Neanthes sanguensis, 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 : 188-190

Neanthes sanguensis n. sp.

Figs 13A – G, 14A – D, Table 2

Material examined. Holotype ( NMNS 1491-003 ), marine aquaculture pond in the Tainan Fisheries Research Institute (23°07.33´N 120°04.25´E), Tainan City, Taiwan, cement bottom, 18 October 1993.

Description. Holotype, complete, body length 52.0 mm with 82 chaetigers, maximum width 2.5 mm at chaetiger 8, excluding parapodia; light brown in alcohol ( Fig. 13A). 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 4 ( Fig. 13B). Two pairs of black eyes, in trapezoidal arrangement, subequal in size. One apodous anterior segment present, about 1.3 times as long as chaetiger 1. Pharynx with dark brown jaws, each with 7 blunt-tipped lateral teeth; brown conical paragnaths as: I=1; II=12 (left), 15 (right), in 2–3 crescentic rows; III=10, in 2 transverse rows; IV=17 (left), 18 (right), in 3 oblique rows; V=1; VI=2 (left), 2 (right), in a transverse row; VII/VIII=33, in 2 rows ( Fig. 13C).

Notopodial dorsal ligule conical on anterior chaetigers, narrow triangular on posterior chaetigers; basal dorsal edge of dorsal ligule greatly expanded and elongated on posterior chaetigers; basal dorsal edge of dorsal ligule filled with glands on posterior chaetigers ( Fig. 13 D–G). Dorsal cirri attached to dorsal edge 1/3 from base of dorsal ligule, robust, slightly longer than dorsal ligule on anterior chaetigers, shorter than dorsal ligule on posterior chaetigers ( Fig. 13 D–G). Notopodial prechaetal lobe present on chaetiger 3 to chaetiger 43, small oval ( Fig. 13D). Notopodial ventral ligule conical on anterior chaetigers, narrowed triangular with a blunt tip on posterior chaetigers. Neuropodium with prominent inferior and superior lobes on anterior chaetigers, both lobes projecting beyond neuropodial postchaetal lobe on anterior chaetigers, both lobes absent on posterior chaetigers. Neuropodial postchaetal lobe present, conical throughout, shorter than neuropodial acicular ligule on posterior chaetigers. Neuropodial ventral ligule digitiform throughout; ventral cirri mid-ventrally attached to ventral edge of parapodia, robust on anterior chaetigers, slender on posterior chaetigers, slightly shorter than ventral ligule ( Fig. 13 D–G).

Notochaetae present from chaetiger 3 to posterior end, homogomph spinigers ( Fig. 14A). Neurochaetae dorsal fascicle: homogomph spinigers ( Fig. 14B), and heterogomph falcigers with short, serrated terminal blade with serrations ( Fig. 14C). Neurochaetae ventral fascicle: heterogomph falcigers with short, serrated terminal blade ( Fig. 14D). Pygidium round, one pair of filamentous anal cirri attached ventrally, extending about 14 chaetigers.

Etymology. The name is derived from the name of nearby village, Sangu, where the worm was collected.

Type locality. Sangu village , Tainan County, Taiwan .

Distribution. Only known from the type locality.

Remarks. Of the 22 Neanthes species reported from East and Southeast Asia, four are noted with a similar number of conical paragnaths on Area V of the pharynx as in N. sanguensis n. sp.: N. donghaiensis (0 – 3 conical paragnath, from China), N. maculata (0 – 1 conical paragnath, from China), N. manatensis Pillai, 1965 (2 conical paragnath, from Philippines), N. negomboensis De Silva, 1965 (1 conical paragnath, from Indonesia), and N. trifasciata ( Ehlers, 1901) (0 – 1 conical paragnath, from Philippines) ( Ehlers 1901: 107, pl. XII, fig. 3 – 4; Pillai 1965: 137, fig. 10A, C, E; Wu et al. 1981: 132, 134 – 135). Neanthes sanguensis n. sp., however, differs from all of above-mentioned species by having notopodial prechaetal lobes on anterior chaetigers, which are not seen in these species ( Ehlers 1901: 107, pl. XII, fig. 1, 2, 5 – 7; Pillai 1965: 137 – 140, figs 10J, K, 11H, I; Silva 1965: 544–545, fig. 4D, E; Wu et al. 1981: 132 – 134, 136, figs 82A, B, 83A, B; Fig. 13D, Table 2). Moreover, N. sanguensis n. sp. is the only species among the above-mentioned species that has greatly expanded dorsal ligule on posterior chaetigers ( Ehlers 1901: pl. XII, fig. 2; Pillai 1965: 137, fig. 10L; Silva 1965: 544, fig. 4F; Wu et al. 1981: 133, 136, figs 82G, 83E; Fig. 13E, F). Four species reported in the present study have notopodial prechaetal lobes as in N. sanguensis n. sp.. However, N. sanguensis n. sp. can be readily distinguished from these four species by the absence of homogomph spinigers in ventral fascicle of the neuropodia, which are observed in these four species ( Table 2). Of these four species, only N. sp. 1 has short neuropodial heterogomph falcigers as in N. sanguensis n. sp. ( Table 2). However, the morphology of short neuropodial heterogomph falcigers of the former species is very different from that of N. sanguensis n. sp. ( Figs 14C, D, 18E).