Marphysa Quatrefages, 1865

Martin, Daniel, Chaibi, Marwa, Lavesque, Nicolas, Daffe, Guillemine, Daramy, Flore, Hutchings, Pat, Jourde, Jérôme & Romano, Chiara, 2025, Integrative taxonomy reveals further hidden diversity of Marphysa (Polychaeta: Eunicidae) in European Atlantic and Mediterranean waters, Zoological Journal of the Linnean Society 204 (3) : -

Genus Marphysa Quatrefages, 1865

Marphysa gaditana Martin et al., 2020 in Martin et al. (2020)

( Figs 4–11)

Marphysa gaditana Martin et al. (2020): 17 –25, figs 3A, B, 4, 5A, B, 6, 7A, B, 8, 9A, B, 10A, D.

Material examined: Tunisia: CEAB.AP.995A–995D, 29 March 2022, Gulf of Tunis, 36.804722°N, 10.294444°E, collected by a professional fisherman in muddy sand bottoms, fixed and preserved in 95% ethanol, four specimens ; MNHNC MB29 :000455 and MB29 :000456, 29 March 2023, Gulf of Tunis, 36°48′16.99′′N, 1017′39.99′′E, collected by a professional fisherman in muddy sand bottoms, fixed and preserved in 95% ethanol, two specimens . France: CEAB.AP.995E–995F, 9 November 2022, Arcachon Bay , collected by NL in mud close to oyster reefs, fixed and preserved in 80% ethanol, three specimens . MNHN-IA-2017-2210, 22 June 2020, Oléron Island , approximate location 45°54′17′′N, 1°11′50′′W, collected by Stéphane Guenneteau and Jacques Pigeot on muddy sediments close to a rocky reef, fixed and preserved in 95% ethanol, one specimen .

Description: Based on Tunisian specimens: CEAB.AP.995A for all characters except mandibular apparatus, CEAB.AP.995B for mandibular apparatus, and CEAB.AP.995A–D to provide ranges.

Body up to 233 cm long, up to 8 mm wide ( Table 2); rounded in cross-section anteriorly, tapering and dorsoventrally flattening posteriorly. Prostomium dorsoventrally flattened, with anterior end elevated and bilobate, with a conspicuous median sulcus ( Fig. 4A, D). One median and two lateral antennae, folding back to middle of chaetigers 2–3; two palps, folding back until beginning of chaetigers 2–3 ( Fig. 4A, C, D). One pair of dark eyes, inserted laterally to ceratophores of lateral antennae ( Fig. 4A, D). Calcareous cutting plates 42 µm long and 79 µm wide, 1/4 longer than sclerotized matrix, overall thick, with thin translucent borders, broadly D-shaped ( Fig. 5A–C); sclerotized matrix c. 13 times shorter than mandible carriers, D–shaped, distally straight, with smooth upper margin and growth ring-like marks seen through translucent calcareous cutting plates ( Fig. 5A–C). MxI c. twice as long as carrier, brown, with white, translucent tips; MxII c. four-fifths of MxI; MxIII arched, with anteriormost teeth more lateral than posteriormost ones, partly ventral to MxII, concave side and posterior part of convex side brownish, anterior part of convex side and teeth border whitish; attachment lamella of MxIII very small, slightly sclerotized; left MxIV as wide as long, D-shaped; right MxIV four times longer than wider, arched; colour of both Mx IV as in MxIII; attachment lamellae of MxIV roughly C-shaped, ventral to MxIII, right one with lower arm (pointed) c. three times shorter than right arm (rounded), left one with both arms rounded, similar in length; MxV roughly square, pale brownish to yellowish; maxillary formula: I = 1 + 1, II = 8 + 7, III = 7 + 0, IV = 3 + 8, V = 1 + 1, VI absent ( Fig. 5D–F). Branchiae starting at chaetigers 19–24, with a maximum of three filaments from chaetigers 50–73, longest filaments 5.3 times longer than notopodial cirri and 4.1 times longer than branchial stem ( Fig. 6A–D). Notopodial cirri triangular, tapering; longer (anterior and median), shorter (posterior), and longer (posteriormost) than chaetal lobes ( Fig. 6A–D). Ventral cirri triangular, with rounded tips, with inflated bases from chaetiger 6 to posterior body end (except about last 6), about three-quarters as long as notopodial cirri in anteriormost chaetigers, two-thirds at midbody and as long as in posterior chaetigers ( Fig. 6A–D). Notopodial aciculae inconspicuous. Neuropodial aciculae, brownish, with golden tips, up to 2–4 (5) per parapodia, with blunt tips non-protruding from acicular lobe ( Table 2; Fig. 6A–D). Chaetae in two distinct bundles. Supracicular bundle with limbate and pectinate chaetae at anterior edge; pectinate chaetae of four types ( Table 2), present from chaetiger 5 till body end; Type 1 present from anterior parapodia, thin, flat to slightly curved, slightly asymmetrical, heterodont with very long external teeth, with c. 25 teeth c. 7–10 µm long, slightly varying in length in different chaetae, evenly tapering to short filiform tips ( Fig. 7A, B); Type 2 thin, flat to slightly curved, heterodont with short external teeth, slightly asymmetrical, with 22–25 teeth c. 5 µm long, narrow, with short filiform tips slightly varying in length in different chaetae ( Fig. 7C); Type 3 thick, flat to slightly curved, isodont with short external teeth, slightly asymmetrical, with 10–14 teeth c. 20 µm long, coarse, with short filiform tips slightly varying in length on different chaetae ( Fig. 7D); Type 4 thick, flat, anodont, asymmetrical, with 4–6 teeth with short filiform tips, c. 55–70 µm long, coarse, c. 7–10 times longer than wider ( Fig. 7E, F). Subacicular bundle with compound spiniger chaetae and one (two in some parapodia) golden subacicular hook, with two guards covering tip, bidentate, with rounded teeth upwards directed, distal one c. half-size of proximal one ( Fig. 7G), starting at chaetiger 40–55 to body end. Two pairs of pygidial cirri, dorsal pygidial cirri c. 5–10 times longer than ventral ones ( Fig. 4E–G) .

