Genetic distances. Table 3 showed the average K2P genetic distances for five genes among Chloeia species. COI showed higher average K2P genetic distances than the other four gene markers. The average interspecific distances ranged from 16.4% (C. conspicua & C. incerta) to 28.4% (C. conspicua & Chloeia sp. D) for COI (590 bp), from 6.56% (C. incerta & C. conspicua) to 16.2% (C. pocicola & C. conspicua) for 16S rRNA (315 bp), from 0.0% (Chloeia sp. A & C. viridis) to 1.28% (C. pocicola & C. conspicua) for 18S rRNA (1284 bp), from 0.48% (C. conspicua & C. incerta) to 3.95% (C. pocicola & C. conspicua) for 28S rRNA (736 bp), and for histone H3 (242 bp), the K2P distance was 13.06% between C. incerta and C. flava. The average intraspecific K2P genetic distances of C. flava (0.48% for COI, 0.13% for 16S rRNA, 0.01% for 18S rRNA, 0.00% for 28S rRNA, and 0.96% for histone H3), C. conspicua (1.03% for COI, 1.00% for 16S rRNA, and 0.00% for 28S rRNA), C. incerta (2.44% for COI, 0.39% for 16S rRNA, 0.09% for 28S rRNA, and 1.25% for histone H3), Chloeia sp. B (0.00% for 18S rRNA), Chloeia sp. C (0.86% for COI), and Chloeia sp. D (0.51% for COI) are much smaller than the respective interspecific distances for each gene sequence among Chloeia species as listed in Table 3.
Table 3
Pairwise average K2P genetic distances for COI (590 bp), 16S rRNA (315 bp), 18S rRNA (1284 bp), 28S rRNA (736 bp) and histone H3 (242 bp) gene sequences of Chloeia species.
Species | N | Species |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
COI(590 bp) | | | | | | | | | |
1. Chloeia bimaculata, Hong Kong, China) | 2 | 0.0103 | | | | | | | |
2.Chloeia flava(Dongshan, Fujian, China) | 6 | 0.2214 | 0.0048 | | | | | | |
3. Chloeia incerta (as C. parva, Hong Kong, China) | 2 | 0.1640 | 0.2307 | 0.0244 | | | | | |
4. Chloeia pocicola (Southern Brazilian coast) | 1 | 0.2343 | 0.2371 | 0.2478 | — | | | | |
5. Chloeia amphora (as C. flava, Tanabe Bay, Japan) | 1 | 0.2251 | 0.2374 | 0.2005 | 0.2364 | — | | | |
6. Chloeia sp. A (Pacific Ocean: CCZ) | 2 | 0.2516 | 0.2362 | 0.2295 | 0.2314 | 0.2291 | 0.0086 | | |
7. Chloeia sp. C (as C. flava, Oahu, Hawaii, USA) | 2 | 0.2840 | 0.2388 | 0.2506 | 0.2626 | 0.2458 | 0.2784 | 0.0051 | |
8. Chloeia viridis (Gulf of Mexico) | 1 | 0.2162 | 0.2177 | 0.2193 | 0.2672 | 0.2307 | 0.2398 | 0.2455 | — |
16S rRNA(315 bp) | | | | | | | | | |
1. Chloeia bimaculata, Hong Kong, China) | 2 | 0.0100 | | | | | | | |
2.Chloeia flava(Dongshan, Fujian, China) | 21 | 0.0933 | 0.0013 | | | | | | |
3. Chloeia incerta (as C. parva, Hong Kong, China) | 4 | 0.0656 | 0.0878 | 0.0039 | | | | | |
4. Chloeia pocicola (Southern Brazilian coast) | 1 | 0.2420 | 0.2276 | 0.2312 | — | | | | |
5. Chloeia amphora (as C. flava, Tanabe Bay, Japan) | 2 | 0.0986 | 0.0767 | 0.0709 | 0.2237 | 0.0000 | | | |
6. Chloeia viridis (Gulf of Mexico) | 1 | 0.0764 | 0.0915 | 0.0968 | 0.2108 | 0.0988 | — | | |
18S rRNA(1284 bp) | | | | | | | | | |
