Eunice hainanensis, Wu, Xuwen, Sun, Ruiping, Liu, Ruiyu & Xu, Kuidong, 2013

Wu, Xuwen, Sun, Ruiping, Liu, Ruiyu & Xu, Kuidong, 2013, Two new species of Eunice Cuvier, 1817 (Polychaeta, Eunicidae) from the coral reefs of Hainan Island with a key to 16 species of Eunice from China seas, Zootaxa 3652 (2), pp. 249-264 : 250-260

Eunice hainanensis n. sp.

( Figs 1–4 )

Material examined. Holotype: MBM119816, SCS, Hainan Island, Daoliao Cun, 19.9°N, 109.5°E, from coral reef, coll. Yanli Lei, 27 Nov. 2007; Paratype: MBM119817 (n=1), SCS, Hainan Island, Linchang Jiao, 19.8°N, 109.5°E, from coral reef, coll. Yongliang Wang, 29 Nov. 2007.

Measurements. The holotype is complete with 570 chaetigers, last 28 chaetigers regenerating in the posterior end, TL = 137 mm, L10 = 2.9 mm, W10 = 1.4 mm, Wm = 1.7 mm (at chaetiger 50). The paratype is also complete, with 348 chaetigers, last 70 chaetigers regenerating in the posterior end, TL = 95 mm, L10 = 2.7 mm, W10 = 1.7 mm, Wm = 1.9 mm (at chaetiger 40).

Description. Preserved animal pale, epithelium slightly iridescent. Body long and slender, with a large number of chaetigers. Anterior 6 or 7 chaetigers cylindrical, becoming dorso-ventrally flattened until chaetigers 70–80, thereafter with slightly convex dorsum and flat ventrum. Posterior body coiled and fragile when preserved. Middorsal furrow present from chaetiger 8 extending posteriorly to end. Body cavity with eggs from approximate chaetiger 282 in holotype.

Prostomium equal to peristomium in length and width, less than 1/2 as deep as peristomium, appearing bilobed separated by shallow ventral groove, continuing dorsally to base of median antenna. Prostomial lobes frontally rounded, dorsally flattened ( Fig. 1 B, C). Prostomial appendages arranged in a shallow semicircle, similar in thickness. Palps and lateral antennae emerging close together, median antenna isolated in posteromedial region. Palpophores and ceratophores wider than length. Palpostyles and ceratostyles tapering, with indistinct articulations. Median antenna slightly shorter than lateral antennae, with five articulations, extending to posterior edge of first peristomial ring; lateral antennae with seven articulations, to chaetiger 1; palps with five articulations, to near posterior edge of first peristomial ring ( Fig. 1 A – C). Eyes black, subspherical, lateral to bases of lateral antennae ( Fig. 1 A). Peristomium cylindrical. Separation between rings distinct dorsally and ventrally, first ring three times longer than second ring. Peristomial cirri tapering, without articulations, extending to middle of first peristomial ring ( Fig. 1 A – C).

Maxillary apparatus brown to dark brown, with five pairs of maxillae and an unpaired plate on left side. MF = 1+1, 5+5, 5+0, 4+5, 1+1, 1+1. MxIII part of distal arc, partly located behind left MxII, with five blunt teeth of similar size. Left MxIV with four teeth arranged in two rows. MxV and MxVI reduced to edentate plates ( Fig. 2 A). Mandibles brown, calcareous pieces on cutting edges missing ( Fig. 2 B).

Branchiae present from chaetiger 69 (72 in paratype) to last chaetiger, more than 65% of total number of chaetigers. Holotype with one branchial filament in chaetigers 69–102, two filaments occuring from chaetiger 103, three from chaetiger 174, maximum 4 filaments from chaetiger 234 ( Fig. 3 D – L). Branchial filaments digitiform, shorter than notopodial cirri in anterior branchial chaetigers ( Fig. 3 D – G), both longer and thicker than notopodial cirri from about chaetiger 170 ( Fig. 3 H – L).