Remarks: The Tunisian specimens of M. gaditana do not differ molecularly from those found in the Bay of Cádiz ( Figs 1–3; Table 1). However, they are 17–33 longer, and have 11–28 more segments and 0.3–0.4 times longer antennae ( Table 2). Their maxillary formula differs in the number of teeth at MXII, III, and IV, and the maxillae show whitish tips (dark in the Iberian specimens) ( Table 2). The branchiae have one more filament, start one segment before, may end about 20 chaetigers before or 30 chaetigers after (depending on the specimens), and show the maximum number of filaments in 10–60 more posterior segments and over 100 less segments the Iberian specimens, while some branchial filaments are ramified in one specimen (might be the result of a malformation) ( Table 2). The maximum number of aciculae is lower than in the Iberian specimens ( Table 2). In some specimens, very few parapodia have subacicular hooks, while two completely lack them, and a single specimen has two subacicular hooks in some parapodia, both bidentate—although one of them could appear eroded—( Fig. 7G). Finally, there is a slight variability in the number of teeth of some pectinate chaetae, with Type 1 having 3–4 fewer, Type 2 having 3–5 more, and Type 4 having 1–4 fewer ( Table 2).

The French specimens from the Bay of Arcachon occur in sympatry with the introduced M. victori , being initially confused with its juveniles. However, as for the Tunisian specimens, our molecular analyses reveal that they cannot be distinguished molecularly from the specimens of M. gaditana from Cádiz, while showing some morphological differences. Among them, they are smaller, with shorter antennae and palps ( Fig. 8A–E; Table 2). Maxillae I, II, III, and IV show different number of teeth and MIV and MV have some whitish colour ( Fig. 9A–E) that is absent in the specimens of Cádiz ( Table 2). The aciculae are less

Hidden diversity of Marphysa • 7 numerous ( Fig. 10A–E; Table 2), the subacicular hooks start in more posterior chaetigers, and the pectinate chaetae show teeth with shorter filiform tips ( Figs 11A–E; Table 2).

While similarly lacking molecular differences ( Figs 1–3), some morphological variability occurs also between the Tunisian and Arcachon specimens. The latter are smaller, with shorter antennae and palps ( Fig. 8A–E; Table 2) and have MxII and MxIV with fewer teeth ( Fig. 9A–E; Table 2). Branchiae have fewer filaments and the maximum number of filaments starts earlier ( Fig. 10A–C; Table 2). Subacicular hooks are present in all chaetigers, a second hook has not been seen, the pectinate chaetae show slight variability in number of teeth, with some types having teeth with shorter filiform tips ( Figs 11A–E; Table 2).

Distribution: Atlantic Ocean: Cádiz Bay ( Spain), Sado Estuary ( Portugal, only sequenced), Arcachon Bay (Biscay Bay, France), Oléron Island (Biscay Bay, France, only sequenced), Cap de la Hague (English Channel, France, only sequenced), Florida and Virginia ( USA, only sequenced); Western Mediterranean: Gulf of Tunis ( Tunisia).

Habitat: Shallow sandy mud bottoms.