Nereis wuchiensis, Hsueh, 2020

Hsueh, Pan-Wen, 2020, New species of Nereis (Annelida, Polychaeta, Nereididae) from Taiwanese waters, Zootaxa 4802 (1), pp. 1-31 : 24-25

Nereis wuchiensis n. sp.

Figs 16A–E, 17A–I

Material examined. Holotype ( NMNS 8174-023 ), Wuchi Port (24°17.61´N 120°31.18´E), Taichung City, Taiwan, subtidal fouling community on cement surfaces of piers, 7 July 2015 . Paratypes: 7 specimens ( NMNS 8174- 024 – 030 ), collection locality, habitat and date information same as holotype ; 3 specimens ( NMNS 8174-031 – 033 ), collection locality, habitat information same as holotype, 20 April 2015 ; 1 specimen ( NMNS 8174-034 ), collection locality, habitat information same as holotype, 7 June 2015 ; 1 specimen ( NMNS 8174-035 ), Shinjei (23˚54.30´N 120˚17.62´E), Changhua County, Taiwan, intertidal soft bottom, 15 January 2009 .

Description. Holotype (NMNS 8174-023), complete, body length 37.5 mm with 74 chaetigers (20.5–23.5 mm with 64 chaetigers, n=3, based on complete specimens), maximum width 2.0 mm at chaetiger 7, excluding parapodia; beige in alcohol (Fig. 16A). Prostomium wider than long, lateral antennae antero-lateral, palpophores globose, palpostyles conical, four pairs of tentacular cirri, longest one reaching chaetiger 2 (2–5, n=9) (Fig. 16B). Two pairs of eyes, in trapezoidal arrangement, subequal in size. Apodous anterior segment about 1.5 (1.3–2.1, n=6) times as long as chaetiger 1. Pharynx with light brown jaws, each with 9 or 10 (6–10, n=10) teeth; I=1 (0–1, n=11, only one individual with zero paragnaths; sample size of Areas II to VII/VIII same as Area I), II=11 (7–16) (left), 11 (9–14) (right), in 2–3 oblique rows; III=7 (9–16), in 1–2 transverse rows; IV=14 (13–20) (left), 14 (12–24) (right), in 2–3 oblique rows; V=0; VI=7 (6–9) (left), 7 (6–10) (right), in 2 transverse rows or a cluster; VII/VIII=182 (110–191), in 4–5 rows (Fig. 16B, C).

Notopodial dorsal ligules narrow triangular (digitiform), acute throughout, gradually shorter and smaller on posterior chaetigers (Fig. 16D, E). Dorsal cirri basally attached to dorsal ligules, slightly longer than dorsal ligules on anterior chaetigers, about 3.0 times as long as dorsal ligules on posterior chaetigers (Fig. 16D, E). Notopodial prechaetal lobes absent. Notopodial ventral ligules narrow triangular (digitiform), acute throughout, gradually shorter and smaller on posterior chaetigers. Neuropodial postchaetal lobes absent. Neuropodial ventral ligule narrow triangular (digitiform) throughout; ventral cirri mid-ventrally attached to ventral edge of parapodia, about as long as ventral ligules throughout (Fig. 16D, E).

FIG. 17. Nereis wuchiensis n. sp.; A, B, F, G, I, holotype (NMNS 8174-023); C, D, paratype (NMNS 8174-024); E, H, paratype (NMNS 8174-031): A, chaetiger 33, notochaetal homogomph spiniger; B, same, notochaetal homogomph falciger; C, chaetiger 36, notochaetal homogomph falciger; D, chaetiger 38, notochaetal homogomph falciger; E, chaetiger 34, notochaetal homogomph falciger; F, chaetiger 12, neurochaetal upper fascicle, homogomph spiniger; G, chaetiger 33, neurochaetal upper fascicle, medium-sized blade heterogomph falciger; H, chaetiger 12, neurochaetal ventral fascicle, heterogomph spiniger; I, chaetiger 33, neurochaetal upper fascicle, medium-sized blade heterogomph falciger. Scale: A, F, H, 0.025mm; B–E, G, I, 0.01 mm.

Notochaetae present from chaetiger 3 to posterior end, homogomph spinigers present on anterior chaetigers (Fig. 17A), homogomph falciger present from chaetiger 21 (19–23, n=12) to posterior segments, blade strongly bent, blunt-tipped, with 2 large teeth and 2 minute teeth (2–4 teeth, n=4) (Fig. 17B–E). Neurochaetae upper fascicle: homogomph spinigers present (Fig. 17F), heterogomph falcigers with serrated medium-sized blade (Fig. 17G). Neurochaetae ventral fascicle: heterogomph spinigers present on anterior chaetigers (Fig. 17H), heterogomph falcigers present throughout, medium-sized blades with serrations (Fig. 17I). Pygidium round, one pair of filamentous anal cirri attached ventrally, as long as last 6 (2–7, n=4) chaetigers (Fig. 16A).

Etymology. The name is derived from the name of Wuchi fishing port where most of the worms were collected.

Type locality. Wuchi fishing port, Taichung City, Taiwan .

Distribution. Only known from the type locality and intertidal flat of Funyen Township, Chunghwa County, Taiwan.

Remarks. As aforementioned, five Nereis species reported from East Asia have Areas VII & VIII with 1 row of large teeth anteriorly and 4 or more rows of small teeth posteriorly. Of these 5 species, morphology of N. paporae n. sp. is similar to that of N. wuchiensis n. sp. Comparisons on similar and different morphological features of the two species has been given in the Remarks section of the former species.

A worth mentioning note is that N. articulata n. sp., N. paporae n. sp., and N. wuchiensis n. sp. reported in the present study were all collected from the fouling community on cement surfaces of piers at Wuchi Port. Of the 16499 individuals of polychaetes collected from seasonal ecological surveys at Wuchi Port in 2015, only twenty-six were belonging to the genus Nereis . Of these Nereis individuals, twenty-four were N. wuchiensis n. sp. (only 15 listed as types in the present study), and N. articulata n. sp., N. paporae n. sp. were only represented by a single specimen. Interestingly, paragnath patterns of these three species are very similar to each other ( Table 2). Morphology of parapodia and notopodial homogomph falcigers of N. articulata n. sp. and N. wuchiensis n. sp. are also quite similar (Figs 1E, F, 2B, C, 16D, E, 17B–E). Nereis articulata n. sp., can only be distinguishing from N. wuchiensis n. sp. by the presence of articulated tentacular cirri and long-bladed neuropodial heterogomph falcigers (Fig. 1C, 2E, G, 16B, C, G, I, Table 2). Nereis articulata n. sp. is more different from N. paporae n. sp. than N. wuchiensis n. sp. by having: 1) articulated tentacular cirri (versus smooth); 2) digitiform notopodial dorsal ligules (versus triangular); 3) notopodial homogomph falcigers with sickle-shaped blade with 2 teeth (versus serrated or smooth blade); and 4) long-bladed neuropodial heterogomph falcigers (Figs 1C, 2B, C, E, G, 7B, 8B, C, E, G, Table 2). The factors contributing to the presence of three new species in such a close vicinity remains unclear.