Scolelepis (Scolelepis) rubra, Lee & Min, 2022

Lee, Geon Hyeok & Min, Gi-Sik, 2022, Two new Scolelepis species (Annelida: Spionidae) from the Yellow Sea in Korea, Zootaxa 5092 (2), pp. 221-237 : 228-234

Scolelepis (Scolelepis) rubra sp. nov.

Figures 6–8

Material examined. Holotype. complete specimen (NIBRIV0000890310), with palps ( Fig. 6A ), formalin, Yellow Sea , Korea, 36°09'41.2"N, 126°31'11.1"E, 20 Oct. 2020, intertidal sand, coll. Lee GH.

Paratypes. one af (NIBRIV0000890311), formalin, Yellow Sea , Korea, 126°31'29.7"E, 35°40'44.2"N, 19 Sep. 2020, intertidal sand, coll. Lee GH ; five af (NIBRIV0000890312–6), formalin, 36°15'42.9"N, 126°32'47.9"E, 21 Oct. 2020, intertidal sand, coll. Lee GH.

Additional material. Yellow Sea , Korea: 4 complete (NIBRIV0000890317–8 for molecular analysis), 1 af (NIBRIV0000890319 for molecular analysis), same data as holotype, 95% ethanol; 2 af, same data as paratype; 1 complete, 3 af, same data as holotype; 1 complete, formalin, 35°35'44.6"N, 126°29'07.9"E, 19 Sep. 2020 , muddy sand, 3 af, formalin, 35°39'16.4"N, 126°29'26.0"E, 21 Sep 2020; 3 af, formalin, 36°14'26.1"N, 126°31'49.1"E, 20 Oct. 2020; 2 complete, 3 af, formalin, 36°13'53.3"N, 126°31'47.2"E, 20 Oct. 2020; 3 af, formalin, 36°15'42.9"N, 126°32'47.9"E, 21 Oct. 2020; 2 complete, formalin, 37°14'38.3"N 126°19'22.2"E, 21 Oct. 2020. All examined materials were collected by Lee GH from sandy intertidal zones.

Diagnosis. Prostomium conical, anteriorly pointed, occasionally with lateral angles, distinctly projecting over peristomium; caruncle reaching end of chaetiger 1, attached to dorsum. Palps rather short, usually thickened basally, reaching to about chaetiger 4; palps with three separated, irregular groups of mucus-secreting cells and accompanying cilia. Chaetiger 1 well developed, with subulate postchaetal lamellae in both rami; notochaetae present. Branchiae from chaetiger 2, present throughout body; branchiae cirriform, about twice as long as notopodial postchaetal lamellae. Notopodial postchaetal lamellae foliate, less folded, almost completely fused to branchiae but distally free; from chaetiger 24, basal part of notopodial postchaetal lamellae becoming detached from branchiae; in posterior chaetigers, notopodial postchaetal lamellae becoming subtriangular. Capillary chaetae and bidentate hooded hooks in neuropodia and notopodia; hooded hooks in neuropodia usually from chaetigers 26–31 and hooded hooks in notopodia present in posteriormost chaetigers; hooded hooks all bidentate with upright apical tooth surmounting main fang. Pygidium slightly broad, rounded, with anus opening dorsally.

Description. Holotype complete with 125 chaetigers, about 0.8 mm wide and about 48.5 mm long ( Fig. 6A ). Paratype af with 66 chaetigers, about 0.8 mm wide and about 21.5 mm long. Other specimens with 55–130 chaetigers, 0.5–1.0 mm wide and 10.0–50.0 mm long.

Prostomium conical, anteriorly pointed ( Fig. 6C, F ), occasionally with lateral angles ( Fig. 6D ), distinctly projecting over peristomium, caruncle reaching end of chaetiger 1, caruncle attached to dorsum ( Fig. 7A, B ); usually two pairs of reddish eyes (absent in holotype) arranged in trapezoid but almost straight in some specimens, anterolateral pair slightly larger, crescent-shaped, widely separated; posterior pair smaller, rounded; occipital antenna absent. Peristomium well-developed, separated from prostomium by furrow ( Fig. 6F ), forming lateral wings partially encompassing prostomium posteriorly ( Fig. 7A, B ). Palps rather short, usually thickened basally, reaching to about chaetiger 4 ( Fig. 7B ); palps with three separated, irregular groups of mucus-secreting cells and accompanying cilia ( Fig. 6G ), longest rows approximately 31 μm long, two short rows approximately 8 μm and 9 μm long ( Fig. 6G ); division between two short rows not as distinct as between longest and short rows ( Fig. 6F inset). Distinct transverse ciliary bands present throughout body.

