Berkeleyia hadala Blake, 2017, new species

Berkeleyia hadala new species

Figure 5

Material examined. Off Western South America, Peru-Chile Trench.—Off Ecuador, R/V Vema Sta. V-15-63, 2681 - 2864 m (1, LACM-AHF Poly 5009).—Off Piura Province, Peru, W of Isla Lobos de Tierra, R / V Anton Bruun Cruise 11, Sta. 69, Milne-Edwards Deep, 4591 m (1, LACM-AHF Poly 5015).— Off Libertad Province, Peru, W of Trujillo, R / V Anton Bruun Cruise 11, Sta. 98, Milne-Edwards Deep, 6052 – 5989 m (2, LACM-AHF Poly 5012); Sta. 111, Milne-Edwards Deep, 3086–3202 m, 18 Oct 1965, 08°23'S, 80°45′W, 1 paratype ( LACM- AHF Poly 5016); Sta. 113, Milne Edwards Deep, 19 Oct 1965, 08°44'S, 80°45′W, 5986–6143 m, 14 paratype s, (LACM-AHF Poly 5019).—Off Chile, W of Isla Mocha, R /V Vema Sta. V-17-5, 16 Mar 1961, 38.25°S, 76.00°W, 3824– 3739 m, 1 paratype ( LACM-AHF Poly 5040); Sta.V-17-6, 21 Mar 1961, 37.95°S, 75.13°W, 4303–4323 m, holotype ( LACM-AHF Poly 5001); Sta. V-17-7, W of Bahia Mansa, 22 Mar 1961, 40°32′S, 75°08′W, 3089–3279 m, 1 paratype (LACM-AHF Poly 5039).

Description. All specimens incomplete, many poorly preserved; holotype 15 mm long, 1 mm wide across thorax for 34 setigers; other specimens with 19–30 setigers, up to 16 mm long and 1.1 to 0.8 mm wide across thorax. Color in alcohol: opaque white, without pigment. Holotype with 11 thoracic setigers; other specimens with 8–11 thoracic setigers; body cylindrical in cross section, throughout; thoracic segments narrower than wide, middle and posterior abdominal segments elongate, longer than wide.

Shape of pre-setigerous region distinctive in dorsal view (Fig. 5 A), with an hour-glass shape; prostomium triangular shaped merging indistinctly with narrow anterior of peristomium, becoming wider in posterior half. Prostomium tapering to narrow pointed apex (Fig. 5 A); without eyespots; nuchal organs paired notches on posterior margin of prostomium at juncture with peristomium (Fig. 5 A). Peristomium with a single achaetous ring, narrow anteriorly, wider posteriorly.

Thoracic segments with short cirriform notopodial postsetal lobes from setiger 1, these increasing in length over subsequent setigers becoming elongate and fingerlike in posterior thoracic setigers (Fig. 5 B); neuropodia similar to notopodia with elongate postsetal lobe (Fig. 5 B); abdominal segments denoted by appearance of prolonged neuropodium bearing long, brass-colored spines (Fig. 5 C); abdominal notopodia initially without postsetal lobe, this appearing over subsequent setigers, becoming elongate, fingerlike in far posterior setigers (Fig. 5 C). Abdominal segments with parapodia gradually shifting to a more dorsal position.

Thoracic setae all long, crenulated capillaries; furcate setae absent. Abdominal neuropodia with 3–4 long projecting smooth brass-colored spines with entire rounded tips (Fig. 5 C, E); abdominal notopodia with similar brass-colored long spinous setae, but with pointed capillary tips (Fig. 5 D). No abdominal camerated setae.

Branchiae from setiger 24 on holotype, short, cirriform and inconspicuous at first, elongating and becoming slightly longer than notopodial postsetal lobe by setiger 34; branchiae slightly swollen on medial border (Fig. 5 C). Branchiae not observed on other specimens, likely due to poor preservation and their fragmented nature. Pygidium unknown.

Remarks. Among the five known species of Berkeleyia, B. hadala n. sp. is unique in the Orbiniidae in having a complete transition from typical orbiniid-like camerated capillaries in thoracic setigers to non-camerated and conspicuous brass-colored smooth setae in abdominal segments. The neurosetae are elongate, thickened blunttipped spines, whereas the notosetae are similarly appearing elongate and thickened setae, but with pointed tips.

Etymology. This species is named for its occurrence in abyssal to ultra-abyssal depths in the Peru-Chile Trench; trench faunas are sometimes called residents of the Hadal Zone.

Distribution. Off western South America, Ecuador to Chile, lower slope, abyssal and ultra-abyssal depths 2681–6143 m.