Pseudonereis jihueiensis, Hsueh, 2021

Hsueh, Pan-Wen, 2021, New species and record of Pseudonereis (Annelida, Polychaeta, Nereididae) from Taiwan, Zootaxa 4996 (3), pp. 492-512 : 493-498

publication ID	https://doi.org/ 10.11646/zootaxa.4996.3.4
publication LSID	lsid:zoobank.org:pub:50282C10-075C-4B2C-B61C-3A772D5BC2F2
persistent identifier	https://treatment.plazi.org/id/0193F211-8CE5-4852-AC05-1021AD667273
taxon LSID	lsid:zoobank.org:act:0193F211-8CE5-4852-AC05-1021AD667273
treatment provided by	Plazi
scientific name	Pseudonereis jihueiensis
status	sp. nov.

Treatment

Pseudonereis jihueiensis View in CoL n. sp.

Figs 1A–F View FIGURE 1 , 2A–F View FIGURE 2 , 3A–D View FIGURE 3 , 4A–H View FIGURE 4

Material examined. Holotype ( NMNS 8383-1 View Materials ), atoke: Jihuei (23°6.97'N 121°24.31'E), Taitung County, Taiwan, rocky intertidal habitats, 9 October 2010 GoogleMaps . Paratypes: 5 specimens ( NMNS 8383-2 View Materials – 6 View Materials ), collection locality, habitat and date information same as holotype ; 2 specimens ( NMNS 8383-7 View Materials – 8 View Materials ), collection locality and habitat information same as holotype, 27 March 2014 ; 2 specimens ( NMNS 8383-9 View Materials – 10 View Materials ), collection locality and habitat information same as holotype, 28 March 2014 ; 5 specimens ( NMNS 8383-11 View Materials – 15 View Materials ), collection locality and habitat information same as holotype, 27 September 2014 ; 1 specimen ( NMNS 8383-16 View Materials ), collection locality and habitat information same as holotype, 29 April 2017 . Epitoke: 7 specimens ( NMNS 8383-17 View Materials – 23 View Materials ), collection locality and habitat information same as holotype, 8–9 October 2010 ; 1 specimen ( NMNS 8383-24 View Materials ), collection locality and habitat informa- tion same as holotype, 27 September 2014 .

Description. Atoke: Based on Holotype (NMNS 8383-1), complete, body length 58.0 mm with 88 chaetigers, chaetiger 10 width 3.0 mm, excluding parapodia, pharynx not everted and dissected for paragnath counts; paratype (NMNS 8383-16) for describing body colour in fresh specimen; paratype (NMNS 8383-5) jaws removed for tak- ing close-up image; paratypes (NMNS 8383-11, 13) pharynx everted and used for taking close-up images to show paragnath and chaetal patterns.

Body colour beige in alcohol; dorsal surface of antennae brownish, palpostyles and tentacular cirri bright yel- lowish, dorsal surface of prostomium and peristomium dark green with yellow-greenish horizontal line on junction of all segments in fresh specimen ( Fig. 1A–B View FIGURE 1 ).

Prostomium wider than long, lateral antennae antero-lateral, longer than palps; palpophores globose, palpo- styles conical. Two pairs of eyes, in trapezoidal arrangement, subequal in size. Apodous anterior segment about 1.3 times longer than chaetiger 1; four pairs of tentacular cirri, longest one reaching chaetiger 5 ( Fig. 1B View FIGURE 1 ). Pharynx with dark brown jaws, each lacking lateral teeth ( Fig. 1D–E View FIGURE 1 ); paragnath pattern: I= 2, in longitudinal row; II= 41 (left), 42 (right), in 5 comb-like rows; III= 91, in 5 comb-like rows; IV= 97 (left), 87 (right), in 7 comb-like rows with addi- tional cones and p-bars in sigmoid towards the jaws; V= 1; VI= 1 (left), 1 (right), shield-shaped bars; VII–VIII= 20 p-bars and cones in two rows, p-bar row slightly behind cone row, one paragnath on each furrow and ridge regions ( Fig. 1E–F View FIGURE 1 ). Ridge pattern of areas VI–V–VI, χ-shaped ( Fig. 1E View FIGURE 1 ).

