Sternaspis scutata (Ranzani, 1817) emended

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 40-43

Sternaspis scutata (Ranzani, 1817) emended Figure 13

Thalassema scutatus Ranzani, 1817: 1458-1462, Pl. 11, figs 10-13.

Sternaspis scutata Claparède 1869: 95-96, Pl. 31, fig. 9; Rietsch 1882: 1-84, Pls. 18-23; Fauvel 1927: 216-218, fig. 76; 1934: 60; Townsend et al. 2006: 282-284, figs 1-2.

Type material.

Eastern Mediterranean Sea, Aegean Sea. Neotype (RBCM 005-140-001) and 9 paraneotypes (RBCM 005-140-002), Turkey, Izmar Bay, 38°30'00"N, 26°50'00"E, 33 m, 11-VII-2000.

Additional material. Aegean Sea, Turkey. 14 spec. (RBCM 005-139-001), Izmar Bay, 38°30'N, 26°50'E, 33 m, 11-VII-200. Croatia. 7 spec. (ECOSUR 2645), Rovigno d'Istria, VI-1983, J. Vidakovic & D. Zavodnik, coll. 2 spec. (ECOSUR 2646), off Rijeka, X-1981, P. Gillet, coll. 2 spec. (ECOSUR 2647), Rovigno d'Istria (no further data). France. 2 spec. (ZMA 1374), Bretagne. Italy. 8 spec. (MNHL 766), Gulf of Naples, 1888. Five spec. (ZMA 1373), Naples, 1893. 3 spec. (ZMA 1372), Triest. Five spec. (ZMA 1373), Bay of Naples, 1893. 2 spec. (ZMUC), Bay of Muggia, 1883. 1 spec. (ZMUC), Naples, Stazione Zoologica, 1882. 9 spec. (RBCM 006-008-001), Bay of Salerno, 40°29'N, 14°46'E, VIII-2002. 3 spec. (ANSP 1880), Bay of Naples. 9 spec. (RBCM 006 -008-001), Bay of Salerno, 40°29'N, 14°46'E, VIII-2002. 4 spec. (IRFA-STE 015), Rijika, Oct. 1981. Portugal. 10 spec. (SMNH 50689), Lisboa, Tajo, 9-36 m, 1869.

Description.

Neotype (RBCM 005-140-001) with anterior region often swollen, bulbous compared to the remaining segments, with a constriction at septum between segments seven and eight. Body usually smooth, white, leathery, sometimes covered by minute cuticular papillae, especially behind seventh segment and near shield on dorsal side; posterior region slightly darker. Body papillae small, evenly spaced. Body up to 35 mm long, 18 mm wide, about 30 segments.

Prostomium hemispherical, without eyespots, opalescent, translucent (Fig. 13A). Peristomium rounded, flattening at the position of the mouth, devoid of papillae. Mouth circular, completely covered with minute papillae, extends from prostomium to edge of second segment.

First three chaetigers with over 10 bronze, widely separated, slightly falcate hooks, each with subdistal dark area (Fig. 13B), more evident in smaller specimens. Larger specimens with paler subdistal areas. Genital papillae protrude ventrally from body wall between segments 7 and 8. Pre-shield region with 7 segments, sometimes bearing a bundle of small, short, fine capillary chaetae laterally.

Ventro-caudal shield flat (Fig. 13C), ribbed, with concentric lines; suture restricted to anterior region. Anterior margins truncate, straight; anterior depression deep; anterior keels not exposed. Lateral margins straight, not expanded medially. Fan smooth, markedly projected beyond posterior corners, with margin smooth, barely crenulated (Fig. 13C, D).

Marginal shield chaetal fascicles include 10 lateral ones, chaetae in an oval arrangement, and six posterior fascicles, chaetae in a slightly curved arrangement. Chaetae of lateral fascicles hirsute, especially longer ones. Peg chaetae about as long as chaetae of first lateral chaetal fascicle and stout basally where chaetae emerge from cuticle, giving them a robust spine-like appearance. Additional chaetae delicate, in a small group.

Branchiae abundant; interbranchial papillae long, filamentous (Fig. 13E). Branchial plates diverging as half-fusiform areas (Fig. 13F).

