Prionospio vallensis, Paterson, Gordon L. J., Neal, Lenka, Altamira, Iris, Soto, Eulogio H., Smith, Craig R., Menot, Lenaick, Billett, David S. M., Cunha, Marina R., Marchais-Laguionie, Claire & Glover, Adrian G., 2016

Paterson, Gordon L. J., Neal, Lenka, Altamira, Iris, Soto, Eulogio H., Smith, Craig R., Menot, Lenaick, Billett, David S. M., Cunha, Marina R., Marchais-Laguionie, Claire & Glover, Adrian G., 2016, New Prionospio and Aurospio Species from the Deep Sea (Annelida: Polychaeta), Zootaxa 4092 (1) : 8-11

Prionospio vallensis sp. nov. Neal & Paterson

( Figures 1 , 2.2, 4, 8g)

Prionospio sp G Curdia et al. 2004:

Prionospio sp A Paterson et al. 2011: 2453

Material examined: 1035 specimens examined.

Holotype: RRS Charles Darwin, cruise 179 April–May 2006, Setúbal canyon St. 56859#1, 39°35.58’N 10°20.00’W 4418m, megacore (NHMUK 2015:1040).

Paratypes: Portuguese margin canyon: Nazaré canyon RRS Discovery 297 August 2005, St.15755#1 39º30.62’N 09°56.19’W 3461m, 175 individuals; St.15760#1 39º30.02’N 09°56.17’W 3465m, 54 individuals; St.15762#1 39º30.02’N 09°56.22’W 3464m, 103 individuals; St.15758#2 39º34.94’N 10°19.00’W 4332m, 26 individuals; St. 15758#6 39º34.99’N 10°19.00’W 4335m, 65 individuals; St.15765#2 39º35.00’N 10°19.04’W 4336m, 39 individuals.

RRS Charles Darwin 179, April/ May 2006, St. 56847#6 39°35.57’N 10°19.99’W 4403m, 33 individuals; St. 56847#7 39° 35.55’N 10° 20.06’W 4404m 33 individuals; St. 56851#1 39° 29.99’N 09° 55.97’W 3517m, 36 individuals; St. 56851#2 39°29.99’N 09°56.01’W 3517m, 76 individuals; St.56856#1 39° 29.95’N 09° 56.00’W 3519m, 40 individuals; St. 56856#2 39°30.00’N 09° 55.98’W 3522m 49 individuals; St. 56859#1 39°35.58’N 10°20.00’W 4418m, 37 individuals; St. 56861#1 39°35.57’N 10°20.02’W 4404m, 44 individuals.

Setúbal canyon: RRS Charles Darwin 179 April/ May 2006, St. 56804#5 38°09.27’N 09°36.93’W 3275m, 75 individuals; St. 56804#6 38°09.26’N 09°36.94’W 3275m, 48 individuals; St. 56806#1 38°09.29’N 09°36.96’W 3275m, 60 individuals; St. 56810#1 38°09.22’N 09°37.02’W 3224m, 23 individuals; St. 56816#1 38°09.27’N 09°36.94’W 3275m, 37 individuals.

Cascais canyon: RRS Charles Darwin 179 April/ May 2006, St. 56821#1 38°17.96’N 09°46.87’W 3219m, 1 individual; St. 56823#2 38°18.01’N 09°47.02’W 3218m, 2 individuals; St. 56823#3 38°17.99’N 09°47.07’W 3219m, 2 individual; St. 56828#1 38°18.02’N 09°46.98’W 3199m, 3 individuals; St. 56837#7 38.3748° -9.8920°, 4243 m, 3 individuals.

Other material studied: Prionospio laciniosa Maciolek, 1985 ; paratypes (USNM 67674-75). Diagnostic features. Wrinkled branchiae on chaetigers 2 and 5, rectangular prostomium, dorsal crests from chaetiger 6 extending to beyond chaetiger 20, distal ends of proximal dorsal lamellae bent toward the mid-line and produced into slender tips.