Dorsal cirri digitiform throughout, basally attached to dorsal ligule on anterior chaetigers, about subeqaul to dorsal ligule ( Fig. 2A–B View FIGURE 2 ), subdistally attached to dorsal ligule on mid-body to anterior half of posterior chaetigers, about 1.3 times longer than dorsal ligule on anterior half of mid-body ( Fig. 2C View FIGURE 2 ), about subequal to dorsal ligule on posterior half of mid-body chaetigers ( Fig. 2D View FIGURE 2 ), distally attached to dorsal ligule on last 31 chaetigers, about 0.6 times as long as dorsal ligule ( Fig. 2E–F View FIGURE 2 ).

Dorsal ligule subconical with blunt tips on anterior chaetigers, subconical on rear half of anterior to mid-body chaetigers, becoming small pennant-like lobe on posterior half of mid-body chaetigers ( Fig. 2A–D View FIGURE 2 ); base of dorsal ligule slightly elongate and broader on mid-body chaetigers ( Fig. 2D View FIGURE 2 ), markedly elongate and broader on posterior chaetigers ( Fig. 2E–F View FIGURE 2 ). Notopodial prechaetal lobe absent.

Median ligule conical on anterior to anterior half of posterior chaetigers, slightly elongate on posterior half of posterior chaetigers ( Fig. 2A–F View FIGURE 2 ).

Neuroacicular ligule with predominant inferior lobe on anterior to mid-body chaetigers, inferior and superior lobes about subequal in length on posterior chaetigers, about 1.25 times longer than ventral ligule on anterior to mid-body chaetigers ( Fig. 2A–D View FIGURE 2 ), about as long as ventral ligule on posterior chaetigers ( Fig. 2E–F View FIGURE 2 ). Neuropodial postchaetal lobe round-tipped present throughout ( Fig. 2B View FIGURE 2 ). Ventral ligule subconical throughout. Ventral cirri ba- sally attached to ventral ligule, about as long as ventral ligule throughout ( Fig. 2A–F View FIGURE 2 ).

Notochaetae present from chaetiger 3 to posterior chaetigers, homogomph spinigers present throughout ( Fig. 3A View FIGURE 3 ). Supra-acicular fascicle of neuropodia: homogomph spinigers and short-bladed heterogomph falcigers with serrations present throughout ( Fig. 3B–C View FIGURE 3 ). Subacicular fascicle of neuropodia: short-bladed heterogomph falcigers with serrations present throughout ( Fig. 3D View FIGURE 3 ).

Pygidium crenulated; anal cirri cirriform, as long as last 7 chaetigers.

Variation. Length ratio of apodous anterior segment to chaetiger 1 ranged from 1.1–1.7 (n= 15); longest ten- tacular cirrus reached chaetiger 3–5 (n= 13). Paragnath numbers in Area II ranged 20–39 (left) and 21–38 (right) in 4–5 rows (n= 14), Area III 49–90 in 4–6 rows (n=14), Area IV 62–112 (left) and 61–106 (right) in 5–6 rows (n= 14), Area VII–VIII 17–22 (n=15), respectively. Length of anal cirri ranged from as long as last 4 to 7 chaetigers (n= 5).

Epitoke: Description based on specimen NMNS 8383-18, male, complete, body length 63.5 mm with 106 chaetigers; beige in alcohol ( Fig. 1C View FIGURE 1 ). Body divided into two regions: 1) pre-natatory region from chaetiger 1 to 11; 2) natatory region from chaetiger 12 to end of body.