Chaetiger 1 well developed, with subulate postchaetal lamellae in both rami; notochaetae present ( Fig. 7A, B ). Branchiae from chaetiger 2, present throughout body; branchiae cirriform, about twice as long as notopodial postchaetal lamellae, with pointed tip distally; largest in anterior and middle chaetigers ( Fig. 8A–E ), becoming thinner and shorter in posterior chaetigers ( Fig. 8F ). Notopodial postchaetal lamellae foliate, less folded, almost completely fused to branchiae but distally free; from chaetiger 24, basal part of notopodial postchaetal lamellae becoming detached from branchiae ( Fig. 8D ); in posterior chaetigers, notopodial postchaetal lamellae becoming subtriangular ( Fig. 8F ). Prechaetal notopodial lamellae small, rounded, most conspicuous in anterior chaetigers, absent on chaetiger 1 ( Figs. 7B , 8 ). Neuropodial postchaetal lamellae rounded from chaetiger 2, from chaetiger 16 slightly notched ( Fig. 8C ), from about chaetiger 27 divided into large rounded neuropodial lamella and inferior conical lobe with rounded tip ( Fig. 8D ); in middle chaetigers, neuropodial postchaetal lamellae with low, flattened middle portion, conical superior part, and inferior lobe becoming shifted ventrally ( Fig. 8E ); in posterior chaetigers, neuropodial superior part becoming thin, digitiform and inferior lobe shifted to inferiormost position ( Fig. 8F ). Prechaetal neuropodial lamellae absent.

Capillary chaetae and bidentate hooded hooks in neuropodia and notopodia. Anterior chaetae all slightly granulated capillaries with narrow sheaths ( Fig. 7D ), arranged in two rows until hook-bearing chaetigers; capillary chaetae of anterior chaetigers with 2–3 thin, long chaetae in superiormost position; capillary chaetae of middle and posterior chaetigers thin, non-granulated, not clearly arranged in rows within fascicle. Hooded hooks in neuropodia usually from chaetigers 26–31 (21 in small and 32–35 in large specimens, 31 in holotype) ( Fig. 8E ), numbering usually 2 (1–3, rarely 4) per fascicle at first, then increasing up to 11 hooks per fascicle more posteriorly; hooded hooks in notopodia present in posteriormost chaetigers (appearing from chaetiger 85 in holotype), numbering usually 2 per fascicle; hooded hooks all bidentate with upright apical tooth surmounting main fang, with open hoods ( Figs. 6E , 7E ); hooks in neuropodia accompanied by a few thin, long, smooth capillaries with very narrow sheaths in about first 8–10 hook-bearing chaetigers, then decreasing to 1–2 in superior position posteriorly ( Fig. 8F ). Inferior capillaries or ventral sabre chaetae absent.

Pygidium slightly broad, rounded, with anus opening dorsally ( Fig. 7C ).

Pigmentation. Color of live and formalin-fixed specimens bright reddish-pink ( Figs. 6A, B ) with orangebrownish pigmentation on middle and posterior margin of prostomium, on the dorsum in the vicinity of the caruncle ( Fig. 6C ), and the basal part of palps ( Fig. 7B ), but some specimens lack any pigmentation.

Methyl green staining pattern. Inconspicuous: Prostomium, peristomium, branchiae, and neuropodial postchaetal lobes were most intensely stained ( Fig. 6D ).

Etymology. The specific name, rubra , originates from the Latin word ruber, meaning red. This name refers to the reddish-pink body.

Habitat and distribution. The new species was found in intertidal sandy beaches on South Korean shores in the Yellow Sea.

