Scolelepis (Parascolelepis) anterobranchiata Lee & Min 2022, sp. nov.
Creators: name: Lee, Geon Hyeok
name: Min, Gi-Sik
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Spionida
Spionidae
Scolelepis
Scolelepis anterobranchiata

description: Scolelepis (Parascolelepis) anterobranchiata sp. nov.
Figures 2–5
Material examined. Holotype. complete specimen (NIBRIV0000890299), without palps (Fig. 2A), formalin, Yellow Sea, Korea, 34°55'12.0"N, 126°03'26.2"E, 4 Oct 2020, intertidal muddy sand, coll. Lee GH.
Paratypes. Seven complete (NIBRIV0000890300–6) and one af (VSJAIV0000001433), formalin, collection details same as holotype, coll. Lee GH.
Additional material. 4 complete (NIBRIV0000890307–9 for molecular analysis), same data as holotype, 95% ethanol; 2 af, formalin, same locality as holotype, 5 Oct 2020, coll. Lee GH.
Diagnosis. Prostomium elongated, anterior conical with broadly rounded point, posteriorly extended into low caruncle attached to dorsum; caruncle extending to end of chaetiger 2 with slight elevation on posterior part. Palps long, thin, with smooth sheath at base, usually distinctly thickened at base part with globular expansions; palps with separated, single row of mucus-secreting cells and accompanying cilia; irregular longitudinal swellings present but not parallel. Chaetiger 1 well developed, with rounded lamellae in both rami; notochaetae absent. Branchiae from chaetiger 2 to chaetigers 18–19. Notopodial postchaetal lamellae foliate with pointed tip, largest on chaetigers 5–12; almost entirely fused but distally free from branchiae; from chaetiger 15 to middle chaetigers notopodia becoming smaller. Neuropodial postchaetal lamellae broadly rounded, from chaetiger 16 slightly notched. Neuropodial hooded hooks from chaetigers 18–19 with 2 pairs of teeth in parallel position surmounting well-developed main fang, apical pair smallest. Pygidium slightly broad, rounded, with anus opening dorsally.
Description. Holotype complete with 58 chaetigers, about 0.9 mm wide and about 7.0 mm long (Fig. 2A). Other specimens complete with 56–63 chaetigers, similar to holotype in width and length. Body dorsoventrally flattened anteriorly, cylindrical posteriorly (Fig. 2A, B).
Prostomium elongated, anterior conical with broadly rounded point, posteriorly extended into low caruncle attached to dorsum; caruncle extending to end of chaetiger 2 with slight elevation on posterior part; two pairs of reddish eyes (in both live and fixed specimens) arranged in trapezoid, anterolateral pair slightly larger, crescent-shaped, widely separated, and posterior pair smaller, rounded; occipital antenna absent (Fig. 3A, B). Peristomium well-developed, separated from prostomium without furrows, not forming lateral wings (Fig. 3B). Palps long, thin, reaching about two-thirds of body in live specimens (Fig. 2B) (but rather thickened in formalin and ethanol-fixed specimens (Fig. 2C), reaching to chaetigers 15–22), with smooth sheath at base, usually distinctly thickened at basal part with globular expansions (weak expansions in two specimens) (Figs. 2C, 5A); palps with separated, single row of mucus-secreting cells and accompanying cilia (Fig. 5B, C); long rows approximately 72 μm long, short rows approximately 10 μm long; irregular longitudinal swellings present but not parallel, with smooth inner portion surrounded by mucus-secreting cells and cilia (Fig. 5B, C). Low but distinct transverse ciliated bands present throughout body.
