Neanthes donggungensis, Hsueh, 2019

Hsueh, Pan-Wen, 2019, Neanthes (Annelida: Nereididae) from Taiwanese waters, with description of seven new species and one new species record, Zootaxa 4554 (1), pp. 173-198 : 177-179

Neanthes donggungensis n. sp.

Figs 3A – G , 4A – E , Table 2

Material examined. Holotype ( NMNS 7946-014 ), offshore from Donggung Port (22°27.99´N 120°26.54´E), Pingtung County, Taiwan, muddy bottom, 200 – 240 m deep, 22 February 2006 . Paratype: 1 specimen ( NMNS 7946-015 ), location and habitat information same as holotype, 250 m deep, 26 April 2001 .

Description. Holotype, complete, ovigerous female, body length 72.0 mm (74.0) with 98 (96) chaetigers, maximum width 6.0 mm (8.0) at chaetiger 17, excluding parapodia; beige in alcohol ( Fig. 3A ). Prostomium wider than long, one pair antennae arise antero-laterally, palpophores spherical and biarticulate with sub-conical palpostyles, four pairs of tentacular cirri, longest posterior tentacular cirri reaching chaetiger 6 (7) ( Fig. 3B ). Two pairs of eyes, in trapezoidal arrangement, subequal in size. One apodous anterior segment present, about 1.4 times as long as chaetiger 1. Pharynx with brown jaws, each with 7–8 (8–9) blunt-tipped lateral teeth; brown conical paragnaths as: I=2 (2), in longitudinal line, anterior cone smaller; II=9 (8) (left), 11 (10) (right), in 2 oblique rows; III=12 (15), in 2–3 transverse rows; IV=15 (17) (left), 17 (right), in 2–3 oblique rows; V=0; VI=10 (7) (left), 13 (7) (right), in a cluster, VII/VIII=91 (76), with 8 (9) large cones in 1 row anteriorly, 83 (67) small and medium cones in 2–3 rows posteriorly ( Fig. 3C ). Paragnaths mostly delicate, not strongly chitinized.

Notopodial dorsal ligule triangular with a pointed tip on anterior chaetigers, wide triangular with a pointed tip on posterior chaetigers; dorsal ligule with base dorsal edge greatly expanded on posterior chaetigers ( Fig. 3 D–G). Dorsal cirri mid-dorsally attached to dorsal notopodial ligule, longer than dorsal ligule throughout ( Fig. 3 D–G). Notopodial prechaetal lobe present on chaetiger 3 to mid-body chaetigers, small triangular flap on anterior chaetigers, less developed on latter chaetigers ( Fig. 3D ). Notopodial ventral ligule narrowed triangular with a pointed tip throughout. Neuropodium with prominent inferior lobe throughout, blunt-tipped. Neuropodial superior lobe present, inconspicuous on anterior chaetigers, slightly shorter than inferior lobe on posterior chaetigers. Neuropodial postchaetal lobe present throughout, triangular with a pointed tip. Neuropodial ventral ligule digitiform throughout; ventral cirri mid-ventrally attached to ventral edge of parapodia, shorter than ventral ligule throughout ( Fig. 3 D–G).

Notochaetae present from chaetiger 3 to posterior end, homogomph spinigers ( Fig. 4A ). Neurochaetae dorsal fascicle: homogomph spinigers ( Fig. 4B ), and heterogomph falcigers with medium-length, serrated terminal blade ( Fig. 4C ). Neurochaetae ventral fascicle: heterogomph spinigers ( Fig. 4D ), and heterogomph falcigers with medium-length, serrated terminal blade ( Fig. 4E ). Pygidium round, one pair of filamentous anal cirri attached ventrally, extending about 9 chaetigers.

Etymology. The name is derived from the name of nearby township, Donggung, where the worm was collected.

Type locality. Offshore from Donggung Port, Pingtung County, Taiwan .

Distribution. Only known from the type locality.