Prostomium and apodous segment similar to atoke except enlarged eyes ( Fig. 1C View FIGURE 1 ). Jaws similar to atoke. Paragnath patterns: I=5, in triangular arrangement; II=24 (left), 29 (right), in 5 comb-like rows; III=51, in 5 comb-like rows; IV=60 (left), 50 (right), in 5 comb-like rows with additional cones and p-bars in sigmoid towards the jaws; V=1; VI=1 (left), 1 (right), shield-shaped bars; VII–VIII=20, p-bars and cones interspaced, p-bar row slightly be- hind cone row, one paragnath on each furrow and ridge regions. Ridge pattern of areas VI–V–VI, χ-shaped.

Pre-natatory region: Dorsal cirri digitiform, basally attached to dorsal ligule, about as long as dorsal ligule ( Fig. 4A View FIGURE 4 ). Dorsal ligule subconical. Notopodial prechaetal lobe absent. Median ligule conical, about as long as neuroacicular ligule. Neuroacicular ligule with predominant inferior lobe, inferior and superior lobes subequal in length on posterior chaetigers, about as long as ventral ligule. Neuropodial postchaetal lobe present. Ventral ligule subconi- cal. Ventral cirri basally attached to ventral ligule, about as long as ventral ligule ( Fig. 4A View FIGURE 4 ).

Natatory region: Dorsal cirri digitiform, basally attached to dorsal ligule, about as long as dorsal ligule on anterior to mid-body chaetigers, subdistally attached to dorsal ligule on anterior half of posterior chaetigers, about 0.5 times as long as dorsal ligule ( Fig. 4B–H View FIGURE 4 ), distally attached to dorsal ligule on last 14 chaetigers, about 0.5 times as long as dorsal ligule ( Fig. 4B–H View FIGURE 4 ); kidney-shaped dorsal cirrus lamella present from chaetiger 12 to 80, progressively enlarged in size to mid-body chaetigers, reduced progressively in size thereafter ( Fig. 4C–H View FIGURE 4 ).

Dorsal ligule subconical with blunt tips on anterior half of anterior chaetigers, subconical with pointed tips on mid-body chaetigers, becoming small pennant-like lobe on posterior chaetigers ( Fig. 4B–H View FIGURE 4 ). Notopodial prechaetal lobe absent.

Median ligule subconical on anterior chaetigers, modified to triangle oar-like structure with narrow bridge connected to parapodium on mid-body to posterior chaetigers (see Fig. 4F View FIGURE 4 for better viewing), lamellae present on ventral edge of median ligule from mid-body to posterior chaetigers ( Fig. 4C–H View FIGURE 4 ).

Neuroacicular ligule with predominant inferior lobe on anterior to mid-body chaetigers, inferior and superior lobes subequal in length on posterior chaetigers, about as long as ventral ligule throughout ( Fig. 4A–H View FIGURE 4 ). Neuropodial postchaetal lobe present throughout, rounded on anterior chaetigers, lamellae present from posterior half of anterior chaetigers to posterior chaetigers ( Fig. 4C–H View FIGURE 4 ). Ventral ligule subconical on anterior half of anterior chaetigers, becoming narrow subconical with triangular lobe on dorsal surface of ventral ligule from chaetiger 25 to posterior chaetigers ( Fig. 4C–H View FIGURE 4 ). Ventral cirri digitiform throughout, basally attached to ventral edge of parapodia, about as long as ventral ligule on anterior half of anterior chaetigers, about 1.5 times longer than ventral ligule from midbody to posterior chaetigers; two ventral cirrus lobes present posterior dorsal surface of ventral cirri from chaetiger 12 to posterior chaetigers, elongated progressively to mid-body chaetigers and shorten progressively thereafter; irregular-shaped lamellae present on posterior ventral surface of ventral cirri from chaetiger 12 to posterior chaetigers, enlarged progressively to mid-body chaetigers and reduced progressively thereafter ( Fig. 4C–H View FIGURE 4 ).

Notopodial and neuropodial chaetae same as atokous stage, paddle-like natatory chaetae absent throughout.

