Sternaspis maureri, Salazar-Vallejo, Sergio I. & Buzhinskaja, Galina, 2013

Salazar-Vallejo, Sergio I. & Buzhinskaja, Galina, 2013, Six new deep-water sternaspid species (Annelida, Sternaspidae) from the Pacific Ocean, ZooKeys 348, pp. 1-27 : 11-14

Sternaspis maureri sp. n. Figures 5, 6

Sternaspis fossor : Maurer and Williams 1988: 694 (non Stimpson 1853).

Sternaspis scutata : Kirkegaard 1996: 71-72 (non Ranzani 1817).

Type material.

Eastern Pacific, Peru. Holotype (LACM 5679), and two paratypes (LACM 5680), R.V. Anton Bruun, Cruise 11, Sta. 100 (08°16S, 81°05W), Menzies trawl, 6156-6489 m, 16 Oct. 1965 (paratypes anterior or posterior fragments; ventro-caudal shield with fan slightly narrower than anterior margins; margin crenulated, median and lateral notches well developed). Six paratypes (LACM 5681), R.V. Anton Bruun, Cruise 11, Sta. 72 (08°25S, 81°05W), Menzies trawl and Beam trawl, 6220-6052 m, 12 Oct. 1965 (one complete, one broken into two pieces, two fragmented introverts. Complete 8.0 mm long, 2.3 mm wide, left shield plate 2.5 mm long, 2.2 mm wide. Shield with margin narrower than anterior margins, margin smooth, paler, median notch shallow, lateral notches well developed; other remaining shield plates 2.0-2.5 mm long, 2.2-2.5 mm wide). Three paratypes (LACM 5682), R.V. Anton Bruun, Cruise 11, Sta. 77 (08°22S, 81°02W), Menzies trawl and Beam trawl, 6052-6260 m, 13 Oct. 1965 (two broken in several pieces; one complete with most shield chaetal bundles broken. Complete with introvert partly evaginated, 7.0 mm long, 2.5 mm wide; left shield plate 2.4 mm long, 2.1 mm wide. Other specimens with left shield plate 2.0-2.5 mm long, 2.3-2.5 mm wide. Fan projected, smooth in smaller specimens, crenulated in larger ones. Median notch visible, smaller than lateral notches; better developed posterolateral corners).

Additional material.

Eastern Pacific. One specimen (LACM 5684), R.V. Anton Bruun, Cruise 11, Sta. 36 (05°43'S, 82°01'W), Menzies trawl, 5047 m, 5 Oct. 1965 (broken into two portions, body wall broken, shield broken, one plate lost, the other missing a lateral part). Eight specimens (LACM 5686), R.V. Anton Bruun, Cruise 11, Sta. 69 (06°19'S, 81°49'W), Beam trawl, 5750 m, 11 Oct. 1965. (label with question mark about stations 55 or 69; herein regarded as part of station 69; two anterior fragments, one posterior fragment, two detached shields, three detached shield plates). 10 specimens (LACM 5683), R.V. Anton Bruun, Cruise 11, Sta. 94 (08°21'S, 81°25'W), Menzies trawl, 1296-1317 m, 14 Oct. 1965 (one broken into two pieces; six with introvert invaginated, three with introvert evaginated; complete specimens 1.8-4.8 mm long, 1.3-2.9 mm wide; left shield plate 0.4-1.0 mm long, 0.5-1.0 mm wide. Other specimens 2.0-4.2 mm long, 1.5-2.8 mm wide; left shield plate 0.5-1.0 mm long, 0.5-0.9 mm wide. Ventro-caudal shield fan starts being smooth or with a poorly defined posterior margin into a crenulated margin in larger specimens. All have the fan narrower than the anterior margin; median notch not developed, lateral notches well developed). One specimen (LACM 5685), R.V. Anton Bruun, Cruise 11, Sta. 98 (08°24'S, 81°15'W), Menzies trawl, 6052-5989 m, 15 Oct. 1965 (body wall broken, gut broken in pieces. Ventro-caudal shield with fan narrower than anterior margins, fan margin smooth, projected beyond the poorly defined posterolateral corners. Left shield plate 2.5 mm long, 2.3 mm wide). Two specimens (LACM 5689), R.V. Anton Bruun, Cruise 11, Sta. 98? (08°24'S, 81°15'W), Campbell grab, 6052 m, 15 Oct. 1965 (label with "Sta. 86 or 98?" but Maurer & Williams did not include station 86; both specimens broken, without introvert, shields detached from the body or still fixed over abdomen. Detached shield left plate 3.2 mm long, 2.6 mm wide. Shield with fan narrower than anterior margins, projected, margin crenulated, lateral notches well defined). One specimen (LACM 5690), R.V. Anton Bruun, Cruise 11, Sta. 101 (08°13'S, 81°09'W), Menzies trawl, 1927-1997 m, 16 Oct. 1965 (ventro-caudal shield with fan narrower than anterior margins, fan margin smooth, projected beyond the poorly defined posterolateral corners; left shield plate 1.2 mm long, 1.2 mm wide). Two specimens (LACM 5688), R.V. Anton Bruun, Cruise 11, Sta. 113 (08°44'S, 80°45'W), Menzies trawl and Beam trawl, 5986-6134 m, 19 Oct. 1965 (larger specimen without introvert; the other very small apparently with introvert invaginated. Larger specimen with ventro-caudal shield with fan narrower than anterior margins, fan margin smooth, projected beyond the poorly defined posterolateral corners; left shield plate 2.2 mm long, 2.2 mm wide. Smaller specimen with shield with fan projected beyond the poorly defined posterolateral corners; margin covered by sediment particles). One specimen (LACM 5691), R.V. Anton Bruun, Cruise 11, Sta. 196 (09°01'S, 80°40'W), Menzies trawl, 4516-4383 m, 7 Nov. 1965 (body broken into two pieces, most of body in one, the shield in another. Ventro-caudal shield with fan narrower than anterior margins, fan margin barely crenulated, projected beyond the poorly defined posterolateral corners. Left shield plate 1.3 mm long, 1.2 mm wide). Southwestern Pacific. One specimen (ZMUC 0000), juvenile, R.V. Galathea, S off Adelaide, Sta. 556 (37°18'S, 138°43'E), 795 m, 6 Dec. 1951 (7 mm long, 3 mm wide, left shield plate 1.2 mm long, 1.0 mm wide). One specimen (ZMUC 0000), R.V. Galathea, S off New Zealand, Sta. 607 (44°18'S, 166°46'E), 3830 m, 17 Jan. 1952 (broken in two parts, partly dehydrated, and the shield is very fragmented, but most pieces remain on site; damage made by removing the sediment and papillae surrounding the anal peduncle lobe; right shield plate 1.8 mm long, 1.3 mm wide).