1. Chloeia flava (As C. viridis, West coast of India) | 1 | — | | | | | | | |
2.Chloeia flava(Dongshan, Fujian, China) | 10 | 0.0008 | 0.0001 | | | | | | |
3. Chloeia pocicola (Southern Brazilian coast) | 1 | 0.0128 | 0.0120 | — | | | | | |
4. Chloeia amphora (as C. flava, Tanabe Bay, Japan) | 2 | 0.0048 | 0.0040 | 0.0112 | 0.0000 | | | | |
5. Chloeia sp. A (as C. sp. r, Salas y Gomez Ridge, Chile) | 1 | 0.0040 | 0.0032 | 0.0088 | 0.0024 | — | | | |
6. Chloeia sp. B (As C. viridis, West coast of India) | 2 | 0.0032 | 0.0024 | 0.0096 | 0.0016 | 0.0008 | 0.0000 | | |
7. Chloeia viridis (Gulf of Mexico) | 1 | 0.0040 | 0.0032 | 0.0088 | 0.0024 | 0.0000 | 0.0008 | — | |
28S rRNA(736 bp) | | | | | | | | | |
1. Chloeia bimaculata (Hong Kong, China) | 2 | 0.0000 | | | | | | | |
2.Chloeia flava(Dongshan, Fujian, China) | 20 | 0.0152 | 0.0000 | | | | | | |
3. Chloeia incerta (as C. parva, Hong Kong, China) | 4 | 0.0048 | 0.0201 | 0.0009 | | | | | |
4. Chloeia pocicola (Southern Brazilian coast) | 1 | 0.0395 | 0.0526 | 0.0416 | — | | | | |
5. Chloeia amphora (as C. flava, Tanabe Bay, Japan) | 2 | 0.0083 | 0.0124 | 0.0103 | 0.0453 | 0.0000 | | | |
6. Chloeia sp. A (as C. sp. r, Salas y Gomez Ridge, Chile) | 1 | 0.0251 | 0.0294 | 0.0272 | 0.0424 | 0.0280 | — | | |
7. Chloeia viridis (Gulf of Mexico) | 1 | 0.0223 | 0.0294 | 0.0215 | 0.0424 | 0.0251 | 0.0252 | — | |
Histone H3(242 bp) | | | | | | | | | |
1.Chloeia flava(Dongshan, Fujian, China) | 22 | 0.0096 | | | | | | | |
2. Chloeia incerta (as C. parva, Hong Kong, China) | 2 | 0.1306 | 0.0125 | | | | | | |
Phylogenetic trees. Taking Euphrosine foliosa as the outgroup (Wiklund et al. 2008), two phylogenetic trees were reconstructed based on 23 and 54 specimens of amphinomids respectively, and both trees showed similar phylogenetic topologies (Fig. 4A, B). Two subfamilies Amphinominae Savigny in Lamarck, 1818 and Archinominae Kudenov, 1991 were classified with high support values (A, BS/BPP = 89/1, 100/1; B, BS/BPP = 90/1, 100/1). Five Chloeia species (i.e. C. viridis, C. conspicua, C. incerta, C. amphora, and C. flava) were clustered in a monophyletic clade in the left tree (Fig. 4A), and seven Chloeia species (i.e. Chloeia sp. A, C. viridis, C. conspicua, C. incerta, Chloeia sp. B, C. amphora, and C. flava) were clustered in a monophyletic clade in the right tree (Fig. 4B). The monophyletic clades in both trees were here regarded as Chloeia (restricted). In both trees, two deep-sea species, C. pocicola from the Southern Brazilian coast (745 m to 775 m) and Amphinomidae sp. B from the South China Sea (1167 m) were first clustered in a single clade and then this clade was sister to the genus Archinome. A Chloeia specimen (GP0175) originally regarded as C. viridis from western coast of India was clustered within the clade of C. flava; another two specimens of Chloeia (GP169, GP170), which were also regarded as C. viridis, were here taken as Chloeia sp. B clustered with the clade including C. amphora and C. flava (Fig. 4B).