Description. A small and slender species, holotype complete with 65 chaetigers, measuring 12.4 mm long and 0.25 mm wide at chaetiger 1. Colour in alcohol pale yellow. Prostomium rectangular for about 2/3 of length, then tapering into caruncle reaching to anterior margin of chaetiger 2; posterior portion surrounded by heavily ciliated nuchal organs ( Fig. 4 a); anterior margin truncated ( Fig.4 ), prostomial peaks absent; eyes absent (1 pair of colourless eyes present in some specimens, positioned on prostomium just before caruncle, best observed on stained specimens). Peristomium well developed ventrally, forming distinct lateral wings; chaetiger 1 reduced, dorsally fused to peristomium.

Branchiae present on chaetigers 2–5, 4 pairs, all apinnate, but wrinkled ( Fig.4 b,c). First pair longest, reaching to the anterior margin of chaetiger 8, approximately six times longer than the corresponding notopodial lamellae, distinctly wrinkled with deep grooves, thickened at the base, then cylindrical, tapering into blunt tip (in some specimens the first pair rather slender, still wrinkled but without deep grooves, possibly regenerating), heavily ciliated; pair 4 similar to pair 1 but shorter, by a ratio of 1:4, approximately four times longer than the corresponding notopodial lamellae; pairs 2 and 3 short and heavily ciliated, only slightly longer than notopodial lamellae, with wrinkled surface, fleshy and triangular, wider at base and tapering distally, both pairs are partially covered by enlarged notopodial lamellae; all branchiae free from notopodial lamellae, positioned laterally and slightly posteriorly in relation to inner edge of notopodial lamellae (branchial pairs 1 and 4 easily lost and missing in majority of specimens).

Notopodial lamellae on chaetiger 1 well developed (Fig.2.2a), rounded with very produced tip pointed dorsally; lamellae largest on branchial segments, particularly on chaetigers 3 and 4, subtriangular and somewhat bent, with tips pointing to the midline of dorsum (Fig.2.2 b,c), notopodial lamellae on chaetiger 6 becoming smaller; from chaetiger 7 lamellae small, triangular, pointed distally, often bent, in mid-body segments becoming low, globular (Fig.2.2d). Distinct dorsal crests present from chaetiger 6 and on subsequent chaetigers ( Fig. 4 a) to beyond chaetiger 20. Interparapodial pouches absent.

Neuropodial lamellae largest in branchial segments; small and rounded in chaetiger 1, neuropodia of chaetiger 2 square-shaped, similar in shape but with distinct tip pointing dorsally on chaetiger 3 (Fig. 2.2), in chaetigers 4 and 5 tip not protruded, lamellae square to slightly rounded in shape; from chaetiger 6 becoming small (low rising) and distinctly globular (Fig. 1.2d).

Anterior chaetae all capillaries, granulated, forming dense fascicles, arranged in two rows in both noto- and neuropodia, neuropodial capillaries become long in middle and posterior segments reaching over 4–5 chaetigers in length. Sabre chaetae first occur in neuropodia of chaetiger 10, up to two per fascicle, robust, curved, heavily granulated. Neuropodial hooks first occur on chaetiger 12 but occasionally start from chaetiger 13, up to eight per fascicle; primary hood inflated and somewhat rectangular in shape, secondary hood present and well developed; each hook with six pairs of smaller teeth sequentially reduced in size above the main fang. Notopodial hooks appear around segment 45 (holotype damaged in this section, all other specimens examined were incomplete and notopodial hooks not observed), two per fascicle, long and slender.

Pygidium conical, without any appendages, but these might have been lost.

Methyl green pattern. The borders of prostomium, including caruncle, peristomium, and dorsal crests on segments 12–20 stain strongly.

Remarks. Prionospio vallensis sp. nov. is characterised by wrinkled branchiae on segments 2 and 5. Prionospio fauchaldi and P. laciniosa , both described by Maciolek, 1985, also possess wrinkled branchiae. Prionospio fauchaldi is recorded from the West Atlantic, SE coast of Africa in 530–4950 m and in the western Pacific in approximately 2500 to 3000 m (Blake et al. 2009), and P. laciniosa is recorded from the west coast of Africa at 527– 542m. Prionospio vallensis sp. nov. further resembles P. fauchaldi by having a similar shape of prostomium and peristomium, with sabre chaetae and neuropodial hooks starting in the same segments. The major differences are that in P. fauchaldi the first and fourth pair of branchiae are of the same length, while the first pair is longer than fourth in P. vallensis sp. nov.; sabre chaetae are slender in P. fauchaldi but robust in P. vallensis sp. nov.; and P. fauchaldi possesses extremely long capillaries on the third chaetiger, but these are lacking in P. vallensis sp. nov.

