Marphysa orientalis Treadwell, 1936

Liu, Yubin, Hutchings, Pat & Kupriyanova, Elena, 2018, Two new species of Marphysa Quatrefages, 1865 (Polychaeta: Eunicida: Eunicidae) from northern coast of China and redescription for Marphysa orientalis Treadwell, 1936, Zootaxa 4377 (2), pp. 191-215 : 202-205

Marphysa orientalis Treadwell, 1936

Figures 1 , 7–8

Material examined. Holotype USNM 20114 , Xiamen (Amoy) , China (24.27°N, 118.04°E).

Description. Holotype complete, with 315 chaetigers, body pale beige coloured, iridescent especially anterior segments. Maximum width at chaetiger 10, 5 mm, excluding parapodia, length to chaetiger 10, 13.25 mm. Specimen slightly damaged and contorted.

Prostomium longer than peristomium, margins dorsally flattened with conspicuous deep median sulcus, with both lobes globular and inflated ( Fig. 7A ). Eyes present, inserted at base of palps. Median antennae inserted slightly more posteriorly to lateral antennae, all of similar length and width. Antennophores short, narrow. Antennal styles digitate, smooth, longest reaching to median or posterior margin of the second peristomial ring. Palps smooth, same length as antennae, inserted more anteriorly to antennae. Length of antennae slightly longer than palps. Peristomial rings well demarcated all around. Jaws previously dissected and placed in a separate vial. Only one mandible remaining with tip broken, with calcareous plate longer than sclerotized matrix, dark brown with paler margins, with longitudinal ridges. Maxillae I more than 3.5 times length of carrier, curved with rounded tips ( Fig. 7D ). Maxillae II 1.5 times length of carrier, with 3 teeth, anterior one largest ( Fig. 7D, E ). Maxillae III arched with 4 equal sized teeth all arranged in a vertical line. Maxillary formula: I=1+1, II=3+3, III=4+0, IV=3+6, V=1+1 ( Fig. 7D–F ).

Parapodia similar throughout, with prechaetal lobe shorter than chaetal lobe, postchaetal lobe longer than chaetal lobe. Dorsal cirrus digitate, initially longer than chaetal lobes, tapering gradually to rounded tip, decreasing in length after chaetiger 37, posteriorly same length as parapodial lobes. Ventral cirri shorter than chaetal lobes, digitate with swollen base, similar in shape throughout body ( Fig. 7B ). Lengths of dorsal and ventral cirri varying: they of same length in anterior chaetigers, dorsal cirrus shorter than ventral cirrus in median chaetigers, and dorsal cirrus shorter than ventral cirrus in posterior chaetigers. Branchiae beginning from chaetiger 37, continuing to chaetiger 287, pectinate throughout. Number of branchial filaments 1–2 in anterior parapodia with maximum number of branchial filaments 3 in median parapodia ( Fig. 7C ). Length of branchial filaments where best developed up to 3 times length of dorsal cirrus. Aciculae present, black, maximum number 3–5. Subacicular hooks unidentate varying in colour, yellow or transparent, ( Fig. 8C ), present only in posterior chaetigers, 1–2 present.

Compound spinigers with blades of similar width along entire body. Number of compound spinigers within a parapodium 26 in anterior chaetigers, then gradually decreases to <10 in far posterior ones. Compound falcigers ( Fig. 8B ) restricted to middle and posterior parapodia, absent before parapodium 67, with very short blades with unidentate tip. Number of compound falcigers within a parapodium 2. Pectinate chaetae present from middle parapodia onwards (parapodium 193) to posterior parapodia. Number of pectinate chaetae 4–19 within a parapodium, numbers of pectinate chaetae increasing posteriorly. Three types of pectinate chaetae present: thin symmetrical isodont with about 30 teeth, present from mid-body to posterior parapodia ( Fig. 8D ), thin asymmetrical anodont with 16 teeth, present from mid-body to posterior parapodia ( Fig. 8F ) and thick asymmetrical anodont with 4–5 teeth, present only in posterior parapodia ( Fig. 8E ). Three types of pectinate chaetae restricted to posterior parapodia. Simple capillary chaetae present along entire body. Number of simple capillaries 28 within a parapodium in anterior body, then gradually decreases to 2–4 in far posterior body.

Pygidium with one pair of elongate ringed pygidial cirri, longer than last 10–12 segments ( Fig. 8A ).

Remarks. Marphysa orientalis was listed by Fauchald (1970) as belonging to Group B 2, however, we observed both compound spinigers and falcigers, which places it in Group D 2. Treadwell (1936) described the species based on a single specimen and while Wu (1962) lists this species from China, he neither examined the type material nor reported any additional specimens, so only the holotype is known. Thus, we only removed parapodia for examination under the light microscope.

Marphysa orientalis belongs to the same group (D) as M. sinensis Monro, 1934 , as both species have compound falcigers and spinigers, but they can be easily distinguished by the different distribution of branchiae, the former having them over most of the body, whereas in the latter they are only present from chaetiger 17 to either chaetiger 30 or 31 on the lectotype (terminates at chaetiger 29 on paralectotype). Both species were collected from the same geographical area, of Amoy.

As M. orientalis is newly placed here in D 2, it can be distinguished from Marphysa maxidenticulata n. sp. from this group, by having subacicular hooks restricted to posterior chaetigers and compound falcigers absent before chaetiger 67, whereas M. maxidenticulata n. sp. has subacicular hooks present from chaetiger 25 onwards, and compound falcigers restricted to anterior chaetigers and absent by chaetiger 50, and has pectinate chaetae with a few large teeth along most of the body.

Habitat. Not given.

Locality. Xiamen (Amoy), China (24.27°N, 118.04°E).

Figures

FIGURE 1. Map showing type localities (blue dots) of M. bulla n. sp., M. maxidenticulata n. sp., M. orientalis Treadwell, 1936 and M.sinensis Monro,1934.

FIGURE 7. Marphysa orientalis holotype USNM 20144 (light microscopy images) A.Anterior dorsal view of holotype.B. Lateral view of anteriorparapodia.C. Lateralview of branchiae from middle region.D. Maxillae I & II, ventral view.E. Maxillae II & III, lateral view.F.Maxillary apparatus, dorsal view. Abbreviations: I, II, III, IV- maxillae I, II, III, IV Scale bars:A, F = 2 mm; B, C = 1 mm; D, E = 0.5 mm.

FIGURE 8. Marphysa orientalis holotype USNM 20144 (light microscopy images) A. Pygidium. B. Compound falcigers, parapodium 130. C. Bidentate subacicular hook from posterior parapodium, arrow pointing to hook. D. Two types of pectinate chaetae with 14 or 18 teeth from parapodium 193. E. Thick asymmetrical anodont pectinate chaetae with coarse teeth from parapodium 256, indicated by arrows. F. Thin asymmetrical isodont pectinate chaetae with numerous teeth, from parapodium 256. Scale bars:A= 0.5 mm; B- F = 0.1mm.