Systematics
Family Amphinomidae Savigny in Lamarck, 1818
Subfamily Archinominae Kudenov,
Genus Chloeia Savigny in Lamarck, 1818
Type species: Amphinome capillata Bruguière, 1789, by monotypy (junior synonym of Aphrodita flava Pallas, 1766).
Type locality: Pallas indicated (1766: 98) that he had one specimen from the Bengal Bay and another one from Amboina. His specimens would be syntypes and the type locality would involve both places (ICZN 1999: Art. 76.1).
Chloeia flava (Pallas, 1766)
(Figs. 1–6, Tables 1–3)
Aphrodita flava Pallas, 1766a: 97–102, Pl. 8, Figs. 7–11.
Amphinome capillata Bruguière, 1789: 45–46 (unnecessary repl. name).
Chloeia capillata: Savigny 1822: 58–59; Milne-Edwards 1837, Pl. 9, Fig. 1.
Terebella flava: Milne-Edwards 1837:31.
Chloeia flava: de Quatrefages 1866: 386–388, Pl. 17, Fig. 4; Willey 1905: 244–245, Pl. 1, Figs. 1, 2 (syn.); Kinberg (1910: 33, Pl. 11, Fig. 1); Augener 1926: 436; Fauvel 1932: 55; Fauvel 1953: 96, Fig. 46d, i; Hartman 1959: 131; Amoureux et al. 1978: 73; Barroso & Paiva 2011: 422, Table 1 (partim); Yáñez-Rivera & Salazar-Vallejo 2022: 516–517, Fig. 6; Salazar-Vallejo 2023: 45–49, Figs. 1D, 19, 20.
Chloeia ceylonica Grube, 1874: 326.
Chloeia flava var. pulchella Horst, 1912: 19, Plate VII Fig. 3; Frickhinger, 1916: 233.
Chloeia flava pulchella: Sabith et al. 2022: 21–24, Figs. 2, 3 (non Baird, 1868).
Material examined. Twenty-three specimens (voucher numbers see Table 1), all complete, 35–75 mm long, 11–18 mm wide, 30–37 chaetigers, Dongshan, Fujian (23°30’N, 117°19’E ~ 23°42’N, 117°35’E), bottom trawl, 19–40 m, sandy and muddy sand, 3 Nov 2021, coll. Zhi Wang.
Diagnosis (modified from Yáñez-Rivera & Salazar-Vallejo 2022). Body fusiform. Middorsal pigmentation in median segments circular, progressively oval-shaped anteriorly and posteriorly. Middorsal spots oval to circular, surrounded by a thin pale margin in live specimens, pale margin expanded in posterior half of each segment in fixed specimens. Bipinnate branchiae from chaetiger 4. Ventral cirri of similar size throughout body. Notochaetae thick bifurcate, harpoon or spinose. Short tine of harpoon notochaetae very short, like a spur. Neurochaetae bifurcate only.
Description (based on XMU-Pol-2021-307, unless otherwise stated). Specimen complete, long, fusiform (Fig. 5A), pale, 68 mm long, 16 mm wide without chaetae, 34 chaetigers.
Dorsum with black spots middorsally, one per segment, oval in chaetigers 4–12, circular in chaetigers 13–21, oval from chaetigers 22 to posterior end, displaced posteriorly on each segment (Fig. 5A). Middorsal spots circular in live specimens (Fig. 1), circular or oval in median segments in fixed specimens (Supplementary Fig. 1). Each black spot surrounded by a pale thin margin in live specimens, pale margin expanded in posterior half of each segment in fixed specimens (Fig. 5A, D-H). Anterior edge of pale margin surrounded by a semi-circular obscure dark pigmentation (guard lines) in each segment, connecting a pair of wide pigmented lines on anterior margin of branchiae and notopodial chaetal fascicles on each segment (Fig. 5D-H); a pair of inner pigmented lines present on posterior margin of notopodial chaetal fascicles; a pair of outer pigmented lines present on anterior margin of neuropodial chaetae fascicles (Fig. 5B, H, J).