Pygidium crenulated; anal cirri cirriform, as long as last 7 chaetigers.

Variation. Length ratio of apodous anterior segment to chaetiger 1 ranged 1.4–1.6 (n= 7); longest tentacular cirrus reached chaetiger 4–6 (n= 7). Paragnath numbers in Area I ranged 0–4, Area II 18–37 (left) and 23–38 (right) in 4–5 rows (n= 7), Area III 53–92 in 4–5 rows (n= 7), Area IV 70–91 (left) and 67–90 (right) in 5 rows (n= 7), Area VII–VIII 17–22 (n= 7), respectively. Number of chaetigers in pre-natatory region ranged 14–17 chaetigers (n= 7), and beginning chaetiger of natatory region ranged from chaetiger 15 to 18 (n= 7). Length of anal cirri ranged from as long as last 4 to 7 chaetigers (n= 5).

Etymology. The name is derived from the name of village, Jihuei, where the worms were collected.

Type locality. Jihuei , Taitung County, Taiwan .

Distribution. Only known from the type locality.

Remarks. Of the 20 known species of the genus, only P. formosa Kinberg, 1865 , P. kihawensis n. sp., and P. podocirra (Schmarda, 1861) have no heterogomph spinigers in the subacicular fascicle of the neuropodia as in P. jihueiensis n. sp. ( Conde-Vela 2018: 270; Kara et al. 2018: 1289; Table 1). However, P. jihueiensis n. sp. can be distinguished from P. formosa by having: 1) edentate jaws (versus 5–7 lateral teeth on the cutting edge of the jaws); 2) smaller ratio of dorsal cirrus to dorsal ligule on anterior and mid-body chaetigers (1.3 and 1.1 versus 2.0 and 1.5, respectively) and greater ratio of dorsal cirrus to dorsal ligule on posterior chaetigers (0.6 versus 0.4); 3) tip of dorsal ligule becoming small pennant-like lobe on mid-body chaetigers (versus rounded); 4) oblong dorsal ligules on posterior chaetigers (versus pear-shaped) ( Bakken 2007: 157–158, fig. 7A–E; Conde-Vela 2018: 270; Figs 1C–D View FIGURE 1 , 2A–F View FIGURE 2 , Table 1). Pseudonereis jihueiensis n. sp. differs from P. podocirra by having: 1) edentate jaws (versus 6 lateral teeth on the cutting edge of the jaws); 2) paragnaths in Area IV distributed in 5–7 rows (versus 4 rows); 3) shield-shaped bars in Area VI (versus bar+cone); 4) fewer number of paragnaths in Area VII–VIII (17–22 versus 40) and two rows of paragnaths distributed in a narrow band (versus 2–4 rows in a broad band); 5) one pa- ragnath on each furrow and ridge regions in Area VII–VIII (versus 2–3 in Area VIII); and 6) greater dorsal cirrus to dorsal ligule ratio on posterior chaetigers (0.6 versus 0.3) ( Kara et al. 2018: 1287–1289, figs 3G–I, 4A–C, table 3; Figs 1C–D View FIGURE 1 , 2F View FIGURE 2 , Table 1). The morphological differences between P. jihueiensis n. sp. and P. kihawensis n. sp. are discussed under the Remarks of the latter species.

Epitokes of nereidids are known to undergo dramatic changes in the body to enable the worms to swim more effectively during swarming in the water column; the swimming abilities are enhanced in part by acquisition ad- ditional lobes on the parapodia and specialised paddle-like natatory chaetae (Bakken et al. in press). However, these two morphological modifications are not present in all epitokes of nereidids. In the present case, only additional lobes on the parapodia, but not the paddle-like natatory chaetae, were observed for both sexes of P. jihueiensis n. sp. A similar case of lacking natatory chaetae in nereidids was also observed for male epitoke of Nereis denhamensis Augener, 1913 ( Glasby et al. 2013).