Variation.

The ventro-caudal shield (Fig. 13 G–H) has a fan with a median notch and its lateral parts extend beyond the posterior corners level, and this is a consistent pattern seen in all specimens regardless of size. The pigmentation is deep orange in smaller specimens (Fig. 13G) and becomes reddish in larger ones (Fig. 13H, I).

Neotype locality.

Izmar Bay, Aegean Sea, Turkey.

Remarks.

Sternaspis scutata (Ranzani, 1817) has been widely recorded and appears to be the most common species of Sternaspis . This is the oldest named species and researchers have suggested that Sternaspis scutata is a senior synonym of at least some of the other species of the family (Ushakov 1955; Hartman 1959), others have suggested that it is in fact the only species in the family ( Pettibone 1954). These ideas are so widespread that over half of the worms loaned for this study were labelled as Sternaspis scutata . However, the species has not been redefined and in order to clarify the current confusion, a neotype is proposed, described and its diagnostic features are illustrated ( ICZN 1999, Art. 75.3.1-75.3.3). Abbot Camilo Ranzani did not deposit the materials he described because it was not a current practice during those times (ICZN, Art. 75.3.4). However, Ranzani’s figure 13 clearly indicates that the ventro-caudal shield had a median, posterior notch, which is consistent with the proposed neotype ( ICZN 1999, Art. 75.3.5), and distinct from the other Mediterranean species, Sternaspis thalassemoides Otto, 1821, because it has a rather straight posterior margin. This feature is consistent and has been found in the studied materials; they included specimens from the eastern Italian coast, which would be similar to the original type locality (Adriatic Sea). However, the best specimen was selected as neotype and it was collected in the Aegean Sea, some distance from the original type locality ( ICZN 1999, Art. 75.3.6). As stated above, there were no differences among the materials studied. The neotype and additional paraneotypes have been deposited in the Royal British Columbia Museum ( ICZN 1999, Art. 95.3.7).

As stated above, Sternaspis scutata differs from Sternaspis thalassemoides by shield features, especially regarding their fan development; in Sternaspis scutata it is notched and markedly expanded beyond the level of the posterior corners, whereas in Sternaspis thalassemoides it is truncate, entire, and not expanded beyond the posterior corners level. Further, Sternaspis scutata is unique in the genus by a combination of features of their shields: the anterior margins are truncate, the lateral margins are straight or barely rounded, and the posterior margin and fan are markedly expanded beyond the posterolateral corners.

Distribution.

Mediterranean Sea to the English Channel, 9-36 m depth. Deeper water records from the Eastern Mediterranean ( Ben-Eliahu and Fiege 1995) deserve a careful comparison to define if they are conspecific with the shallow water material. Some records from non-Mediterranean or Northeastern Atlantic localities might belong to other, probably undescribed species. Thus the following records need to be checked: Arctic and Subarctic waters ( Wesenberg-Lund 1950a: 104-105, 1950b: 46, 1951: 98, 1953: 88), Northwestern Pacific (Ushakov 1955: 353-354, fig. 131; Levenstein 1961: 167, 1966: 59, Buzhinskaja 1985: 166; Imajima 2005: 91), or Northeastern Pacific Ocean ( Hartman 1971: 1422), Western Pacific ( Gallardo 1968: 114), Red Sea ( Fauvel 1957: 218), Indian Ocean ( Wesenberg-Lund 1949: 345-346; Fauvel 1932: 213, 1953: 401-402, fig. 210 a–g; Hartman 1976a: 199, 1976b: 627), Western Central ( Gilbert 1984: 45.3-45.4, fig. 45.2 a–f; Ibarzabal 1986: 14), Eastern Central ( Fauvel 1936: 88), southeastern Atlantic ( Day 1967: 648, fig. 31.1 a–d), from New Zealand ( Augener 1926: 283-286, fig. 22), and from the Antarctic Ocean ( Hartman 1966: 55, Pl. 18, fig. 1; Hartman 1967: 141; Hartmann-Schröder 1986: 85; Hartmann-Schröder and Rosenfeldt 1989: 76, 1991: 77; Gambi and Mariani 1999: 238).