Notopodial cirri tapering, without articulations, medially slightly inflated in prebranchial region ( Fig. 3 A–C), becoming gradually thinner posteriorly, about half as thick in posterior parapodia ( Fig. 3 I–L); all of similar length ( Fig. 3 A–L). Ventral cirri tapering in chaetigers 1–5, with inflated bases from chaetiger 6 until chaetiger 180; inflated bases ovate, narrow tips digitiform or tapering, distinctly separated from bases; bases of posterior ventral cirri transverse welts ( Fig. 3 A–L). Prechaetal lobes low transverse folds in all chaetigers. Posterior lobes rounded in anterior chaetigers, about as high as acicular lobes; becoming low transverse folds from chaetiger 100. Chaetal lobes distally truncate to rounded with aciculae emerging slightly dorsal to midline in anterior chaetigers, dorsal portion longer covering acicular tip; chaetal lobes tapering from about chaetiger 100; aciculae emerging at midline from about chaetiger 200 ( Fig. 3 A–L).

Limbate chaetae, tapering, with narrow wings. Shafts of pectinate chaetae strongly hirsute; blades furled, heterodont with 7–10 teeth; pectinate chaetae of similar size and shape in anterior and posterior chaetigers ( Fig. 4 M, N). Shafts of compound falcigers slightly inflated, marginally serrated ( Fig. 4 G–L). Appendages bidentate, blade in anterior chaetigers slender, proximal tooth blunt, slightly larger than distal tooth, directed laterally; distal tooth gently curved, directed upward ( Figs 4 G, H). Blade in median and posterior chaetigers wider than in anterior chaetigers, proximal tooth triangular, much larger than distal tooth, directed laterally; distal tooth gently curved, directed slightly laterally ( Fig. 4 I–L). Guards marginally serrated, distally tapering in anterior chaetigers, obliquely truncate from chaetiger 80. Aciculae straight or slightly curved, tapering with blunt or pointed tips; 2–3 aciculae per parapodium in anterior 30 chaetigers ( Fig. 4 A), single in most chaetigers thereafter ( Fig. 4 B–D). Aciculae black to dark brown in anterior chaetigers, becoming light posteriorly, brown to light brown in posterior chaetigers ( Fig. 4 A–D). Subacicular hooks translucent, bidentate, present from chaetigers 90 (83 in paratype), missing in some chaetigers, single per parapodium in most chaetigers thereafter. Proximal tooth triangular, much larger than distal tooth; distal tooth directed upward ( Fig. 4 E, F).

Pygidium with two pairs of anal cirri, without articulation, dorsal pair twice as long as ventral pair.

Distribution. The species has been found only in dead coral rocks from the reefs in the northwestern region of Hainan Island, northern South China Sea.

Etymology. Named after the Hainan Island (province) where the species was discovered.

Remarks. The new species Eunice hainanensis has translucent bidentate subacicular hooks and branchiae present more than 65% of total number of chaetigers. With these characters the species can be classified into the Eunice group A-2, as proposed by Fauchald (1992). So far, ten species have been included in the group (Fauchald 1992; Hartmann-Schröder & Zibrowius 1998; Nogueira et al. 2001; León-González et al. 2004). Among these species, E. hainanensis only resembles E. schizobranchia Claparède, 1870 , in having a long and slender body with numerous chaetigers and a very late start of branchiae: the new species has 348–570 chaetigers with branchiae starting from the chaetigers 69–72, and E. schizobranchia has about 731 chaetigers with branchiae from the chaetiger 67. However, E. hainanensis differs distinctly from the latter by the presence of MxVI (vs. absence). Besides, E. hainanensis is much smaller (1.7–1.9 mm vs. 5 mm in maximal width) and stouter (body length to width ratio 50–80: 1 vs. 130: 1). Furthermore, Eunice hainanensis differs from E. schizobranchia by the following minor characters: (i) prostomial appendages are articulated (vs. smooth); (ii) subacicular hooks emerge not exceeding ventral cirri with proximal teeth directed laterally and distal teeth directed upward (vs. project beyond ventral cirri with both teeth directed distally); and (iii) anterior compound falcigers have both teeth short and blunt with proximal teeth larger than distal teeth (vs. both teeth are long and slender or reduced to small knobs with proximal teeth smaller than distal teeth). These differences justify the validity of the new species.