Remarks. The most noticeable morphological characters of N. donggungensis n. sp. are the numerous conical paragnaths (76–91) on Area VII/VIII of the pharynx ( Table 2) and the greatly expanded dorsal ligule on posterior chaetigers ( Fig. 3E, F ). Of the 22 Neanthes species reported from East and Southeastern Asia, three also have numerous conical paragnaths on Area VII/VIII of the pharynx: N. acuminata ( Ehlers, 1868) (type locality in Italy, reported from China, Japan & Philippines) (= N. caudata (Delle Chiaje, 1828) , from Japan), N. crucifera ( Grube, 1878) (from Philippines), and N. verrillii ( Grube, 1878) (from Philippines) ( Ehlers 1868: 552, pl. XXII fig 24; Grube 1878: 79, 81, pl. V, figs 2, 2 a, 6; Imajima 1972: 105–107, fig. 31b–e; Sun & Young 2004). However, N. acuminata has a greater number of conical paragnaths on Area I of the pharynx than that of N. donggungensis n. sp. (10 versus 3) ( Ehlers 1868: 552; Table 2). Conical paragnaths on Areas V-VIII of N. acuminata formed a continuous broad band, which is not observed in N. donggungensis n. sp. ( Ehlers 1868: 552; Fig. 3C ) Neanthes crucifera and N. verrillii have similar numbers of conical paragnaths on Area I as in N. donggungensis n. sp., but both have several conical paragnaths on Area V (6 & 8–9, respectively) in comparison to none in N. donggungensis sp. nov. ( Grube 1878: 78, 81, pl. V, figs 2, 5; Table 2). Of the nine species reported in the present study, only N. donggungensis n. sp., N. kaomeiensis n. sp. and N. cf. nanhaiensis have no paragnaths on Area V of the pharynx ( Table 2). Neanthes donggungensis n. sp., however, can be distinguished from N. kaomeiensis n. sp. by the absence of neuropodial sesquigomph spinigers and falcigers and by the absence of short heterogomph falcigers in the neuropodia ( Table 2). Unlike N. cf. nanhaiensis , which have zero to one conical paragnath on Areas I, VI & VII/ VIII, the number of conical paragnaths on that of N. donggungensis n. sp. are 3–7, 2–4 & 51–66, respectively ( Table 2). Moreover, N. cf. nanhaiensis has both medium-length and long heterogomph falcigers in neuropodia, whereas N. donggungensis n. sp. has only medium-length heterogomph falcigers in neuropodia ( Figs 4C, E ; 12C – F ; Table 2).

Figures

FIGURE 3. Neanthes donggungensis n. sp.; A–C, holotype (NMNS 7946-014), D–G paratype (NMNS 7946-015): A, whole animal; B, anterior body; C, paragnaths of the pharynx; D, right parapodium, anterior view, chaetiger 10; E, right parapodium, posterior view, chaetiger 10; F, right parapodium, anterior view, chaetiger 74; G, right parapodium, posterior view, chaetiger 74. The Roman numeral represents the pharyngeal area VI. Abbreviation: NoPL, notopodial prechaetal lobe. Scale: A, 10.0 mm; B, 1.0 mm; C–G, 0.5 mm.

FIGURE 4. Neanthes donggungensis n. sp.; paratype (NMNS 7946-015): A, notochaeta, homogomph spiniger, chaetiger 150; B, neurochaeta of dorsal fascicle, homogomph spiniger, chaetiger 74; C, neurochaeta of dorsal fascicle, medium heterogomph falciger, chaetiger 74; D, neurochaeta of ventral fascicle, heterogomph spiniger, chaetiger 74; E, neurochaeta of ventral fascicle, medium heterogomph falciger, chaetiger 74. Scale: A–E, 0.05 mm.

FIGURE 12. Neanthes cf. nanhaiensis Wu, Sun & Yang, 1981 (NMNS 7946-029): A, notochaeta, homogomph spiniger, chaetiger 32; B, neurochaeta of dorsal fascicle, homogomph spiniger, chaetiger 32; C, neurochaeta of dorsal fascicle, medium heterogomph falciger, chaetiger 32; D, neurochaeta of ventral fascicle, homogomph spiniger, chaetiger 32; E, neurochaeta of ventral fascicle, medium heterogomph falciger, chaetiger 32; F, neurochaeta of ventral fascicle, long heterogomph falciger, chaetiger 32. Scale: A–B, D, 0.05 mm; C, E–F, 0.01 mm.