Ophelia yangi Wang, Zheng, Zeng, Zhang, Pan & Yang, 2026, sp. nov.

Ophelia yangi sp. nov. Figs 2, 3; Tables 1–3 Ophelia cf. limacina: Yang and Sun 1988: 247 –248, fig. 114 C, D. Material examined. Holotype: China • complete specimen (A 003, YZZ 001323); Fujian Province, Quanzhou, Yueliangwan (Moon Bay), transect CJD 01, low intertidal zone; 24.88460°N, 118.86395°E; 16 Mar. 2026; Zeyang Lin & Biqi Zheng leg.; sand; GenBank: QB 077085 (COI), QB 085327 (16 S). Paratypes: China • 1 spec. (A 004, YZZ 001324); same beach, transect and date as holotype; GenBank: QB 077084 (COI), QB 085329 (16 S) • 2 specs (A 001, YZZ 001321; A 002, YZZ 001322); same beach, transect and date as holotype; GenBank: A 001 QB 077087 (COI), QB 085328 (16 S); A 002 QB 077086 (COI), QB 085330 (16 S). Additional material examined. China • 10 specs (A 008 – A 014, A 021 – A 023; YZZ 001325 – YZZ 001334); same beach and date as holotype, transects CJD 01 (A 008 – A 014) and CJD 04 (A 021 – A 023) • 7 specs (A 007, YZZ 001440; A 015 – A 020, YZZ 001335 – YZZ 001340); Fujian Province, Quanzhou, Yueliangwan (Moon Bay), transect CJD 04; 24.87982°N, 118.94202°E; 16 Mar. 2026; Zeyang Lin & Biqi Zheng leg.; sand; GenBank: A 007 QB 077083 (COI), QB 085326 (16 S). China • 1 spec. (MBM 193650); Shandong Province, Qingdao, Jiaonan, Xiaofang; 29 Jan. 1983 • 2 specs (2221-15, 2221-16); Zhejiang Province, Wenzhou, Oujiang River estuary, station 2223-1 H 14 - B 004, subtidal zone, 8.5 m; 27.96558°N, 120.97283°E; 26 May 2022; muddy sand • 1 spec. (FJCL-NHY 001-20180702); Fujian Province, Changle, Haibang Reserve, subtidal zone; 25.90518°N, 119.64348°E; 2 Jul. 2018; sand. Diagnosis. Body with 32 chaetigers: ten anterior abranchiate, 16 branchiate, and six posterior abranchiate (body formula 10 a + 16 b + 6 a = 32); posterior achaetous segments absent. Branchiae simple, cirriform, on chaetigers 11–26; branchial fenestrations present. Pygidium with two large ventral papillae and 18 small dorsal papillae (9 on each side). Description. Holotype 25 mm long for 32 chaetigers, and 3 mm wide at the widest chaetiger. Preserved specimens white (Fig. 2 A, C). Black spicules, straight or Y-shaped, visible through the body wall (Fig. 2 C). Body stout, widest in anterior region and tapering gradually towards posterior end (Figs 2 A – D, 3 A). Anterior region (chaetigers 1–10) cylindrical, smooth, finely annulated, annulations encircling body dorsally and ventrally; posterior region (from chaetiger 11) ventrally flattened, with a pair of lateral grooves along which parapodia and branchiae are inserted (Fig. 2 B, D). Ventral groove from chaetiger 3 (Fig. 2 E), deep in posterior region. Dorsum of posterior region smooth and rounded, with posterior dorsal longitudinal ridges in last three chaetigers (Figs 2 A, 2 B, 3 O). Prostomium small, conical, tapering to a pointed tip; eyes and appendages absent (Figs 2 E, 3 A); a pair of nuchal organs on posterolateral margins of prostomium (Figs 2 D, 3 B, 3 E). Mouth ventral, on chaetiger 1. Chaetigers 32. Chaetigers 1–10 and 27–32 abranchiate; posterior achaetous segments absent. Branchiae 16 pairs, on chaetigers 11–26, simple, cirriform, with crenulated margins (Figs 2 A – D, 3 I – K, 3 N); longest in middle of branchial region, becoming shorter anteriorly and posteriorly (Figs 2 B, 3 A). Branchial fenestrations (vertical rows of small pores in the lateral grooves of the branchial region; Tebble 1953) present from chaetiger 11 (Figs 2 D, 3 L). Parapodia biramous, reduced (Fig. 3 C, H); interramal pore (lateral organ) between notopodium and neuropodium present on all chaetigers (Fig. 3 D, G, M). All chaetae simple capillaries (Fig. 3 F, N, O), posterior achaetous segments absent (Figs 2 F, 3 O). Nephridiopores six pairs, small, intersegmental, close to neuropodia, from between chaetigers 11 and 12 to between chaetigers 16 and 17 (Fig. 3 I). Pygidium with an anal funnel bearing two large, digitiform ventral papillae and 18 smaller dorsal papillae, nine on each side (Fig. 2 F). Methyl green staining pattern. Body stained evenly pale blue, without distinct bands or spots; staining slightly more intense along ventral groove (Fig. 2 B, D – F). Variation. Measurements and counts are given in Suppl. material 1: table SS 3. Twenty specimens from Quanzhou were examined in detail and measured; the other four were examined only for the body formula, which was also 10 a + 16 b + 6 a. In the 20 measured specimens, body length ranged from 13 to 32 mm and width from 2 to 3 mm (mean 22.9 and 2.6 mm, respectively; n = 20), and all had 32 chaetigers, two ventral and 18 dorsal anal papillae and no posterior achaetous segments. The body formula was 10 a + 16 b + 6 a on both sides in 19 of the 20 specimens examined in detail; only one specimen (A 011) was asymmetrical, with 10 a + 16 b + 6 a on the left and 11 a + 15 b + 6 a on the right side. The body formula did not change with body size: the smallest (13 mm) and the largest (32 mm) specimens had the same formula. Black spicules were