Eunice carrerai n. sp. ( Figs 5–8 )

Material examined. Holotype: MBM 191171, SCS, Hainan Island, Yalong Bay, the north part of Yezhu Isl., 18.2°N, 109.6°E, coral reef, diving 5 m, coll. Dieter Fiege and Ruiping Sun, 26 Mar. 1992. Paratypes (13 specimens): MBM 191172 (n=1), collected at the same time and locality as the holotype; MBM 191176 (n=2), SCS, Hainan Island, Yalong Bay, the south part of Yezhu Isl., coral reef, 18.2°N, 109.6°E, diving 10 m, coll. Dieter Fiege and Ruiping Sun, 25 Mar. 1992; MBM 191174 (n=2), same locality, coral reef, diving 6–10 m, 21–25 Nov. 1990; MBM 191111 (n=3), SCS, Hainan Island, Yalong Bay, Yezhu Isl., 18.2°N, 109.6°E, coral reef, diving 3–7 m, coll. Dieter Fiege and Ruiping Sun, 20 Mar. 1992; MBM 191112 (n=1), same locality, coral reef, diving 6–11m, coll. Dieter Fiege and Ruiping Sun, 20 Mar. 1992; MBM 191173 (n=1), SCS, Hainan Island, Hainan, Shalao, 19.2– 19.4 °N, 110.6– 110.7 °E, diving 3–5 m, coll. Dieter Fiege and Ruiping Sun, 5 Apr. 1992; MBM 191114 (n=1), same locality, coral reef, diving 3–5 m, coll. Dieter Fiege and Ruiping Sun, 5 Apr. 1992; MBM 191170 (n=1), SCS, Hainan Island, Yalong Bay, Xizhou Isl., 18.19°N, 109.67°E, 20 Nov. 1990; MBM 191113 (n=1), SCS, Hainan Island, Linchang Jiao, 19.8°N, 109.5°E, coral reef, coll. Dieter Fiege and Ruiping Sun, 11 Apr. 1992.

Measurements. The holotype has 137 chaetigers, TL = 97 mm, L10 = 9.2 mm, W10 = Wm = 5.1 mm. The paratype MBM 191172 is broken into two fragments: anterior part with 47 chaetigers and 55 mm long, L10 = 8.4 mm, W10 = Wm = 4.0 mm (at chaetiger 5). The paratypes MBM 191176 consist of a complete specimen and the anterior fragment of a broken specimen: the complete one has 135 chaetigers, TL = 122 mm, L10 = 8.6 mm, W10 = 4.3 mm, Wm = 4.7 mm (at chaetiger 12), and the broken one has 58 chaetigers, about 56 mm long, L10 = 6.8 mm, W10 = Wm = 4.0 mm.

Description: Preserved animals pink-colored, epithelium slightly iridescent. Body long, more or less cylindrical. Anterior chaetigers distinctly convex dorsally, ventrum less convex to almost flattened ( Fig. 5 D).

Prostomium shorter and narrower than first peristomial ring, less than 1/2 as deep as peristomium, bilobed anteriorly, median sulcus deep, V-shaped. Prostomial lobes frontally rounded, dorsally inflated ( Fig. 5 A–C). Prostomial appendages arranged in a semicircle, similar in thickness. Palps and lateral antennae emerging slightly closer together, median antenna isolated. Palpophores and ceratophores wider than length, ceratophores covered by peristomial fold ( Fig. 5 A, B). Palpostyles and ceratostyles digitiform with moniliform articulations, articulations indistinct in inner 1/3 to 1/5 of each ceratostyle. Median antenna longer than lateral antennae, with 10 articulations, extending to chaetiger 2; lateral antennae with up to 12 articulations, to chaetiger 3; palps with nine articulations, to posterior edge of first peristomial ring ( Fig. 5 B). Eyes spherical, lateral to bases of lateral antennae, hidden bellow peristomial fold ( Fig. 5 A, D). Peristomium cylindrical. Separation between rings distinct dorsally and ventrally, first ring three times longer than second ring. Peristomial cirri tapering, with six indistinct articulations, extending to anterior edge of first peristomial ring ( Fig. 5 A, D).

Maxillary apparatus brown to dark brown, with five pairs of maxillae and an unpaired plate on left side. MF = 1+1, 5+5, 7+0, 6+10, 1+1, 1+1. MxIII part of distal arc, with seven blunt teeth of similar size. MxV with a large square ridge. MxVI reduced to an edentate plate ( Fig. 6 A). Mandibles brown, hard; cutting edges marked with concentric lines, covered by a pair of white calcareous pieces (easily detached) ( Fig. 6 B).

