Sternaspis islandica Malmgren, 1867

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 34-35

Sternaspis islandica Malmgren, 1867 Figure 10

Sternaspis islandica Malmgren, 1867: 196-197, Pl. 14, fig. 85 A–D 1.

Type material

Iceland. Eight syntypes (SMNH 5135), Berufjord, 64°48'N, 14°30'W, 27-55 m, 1857.

Additional material

Iceland. 1 spec. (ZMUC "Ingolf 129"), N off Flateyri, 66°35'N, 23°47'W, 220 m, 3-VIII-1896. 4 spec. (ZMUC Dana 6131), near Keflavik, 64°02'N, 22°31'W, 33 m, 22-VII-1939. 9 spec. (ZMUC 51), Faxelfjord, 3m, 17-VIII-1901. 31 spec. (ZMUC), Faxelfjord, Hammisvork. Seven spec. (ZMUC), Faxefj., 2 km N off Keflark, 6 m, 7-VIII-1901. 1 spec. (ZMUC), Faxefjord, 7-9 m, 7-VII-1899. 50 spec. (IMNH 2526), NW off Flateyri, 66°36'20"N, 23°58'37"W, 226 m, 13-VII-1993. 9 spec. (IMNH 2568), N off Flateyri, 66°55'18"N, 23°30'58"W, 196 m, 15-VII-1993. 5 spec. (IMNH 2994), SE off Hofn, 63°45'36"N, 14°50'36"W, 216 m, 5-VII-1997. 2 spec. (IMNH 3062), E off Hofn, 63°59'32"N, 14°08'49"W, 218 m, 10-VII-1997. 9 spec. (MNHN 451), off Northern Iceland, R.V. Pour-quoi pas?, Stat. 24 (66°37'N, 23°50'W), 160 m, 25 Jul. 1912. Denmark, Faroe Islands. 3 spec. (ZMUC), Aknoeyr, 4 m, 8-IX-1901.

Description

(Based on best syntype). Body with first six segments smooth, pale, without cuticular papillae (Fig. 10A). Segments seven and eight with many small cuticular papillae, decreasing in density ventrally on remaining posterior segments, more numerous on the dorsal surface opposite the shield. Single rows of clusters of longer filamentous cuticular papillae present especially dorsally near ventro-caudal shield (Fig. 10D). Body 10 mm long, 5.5 mm wide, 30 segments.

Prostomium hemispherical, opalescent, finely granular. Peristomium round, flattened at mouth, without papillae. Mouth oval, covered by papillae, extends from edge of prostomium to the anterior border of segment 2 (Fig. 10B).

First three chaetigers with six to 12-14 bronze, slightly falcate introvert hooks, each with subdistal dark areas. Genital papillae protrude ventrally from intersegmental groove between segments 7 and 8. Pre-shield region with 7 segmentswithout chaetae.

Ventro-caudal shield rust red, with fine oblique ribs, and regularly spaced concentric lines; suture extended throughout shield (Fig. 10C); dried out syntypes with a darker, blackish shield (Fig. 10E). Anterior margins rounded; anterior depression deep; anterior keels not exposed. Lateral margins expanded posteriorly. Fan truncate, margin smooth, slightly sigmoid, with two shallow lateral, and median deeper notches.

Marginal chaetal fascicles include 10 lateral ones, ovally arranged, and six posterior fascicles, also in oval arrangement. Chaetae of fascicles nine and ten are about 1.5 x the length of the remaining lateral fascicles. Peg chaetae short, broad, oval in cross section at the base. Additional delicate capillary chaetae between peg chaetae and first posterior fascicle of shield chaetae.

Branchiae coiled filaments, emerge from two branchial plates, oriented close to parallel. Few long filamentous interbranchial papillae among branchiae.

Variation.

Most syntypes with dark brown body walls, probably after some dehydratation and variably damaged; one broken into two parts, others with shield completely detached or one plate dislodged. Other specimens (MNHN 451) show that shields become progressively darker and that their ribs are progressively better defined as body grows; at the same time, the fan can be slightly to markedly projected beyond the level of the posterolateral corners.

Remarks.

Sternaspis islandica Malmgren, 1867 does not appear in the literature except in some faunal accounts where the name was considered a junior synonym of Sternaspis scutata , such as Fauvel (1927), Wesenberg-Lund (1950, 1951), and Ushakov (1955).

Sternaspis islandica and Sternaspis rietschi Caullery, 1944 are very similar because their ventro-caudal shields have shallow anterior depressions, and their concentric lines are more visible than the radial ribs. However, these two species differ because in Sternaspis islandica the posterior shield corners are projected, whereas in Sternaspis rietschi they are not prominent at all. A lectotype was not selected because of the general condition of the type materials.

Distribution.

Apparently restricted to the Norwegian Sea and Northeast Atlantic Ocean around Iceland and the Faroe Islands, 7-226 m depth.