present in all 20 specimens examined in detail. The origin of the ventral groove varied from chaetiger 1 to chaetiger 10 (n = 20), most often chaetiger 3 (n = 10). Posterior dorsal longitudinal ridges were absent in some specimens. The branchiae were longest in the middle of the branchial region and shortest at both ends. Their length and shape varied among specimens: in some (e. g., A 009) they were short, stout and strongly wrinkled, in others (e. g., A 014) long and slender. Branchial fenestrations were present from chaetiger 11 in all specimens examined in detail and were most clearly visible in A 018. Nephridiopores were distinct in only a few specimens; where visible, six pairs were present (e. g., A 001 and A 002). Interramal pores (lateral organs) were examined in detail in only some specimens (e. g., A 001 – A 004, A 022 and A 023); in all of these, they were visible on all chaetigers. Etymology. The species is named in honor of Prof. Dejian Yang (杨德渐), Ocean University of China, who first reported Ophelia from Chinese waters (Yang and Sun 1988). The specific name is a noun in the genitive case, formed from the surname of a man (ICZN Art. 31.1. 2). Habitat. The Quanzhou specimens were collected from sand in the intertidal zone of a sandy beach (transects CJD 01 and CJD 04). At the five stations where the species occurred, density was 8–28 ind. / m 2 (mean 17.6 ind. / m 2), and wet-weight biomass was 0.20–3.68 g / m 2. The specimen from Changle was collected from sand in the subtidal zone. The two Wenzhou specimens were collected from muddy sand in the subtidal zone at station 2223-1 H 14 - B 004, at a depth of 8.5 m. Distribution. China: Yellow Sea (Shandong Province: Jiaonan) and East China Sea (Zhejiang Province: Wenzhou; Fujian Province: Changle and Quanzhou). Remarks. Ophelia yangi sp. nov. is distinguished from all congeners by its body formula (10 a + 16 b + 6 a = 32) and 18 small dorsal anal papillae: no other species of Ophelia has 16 branchiate chaetigers followed by six posterior abranchiate chaetigers (Table 3; Suppl. material 1: table S 7). Ophelia limacina was described from Norway with the body formula 10 a + 23 b + 4 a = 37 (Rathke 1843). Tebble (1952) gave 10 a + 22 b + 7 a = 39 for non-type material from northern Norway, Spitsbergen and Greenland; this formula differs from the original one in the numbers of branchiate and posterior abranchiate chaetigers. Regardless of which formula is adopted, O. yangi sp. nov. has fewer chaetigers than O. limacina: 32 vs 37 in the original description and 37–39 in the later descriptions (Table 1). The Yellow Sea specimens described by Yang and Sun (1988) as O. cf. limacina agree with O. yangi sp. nov. in having ~ 31–33 chaetigers, 15–16 branchiate chaetigers and 5–7 posterior abranchiate chaetigers (Table 1). Moreover, a specimen from the Yellow Sea coast (Jiaonan, Shandong Province; MBM 193650) examined by us agrees with the type series in the body formula (10 a + 16 b + 6 a = 32). The only difference from the description of Yang and Sun (1988) is the number of small dorsal anal papillae (16 vs 18), which may reflect the difficulty of counting them. We therefore tentatively refer the record of Yang and Sun (1988) to the new species. Note: a, abranchiate chaetigers; b, branchiate chaetigers; –, not stated. Sources and notes in Suppl. material 1: table S 6. Previous records from the Northwest Pacific. Imajima and Hartman (1964) recorded O. limacina from Muroran, Hokkaido, Japan. Their diagnosis (body 15–40 mm long, 37–38 chaetigers, 21–24 branchiate chaetigers from chaetiger 11, dorsal ridges on the last four chaetigers and 8–12 dorsal anal papillae) is most similar to the descriptions of O. limacina by Tebble (1952) and Hartman (1969) (Table 1) and clearly differs from O. yangi sp. nov. (32 chaetigers, 16 branchiate chaetigers and 18 dorsal anal papillae). Whether the Japanese record represents O. limacina requires further study. The Korean records of O. limacina from the Yellow Sea (Khim et al. 2021) are given without descriptions. Because they come from the same sea as the record of Yang and Sun (1988) and the Jiaonan specimen examined here, they may belong to O. yangi sp. nov., but this needs to be verified on voucher material. To facilitate identification, the species of Ophelia can be arranged in two groups according to the branchiae and the number of anterior abranchiate chaetigers (Table 2): (A) branchiae absent (5 species); (B) branchiae present, with (B 1) branchiae bifid (1 species) and (B 2) branchiae simple, with (B 2 a) one anterior abranchiate chaetiger (1 species); (B 2 b) 7–9 anterior abranchiate chaetigers (13 species); and (B 2 c) 10 or 11 anterior abranchiate chaetigers (16 species). Ophelia glabra Stimpson, 1853 and O. simplex Leidy, 1855 are currently accepted as valid (Read and Fauchald 2026), but their original descriptions are brief and unillustrated, and their validity is doubtful (Tebble 1953; Amoureux and Dauvin 1981; Riser 1987); they were therefore not