Raricirrus jennae Magalhães & Linse & Wiklund 2017, sp. nov.

Raricirrus jennae sp. nov.

Zoobank registration number: Genbank registration number: Figures 1 –3

Material examined. Holotype: Monterey Bay, California, “Deadwood 2” site, 36°15.41 ʹ N, 122°40.41ʹ W, associated with deployed fragments of yew (Torreya californica), deployed on October 18, 2011 and retrieved on October 26–28, 2013 by a benthic elevator and ROV Doc Ricketts on an MBARI cruise aboard the R/V Western Flyer, 3100 m (USNM 1437642). Paratypes same locality, date, collector and wood type as holotype (5, USNM 1437643; 5, USNM 1437644; 5, FMNH 15516; 7, FMNH 15517). Molecular voucher specimens were collected at same localities and dates as type material.

Additional non-type material examined: Same locality, date and collector as type series, associated with Spice bush (Calycanthus occidentalis), Sta. WB21 (4); Lyon, Sta. WB31 (2) and Sta. WB32 (118; 1 DNA voucher NHMUK 2017.105); yew (Torreya californica), Sta. WB34 (1), Sta. WB35 (87) and Sta. WB36 (57); fern genus Cyathea, Sta. WB37 (2). East Scotia Ridge E2, "Cindy's Castle", 56°5.33ʹ S, 30°19.11ʹ W, associated with tubes of Maldanidae polychaetes, collected December 12, 2012 by ROV ISIS on research cruise JC80 aboard RRS James Cook, 2646 m (2, NHMUK 2017.101-102; 1 DNA voucher, NHMUK 2017.103).

Description. Holotype 6 mm long, 1 mm wide on mid-body segments, with 29 chaetigers (Figs 1A; 2A). Twenty-two paratypes measured 4–9.8 mm long, 0.5–1.2 mm wide for 19–31 chaetigers. Body short, stout to elongate, segments distinct, rounded dorsally, ventrally flat (Fig. 1A, G); ventral groove along body (Fig. 2A); posterior chaetigers with a ventral ridge along 8–10 segments, slightly widened (Fig. 1G). Live specimens not observed. Preserved specimens with uniform color, light, golden brown (Fig. 2B) to dark brown (Fig. 2A); branchiae same color of body (Fig. 2A). Dark body pigmentation precludes observation of internal features heart body only observed in one specimen from chaetigers 10–16 (Fig. 1I); one dissected specimen with heart body from chaetigers 10–15 (Fig. 2C).

Prostomium conical, rounded anteriorly with a pair of elongate, postero-lateral nuchal organs (Figs 1A, B; 2A); eyes absent. Prostomium clearly separated from peristomium by deep lateral groove and shallow dorsal groove (Fig. 2A, B). Peristomium slightly longer than prostomium, with a shallow lateral groove forming two equivalent annuli (Figs 1A; 2A, B). Dorsal region of peristomium slightly elevated, forming a crest extending posteriorly over chaetiger 1–2 (Fig. 2A). Dorsal tentacles absent. Branchiae usually short, present in limited number of anterior body segments, arising posterior to notopodial lobe (Figs 1A, I; 2A); segmental origin of first branchia not related to size (Fig. 3B); branchiae smooth or crenulated in some specimens (Fig. 1I). Holotype with branchiae on right side of chaetigers 8 and 9 and left side of chaetiger 6 (Figs 1A; 2A). Presence and number of branchiae variable, present on anterior half of body usually between chaetigers 3–15 (see Table 1).

Parapodia lateral throughout with chaetae emerging from low parapodial ridges (Fig. 1C, D). Chaetae of three types: normal capillaries, long capillaries (natatorial) and acicular spines; capillaries showing serrations along one side of blades under oil immersion. Notopodia of chaetiger 1 with two rows of normal capillaries numbering 5–6 (paratypes ranging from 2–8 capillaries; see Table 1); notopodia of chaetiger 15 with 8–10 long capillaries (paratypes with 4–12 either long or normal capillaries). Notopodial capillaries always longer than neurochaetae. Notopodial acicular spines from chaetiger 16 in holotype (paratypes from chaetigers 15–20); with three spines and three companion capillaries (paratypes with 1–3 spines and 2–6 companion capillaries); segmental origin of notopodial spines clearly size-dependent (Fig. 3A); a juvenile individual (1.2 mm long, 0.2 mm wide) with notopodial spines from chaetiger 5. Notopodial acicular spines colorless, straight with blunt tip (Figs 1F; 2F). Neuropodia with acicular spines and companion capillaries throughout; neuropodial acicular spines colorless, straight and with blunt tips (Figs. 1E; 2D, E). Some specimens with long natatorial capillaries on notopodia only, slightly longer than body’s width. Anterior neuropodia of holotype with one acicular spine and one companion capillary (paratypes with 1–2 spines and 2–4 companion capillaries); mid-body neuropodia with two acicular spines and four companion capillaries (paratypes with 2–3 spines and 2–6 companion capillaries); last segments with two spines and two companion capillaries (paratypes 1–2 spines and 2–4 capillaries). Acicular spines from mid-body and posterior end segments slightly longer than neuropodial spines from anterior end but of similar shape and width (Fig. 1E, F).

Pygidium simple segment with a ventral round lobe and dorso-terminal anal aperture (Fig. 1H).

Remarks. See Table 2 and Discussion for comparison among species of Raricirrus.

Comparative material examined: Raricirrus beryli Petersen & George, 1991, holotype, ZB 1990.52, Beryl oilfield, North Sea, 100-115 m, 12 May 1982. Raricirrus variabilis Dean, 1995, 8 Paratypes, USNM 170552, Virgin Islands. Raricirrus jennae sp. nov. is readily distinguished from all other Raricirrus species by the lack of serrated chaetae, presence of acicular spines, presence of capillaries on neuropodia in addition to notopodia and absence of enlarged modified (genital) spines.

Etymology. This species is named after Dr. Jenna Judge who kindly donated the samples collected as part of her dissertation for identification and description.

Distribution. Type locality is Monterey Bay, off California, U.S. in 3,100 m. This species has also been collected from 2,100–2,600 m at deep-sea hydrothermal vent sites E2 and E 9 in East Scotia Ridge, Southern Ocean (Fig. 4).

Phylogenetic results. The two Raricirrus jennae sp. nov. specimens from California wood and East Scotia Ridge vent are sister taxa to Raricirrus beryli from shallow water (115 m depth) in the North Atlantic, with strong support for the clade (Fig. 5). The K2P distance between the two R. jennae sp. nov specimens from different ocean basins is 0.01 in 16S and 0.02 in COI, while the K2P distance between them and R. beryli is 0.11 in 16S and 0.24 in COI. The genus Raricirrus, represented by the species R. jennae sp. nov. and R. beryli, appears as sister group to a clade composed of Dodecaceria and Ctenodrilus (Fig. 5).