abbreviations: DC, dorsal cirrus; NeVL, neuropodial ventral ligule; NoDL, notopodial dorsal ligule; NoVL, notopodial ventral ligule; VC, ventral cirrus). Scale: A, 2.5 mm; B, 0.5 mm; C–E, 0.25 mm.