Eunice denticulata Webster, 1884

Carrera-Parra, Luis F. & Salazar-Vallejo, Sergio I., 2011, Redescriptions of Eunice filamentosa and E. denticulata and description of E. tovarae n. sp. (Polychaeta: Eunicidae), highlighted with morphological and molecular data, Zootaxa 2880, pp. 51-64 : 56-59

Eunice denticulata Webster, 1884

Figure 2

Eunice denticulata Webster 1884:316 –317, Pl. 10, Figs. 41, 41a–b, 42–45; Fauchald 1992:119 –121, Fig. 37, Tabs. 33, 39; Carrera-Parra & Salazar-Vallejo 1998:1501, Figs. 3 a–e.

Eunice conglomerans Ehlers 1887:93 –95, Pl. 23, Figs. 1 –9, Pl. 24, Figs. 1–4 ; Fauchald 1992:114 –116, Figs. 35a–i; Tabs. 33, 36.

Material examined. Type material: Syntypes of Eunice denticulata USNM 4790 (2 specimens + 7 slides with parapodia), Bermuda Island. 1976–77, col. G.B. Goode. Syntypes of Eunice conglomerans ZMB 6730, Key West, 2–3 m, coll. A. Agassiz. Additional material: USA: Florida, Miami, ECOSUR-OH-P0161(1), 25°44ʹ7ʺ N, 80°09ʹ59.1ʺ W, Virginia Key, Biscayne Bay, Miami Seaquarium beach, 29 May 2008, in sponge. Caribbean, Mexico: Quintana Roo, EUNI-6 IMU1(1), Isla Mujeres, Quintana Roo, col. M.E Caso, 26 May 1962. Guatemala: UMML, sta. P- 614 (1), 16°02ʹN 88°33ʹW, 30 Km off Cabo Tres Punta, 18–31m, 19 Mar 1968. Republica Dominicana: UMML sta. P- 1272 (1), 17°52ʹN 71°41ʹW, 3.5 km off Cabo Rojo, 24m, 18 Jul 1970. UMML sta. P- 1283 (1), 17°31ʹN 71°32ʹW, South of Isla Beata, 18–26m, 19 Jul 1970.

Description. Type materials incomplete (see remarks below). Complete specimen (UMML P-1283) with 395 chaetigers; L10 = 10.3 mm W10 = 4.5 mm. LT = 21.8 cm. Anterior region of body with highly convex dorsum and flat ventrum; body depressed from chaetiger 31. Prostomium clearly shorter than peristomium, prostomial lobes frontally rounded, dorsally swollen; median sulcus deep ( Fig. 2 A). Prostomial appendages in a horseshoe pattern, attached in prostomial furrow, median antenna isolated by gap. Palps digitiform, reaching the posterior end of first peristomial ring. Antennae tapering, lateral antennae reaching second chaetiger, median antenna reaching third chaetiger. Palpophores and ceratophores longer than wide, slightly shorter on median antenna. Palpostyles and ceratostyles without articulation. Eyes rounded, lateral between palp and lateral antenna. Peristomium with first ring seven times longer than second ring, separation between rings dorsal and ventral; peristomial cirri tapering, barely exceeding the middle of first peristomial ring; without articulation ( Fig. 2 A).

Maxillary apparatus with five pairs and one single maxillae; MF = 1+1, 4+4, 6+0, 2+8, 1+1, –+–. MIII part of distal arc, sharp curved teeth, medial teeth longer. Left MIV with both teeth on distal end followed by a long edentate plate ( Fig. 2 L). Right MIV with sharp curved teeth, medial teeth longer. MVI reduced to an edentate plate.

Branchiae pectinate ( Fig. 2 D), in chaetigers 31 to 382, longer and thicker than dorsal cirri, except in last 57 chaetigers where notopodial cirri become longer. One filament per branchia in first 11 and last 19 branchiferous segments; up to three filaments in chaetigers 67–239. Prechaetal lobes inconspicuous transverse fold. Postchaetal lobes rounded in chaetigers 1–54, always shorter than chaetal lobe, inconspicuous in posterior chaetigers. Chaetal lobes rounded to auricular, in chaetigers 1–92 with acicula emerging dorsal to midline; in first 56 chaetigers with a papilla covering acicular tip. From chaetiger 93 conical, with acicula emerging by the middle of neuropodial lobes ( Figs. 2 B–E).

Notopodial cirri without articulation, tapering; in first five chaetigers longer and thicker, becoming thinner gradually, most evident in branchial region, all of similar length until chaetiger 352, posterior ones longer. Ventral cirri in chaetigers 1–3 digitiform, thick; in chaetigers 4–103 with swollen base, transverse welt with digitiform tip; posterior ones digitiform, becoming much longer and thicker on the last 92 chaetigers, always shorter than notopodial cirri ( Figs. 2 B–E).

