Marphysa nobilis Treadwell, 1917

Molina-Acevedo, Isabel C. & Carrera-Parra, Luis F., 2015, Reinstatement of three species of the Marphysa sanguinea complex (Polychaeta: Eunicidae) from the Grand Caribbean Region, Zootaxa 3925 (1), pp. 37-55 : 44-48

Marphysa nobilis Treadwell, 1917

Figures 4–6 , 10

Marphysa nobilis Treadwell, 1917: 265 –266, Pl. 3, Figs 3–9 ; 1921:71–73, Pl. 6, Figs 9 –12, text–figs 245–256.

Material examined. Type material: Holotype AMNH VI–1915 –1350, Florida, Mangrove Key, 25°23' N 80°18' W, Jun 1915, in sand exposed at extreme low tide. Paratype MCZ 2493, Florida, Dry Tortugas, Long Key, 24°37' N 82°51' W, Jun 1915. Additional material: ECOSUR-OH-P0121 (1), ECOSUR-OH-P0122 (1), ECOSUR-OH- P0123 (1), ECOSUR-OH-P0125 (1), ECOSUR-OH-P0126 (1), ECOSUR-OH-P0127 (1), ECOSUR-OH-P0128 (1), Xmapoit beach, Contoy Island, Quintana Roo, Mexican Caribbean 21°28'19'' N 86°47'22.5'' W, 22 Feb 2008, in sediment with turtle grass Thalassia testudinum .

Description. Holotype complete, with 350 chaetigers, L10= 13.6 mm, W10= 6.5 mm, TL= 315 mm. Anterior region with convex dorsum, venter flat without groove; body depressed from chaetiger 5, widest at chaetiger 14, tapering after chaetiger 39.

Prostomium bilobed, 2.1 mm long, 3.5 mm wide; lobes frontally oval; median sulcus shallow ( Fig. 4 A–B), ventral sulcus deep. Prostomial appendages in semicircle, median antenna isolated by gap. Palps reaching first peristomial ring; lateral antennae reaching anterior end of second peristomial ring; median antenna incomplete, in paratype median antenna reaching anterior end of third chaetiger. Palpophores and ceratophores ring-shaped, short, thick; palpostyles and ceratostyles digitiform, slender, without articulation. Eyes rounded, translucent, between palp and lateral antenna.

Peristomium longer and wider than prostomium (3 mm long, 5 mm wide), first ring four times longer than second ring; separation between rings distinct on ventral and lateral sides, faintly visible dorsally ( Fig. 4 A–C). Inferior lip with a slight central depression with shallow wrinkles ( Fig. 4 C).

Maxillary apparatus lost in holotype, in paratype maxillary apparatus partially everted, some maxillae damaged, with four pairs and one single maxilla, MF= 1+1, 3+3, 4+0, 4+7, 1+1. In one specimen (ECOSUR-OH- P0128) MF= 1+1, 3+3, 5+0, 3+7, 1+1 ( Fig. 4 D). Maxillary carriers 4 times shorter than MI, anterior region rectangular, posterior end triangular, with a pair of oval wings situated at the lateral margins of maxillary carriers. MI forceps-like, without attachment lamella; maxilla with falcal arch at right angle, well developed. Closing system 7 times shorter than MI ( Fig. 4 D); ligament between MI and MII rectangular, dark. MII wide, without attachment lamella; with triangular recurved teeth; cavity opening oval, 3.5 times shorter than MII ( Fig. 4 D), rectangular ligament between MII and MIII and right MIV, sclerotized ( Fig. 4 E). MIII short, curved, forming part of distal arc; with blunt teeth, basal tooth smaller; with short attachment lamella situated only in the center of posterior edge of maxilla ( Fig. 4 E). Left MIV with wide rounded base; distal tooth longer; attachment lamella semicircular, more developed in the base of maxilla, situated 2/3s of distance from posterior edge of maxilla ( Fig. 4 E). Right MIV with first three teeth larger, triangular; attachment lamella wide, more developed in the central portion, situated along posterior edge of maxilla ( Fig. 4 D). MV rectangular, longer than wide, with a blunt short tooth, located on top of maxilla. Mandibles dark; cutting plates whitish, without distinct growth rings ( Fig. 4 F).

Branchiae pectinate with up to 5 filaments, present from chaetigers 24L–25R to 310L–313R ( Fig. 5 B). First pair and last 15 with one filament; with five filaments in chaetigers 46–252 ( Fig. 10 ). Branchial filaments longer than dorsal cirri.

