Sternaspis princeps Selenka, 1885

Sendall, Kelly & Salazar-Vallejo, Sergio I., 2013, Revision of Sternaspis Otto, 1821 (Polychaeta, Sternaspidae), ZooKeys 286, pp. 1-74 : 38-39

Sternaspis princeps Selenka, 1885 Figure 11H, I

Sternaspis princeps Selenka, 1885: 5-6, Pl. 1, fig. 1.

Type material.

South Pacific Ocean. New Zealand. Two syntypes (NHM 1885.12.3.1), R.V. Challenger, North Island, NE off Gisborne, 37°34'S, 179°22'E, 1274 m, 10-VII-1874.

Description.

Syntypes (NHM 1885.12.3.1) body smooth, except for longitudinal wrinkles starting on segment eight, probably an artefact of fixation and/or preservation process (Fig. 11H). Colour white, slightly opalescent, dirty white on posterior segments. Cuticle covered by minute papillae, especially on segments seven and eight and the segments near ventro-caudal shield. Body up to 29 mm long, 11 mm wide, 30 segments.

Prostomium hemispherical, opalescent, light yellow in colour. Peristomium rounded, raised at position of mouth and without papillae. Mouth oval, covered by minute papillae, extends from edge of second segment halfway to the border of prostomium.

First three chaetigers with about 10-15 bronze, widely separated, slightly falcate introvert hooks, each with subdistal, narrow dark areas. Genital papillae protrude ventrally from intersegmental groove between segments 7 and 8 (Fig. 11I). Pre-shield region with 7 segments, sometimes with row of small, short fascicles of fine capillary chaetae, barely protruding from body wall laterally.

Ventro-caudal shield surface almost flat. Shield surface faintly ribbed with one larger oblique rib; suture indistinct, barely defined anteriorly, poorly defined posteriorly (Fig. 11I); larger syntype with faint concentric lines, smaller individual with more distinct concentric lines. Anterior margins rounded; anterior depression deep; anterior keels not exposed. Lateral margins straight, barely expanded posteriorly. Fan truncate, margin crenulated, with shallow median notch.

Marginal chaetal fascicles include ten lateral ones, and six posterior fascicles; all chaetae broken on both syntypes, except for first two lateral fascicles. Peg chaetae present as stubs. Additional chaetae damaged.

Branchiae lost; branchial plates visible, oriented close to parallel with respect to each other.

Remarks.

Selenka (1885) indicated a shallow furrow running along the middle of the ventral surface, dividing each half into a larger anterior triangle and a smaller posterior triangle. Although he did not indicate this specifically, he was probably referring to the anterolateral and posterior portions of the shield. He also counted 40 tufts of chaetae along the margins of the shield. If the secondary groups of chaetae, such as the delicate fascicles at the posterolateral edges are included, there are still only 34. Because one syntype is very large, and chaetal fascicles may be irregularly broken, he might have inadvertently counted a few of the fascicles more than once.

There are five species having shields with straight posterior margins: Sternaspis princeps , Sternaspis rietschi , Sternaspis spinosa , Sternaspis thalassemoides and Sternaspis thorsoni sp. n. Sternaspis princeps is most similar to Sternaspis thalassemoides because both have deep anterior depressions and rounded anterior margins. However, they differ because in Sternaspis princeps only the larger, radial rib is more or less visible, but concentric lines are not, whereas in Sternaspis thalassemoides the shield has radial ribs and concentric lines. An additional difference is that in Sternaspis princeps the shield anterior keels are exposed whereas they are covered in Sternaspis thalassemoides .

Distribution.

Only known from the type locality, off North Island, New Zealand, about 1274 m depth.