Sternaspis williamsae, 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 : 18-23

Sternaspis williamsae sp. n. Figures 9, 10

Sternaspis fossor : Hartman 1963: 59; Fauchald and Hancock 1981: 35 (partim, non Stimpson 1853).

Type material.

Northeastern Pacific, Oregon. Holotype (LACM 5353), and five paratypes (LACM 5354), off Columbia River, R.V. Acona, Sta. AD 33, NAD 21 (44°30.0'N, 125°34.0'W - 44°39.0'N, 125 33.2 W), 2800 m, 25 Jan. 1963 (paratypes 2.2-9.8 mm long, 1.4-4.5 mm wide, abdomen 2.2-6.0 mm long; left shield plate 0.9-1.8 mm long, 0.8-2.2 mm wide).

Additional material.

Northeastern Pacific, Oregon. One specimen (CAS 129027w), Sta. BMT 557 (48°9.0'N, 127°4.2'W), 2519 m, 10 Sep. 1971, A. Carey, coll. (9 mm long, 4.8 mm wide; left shield plate 2.0 mm long, 1.8 mm wide). One specimen (LACM 5359), too damaged, broken into two pieces, shield almost completely lost, off Columbia River, R.V. Acona, Sta. AD 9, NAD 21 (44°36.4'N, 125°24.8'W), 2800 m, 13 Aug. 1962. One specimen (LACM 5355), off Columbia River, R.V. Acona, Sta. AD 32, NAD 19 (44°38.6'N, 125°20.1'W - 44°37.6'N, 125°21.0'W), 2400 m, 25 Jan. 1963 (4.5 mm long, 2 mm wide, abdomen 3 mm long; left shield plate 1.1 mm long, 0.9 mm wide). Two specimens (LACM 5358), juveniles, Cascadia Abyssal Plain, W off Yaquina Bay, R.V. Acona, Sta. AD 141, NAD11B NAD 19 (44°38.6'N, 125°20.1'W - 44°37.6'N, 125°21.0'W), 2400 m, clayey silt, 8 Apr. 1965 (3.5-4.0 mm long, 2.0-2.5 mm wide, abdomen 2.5-3.0 mm long; left shield plate 0.5-0.7 mm long, 0.5-0.9 mm wide). One specimen (LACM 5356), juvenile, too contracted, introvert damaged, Cascadia Abyssal Plain, W off Yaquina Bay, R.V. Acona, Sta. AD 148, NAD 12 (44°40.7'N, 125°10.0'W - 44°41.1'N, 125°10.0'W), 1000 m, 5 Jun. 1965 (genital papillae small, digitate; body 2 mm long, 2.2 mm wide, left shield plate 0.6 mm long, 0.8 mm wide). Five specimens (LACM 5357), juveniles, Cascadia Abyssal Plain, W off Yaquina Bay, R.V. Acona, Sta. AD 149, NAD 15 (44°41.2'N, 125°15.0'W - 44°91.9'N, 125°15.1'W), 1600 m, silty sand, 5 Jun. 1965 (0.7-4.5 mm long, 0.8-3.0 mm wide, abdomen 0.6-3.0 mm long; left shield plate 0.4-0.6 mm long, 0.5-0.9 mm wide). Northeastern Pacific, Southern California, canyons. Fifteen specimens (LACM 5363), juveniles, 4.9 km off Gull Island, Santa Cruz Island, R.V. Velero IV, Sta. 6808 (33°54'30"N, 119°47'22"W), green sandy mud, 878 m, 22 Dec. 1959 (3.0-5.0 mm long, 1.5-3.0 mm wide, abdomen 2.0-3.0 mm long; left shield plate 0.5-0.8 mm long, 0.5-0.8 mm wide). Five specimens (LACM 5364), two juveniles, 10.7 km off Ribbon Rock, Santa Catalina Island, R.V. Velero IV, Sta. 6828 (33°20'30"N, 118°39'05"W), green mud, 1246 m, 28 Jan. 1960 (3.0-6.5 mm long, 2.0-3.0 mm wide, abdomen 2.0-3.5 mm long; left shield plate 0.7-0.9 mm long, 0.8-1.1 mm wide). BLM (= Bureau of Land Management) Baseline Study, Southern California Bight. One specimen (LACM 5327), dried out, BLM 81202, R.V. Thomas G. Thompson, Sta. 812 (33°46.384'N, 119°35.818'W), 1419 m, olive green soupy mud, biological box core, rep. 2 BFI/ B3-5, 22 Aug. 1977, K. Fauchald, G. Jones, coll. One specimen (LACM 5328), bent over itself, body wall broken, BLM 81236, R.V. Thomas G. Thompson, Sta. 812 (33°46.25'N, 119°36.30'W), 1419 m, olive green soupy mud, biological box core, rep. 36 BFI/ B3-5, 31 Aug. 1977, K. Fauchald, G. Jones, coll. One specimen (LACM 5329), body wall broken, BLM 81237, R.V. Thomas G. Thompson, Sta. 812 (33°46.24'N, 119°36.25'W), 1419 m, olive green soupy mud, biological box core, rep. 37 BFI/ B3-5, 31 Aug. 1977, K. Fauchald, G. Jones, coll. (4 mm long, 3 mm wide, abdomen 3.5 mm long, left shield plate 1 mm long, 1 mm wide). Two specimens (LACM 5330), one with introvert invaginat ed, BLM 81238, R.V. Thomas G. Thompson, Sta. 812 (33°46.24'N, 119°36.26'W), 1419 m, olive green soupy mud, biological box core, rep. 38 BFI/ B3-5, 31 Aug. 1977, K. Fauchald, G. Jones, coll. (5 mm long, 2 mm wide, abdomen 3 mm long, left shield plate 1 mm long, 1 mm wide). One specimen (LACM 5331), BLM 81302, R.V. Thomas G. Thompson, Sta. 813 (33°46.24'N, 119°36.26'W), 1758 m, olive brown silty mud, biological box core, rep. 02 BFI/ B4-1, 23 Aug. 1977, K. Fauchald, G. Jones, coll. (abdomen 3 mm long, 3 mm wide; left shield plate 1 mm long, 1 mm wide). Three specimens (LACM 5332), one mature female, BLM 81303, R.V. Thomas G. Thompson, Sta. 813 (33°0.951'N, 119°1.987'W), 1756 m, olive brown silt, biological box core, rep. 03 BFI/ B4-1, 23 Aug. 1977, K. Fauchald, G. Jones, coll. (abdomen 1.8-2.5 mm long, 1.5-2.0 mm wide; left shield plate 0.4-0.8 mm long, 0.5-0.8 mm wide; oocytes 180-200 µm in diameter). Two specimens (LACM 5332a), dried-out, BLM 81305, R.V. Thomas G. Thompson, Sta. 813 (33°1.003'N, 119°1.977'W), 1758 m, olive brown silt, biological box core, rep. 05 BFI/ B4-1, 23 Aug. 1977, K. Fauchald, G. Jones, coll. Two specimens (LACM 5338), BLM 81402, R.V. Thomas G. Thompson, Sta. 814 (32°48.483'N, 119°7.909'W), 931 m, olive green silty mud with shells, biological box core, rep. 02 BFI/ B4-2, 24 Aug. 1977, K. Fauchald, G. Jones, coll. (5 mm long, 2.5-2.8 mm wide, abdomen 3.0-3.5 mm long, left shield plate 0.7-0.9 mm long, 0.7-0.9 mm wide). One specimen (LACM 5339), BLM 81404, R.V. Thomas G. Thompson, Sta. 814 (32°48.481'N, 119°7.872'W), 933 m, olive green silty mud, biological box core, rep. 04 BFI/ B4-2, 24 Aug. 1977, K. Fauchald, G. Jones, coll. (3 mm long, 2 mm wide, abdomen 2 mm long, left shield plate 0.6 mm long, 0.6 mm wide). Two specimens (LACM 5341), dried-out, BLM 81407, R.V. Thomas G. Thompson, Sta. 814 (32°48.465'N, 119°7.946'W), 922 m, olive green silty mud, biological box core, rep. 07 BFI/ B4-2, 24 Aug. 1977, K. Fauchald, G. Jones, coll. One specimen (LACM 5342), dried-out, BLM 81408, R.V. Thomas G. Thompson, Sta. 814 (32°48.440'N, 119°7.828'W), 940 m, olive green silty mud, biological box core, rep. 08 BFI/ B4-2, 24 Aug. 1977, K. Fauchald, G. Jones, coll. Two specimens (LACM 5343), dried-out, BLM 81418, R.V. Thomas G. Thompson, Sta. 814 (32°48.53'N, 119°7.89'W), 920 m, olive green silty mud, biological box core, rep. 18 BFI/ B4-2, 24 Aug. 1977, K. Fauchald, G. Jones, coll. Two specimens (LACM 5344), dried-out, BLM 81422, R.V. Thomas G. Thompson, Sta. 814 (32°48.48'N, 119°7.81'W), 920 m, olive green silty mud, biological box core, rep. 22 BFI/ B4-2, 24 Aug. 1977, K. Fauchald, G. Jones, coll. One specimen (LACM 5345), BLM 82502, 14 km S of Huntington Beach, R.V. Thomas G. Thompson, Sta. 825 (33°33.035'N, 118°0.820'W), 250 m, olive green gray silty clay mud, biological box core, rep. 2 BFI/ B6-2, 3 Feb. 1977, K. Fauchald, G. Jones, coll. (abdomen 3 mm long, 2.3 mm wide; left shield plate 0.8 mm long, 0.8 mm wide). One specimen (LACM 5346), dried-out, BLM 84005, R.V. Thomas G. Thompson, Sta. 840 (33°24.56'N, 119°30.12'W), 713 m, olive green silty mud, biological box core, rep. 5 BFI/ D2-1, 3 Feb. 1977, K. Fauchald, G. Jones, coll.

Description.

Holotype (LACM 5353) with body brownish, paler over remaining integument with papillae (Fig. 9A). Introvert exposed, narrower than abdomen, covered with abundant papillae, eroded in some areas. Abdomen with integument smooth without papillae in swollen areas, otherwise with abundant small papillae. Body 7.5 mm long, 3.7 mm wide, abdomen 5.5 mm long; about 29 segments; left shield plate 1.6 mm long, 1.5 mm wide.