Prostomium with anterior and posterior lobes (Fig. 5B). Anterior lobe with cirriform palps, pale; posterior lobe with lateral antennae arising from its anterior margin, pigmented dorsally, as long as palps; median antenna fully pigmented, arising from anterior margin of caruncle, slightly stouter and about as long as lateral antennae, and 2/5 as long as caruncle (Fig. 5B). Two pairs of black eyes, trapezoidally arranged on posterior prostomial lobe (Fig. 5B). Caruncle with one wider median lobe (crest) and two narrower lateral lobes (crests), each with ~ 35 transverse folds; a chain of black spots present along mid-central lobe (Fig. 5B). Caruncle fused to dorsum of first two chaetigers, with a free end extending posteriorly to middle of chaetiger 4 (Fig. 5B). Lips fused, forming a shallow middorsal groove, and a mid-ventral longitudinal groove extending to mouth (Fig. 5B, C). Mouth surrounded by ventral lips and ventral side of first three chaetigers (Fig. 5B).
Parapodia biramous with widely separated dorsal and ventral rami (Fig. 5I, J). Cirriform branchiae pale, more dorsal to, and slender and shorter than notopodial cirri, only present along chaetigers 1–3 (Fig. 5B). Notopodial cirri biarticulate, dorsally pigmented, located posteriorly to notopodial chaetal fascicles (Fig. 5B, I, J); cirrophore with several rings (Fig. 5I, J), cirrostyle more than 5 times longer than cirrophore in middle parapodia in live specimens. Neuropodial cirri biarticulate, located below neurochaetal fascicles, pale; cirrophore short, cirrostyle more than 10 times longer than cirrophore in middle parapodia (Fig. 5L).
Branchiae bright or dark red in live specimens, bipinnate, present from chaetiger 4 to posterior end (Fig. 5A); with 12–20 alternating branches arising from primary stem, each terminating in smaller branches or digitiform terminal filaments (Fig. 5A, H-G). Branchiae smaller in anterior chaetigers, best developed from median chaetigers to near end and decreasing in size in last few chaetigers (Fig. 5A, H-G). All branchial stem pale, smaller branches pale or yellowish-brown (Fig. 5A, H-G).
Notochaetae three types: (1) bifurcates (Fig. 6A, B), longer tines 3.5-6.0 times longer than shorter tines, only present in first four chaetigers; (2) harpoon chaetae (Fig. 6C-G), with serrations on one side and a very small tine (or “spur”) opposite to serration side; 5–10 denticles in anterior chaetigers to ~ 30 in middle and posterior chaetigers, present from chaetiger 5 to posterior end; (3) spinose chaetae (aciculars) (Fig. 4H), without serrations, located in superior chaetal fascicle, present from anterior to posterior parapodia, several in number, with or without tiny tine (“spur”). Subterminal region of some notochaetae yellowish, throughout body (Fig. 5J, K; Fig. 6B, C, E-H). All notochaetae with tubular cavity extending into longer tines (Fig. 6A-H). Neurochaetae thinner, longer, and more numerous than notopodial chaetae in most chaetigers (Fig. 5J). Neurochaetae bifurcates (Fig. 4I–L), similar to bifurcate notochaetae (Fig. 6A, B), tines short, blunt in anterior parapodia, becoming longer and sharper in posterior parapodia (Fig. 6I-L).
Pygidium with anus dorsal (Fig. 3M); anal cirri digitiform, four times longer than wide (Fig. 5M, N).