Chaetiger 1 well developed, with rounded lamellae in both rami; notochaetae absent (Fig. 3A, B). Branchiae from chaetiger 2 to chaetigers 18–19, longest on chaetigers 5–12, quickly decreasing in size posteriorly; branchiae long cirriform with pointed tips, longer than notopodial postchaetal lamellae until chaetiger 15; accessory branchiae absent (Fig. 4). Notopodial postchaetal lamellae foliate with pointed tips, largest on chaetigers 5–12; almost entirely fused but distally free from branchiae (Fig. 4B–D); from chaetiger 15 to middle chaetigers notopodia becoming smaller (Fig. 4E); notopodia of middle to posterior chaetigers becoming slightly larger with foliate but less folded notopodial postchaetal lamellae (Fig. 4F). Neuropodial postchaetal lamellae broadly rounded (Fig. 4A–D), from chaetiger 16 slightly notched (Fig. 4E), from chaetiger 23 divided into rounded lobe in interramal position and low flattened postchaetal lamella; interramal lobe becoming conical with rounded tip on posterior chaetigers (Fig. 4F).
Anterior chaetae all non-granulated capillaries with narrow sheaths (Fig. 3D), arranged in two rows in both rami, anterior row slightly shorter than posterior row; from about chaetiger 18, 3–5 long, thin non-limbate notochaetae arranged in irregular rows, more posteriorly arranged in bundle (Fig. 4F). Neuropodial hooded hooks from chaetigers 18–19 (18 in holotype), numbering 7–8 per fascicle at first, then increasing to 15–16 per fascicle posteriorly; hooded hooks with strongly curved shaft, with open hoods (Figs. 2D, 3E, 5D); hooks with 2 pairs of teeth in parallel position surmounting well-developed main fang, apical pair smallest (Fig. 3E); hooks not accompanied by capillaries. Ventral sabre chaetae absent.
Pygidium slightly broad, rounded, with anus opening dorsally (Figs. 3C, 5E).
Pigmentation. Whitish color in live specimens with orange-brownish pigmentation on the prostomium, peristomium, and base of palps. In formalin- or ethanol-fixed specimens, orange-brownish pigmentation usually fades or is completely lost (pigmentation well-preserved in only two fixed specimens); if pigmentation is preserved, conspicuously present on the caruncle and basal sheaths of palps (Fig. 2C).
Methyl green staining pattern. Stain retained on prostomium, posterior part of caruncle, peristomium, notopodial postchaetal lamellae, and distal tips of branchiae. Anterior and middle segments with horizontal bands of deeply staining cells on venter.
Etymology. The Latin name of the new species refers to having branchiae only on the anterior body region.
Habitat and distribution. The new species was found in the muddy sand of the intertidal zone of the Yellow Sea.
Remarks. Scolelepis (Parascolelepis) anterobranchiata morphologically is most similar to S. (P.) globosa from China, in having the palps with smooth globular expansions at the base, absence of notochaetae on chaetiger 1, notopodial postchaetal lamellae partially fused with branchiae in anterior chaetigers, and neuropodial hooded hooks appearing tridentate in lateral view (Wu & Chen 1964, Blake et al. 2019). Based on the current knowledge, only these two species have palps with smooth globular expansions in this subgenus. However, the new species differs from S. (P.) globosa by the absence of an occipital antenna instead of presence, branchiae appearing in the anterior part of the body instead of the whole body, and neuropodial hooded hooks from chaetigers 18–19 instead of 21 (Wu & Chen 1964). The new species is also similar to S. (P.) geniculata from Japan in the absence of an occipital antenna and flattened postchaetal neuropodial lamellae but differs in the absence of papillae on palps instead of presence, the absence of notochaetae on first chaetigers instead of presence, notopodial postchaetal lamellae partially fused to branchiae in the anterior part of the body instead of completely fused, and two pairs of apical teeth instead of three pairs (Imajima 1992).
The palp ciliation patterns are of important taxonomic character (Williams 2007). The palps of the new species have a single row of mucus-secreting cells and accompanying cilia with irregular longitudinal swellings. This is the first palp ciliation pattern described in detail for the subgenus Parascolelepis and it is unique among the species of Scolelepis studied to date.
description: Published as part of Lee, Geon Hyeok & Min, Gi-Sik, 2022, Two new Scolelepis species (Annelida: Spionidae) from the Yellow Sea in Korea, pp. 221-237 in Zootaxa 5092 (2) on pages 224-228, DOI: 10.11646/zootaxa.5092.2.5, http://zenodo.org/record/5876652