First three parapodia smaller; best developed from chaetigers 4 to 13, posterior ones becoming gradually smaller. Notopodial cirri without articulation; slightly longer than ventral cirri, digitiform with a swollen expansion near its base, best developed from chaetigers 5 to 23, posterior ones gradually decreasing in size, becoming slender about chaetiger 33 ( Fig. 5 A–C). Prechaetal lobes as transverse fold in all chaetigers ( Fig. 5 A–C). Chaetal lobes rounded in all chaetigers, in anterior chaetigers with aciculae emerging dorsal to midline, shorter than postchaetal lobe; in posterior chaetigers with aciculae emerging slightly in midline, longer than other lobes ( Fig. 5 A–C). Postchaetal lobes well developed from chaetigers 1 to 79, first four conical, from chaetigers 5 to 79 rounded, larger than other lobes; posterior ones inconspicuous ( Fig. 5 A–C). Ventral cirri conical in chaetigers 1–11; in chaetigers 12–306 with oval swollen base and digitiform tip, gradually reducing in size; from chaetiger 307 conical ( Fig. 5 A–C).

Aciculae dark, tapering, with up to 3 in anterior chaetigers; from chaetiger 15 with up to 2; from chaetiger 193 with one acicula, occasionally two.

Chaetae limbate supracicular of two sizes in same chaetiger, larger in anterior region, reduced in number around chaetiger 22. Two types of pectinate chaetae, isodonts wide with short and fine teeth present in all chaetigers, in anterior chaetigers with 6–7 pectinate chaetae with up to 14 teeth, in posterior ones with 12 pectinate chaetae with about 17 teeth ( Fig. 5 D). Anodonts wide with long and thick teeth in median and posterior chaetigers, with 2–3 pectinate chaetae in median chaetigers with up to 16, in posterior chaetigers with 7 pectinate chaetae with up to 14 teeth ( Fig. 5 E). Compound spinigers present in all chaetigers ( Fig. 5 F), blades of two sizes in same chaetiger, shorter blade in anterior region, abundant in chaetigers 5–30. Subacicular hooks unidentate, tapering, translucent on distal end, dark in basal end ( Fig. 5 G), with discontinuous distribution in median region, from chaetigers 255 to 344 with one hook per chaetiger; last six chaetigers without hooks.

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

Variation. Material examined varied in L10 from 6 to 13.6 mm, and in W10 from 3.7 to 7.5 mm and varied in the following features: palps reaching first peristomial ring or second peristomial ring; lateral antennae reaching second peristomial ring or chaetiger 2; median antenna reaching posterior end of second peristomial ring or posterior end of chaetiger 2. Maxillary formula varied as follows: MII 3–4+3–4, MIII 5–6, MIV 3–4+7–8. Attachment lamella of MIII was not observed in two specimens (ECOSUR-OH-123,128). Branchiae start in chaetigers 17–27; only two specimens were complete (holotype and ECOSUR-OH-121), last 37 and 34 chaetigers lacked branchiae, respectively. Maximum number of branchial filament varied from 4 to 6; some incomplete specimens did not possess enough segments to reach the region with the highest number of filaments; therefore, it is possible that these specimens could reach a higher number. A positive length-dependent variation of the beginning of branchiae was found (R2= 0.48, n=8; Fig. 6 ). The last chaetiger with well developed postchaetal lobe varies from chaetigers 39 to 71; it appears that the number of chaetigers with well developed postsetal lobe increases with body size. The start of ventral cirri with swollen base varies from chaetiger 10 to 11; in the two complete specimens, the ventral cirri with swollen base end at chaetigers 44 and 51 before the pygidium, respectively. Start of subacicular hooks varies from chaetigers 31 to 94; apparently, this is a length dependent feature. Furthermore, subacicular hooks seem to be continuously present in specimens with L10 less than 6 mm, above this length the presence of hooks is discontinuous.

Habitat. In sand ( Treadwell 1917), and sediment with seagrasses ( Thalassia testudinum ).

Distribution. Dry Tortugas, Florida; Contoy Island, Mexican Caribbean; Montego Bay, Jamaica and Buccoo Bay, Tobago.

Discussion. Treadwell (1917) described the live specimen as flesh colored, iridescent in the anterior region; with some green bands on prostomial appendages and numerous yellowish spots scattered along the anterior body region. This color pattern agrees with the specimens collected in the Mexican Caribbean ( Fig. 4 B).

In the original description, Treadwell (1917) stated that the subacicular hooks are bidentate; however, the examination of type material and additional material enabled us to clarify that subacicular hooks are unidentate and they could be lost in some chaetigers.

