INTRODUCTION
During a 2008 environmental impact study of a proposed site for a tethered wave power device just south of the Isles of Scilly, two small nereidid polychaetes were discovered that at first appeared to be similar to Eunereis longissima Johnston, 1840. The significant number of parapodia having reduced or absent dorsal ligules led to inconclusive identifications and they were subsequently recorded as Nereididae. Later investigation regarding these reduced ligules and other features pointed to the genus Rullierineries Pettibone, Reference Pettibone1971 (Pettibone, Reference Pettibone1971). A search through all E. longissima in the historical reference collection of Marine Ecological Surveys Ltd. uncovered three more similar specimens from a 2007 benthic sample taken from near the Isle of Wight. All five of these specimens have subsequently been assigned to Rullierinereis ancornunezi Núñez & Brito, Reference Núñez and Brito2006 (Núñez & Brito, Reference Núñez and Brito2006). This species was described from Lanzarote and the discovery of British material is a significant expansion of the known range. It is possible that this species has been unrecorded in the UK due to its small size and similarity to E. longissima.
MATERIALS AND METHODS
Site one
Orecon Ltd, a Cornish wave power company, initiated an environmental impact assessment of a proposed site for the installation of a wave device south of the Isles of Scilly. The site was exposed to Atlantic swells and in 80 m depth of water on a sandy shell substrate with large amounts of dead Cellaria Ellis & Solander, 1786, a genus of erect Cheilostomata Bryozoa. The benthos was sampled in September 2008 using a Mini-Hamon grab and the samples were fixed in 4% formaldehyde. In the laboratory the samples were processed over a 1 mm sieve and the fauna transferred into Industrial Methylated Spirits for storage and subsequent species identification. Two specimens originally assigned to Nereididae but subsequently identified as Rullierinereis ancornunezi were found in a replicate sample. The sample that yielded the specimens was taken randomly between 100 and 200 m west of one of the sampling stations which was located at 49°49.75′N 06°16.42′W.
Site two
A benthic study was carried out in September 2007 near the Isle of Wight by Marine Ecological Surveys Ltd. in relation to ecological monitoring of aggregate extraction. The extraction and processing of the samples followed the same method as site one. The sample was taken from 50°30.32′N 01°45.00′W at 39 m depth on a substrate of gravelly sand with pebbles and contained three specimens of R. ancornunezi that were originally assigned to Eunereis longissima.
RESULTS AND DISCUSSION
The Rullierinereis ancornunezi specimens collected from the Isles of Scilly and the Isle of Wight are similar to those from the Canary Islands and were verified by the author J. Núñez. The largest complete specimen had 103 chaetigers and was 27 mm in length and 0.9 mm in width, excluding the parapodia. Rullierinereis ancornunezi mainly differs from other species of the genus by two characters: development of the dorsal notopodial ligule and the shape and distribution of notopodial homogomph falcigers (Núñez & Brito, Reference Núñez and Brito2006). The characteristics of a body width of less than 1 mm and poorly developed eyes are probable adaptations to living interstitially in subtidal sands.
The development of the upper notopodial ligule in specimens from the UK is variable. Chaetigers 3–5 lack an upper notopodial ligule. Chaetigers 6–9 have two notopodial ligules present, the upper ligule being shorter (Figure 1A). The upper ligule of chaetiger 6 is incipient. In chaetigers 11–12 the upper notopodial ligule is again absent (Figure 1B). Among chaetigers 21–44 the upper notopodial ligule is again incipient (Figure 1C) and in chaetigers 45–47 the upper ligule is absent. From chaetigers 48–56 there is a small upper ligule, which reduces in size to chaetiger 63 and from there is absent in posterior segments.
Rullierinereis ancornunezi Núñez & Brito, 2006: (A) biramous parapodium with small notopodial dorsal ligule, chaetiger 7; (B) biramous parapodium without notopodial dorsal ligule, chaetiger 11; (C) biramous parapodium with incipient notopodial dorsal ligule, chaetiger 29; (D) notopodial homogomph falcigers from posterior chaetigers; (E) anterior end, dorsal view. Scale bar for all figures: A, B 250 µm; C, 31.25 µm; D, 12.5 µm; E, 1.1 mm. A, C and E from an Isle of Wight specimen; B and D from an Isles of Scilly specimen.
Notopodial homogomph falcigers first appear on chaetigers 11–14. These begin as longer-bladed toothed falcigers and towards the posterior region these blades become shorter and smoother. From chaetiger 43 the homogomph notochaetae have a short blade and smooth edge, without spines (Figure 1D).
Two other species of Rullierinereis have been described from the Atlantic–Mediterranean region (Read et al., Reference Read, Fauchald, Bellan, Read and Fauchald2012). These are Rullierinereis anoculata Cantone, Reference Cantone1982 from the Gulf of Catania (Cantone, Reference Cantone1982) and Rullierinereis faroensis Kirkegaard, Reference Kirkegaard1998 from the Faroe Bank (Kirkegaard, Reference Kirkegaard1998). These two species are easily distinguished from R. ancornunezi. In R. anoculata all biramous parapodia have two notopodial ligules subequally well developed throughout the body and notopodial homogomph falcigers from chaetiger 40. In R. faroensis all biramous parapodia have two notopodial ligules, although the upper ligule is shorter than the lower, and the notopodial homogomph falcigers first appear in the posterior region. In addition, both R. anoculata and R. faroensis lack eyes, while R. ancornunezi has two pairs of lightly pigmented eyes.
Rullierinereis ancornunezi could also be confused with Eunereis longissima. The two genera can be differentiated by the presence of paragnaths on the eversible pharynx in the case of Eunereis, or soft papillae in the case of Rullierinereis (Fauchald, Reference Fauchald1977). This is a difficult feature to use, especially in small specimens as the pharynx has a tendency to be withdrawn during routine preservation practices. However E. longissima and Eunereis elittoralis (Eliason, 1962), the only two species of the genus in the Atlantic–Mediterranean region, both have two notopodial ligules present on all biramous parapodia. The overall similarity of R. ancornunezi to species of the genus Eunereis may be of concern to marine faunal analysts as this genus, especially E. longissima, is widely distributed and fairly common.
All the R. ancornunezi specimens referred to in this study have been deposited in the collection of the National Museum of Wales for future reference. The Isle of Wight specimens have the catalogue number 2012.057.1 and the Isles of Scilly specimens 2012.057.2.
ACKNOWLEDGEMENTS
We thank Nikki Meek of Orecon Ltd. and Miles Hoskin of Coastal and Marine Environmental Research (CMER), Cornwall, whose project yielded the first specimens from the Isles of Scilly. The Isle of Wight specimens came from a project funded by the Marine Aggregate Levy Sustainability Fund (MALSF). The first author would also like to thank Peter Garwood and Andy Mackie for their advice and encouragement and Mat Connolley for help with image formatting.