Prostomium small ovoid, paler distally, darker basally (Fig. 9B), smaller than mouth. Peristomium rounded, with a band of abundant papillae not reaching base of introvert hooks of chaetiger 1. Mouth oval, slightly projected, papillose.

First three chaetigers with 12-14 bronze, slightly falcate hooks per bundle, each with subdistal dark areas. Genital papillae lost, eroded from the intersegmental groove between segments 7 and 8 (not visible in paratypes either).

Pre-shield region with 7 segments, with papillae abundant in protected areas (some paratypes with papillae arranged in single transverse series per segment). Short, few capillary chaetae present in one segment (in up to three segments in paratypes).

Ventro-caudal shield pale orange (Fig. 9C), with ribs, concentric lines poorly developed; suture distinct throughout shield. Anterior margins rounded; anterior depression deep; anterior keels exposed (also exposed in two paratypes). Lateral margins rounded, reduced posteriorly. Fan truncate, half as wide as anterior margins width, slightly projected beyond posterior shield corners, median notch moderate, fan margin smooth (barely crenulated in two paratypes).

Marginal chaetal fascicles include 10 lateral ones; chaetae ovally arranged, and 5 posterior fascicles (6-7 in paratypes). Peg chaetae or associated capillaries not visible (neither in paratypes).

Branchiae lost in holotype (paratypes with abundant filaments, some 2-3 times thicker, and half as long as the others). Branchial plates parallel, anteriorly rounded.

Variation.

There are several modifications in the shield development with roughly defined ribs and the general outline has lateral margins rounded, medially expanded, some distortions were noticed probably due to sample handling since the body is rather delicate. The shield pigmentations is dark yellow in smaller paratypes (Fig. 9E) with radial ribs barely visible and no concentric lines; the posterior margin is smooth with the fan not projected beyond the posterior corners. Slightly larger paratypes have a better defined diagonal rib (Fig. 9F), but concentric lines appear later (Fig. 9G), together with slight lateral notches. The largest paratype was severely damaged (Fig. 9D), and its shield is almost completely detached and bent dorsally, such that its outline is apparently different (Fig. 9H); it has a well-developed diagonal rib but concentric lines are barely visible, and the lateral notches are not as distinct as in smaller specimens.

Early shield development.

Very small juveniles show a transition in pigmentation and development of the ventro-caudal shield (Fig. 10A). The smallest specimen, being 0.7 mm long (Fig. 10B) has no pigmentation but chaetae are already arranged in lateral and posterior bundles, each with 1-3 chaetae. When the body doubles its size, being about 1.5 mm long (Fig. 10C) the shield has some sediment particles and becomes slightly more pigmented than in smaller specimens. The following stage, when the body reaches about 3 mm long (Fig. 10D), is not markedly different from the previous stage. Darker pigmentation and better defined shield margins are attained when the specimens are 3.5 mm long (Fig. 10E, oblique illumination resulted in a darker shield) but the ribs or the median notch are not well defined. These last two modifications apparently appear soon afterwards because in a similar-sized specimen (Fig. 10H), the shield (with a more incident angle) shows a dark yellow shield bordered by a paler region, and with better defined ribs and median notch (Fig. 10G).

Etymology.

This species is named after Susan Williams, in recognition of her taxonomic work on trichobranchids, and because she left some notes indicating that she regarded some of the materials herein included for this description as representing a different pattern which deserved a name. The epithet is a noun in the genitive case.

Type locality.

W off Yaquina Bay, Oregon, 2800 m depth.

Remarks.

Sternaspis williamsae sp. n. is very similar to Sternaspis maior Chamberlin, 1919 as redescribed elsewhere ( Sendall and Salazar-Vallejo 2013) because both have shield with ribs and poorly-developed concentric lines. They differ, however, because of the relative development of some shield features. In Sternaspis williamsae the main ribs are moderately divergent, and the fan is narrower than that of the anterior margin, being up to half as wide as the anterior margin, whereas in Sternaspis maior the main ribs are markedly divergent, and the fan is as wide or wider than that of the anterior margin. On the other hand, Sternaspis williamsae is similar to Sternaspis annenkovae because both species have shields with fan narrower than that of the anterior margin. These two species differ because in the shield of Sternaspis williamsae the concentric lines are poorly developed, the fan is medially continuous, and its prostomium is smaller than the mouth, whereas in Sternaspis annenkovae concentric lines are better developed, the fan is medially discontinuous, and the prostomium is larger than the mouth. As stated above, Sternaspis williamsae resembles Sternaspis maureri because of their shields. They differ, however, in three main features. In Sternaspis williamsae the ribs are poorly developed, its median notch is deep or well defined, and its lateral notches are poorly developed or indistinct, whereas in Sternaspis maureri the ribs are better developed, its median notch is shallow or very slightly developed, and its lateral notches are better developed.

Distribution.

Only known from Oregon to California, 1000-2800 m depth.