Marphysa nobilis belongs to group B2 ( Fauchald 1970) and it is close to M. aransensis (from Texas), M. borradailei Pillai, 1958 (from Sri Lanka), M. furcellata Crossland, 1903 and M. macintoshi Crossland, 1903 (both from Zanzibar) by having unidentate subacicular hooks. The last three species differ from M. nobilis by having compound spinigers restricted to anterior chaetigers; while M. nobilis has compound spinigers in all chaetigers. Furthermore, M. nobilis differs from M. aransensis by having eyes, subacicular hooks with translucid distal end and dark basal region, and branchiae beginning from chaetiger 17; while M. arasensis lacks eyes, has translucent subacicular hooks, and branchiae beginning from chaetiger 28.

As mentioned above, M. nobilis was synonymized with M. sanguinea due to the supposed morphological similarity; nevertheless, we found enough differences to consider them as distinct species. Marphysa nobilis differs mainly from M. sanguinea by having unidentate subacicular hooks, and dorsal cirri with a swollen expansion near their bases; whereas M. sanguinea has bidentate subacicular hooks, and triangular dorsal cirri.

Figures

FIGURE 3. Marphysa acicularum Webster, 1884. Syntype USNM 4793. A. Isodont pectinate chaetae, wide with short and fine teeth, anterior chaetiger; B. Anodont pectinate chaetae, wide with long and slender teeth, posterior chaetiger; C. Compound spiniger, chaetiger 103; D. Aciculae, median chaetiger (left acicula with distal end partially broken); E. Bidentate subacicular hook, median chaetiger; F. “ Unidentate ” subacicular hook, median chaetiger. Scale bars: A, 5 µm; B, 5.5 µm; C, 20 µm; D, 18 µm; E – F, 14 µm.

FIGURE 4. Marphysa nobilis Treadwell, 1917. A. Anterior end, dorsal view; B. Anterior end, dorsal view, live specimen; C. Anterior end, ventral view; D. Maxillary apparatus, dorsal view; E. Left MII-MV, dorsal view; F. Mandibles. A from holotype AMNH VI – 1915 – 1350; B – C from ECOSUR-OH-P 0128; D – F from ECOSUR-OH-P 0126. Scale bars: A, 1.5 mm; B – C: 2 mm; D – F, 1 mm.

FIGURE 5. Marphysa nobilis Treadwell, 1917. Holotype AMNH VI – 1915 – 1350. A. Parapodium 9, anterior view; B. Parapodium 139, anterior view; C. Parapodium 321, anterior view; D. Isodont pectinate chaetae, wide with short and fine teeth, chaetiger 139; E. Anodont pectinate chaetae, wide with long and thick teeth, chaetiger 139; F. Compound spiniger, chaetiger 321; G. Subacicular hook, distal end, chaetiger 321. Scale bars: A, 300 µm; B, 427 µm; C, 137 µm; D, 15 µm; E, 45 µm; F, 56 µm; G, 24 µm.

FIGURE 6. Length-dependent variation of beginning of branchiae in Marphysa nobilis (n = 8).

FIGURE 7. Marphysa viridis Treadwell, 1917. A. Anterior end, dorsal view; B. Anterior end, ventral view; C. Maxillary apparatus, dorsal view; D. Left MI-MV, dorsal view; E. Mandibles. A – B from holotype AMNH VI – 1915 – 1293; C – E from ECOSUR-P 2677. Scale bars: A – E, 1 mm.

FIGURE 8. Marphysa viridis Treadwell, 1917. A. Parapodium 3, anterior view; B. Parapodium 14, anterior view; C. Parapodium 103, anterior view; D. Parapodium 167, anterior view; E. Parapodium 200, anterior view; F. Subacicular hook, distal end, chaetiger 155; G. Isodont pectinate chaetae, narrow with short and fine teeth, chaetiger 14; H. Isodont pectinate chaetae, wide with short and fine teeth, chaetiger 103; I. Anodont pectinate chaetae, wide with long and thick teeth, chaetiger 103; J. Compound spiniger, chaetiger 110. A, E – J from ECOSUR-P 2677; B – D from holotype AMNH VI – 1915 – 1293. Scale bars: A, 267 µm; B, 234 µm; C, 347 µm; D, 267 µm; E, 347 µm; F – G, 15 µm; H: 25 µm; I, 52 µm; J, 12 µm.

FIGURE 9. Length-dependent variation of some morphological features in Marphysa viridis Treadwell, 1917. A. Maximum number of branchial filaments (n = 22); B. Last chaetiger with well developed postchaetal lobe (DPL) (n = 33); C. Last chaetiger with ventral cirri with swollen base (VCSB) (n = 9); D. Start of subacicular hooks (n = 33).

FIGURE 10. Distribution of branchial filaments throughout the body in Marphysa acicularum Webster, 1884, M. nobilis Treadwell, 1917 and M. viridis Treadwell, 1917.