Branchiae present from chaetiger 3 to chaetiger 130, more than 65% of total number of chaetigers. One branchial filament in chaetiger 3, four filaments in chaetiger 4, six filaments in chaetiger 5, maximum 10 filaments in chaetiger 10. In chaetigers 6–17 with 8–10 filaments, 5–7 filaments in chaetigers 18–47, 3–5 filaments in chaetigers 48–80, 1–2 filaments in chaetigers 81–130, last five branchiae single, very small. Branchial filaments digitiform, shorter and thinner than notopodial cirri in all branchial chaetigers ( Fig. 7 B–J).

Notopodial cirri digitiform, with 2–5 indistinct articulations limited to anterior 80 chaetigers, without articulations in following chaetigers ( Fig. 7 A–J); anterior notopodial cirri long and thick ( Fig. 7 A–D), gradually becoming shorter and narrower posteriorly ( Fig. 7 E–J). Ventral cirri thick, tapering in chaetigers 1–5 ( Fig. 7 A), with inflated bases in chaetigers 6–30 ( Fig. 7 B–D); inflated bases ovate, narrow tips tapering; from chaetiger 31 ventral cirri gradually becoming short and slender, tapering or digitiform without inflated bases ( Fig. 7 E–J). Pre- and postchaetal lobes low transverse folds in all chaetigers. Postchaetal lobes inflated in anterior chaetigers, becoming flat from chaetiger 21. Chaetal lobes distally obliquely truncate, dorsal portion longer; aciculae emerging slightly dorsal to midline in anterior chaetigers, at midline from about chaetiger 50 ( Fig. 7 A–J).

Limbate chaetae tapering, with narrow wings. Shafts of pectinate chaetae hirsute; blades flat, heterodont with 13–16 teeth; pectinate chaetae of similar size and shape in anterior and posterior chaetigers ( Fig. 8 K, L). Shafts of compound falcigers slightly inflated, marginally smooth. Appendages bidentate, of similar size and shape in anterior and posterior chaetigers ( Fig. 8 F–J). Proximal tooth in anterior chaetigers triangular, shorter than distal tooth, directed laterally; distal tooth curved and sharp, directed upward ( Fig. 8 F–H); in posterior chaetigers proximal tooth larger than that in anterior chaetigers, distal tooth strongly curved, directed slightly laterally ( Fig. 8 I, J). Guards marginally serrated ( Fig. 8 F–J). Aciculae straight or slightly bent, tapering with blunt tips; Aciculae brown to dark brown, projecting from chaetal lobes, paired in most parapodia ( Fig. 8 A, C), but up to three aciculae per parapodium in some chaetigers ( Fig. 8 B). Subacicular hooks similar to aciculae in color and thickness, bidentate, starting from chaetiger 24, single per parapodium in all chaetigers thereafter. Proximal tooth triangular, larger than distal tooth; distal tooth directed upward ( Fig. 8 D, E).

Pygidium bearing one pair of anal cirri, with six moniliform articulations, extending to last 5th chaetiger ( Fig. 5 E).

Variations. Most of the specimens examined ranged from 6.5 to 9.2 mm in L10, and from 3.3 to 5.1 mm in W10, and a small specimen likely juvenile is 4.5 mm in L10 and 1.8 mm in W10. The chaetiger on which subacicular hooks start varies from 22 to 26. The last chaetiger with ventral cirri possessing inflated bases varies from 25 to 30. The chaetiger on which branchiae start varies from 3 to 4. The maximum number of branchial filaments varies from 5 to 10, depending on the size of specimens: specimens with W10 = 3.3–4.6 mm have a maximum number of 5–7, while the holotype (W10 = 5.1 mm) has up to 10 filaments.

Distribution and habitat. The species has been found in the coral reefs of Yalong Bay, Shalao and Linchang Jiao, at the southern, eastern and northwestern part of Hainan Island, respectively. All specimens were collected from dead corals at depths of 3– 11 m.

Etymology. Eunice carrerai is named in honor of Dr. Luis F. Carrera-Parra, for his great contributions to the field of polychaete taxonomy, and in appreciation of his help to the first author.