Description.

Holotype (LACM 0000) complete. Body wall broken and inner organs lost (Fig. 5A). Body brownish, integument papillose throughout body, dark brown (eroded leaving a paler body wall in smaller paratypes; larger ones with darker body wall). Body 7 mm long, 3 mm wide, about 29 segments; left shield plate 2.5 mm long, 2.1 mm wide.

Prostomium eroded, small, ovoid, paler than surrounding areas, smaller than mouth (Fig. 5B). Peristomium rounded, abundantly papillose (especially in some paratypes), papillae extended throughout introvert. Mouth rounded, papillose, slightly projected.

First three chaetigers with 12-14 bronze, slightly falcate hooks per bundle, each with subdistal dark areas (up to 16-18 in some paratypes). Genital papillae lost (pale, blunt, short lobes in some paratypes, from the intersegmental groove between segments 7 and 8).

Pre-shield region with 7 segments, with papillae mostly eroded from segmental ridges, but present in intersegmental furrows or along some areas, homogeneously distributed. Short, about 4-5 capillary chaetae in some segments.

Ventro-caudal shield dark orange, with ribs partly eroded, concentric lines poorly developed; suture distinct throughout shield (Fig. 5A, C). Anterior margins rounded (broken in Fig. 5A), anterior depression shallow; anterior keels not exposed, barely developed. Lateral margins rounded, reduced posteriorly. Fan truncate, one-half to two-thirds as wide as anterior margins width, slightly projected beyond posterior posterior shield corners, median notch shallow, barely developed, lateral notches deeper, better developed, fan margin smooth to barely crenulated (paler in some paratypes).

Marginal chaetae fascicles damaged; eight or nine lateral ones (10 in one paratype Sta. 72), chaetae ovally arranged, and six posterior ones (paratypes more damaged). Peg chaetae visible, not broken, but detached, and a single long, delicate chaetae.

Branchial plate missing (one paratype (Sta. 72) with one plate left but no branchial or interbranchial filaments left; branchial plate ovoid, tapering anteriorly; another paratype from the same station with branchial plates anteriorly converging).

Variation.

There are several ontogenetic changes in the ventro-caudal shield, although the anterior depression remains shallow throughout their development (Fig. 6). Smaller specimens (Fig. 6A, D) have yellowish or pale orange shield, with ribs barely visible. Medium-sized specimens have shields slightly darker, with ribs better defined but the main, diagonal rib is still poorly developed (Fig. 6B, E). In larger specimens, the shield becomes thicker, stronger and its ribs, including the diagonal one are better defined (Fig. 6C, F) and the lateral notches, over its posterior margin or fan, become deeper.

Etymology.

The species name is after Dr Don Maurer in recognition of his many publications, mostly on benthic ecological studies and especially dealing with polychaetes. He also studied the material employed for this description. The epithet is a noun in the genitive case.

Type locality.

W off Trujillo, Perú, 6156-6489 m depth.

Remarks.

Sternaspis maureri sp. n. resembles Sternaspis annenkovae sp. n. and Sternaspis williamsae because they all have ventro-caudal shield fans narrower than the width of the anterior margin. However, the shield in Sternaspis maureri sp. n. is more similar to the one found in Sternaspis williamsae because both are medially fused. Their main differences are in the relative shield’s size, radial ribs’ development, and on the relative depth of the fan’s lateral and median notches. In Sternaspis maureri the shield is proportionally larger (body length: shield length 7.0:2.5 mm, one paratype Sta. 77, 6.5:2.5 mm), the ribs are better developed, the median notch is shallow or very slightly developed, and the lateral notches are better developed, whereas in Sternaspis williamsae the shield is smaller (7.5:1.6 mm), the ribs are poorly developed, its median notch is deep or well defined, and the lateral notches are poorly developed or indistinct.

Distribution.

Abyssal sediments off Peru, Eastern Pacific, in 1296-6489 m water depths, and in the Southwestern Pacific in 795-3830 m.