Prionospio vallensis sp. nov. is most similar to P. laciniosa , which also has the first wrinkled pair of branchiae longer than the fourth, but differs from P. vallensis sp. nov. in having a triangular rather than rectangular prostomium and presence of distinct dorsal flaps, which were not seen in P. vallensis sp. nov. The dorsal crests in P. laciniosa are present only on chaetigers 5–13 while in P. vallensis sp. nov. they start on chaetiger 6 and continue beyond chaetiger 20. The shape of notopodial lamellae of the branchial region is also different, whilst subtriangular in both species, the distal ends are bent and directed to the middle and extend into slender tips in P. vallensis sp. nov., whereas in P. laciniosa this bend is less prominent and the tips are more robust. The sabre chaetae in P. vallensis sp. nov. are more robust and shorter than in P. laciniosa . The specimens of both species were of similar size, therefore these differences, particularly presence/absence of dorsal flaps are unlikely to be of result of different developmental stages.

Etymology. vallensis from the Latin valles, meaning valley, the closest Latin expression for canyon.

Ecology. P. vallensis sp. nov. was previously recorded from Setúbal canyon at 3400 m during the RRS Discovery cruise 186 in 1989; although not formally described, it was recorded as Spionidae H. It was the second most abundant species in that study. Examination of photographs of polychaete specimens collected in 1999 during OMEX II from Nazaré canyon and reported by Curdia et al. (2004) as Prionospio sp. G is likely to be Prionospio vallensis . It was reported as the most abundant macrofaunal species at 3514 m and 4141 m.

Prionospio vallensis sp. nov. was the single most abundant polychaete in Portuguese canyons, achieving densities of 784 ind./m 2 in Setúbal canyon (3400 m) and up to 918 ind./m 2 in Nazaré canyon (3400 m) ( Cunha et al. 2011; Paterson et al. 2011). The difference in the abundance between our study and previous ones may be a reflection of different sampling design used during RRS Discovery cruise186, where macrofauna was sieved on 300-micron mesh. However, it was not present in Portuguese canyon samples collected at 1000 m or on the Tagus Abyssal Plain, which is adjacent to Setúbal and Cascais canyons. It is possible that this is a deep canyon “specialist” able to utilize the organically enriched sediments found within the canyon (compared to similar noncanyon depths) and/or rapidly occupy sediments following frequent disturbances, which occur within canyons. Data from previous studies in these canyons (Gage et al. 1995; Curdia et al. 2004) suggest that P. vall ensis sp. nov. has been able to maintain high-density populations in Portuguese canyons on more than a decadal timescale (sampling in 1989, 1999, 2005, 2006).

Distribution. Nazaré, Setúbal, and Cascais canyons along the Portuguese margin, 3199–4419 m.

Figures

FIGURE 1. Maps showing location of collecting sites and distribution of species. a. Locations of the collection sites. CCFZ- Clarion—Clipperton Fracture Zone, W = west site, E = east site, A = UK concession area; CR—Crozet Island; CVAP Cap Verde Abyssal Plain; EP—Equatorial Pacific (EqPac); MAP—Madeira Abyssal Plain; PAP—Porcupine Abyssal Plain; PC— Portuguese Canyons. b. Distribution of Prionospio amarsupiata sp. nov (blue squares), Aurospio abranchiata sp. nov (orange triangles); c. Distrubutions of Prionospio branchilucida sp nov (purple stars), P. vallensis sp. nov (blue triangle); d. Distributions of Prionospio kaplani sp. nov (solid green hexagons); P. hermesia sp. nov (yellow circle), Aurospio tribranchiata sp. nov. (inverted orange triangle)

FIGURE 4. Prionospio vallensis sp. nov. a) Dorsal view of anterior chaetigers; scale bar = 200 µm. b) Lateral view of anterior chaetigers; scale bar = 200 µm. c) Detail of branchial arrangement; scale bar = 200 µm. d) Photomicrograph of neuropodial hooded hooks; scale bar = 10 µm.