Remarks. Seven species of the subgenus Scolelepis are known for the presence of notopodial chaetae in chaetiger 1, notopodial hooded hooks, neuropodial bidentate hooded hooks, notopodial postchaetal lamellae partially fused to branchiae in the anterior body, and absence of the occipital antenna: S. (S.) blakei Hartmann-Schröder, 1980 ; S. (S.) bifida Hutchings & Turvey, 1984 ; S. (S.) carunculata Blake & Kudenov, 1978 ; S. (S.) chilensis ( Hartmann-Schröder, 1962) ; S. (S.) daphoinos , S. (S.) kudenovi ; and S. (S.) hutchingsae Dauer, 1985 ( Hartmann-Schröder 1962, 1980; Blake & Kudenov 1978; Hutchings & Turvey 1984; Dauer 1985; Williams 2007; Zhou et al. 2009; Meiβner & Götting 2015). Among these, the new species is morphologically most similar to S. (S.) kudenovi and S. (S.) hutchingsae from Lizard Island, Australia, with notopodial postchaetal lamellae approximately half the length of the branchiae in anterior chaetigers and hooded hooks with a strikingly upright apical tooth ( Dauer 1985; Williams 2007; Meiβner & Götting 2015). However, the new species differs from S. (S.) kudenovi from Lizard Island by having reddish-pink color in both live and fixed specimens instead of white in fixed specimens, the presence of pigmentation on the anteriormost body instead of absence, and neuropodial hooks starting from chaetigers 26–34 vs. chaetigers 38–44; it differs from S. (S.) hutchingsae by the neuropodial hooded hooks starting from chaetigers 26–34 vs. chaetigers 18–20, and notopodial hooks starting much later than neuropodial hooks posteriorly instead of starting in a chaetiger close to the first appearance of neuropodial hooks ( Dauer 1985; Williams 2007; Meiβner & Götting 2015). In the Far East, the new species also resembles S. (S.) angulata in having lateral angles on prostomium, the notopodial postchaetal lamellae partially fused, and approximately half the length of the branchiae in anterior chaetigers, and the presence of pigmentation on the posterior part of the prostomium ( Zhou 2014). However, the new species is clearly distinguished from the latter species by the reddish-pink color in both live and fixed specimens instead of yellowish in alcohol-fixed specimens, branchiae present along the entire body instead of ending in the middle body, absence of neuropodial prechaetal lamellae instead of presence, and presence of notopodial hooks instead of absence ( Zhou 2014). In Korean waters, S. (S.) kudenovi sensu Choi & Yoon, 2016 has hooks with a small apical tooth above the main fang and hook-bearing neuropodial chaetigers with 5–6 capillaries in the inferior position [see figure 1 in Choi & Yoon (2016)] that clearly differs from S. (S.) rubra sp. nov. of the present study and S. (S.) kudenovi from Australia ( Hartmann-Schröder 1981; Meiβner & Götting 2015). Unfortunately, Choi & Yoon (2016) did not describe body color, pigmentation and palp ciliation pattern, and all examined specimens they used were anterior fragments. Re-examination of S. (S.) kudenovi in Korea is needed for verification of this identification.

The palp ciliation pattern of the new species is similar to those of S. (S.) lefebvrei , S. (S.) squamata (Müller, 1806) , S. (S.) vazaha Eibye-Jacobsen & Soares, 2000 , and S. (S.) villosivaina Williams 2007 in having long and short rows of cilia that are distinctly separated ( Dauer 1983; Eibye-Jacobsen & Soares 2000; Williams 2007). However, the new species differs from the latter by the presence of two indistinctly divided short rows on the palps.

Figures

FIGURE 6 Scolelepis (Scolelepis) rubra sp. nov. A, Whole body with palps, fixed in formalin; B, Live specimen in seawater, lateral view; C, Anterior end with orange-brownish pigmentations; D, Anterior end stained methyl green, dorsal view; E, Neuropodial hooded hooks from chaetiger 77, Lateral view (left) and front view (right); F, Anterior end with palps, dorsal view, arrow in inset indicates division between two short rows of mucus-secreting cells and accompanying cilia; G, Ciliation of the inner side of the palp, upper arrow indicates division between long and short rows and lower arrow indicates division between two short rows. A, C, Holotype (NIBRIV0000890310), B, Paratype (NIBRIV0000890314), D, Paratype (NIBRIV0000890311), E, Paratype (NIBRIV0000890312), F, G, Paratype (NIBRIV0000890313). Scale bars: A=5 mm, B=0.5 mm, C, D=0.2 mm, E=10 μm, F=0.1 mm, G=4 μm.

FIGURE 7 Scolelepis (Scolelepis) rubra sp. nov. A, Anterior end, dorsal view; B, Anterior end, lateral view; C, Posterior end, dorsal view; D, Neurochaetae from chaetiger 2; E, Neuropodial hooded hooks from chaetiger 45. A–C, Holotype (NI- BRIV0000890310), D, E, Paratype (NIBRIV0000890312). Scale bars: A–C=0.2 mm, D=50 μm, E=20 μm.

FIGURE 8 Scolelepis (Scolelepis) rubra sp. nov., paratype (NIBRIV0000890312). A–F, Parapodium from chaetiger 2, 6, 20, 29,75, and 21st last chaetiger, all anterior views. Scale bars: 0.2 mm.