Chaetae limbate supracicular; pectinates heterodont with up to 12 teeth, fewer pectinates in anterior and posterior chaetigers, abundant in middle chaetigers. Compound falcigers bidentate, with long, thin blade in anterior chaetigers, proximal tooth thicker, sharp, directed laterally; distal tooth sharp, directed upward; both teeth of similar length ( Fig. 2 F). Falcigers in posterior chaetigers with short, wide blade, proximal tooth large, thick, directed laterally; distal tooth short, directed laterally ( Fig. 2 G). Aciculae reddish, tapering, with a small mucro in first three chaetigers; in chaetigers 4–26 with tip slightly expanded to one side ( Fig. 2 H); in chaetigers 27–383 with tip laterally expanded, T-shaped, one side slightly longer ( Fig. 2 J); last 14 chaetigers with aciculae thin, tapering with small mucro. Subacicular hooks from chaetiger 31, bidentate; reddish with distal end darker. Proximal tooth much larger than distal tooth, straight or slightly curved, directed laterally. Distal tooth straight, directed laterally ( Fig. 2 K); paired in some median chaetigers.

Pygidium with two pairs of anal cirri, without articulation; dorsal pair as long as the last seven chaetigers, ventral pair short, as long as the last two chaetigers.

Variation. Material examined varied in L10 from 5.8 to 14 mm, and in W10 from 3.0 to 6.0 mm and varies in the following features: Subacicular hooks begin from chaetiger 19 to 40, Branchiae start from chaetiger 23 to 31, and the last chaetiger with ventral cirri with swollen base varies from 78 to 150. Although there were few specimens, these features seem to be size-dependent. Only the two smallest specimens had the first subacicular hooks in the prebranchial region, in all other specimens, the subacicular hook started posterior to the first branchiae. The maximum number of filaments varied from three to four, with the best development observed in the middle body region, the greater number filaments is present in specimens with L10 greater than 10 mm, and seems to be sizedependent. The number of teeth in some maxillae varies, without any size-dependence, as follows: MIII 6–7, MIV right 7–9.

Barcode. A nucleotide sequence of 660 bp of the section of COI gene used for barcoding was obtained from one specimen collected from Florida, USA (ECOSUR-OH-P0161).

Remarks about type materials. Two syntypes of E. denticulata , both incomplete with 76 and 125 chaetigers (L10= 6–7 mm, W10= 3–3.5 mm), and seven slides with parapodia were examined. Two syntypes of E. conglomerans , both incomplete with 228 and 223 chaetigers (L10 = 13–14 mm, W10 = 6 mm), and a posterior fragment inside a tube were also examined. The examination of type materials enabled us to clarify some issues given in the most recent redescription of these species ( Fauchald 1992). The prostomial appendages of E. conglomerans were described as being arranged in a straight line, evenly spaced, with cylindrical articulations and ring-shaped ceratophores; these appendages are actually arranged in a horseshoe pattern, with the median antenna isolated by a gap, they are without articulations but have long ceratophores. The maxillary apparatus of both species was redescribed without maxilla VI, but in all cases this maxilla is present as an edentate plate; furthermore, maxilla III of E. denticulata was described with three teeth, but it only has two. The branchial pattern was described as palmate for both species, but it is really pectinate; this condition is most evident in the region where branchiae are best developed and certainly difficult to be interpreted when the branchiae have fewer filaments. On the other hand, for E. conglomerans , it was stated that the end of the region with basally swollen ventral cirri was about chaetiger 100; this region is actually larger, ending around chaetigers 144–150. The start of subacicular hooks for E. conglomerans was described as being from chaetiger 22, but in fact they start in chaetigers 35–40.

Discussion. Treadwell (1921) concluded that E. conglomerans must be regarded as a junior synonym of E. denticulata . Later, Monro (1933a) regarded E. denticulata and E. conglomerans as junior synonyms of E. filamentosa . Fauchald (1992), however, considered all three species as valid. But these species have been considered as part of a species complex ( Zanol et al. 2010). Herein, we support Treadwell’s conclusion and agree that there are no differences between E. denticulata and E. conglomerans . We think that Fauchald (1992) regarded these species as valid because of some confusion in his redescriptions, as noted above.