Remarks. Eunice carrerai n. sp., has dark bidentate subacicular hooks and branchiae present more than 65% of total number of chaetigers and thus belongs to the Eunice group B-2 proposed by Fauchald (1992). So far, about 70 species can be classified into the group. The new species has two very distinct features: (i) the branchiae starting in the chaetigers 3–4 and (ii) the prostomial appendages having conspicuous moniliform articulations. Among the species in group B-2, only six species possess these features and thus should be compared: E. laurillardi Quatrefages, 1866 , E. longicirris Grube, 1869 , E. biformicirrata (Treadwell, 1922) , E. grubei Gravier, 1900 , E. northioidea Moore, 1903 , and E. marcusi Zanol et al., 2000 (Table 1). Eunice carrerai can be easily distinguished from the first five species by the presence of MxVI (vs. absence). It differs from E. marcusi by the notopodial cirri with indistinct articulations limited to the anterior chaetigers (vs. moniliform throughout), the peristomial cirri reaching the anterior edge of first peristomial ring (vs. reaching the anterior edge of prostomium) and the branchiae with up to 5–10 filaments (vs. 3–4 filaments).

Comparison of all the seven species of the group B-2 is provided in Table 1. We summarize the key morphological characters of the total 16 species of Eunice recorded in China seas in Table 2 and provide the following key to these species with notes on their distribution.

It is worthy of note that the key probably does not include all the species of Eunice present in China seas. It is important to check table 2 as well as species descriptions to make sure the identification is correct.

Figures

FIGURE 1. Eunice hainanensis n. sp., paratype (MBM 119817). A. Anterior chaetigers, lateral view; B. Anterior chaetigers, dorsal view; C. Anterior chaetigers, ventral view. Scale bar = 1 mm (A – C).

FIGURE 2. Jaw apparatus of Eunice hainanensis n. sp., paratype (MBM 119817). A. Maxillae, dorsal view; B. Mandibles, ventral view, calcareous pieces missing. Scale bar = 0.5 mm (A, B).

FIGURE 3. Parapodia of Eunice hainanensis n. sp., paratype (MBM 119817). A. Parapodium 12; B. Parapodium 29; C. Parapodium 50; D. Parapodium 76; E. Parapodium 102; F. Parapodium 118; G. Parapodium 139; H. Parapodium 173; I. Parapodium 191; J. Parapodium 204; K. Parapodium 223; L. Parapodium 276. A, B, E – G, I – L: anterior views; C, D, H: posterior views. Scale bar = 100 μm.

FIGURE 4. Chaetae of Eunice hainanensis n. sp., paratype (MBM 119817). Aciculae (A – D): A. chaetiger 13; B. chaetiger 55; C. chaetiger 98; D. chaetiger 281; Subacicular hooks (E, F): E. chaetiger 93; F. chaetiger 281; Compound falcigers (G – L): G. chaetiger 10; H. chaetiger 28; I. chaetiger 55; J. chaetiger 98; K. chaetiger 181; L. chaetiger 281; Pectinate chaetae (M, N): M. chaetiger 100; N. chaetiger 181. Scale bars = 100 mm (A – D), 50 mm (E – L) and 20 mm (M, N).

FIGURE 5. Eunice carrerai n. sp. A. Anterior chaetigers, dorsal view; B. Prostomial appendages (left part), dorsal view; C. Anterior chaetigers, ventral view; D. Anterior chaetigers, lateral view; E. Posterior chaetigers, dorsal view. A, C – E: paratype from MBM 191176; B: the other one from MBM 191176. Scale bars = 2 mm (A – E).

FIGURE 6. Jaw apparatus of Eunice carrerai n. sp., holotype (MBM 191171). A. Maxillae, dorsal view, proximal end of maxillary carriers broken; B. Mandibles, ventral view, left calcareous piece detached, right one broken. Scale bar = 1 mm (A, B).

FIGURE 7. Parapodia of Eunice carrerai n. sp., paratype (MBM 191176). A. Parapodium 3; B. Parapodium 8; C. Parapodium 17; D. Parapodium 24; E. Parapodium 31; F. Parapodium 48; G. Parapodium 60; H. Parapodium 79; I. Parapodium 92; J. Parapodium 119. F, G, I, J: anterior views; A – E, H: posterior views. Scale bar = 1 mm (A – J).

FIGURE 8. Chaetae of Eunice carrerai n. sp., paratype (MBM 191172). Aciculae (A – C): A. chaetiger 25; B. chaetiger 86; C. chaetiger 108; Subacicular hooks (D, E): D. chaetiger 27; E. chaetiger 108; Compound falcigers (F – J): F. chaetiger 5; G. chaetiger 5; H. chaetiger 25; I. chaetiger 75; J. chaetiger 108; Pectinate chaetae (K, L): K. chaetiger 25; L. chaetiger 108. Scale bars = 100 mm (A – E), 50 mm (F – J) and 20 mm (K, L).