Variation. The 23 C. flava specimens collected from Dongshan coastal waters had 30–37 chaetigers, were 35–75 mm long and 11–18 mm wide. Middorsal black spots varied in the ratio of longitudinal length/width (from 1.0 to 3.2) among chaetigers and among specimens. In some specimens (e.g. XMU-Pol-2021-302, 64 mm long; XMU-Pol-2021-307, 68 mm long; and XMU-Pol-2021-310, 37 mm long), circular black spots are present in middle segments; while in some other specimens (e.g. MBM287618, 64 mm long; XMU-Pol-2021-316, 67 mm long; and XMU-Pol-2021-319, 45 mm long), only oval black spots are present throughout the worm dorsum. The sizes of these C. flava specimens as shown in Table 1 indicated that the shape of middorsal spots in median segments were not size-dependent, i.e. circular and oval middorsal spots could be noted in both large- and small-sized specimens.
According to previous studies, 12 specimens of C. flava originally collected from India, Myanmar, Thailand, Singapore, Indonesia, China and Australia have much wider morphological variations in total number of chaetigers (28–42), body length (30–150 mm) and body width (6–26 mm) (Yáñez-Rivera & Salazar-Vallejo 2022; Salazar-Vallejo 2023). Dorsal pigmentation of two of those specimens (i.e. neotype MNHN IA-TYPE 247 and paraneotype MNHN IA-TYPE 252) collected from eastern coast of India had faded seriously, with only middorsal spots left visible.
Remarks. According to the phylogenetic analyses in this study, the 23 specimens of C. flava form a single clade (Fig. 4B), and these specimens have varied-shaped middorsal spots, such as circular, oval, almond, or even blunt rectangular (Fig. 5D-H; Supplementary Fig. 1). The molecular results confirmed Monro (1924)’s opinion that shapes of middorsal spots in C. flava specimens may have a wide variation. Due to the lack of molecular data on C. pulchella specimens, the phylogenetic relationships between C. pulchella and C. flava remain to be solved.
Morphological differences between Chloeia flava and C. pulchella could be noted by checking the type materials. The syntype (BMNH 1971.238) of C. pulchella have oval-shaped but apparently smaller middorsal spots, i.e. shorter than 1/2 of the length of each segment (Salazar-Vallejo 2023: Fig. 45), than either C. flava from India, Thailand, Singapore, Japan, and China (McIntosh 1885: 11; Salazar-Vallejo 2023: Fig. 20; this study, Fig. 5D-H; Supplementary materials) or those specimens previously identified as C. pulchella from India, Indonesia, Thailand and Japan (Horst 1912: Pl. VII, Fig. 3; Izuka 1912: Pl. II, Fig. 4; Salazar-Vallejo 2023: Figs. 46D-F, 47), which have middorsal spots as long as about 2/3 of the length of each segment. Besides, C. pulchella bears acicular neurochaetae and its harpoon notochaetae bear no spurs (Salazar-Vallejo 2023: Fig. 45F, G); while in C. flava, harpoon notochaetae bear tiny spurs, and neurochaetae with only bifurcates (McIntosh 1885: PI. IA. Figure 7, 9; Salazar-Vallejo 2023: Fig. 20E-G; this study: Fig. 6C-G, I-L). Therefore, C. pulchella is obviously a distinct species from C. flava, and C. pulchella should be restricted to only include those specimens that have smaller-sized oval middorsal spots.
The suggested Chinese name of Chloeia flava is “海毛虫”. Some other Chinese names such as “黄海毛虫” or “黄斑海毛虫” for this species were also used, which refers to the remarkable yellowish colour along subdistal areas of notochaetae. But since yellowish notochaetae also present in C. fusca, we suggest using “海毛虫” for this species.
Habitat. Subtidal sandy, sandy mud and muddy sand sediment, in shallow water.
Distribution. Currently known from India (neotype), Indian Ocean, Myanmar, Thailand, Singapore, Indonesia, New Guinea, China, Japan, and Australia. In the China Seas, this species was only collected from the South China Sea and the East China Sea.