On the other hand, we fully agree with Fauchald’s approach to recognize E. filamentosa and E. denticulata as different species, but under the following arguments: E. filamentosa and E. denticulata differ mainly in the shape of maxillae III (MIII) and in right maxilla IV (MIVr). Thus, E. filamentosa has MIII and MIVr with blunt teeth of similar size, while E. denticulata has MIII and MIVr with sharp, curved teeth, with the medial teeth longer. Further, E. filamentosa has short, wider than long palpophores and ceratophores, while E. denticulata has longer than wide palpophores and ceratophores. Furthermore, both species differ regarding the length of the body region with ventral cirri with swollen bases (VCSB); in E. filamentosa this region extends from chaetigers 33 to 66, and in E. denticulata from about chaetigers 78 to 150. Although this feature is size-dependent, there are significant differences between both species; a specimen of E. denticulata with a L10 of 5.8 mm has VCSB until chaetiger 78; while specimens of E. filamentosa with a L10 of 5.8 mm have VCSB until chaetiger 60; even in a larger specimen of E. filamentosa (L10= 7.6 mm) the VCSB region ends at chaetiger 66.

Another important difference relates to the region with the most developed branchiae. In E. filamentosa , this region is found in the last third of the body, while in E. denticulata this occurs by the middle body. Furthermore, a small specimen of E. filamentosa had a higher number of branchial filaments (bf) (L10 = 4.5 mm, 4 bf), than a large specimen of E. denticulata (L10 = 7.0 mm, 3 bf), reaching four branchial filaments when the size (L10) is 10 mm. Also, E. filamentosa has branchiae which are always larger than notopodial cirri, while in E. denticulata they are shorter than the notopodial cirri in most posterior parapodia.

Other useful parapodial features must be included. In E. filamentosa , the notopodial cirri are equal-sized throughout the body, unlike E. denticulata which has larger notopodial cirri in the posterior parapodia. Other differences can be seen in the chaetae, E. filamentosa has composite falcigers with blades of similar length in anterior and posterior chaetigers, whereas in E. denticulata the blades in anterior chaetigers are larger than those in posterior ones.

The morphological differentiation of E. filamentosa and E. denticulata is further supported by the barcoding data, since they have a genetic divergence of 19.6%. Figure 4 shows a clear divergence between these species. The main variation in the sequences of both species was in the GC% of the third codon position; in E. denticulata the content was of 45% while in E. filamentosa it varied from 33.2 to 33.6%.

Distribution. Grand Caribbean Region.

Figures

FIGURE 1. Eunice filamentosa. A. Anterior end, dorsal view; B. Chaetiger 3, frontal view; C. Chaetiger 17, frontal view; D. Chaetiger 31, frontal view; E. Chaetiger 230, frontal view; F. Maxillae III and IV, ventral view; G. Compound falcigers, chaetiger 3; H. Compound falcigers, chaetiger 281; J. Subacicular hook, chaetiger 230; K. Acicula, chaetiger 17; L. Acicula, chaetiger 93; M. Acicula, chaetiger 281. A. from specimen ECOSUR-OH- 562; B – M. from specimen ECOSUR-OH- 158. Scale bars: A, 1.5 mm; B, C, E, 0.12 mm; D, F, 0.15 mm; G, H, 0.01 mm; J, K, L, M, 0.02 mm.

FIGURE 2. Eunice denticulata. A. Anterior end, dorsal view; B. Chaetiger 3, frontal view; C. Chaetiger 17, frontal view; D. Chaetiger 134, frontal view; E. Chaetiger 384, frontal view; F. Compound falciger, chaetiger 3; G. Compound falciger, chaetiger 267; H. Subacicular hook, chaetiger 267; J. Acicula, chaetiger 17; K. Acicula, chaetiger 134; L. Maxillae III and IV, ventral view. A, D, F. from syntype of E. conglomerans ZMB 6730; B, C, E, G – L. from specimen UMML P- 1283. Scale bars: A, 0.4 cm; B, C, D, 2.0 mm; E, 1.4 mm; F, G, H, 0.01 mm; J, 0.02 mm; K, 0.025 mm; L, 0.2 mm.

FIGURE 3. Eunice tovarae n. sp. A. Anterior end, dorsal view; B. Chaetiger 3, frontal view; C. Chaetiger 17, frontal view; D. Chaetiger 118, frontal view; E. Chaetiger 231, frontal view; F. Maxillae III and IV, ventral view; G. Compound falciger, chaetiger 3; H. Compound falciger, chaetiger 215; J. Acicula, chaetiger 17; K. Acicula, chaetiger 118; L. Acicula, chaetiger 231; M. Subacicular hook, chaetiger 84. A – E, G – M. from holotype ECOSUR- 104; F. from paratype ECOSUR- 105. Scale bars: A, 1.0 mm; B, C, E, 0.11 mm; D, 0.22 mm; F, 1.3 mm; G, H, 0.01 mm; J, K, L, 0.02 mm; M, 0.03 mm.

FIGURE 4. Simplified neighbour-joining tree of COI sequences included in this study using K 2 P distances.