Berkeleyia lelievrei new species

Figure 10

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Berkeleyia sp. nov. Lelièvre et al. 2018: 2633.

Material examined. NE Pacific Ocean, off Washington, Juan de Fuca Ridge, Endeavour Segment, R / V T . G. Thompson Cruise TN328, coll. Y. Lelièvre, Grotto Site, Sta. ROV Jason dive J2-831, 07 Sep 2015, 47°56.958′N, 129°5.899′W, 2196 m, holotype (MCZ 154094), 4 paratypes (MCZ 154095) .

Description. A moderately sized species; all specimens incomplete, some damaged. Holotype 14.7 mm long, 1.6 mm wide across middle of thorax, 0.8 mm wide across abdominal segments, with 55 setigers. Paratypes 14–16 mm long with 38–50 setigers. Body with broad thoracic region more or less dorso-ventrally flattened, with 10–11 setigers, fusiform in shape (Fig. 10A); dorsum weakly rounded; venter flattened with mid-ventral groove. Individual thoracic segments narrow, middle segments about ten times wider than long (Fig. 10A). Abdominal segments narrow, about six times as wide as long. Eggs present in some specimens, up to 230 µm in diameter. Color in alcohol: tan with dark dusky pigment on prostomium and dorsum of thorax on some specimens.

Prostomium, conical, narrowing to rounded apex (Fig. 10A); nuchal organs lateral grooves on posterior margin; eyespots absent. Peristomium about twice as long as first setiger; composed of one or two rings; holotype with two distinct peristomial rings (Fig. 10A), paratypes with a single ring or with groove separating two rings weakly defined. Proboscis everted in two paratypes, composed of about seven thin lobes.

Thoracic parapodia with triangular postsetal lamellae, narrowing apically (Fig. 10B). Transition to abdominal segments abrupt, denoted by enlargement and elongation of neuropodium and reduced number of setae. Abdominal notopodia conical with narrow, elongate postsetal lamellae; neuropodia of anterior abdominal segments with rounded apex, becoming bi-lobed in middle and posterior segments (Fig. 10C). Branchiae from setiger 12, short at first, becoming longer, tapering in subsequent segments (Fig. 10C); individual branchiae ciliated, with lateral folds best seen in posterior segments.

All thoracic setae numerous camerated or bristled capillaries arranged in 3–4 rows; thoracic notosetae may include a superior tuft of thin capillaries (Fig. 10B); neurosetae may include an inferior tuft of thin capillaries (Fig. 10B). Abdominal notosetae initially include 4–5 thin capillaries, transitioning to long, brass-colored spinous setae continuing throughout. Abdominal neurosetae initially with 1–3 short, thin capillaries transitioning to 1–2 long brass-colored spines, continuing throughout. Spinous noto- and neurosetae of abdominal segments all smooth, not camerated or with any evidence of bristles or barbs, terminating in rounded tip (Fig. 10C inset). Furcate and flail setae entirely absent.

Pygidium not observed.

Methyl Green stain. No pattern, body stains uniformly green; de-stains rapidly.

Remarks. All five specimens are incomplete and exhibit evidence of poor preservation or handling, mainly in abdominal segments (Blake 2017). Setae of thoracic segments are generally intact, but many abdominal setae are broken or sheared off. Some middle abdominal segments are soft and fragile suggesting they were not preserved soon enough after collection. Nevertheless, there is sufficient intact morphology to define the specimens as a new species.

Berkeleyia lelievre n. sp. is the sixth species of the genus and is most similar to B. hadala Blake, 2017 from the Peru-Chile Trench in the transition of typical camerated or bristled capillaries in thoracic setigers to smooth, non-bristled brass-colored spinous setae in abdominal segments. The two species differ in that B. hadala has a triangular-shaped prostomium pointed on the tip, a peristomium that has a single ring merged with the prostomium, and branchiae from setiger 24. In contrast, B. lelievre n. sp. has a prostomium that is conical and rounded on the tip, a peristomium that has one or two rings that are distinctly separated from the prostomium, and branchiae from setiger 12.

Biology. The specimens of Berkeleyia lelievre n. sp. were collected from dense assemblages of Ridgeia piscesae Jones, 1985, a common siboglinid tubeworm at the Grotto hydrothermal site on the Endeavour Segment, Juan de Fuca Ridge. Associated organisms, including B. lelievre n. sp., were collected with the tubeworms. A total of 35 macrofaunal taxa, including 19 polychaete species were removed from the tubeworm habitat. The dominant macrofaunal taxa were the gastropods Lepetodrilus fucensis McLean, 1988 and Depressogyra globulus Warén & Bouchet, 2001, and the ampharetid polychaete Amphisamytha carldarei Stiller et al., 2013 .

Etymology. This species is named for Dr. Yann Lelièvre, Université de Montréal, benthic biologist who participated in the survey and published an important paper on the ecology and biodiversity of the site (Lelièvre et al. 2018). Distribution. Eastern Pacific Ocean, hydrothermal vents, Juan de Fuca Ridge, 2196 m.