Ampharete oculicirrata, Parapar & Moreira & Barnich, 2019

Parapar, Julio, Moreira, Juan & Barnich, Ruth, 2019, A new species of Ampharete (Annelida: Ampharetidae) from the West Shetland shelf (NE Atlantic Ocean), with two updated keys to the species of the genus in North Atlantic waters, European Journal of Taxonomy 531, pp. 1-16 : 4-11

Ampharete oculicirrata sp. nov.

urn:lsid:zoobank.org:act:

Figs 1 –7; Table 1

Diagnosis

MEASUREMENTS. Small-sized species of up to 10 mm in length and 1.0 mm in width.

PROSTOMIUM AND PYGIDIUM. Provided each with a pair of dark eyes.

BRANCHIAE. Arranged in two groups separated by a short gap.

PALEAE. Thin and slender with filiform tips, 5–7 on each side; slightly longer and wider than regular thoracic notochaetae.

THORAX AND ABDOMEN. Twelve thoracic uncinigers and 11 abdominal uncinigers without dorsal neuropodial cirrus (first two of thoracic shape).

PYGIDIUM. Lobulated with two long lateral cirri.

Etymology

The epithet oculicirrata from the Latin ‘ oculi ’, meaning ‘eyes’, and ‘ cirrata ’, meaning ‘in cirrus’ refers to the conspicuously pigmented eyespots laterally on the long pygidial cirri.

Material examined

Holotype

SCOTLAND • holotype; West Shetland shelf, west of the Orkneys ; station number 1517 S WSS 13 S 103; 59.40° N, 5.92° W; 130 m depth; 2 Nov. 2017; EtOH preserved; NMS. Z. 2019.8.1.

Paratypes

SCOTLAND • Eighty-one specimens; same area as for holotype but from different sampling localities; either preserved in EtOH, in the same way as the holotype, or prepared for SEM ( MNCN 16.01 /18482) • 2 ♀♀ with oocytes; collection data of each sampling station and museum registration numbers for each group of paratypes are detailed in Table 1; MNCN 16.01 /18475, MNCN 16.01 /18481 .

Description of holotype (SEM images from paratypes MNCN 16.01/18482)

MEASUREMENTS. Complete specimen of 7.5 mm length and 0.5 mm width in thorax.

PROSTOMIUM. Trilobed; rather narrow and protruding median lobe delimited by deep lateral grooves; a pair of nuchal organs as circular ciliated spots located at the base of the median prostomial lobe; prostomial glandular ridges absent ( Figs 1C, 2A, 4 A–B).

EYES. Two small black, circular eyespots located posteriorly on median prostomial lobe next to the lateral grooves ( Fig. 1A, C).

PERISTOMIUM. Forming a well-developed buccal lip ( Figs 1B, 5B, 7A).

BUCCAL TENTACLES. Without groove, with two ventrolateral rows of long and slender pinnae (longer than tentacle diameter); tips of pinnae covered by cilia (Fig. 7B).

BRANCHIAE. Four pairs located in fused segments II+III and arranged in two groups with a short median gap, about one branchia wide ( Figs 1A, C, 4B); branchiophores fused at base ( Figs 1C, 2 A–B); branchiae of same width throughout, but slightly tapering at distal end, about 3 times as long as the prostomium and 3⁄5 as long as the thorax ( Figs 1A, 4 A–B), reaching about TC6 and provided with parallel ciliated rings from base to distal end ( Fig. 4B). Anterior three pairs of branchiae arranged in transverse row, fourth pair posterior to anterior row, between second outermost and innermost branchiae ( Fig. 1A, C). Fused segments II+III (SG2+3) provided with 5–6 long, thin and slender chaetae (paleae), slightly longer than following regular notochaetae ( Figs 1 A–C, 2A–B, 4A–B).

THORAX. Longer and wider than abdomen ( Fig. 1A). Fourteen thoracic segments with notopodia and capillary chaetae (SG4 to SG17); last 12 segments also with neuropodial tori bearing single row of uncini. Nephridial papillae not observed. Thoracic notopodia as simple lobes from SG4 and up to three times longer than wide; first notopodium somewhat reduced ( Figs 1 A–C, 2A–B). Notochaetae as simple spinulose capillaries, tapering to slender tips; arranged in two rows, capillaries from anterior row much thinner and shorter than those of posterior row ( Fig. 2C). Thoracic neuropodia from SG6; anterior ones usually oval-shaped, about three times higher than wide ( Figs 1B, 2A, D); gradually decreasing in size, becoming more rounded in posterior part of thorax ( Fig. 3B). Cirri and papillae in thoracic parapodia absent. Thoracic uncini with about ten teeth in two vertical rows above rostrum ( Fig. 2D). Well-developed ventral shields present to TU10, weakly developed in TU11 and absent in TU12 ( Fig. 5A). Elevated or modified notopodia absent.

ABDOMEN. Shorter and thinner than thorax. Eleven uncinigers, anterior two (AU1–2) with neuropodia of thoracic type (‘intermediate uncinigers’) ( Figs 1A, 3 C–D, 5A); remaining nine abdominal uncinigers (AU3–11) with enlarged neuropodial ‘pinnules’, without dorsal neuropodial cirrus ( Figs 1A, 3E, F, 5A, 7C–D). Glandular pads above pinnules not observed in intermediate or abdominal uncinigers. Abdominal uncini of AU1–2 similar to thoracic ones ( Fig. 3 B–D); following ones of typical abdominal shape, with about eight teeth in two vertical rows above rostrum (Fig. 6).

PYGIDIUM. Crenulated due to the presence of low pygidial papillae; with a pair of long lateral cirri ( Figs 1D, F, 3F, 7D), each with a pygidial eye located in the proximal third of the cirrus; eyes consisting of two dark pigmented spots ( Fig. 1D, F). Fixed specimens creamy white in colour.

STAINING. Head (prostomial tip especially) and ventral thoracic shields dyed by methyl blue.

TUBE. Unknown.

Variations

Complete specimens measure 4.0–10.0 mm in length and 0.5–1.0 mm in width, although most complete specimens are about 4.0–5.0 mm long. One specimen (MNCN 16.01/18482) observed with the ventral pharyngeal organ protruded (Fig. 7A). The buccal lip may appear smooth or rough depending on the state of contraction of the buccal opening ( Figs 5B vs 7A). The gap between groups of branchiae is difficult to see in many specimens, but it is obvious in the holotype ( Fig. 1C) and several paratypes. Some paratypes have pygidial eyes consisting only of a single pigmented spot ( Fig. 1F). Two females (MNCN 16.01/18475, 7 mm long and MNCN 16.01/18481, 10 mm long) bear oocytes in the coelomic cavity.

Fig. 6. Ampharete oculicirrata sp. nov., paratype MNCN 16.01/18482_spec. 3. A. Abdominal unciniger 7, posterior view. B. Detail of abdominal uncini, frontal and lateral view. Scale bars: A = 150 µm; B = 5 µm.

Distribution and ecology

Ampharete oculicirrata sp. nov. was found in many localities on the West Shetland shelf in offshore sand and gravel habitats at depths of between 113 and 138 m (see also Table 1).