Guide and keys for the identification of Syllidae (Annelida, Phyllodocida) from the British Isles (reported and expected species)

Abstract In November 2012, a workshop was carried out on the taxonomy and systematics of the family Syllidae (Annelida: Phyllodocida) at the Dove Marine Laboratory, Cullercoats, Tynemouth, UK for the National Marine Biological Analytical Quality Control (NMBAQC) Scheme. Illustrated keys for subfamilies, genera and species found in British and Irish waters were provided for participants from the major national agencies and consultancies involved in benthic sample processing. After the workshop, we prepared updates to these keys, to include some additional species provided by participants, and some species reported from nearby areas. In this paper, we provide the revised keys to enable rapid identification of Syllidae from the seas around Britain and Ireland. One new combination, Palposyllis propeweismanni, is proposed.

Another 18 syllid taxa were also reported, but they are synonyms of other species, invalid, or doubtful species, or even not recognized as Syllidae.
This number of species is quite low for such an area and it is certain that many other species live in British waters. In the keys below, we have included all previously reported species (excluding invalid or doubtful ones) plus those that have been reported from nearby areas of the NE Atlantic and that could be also present in the study area. Some of these were noted at the NMBAQC workshop or since that time but are not yet formally recorded. It is important to remember the possibility that other species, not in the keys presented here, may yet be found in the area and reference should be made to additional literature for any specimens that do not fit descriptions. Books with keys for syllids of nearby areas include those by Fauvel (1923) (France), Hartmann-Schröder (1996) (Germany), and San Martín (2003) (Iberian Peninsula). A previous NMBAQC workshop (2006) included work on syllids led by Peter Garwood but the resulting key was not published or circulated via the website. Recently, Dietrich et al. (in press) revised the Autolytinae from the area (North Sea and NE Atlantic). Their results are followed here; we strongly recommend use of these keys as a complement to ours for that subfamily.

Body
Cylindrical in section (Fig. 1A, B, E, F), but may be flattened, ribbon-like (Fig. 1C). The surface is smooth ( Fig. 1A-C, F), but may also bear papillae on the dorsal (Fig. 1E) and ventral surface, and on the parapodia. Some bear rugosities, tubercles, rows of cilia, etc.

Prostomium
Semicircular to pentagonal or oval and has four eyes and, sometimes, also a pair of ocular spots, three antennae, which may be smooth (Fig. 1B, E, F) or articulated (also known as moniliform) (Fig. 1A, C), short or long, and one pair of palps, triangular in shape, rounded or oval, that may be fully separated from each other (Fig. 1D), basally fused or fused along their entire length (Fig. 1E).

Dorsal cirri
May be long or short, alternating between long and short, smooth (Figs 1B, E, F, 2B-D) or moniliform (Figs 1A,C,2A). Typically filiform, but may be of different shapes.

Ventral cirri
Present, except in the subfamily Autolytinae, in which they appear to be absent ( Fig. 2D) but are in fact fused to parapodial lobes.

Pharynx
Usually straight, but coiled in some genera, sometimes very slender and complex (Fig. 1F).

Proventriculus (= Proventricle)
Rectangular, squared or barrel-shaped. Size (number of segments) and number of muscle cell rows vary between species.
Sometimes, there may be thick simple chaetae due to the loss of blades and enlargement of shafts (Fig. 3G) or by fusion of blade and shaft (Fig. 3H). The capillary dorsal and ventral simple chaetae are usually very slender, bifid or entire, with or without subdistal spines. Typically, these capillary simple chaetae are present only on posterior parapodia.    (