Introduction
Terebellides Sars, Reference Sars1835, is the most speciose of the three genera in the family Trichobranchidae, with 94 valid species worldwide (Read and Fauchald, 2026). For many years, the type species for the genus, Terebellides stroemii Sars, Reference Sars1835, was recorded from many different habitats across the world (Parapar and Hutchings, Reference Parapar and Hutchings2015), but the total number of species known in the genus was far lower than today. In 1984, Williams assessed the status of T. stroemii as a cosmopolitan species and published the descriptions of four new species. In the 30 years that followed, another 30 Terebellides species were described and then, in 2015, a neotype was established for T. stroemii in conjunction with a detailed redescription that included several key characters (Parapar and Hutchings, Reference Parapar and Hutchings2015). In only 10 years since that redescription, 37 new Terebellides species have been described from around the world (including Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019: Europe, 8 species; Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a: Europe, 5 species, Reference Parapar, Martin and Moreira2020b: West Africa, 7 species; Lavesque et al., Reference Lavesque, Nogueira, Daffe and Hutchings2024: Papua New Guinea, 5 species; Lavesque and Hutchings, Reference Lavesque and Hutchings2025: South Africa and Prince Edward Islands, 3 species), many with supporting molecular data, which itself has played a key role in supporting recognition of distinct species.
For the northeast Atlantic, a molecular study by Nygren et al. (Reference Nygren, Parapar, Pons, Meißner, Bakken, Kongsrud, Oug, Gaeva, Sikorski, Johansen, Hutchings, Lavesque and Capa2018) was key in highlighting the presence of numerous undescribed Terebellides species, only some of which have now had descriptions added (Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019; Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a; Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022). In this region alone, 15 new species were described in the period 2015–2022, with T. stroemii itself seemingly restricted to near the type locality in southern Norway. The majority of the new species, however, are still only known from their type localities with little information available on their wider distribution in the area. Historically around the British Isles, the only Terebellides species recorded from surveys and samples was T. stroemii, as identification guides and faunal lists that covered both the British Isles and nearby waters (Fauvel, Reference Fauvel1927; MBA, 1957; Holthe, Reference Holthe1986; Hayward and Ryland, Reference Hayward and Ryland1990, Reference Hayward and Ryland2017; Hartmann-Schröder, Reference Hartmann-Schröder1996) only indicated the presence of that species. As of 2024, with T. stroemii no longer believed to be present, the Terebellides species reported around the British Isles were Terebellides shetlandica Parapar, Moreira & O’Reilly, 2016 (east and northeast Scotland and southwest England – Parapar et al., Reference Parapar, Moreira and O’reilly2016), Terebellides europaea Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 (northeast Scotland & Irish Sea – Nygren et al., Reference Nygren, Parapar, Pons, Meißner, Bakken, Kongsrud, Oug, Gaeva, Sikorski, Johansen, Hutchings, Lavesque and Capa2018; Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a), and Terebellides scotica Parapar, Capa, Nygren & Moreira, 2020 (northeast Scotland – Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a), although each species was only recorded from a handful of sites, respectively. Of these, the latter two species are indistinguishable morphologically, requiring molecular means to identify.
In the marine invertebrate collections held by Amgueddfa Cymru – Museum Wales (AC-MW), there are over 1600 Terebellides specimens from the northeast Atlantic, mainly from around Britain, all bearing the name T. stroemii. The purpose of this project was therefore twofold. Firstly, to investigate what species were actually present in the collection under the name T. stroemii, to enable us to separate and label specimens appropriately, and secondly, to provide much-needed data on the distribution of Terebellides species around the British Isles. Whilst a combination of molecular and morphological investigations would have been preferable, this study was solely focused on one museum collection, where the majority of specimens available were collected prior to 2000, and thus were fixed in formalin. Only six specimens were therefore available for use in molecular analysis (COI and 16S), with the rest suitable for morphological analysis only (light microscopy, scanning electron microscopy (SEM), and photographic imaging). As expected, the three Terebellides species already reported for the UK were identified within the collection. In addition, Terebellides bonifi Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 was identified from several localities in the northern North Sea, and Terebellides gentili Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 was identified from a single locality on the south coast of England.
Materials and methods
All specimens from the AC-MW collections (museum accession acronym NMW.Z), identified as either T. stroemii or Terebellides sp. from the UK, Ireland, and Norway, were investigated. Specimens were collected over a period ranging from 1977 to 2018 by different environmental consultancies and marine monitoring agencies, as well as through in-house benthic sampling, and utilised a range of methods and equipment. Details of localities and collection details are provided in a spreadsheet table as supplementary material S1.
Observations of body morphology were made using a Leica MZ9.5 or Nikon SMZ-U stereo microscope. Sample uncini from both the thorax and abdomen were removed and observed using a Nikon Labophot-2 or Eclipse E400 compound microscope. More detailed observations of some characters were made with a JEOL Neoscope JCM-7000 benchtop SEM. Specimens for SEM were prepared using a Quorum K850 critical point drier or through use of HMDS (hexamethyldisilazane) (following protocols in Barré et al., Reference Barré, O’neil and Bricelj2006) and were subsequently coated with gold using an Agar sputter coater (AGB7341). SEM images were then used to compare and contrast the branchial papillae, thoracic and abdominal uncini, and geniculate chaetae.
Light microscope photographs were compiled and stacked using a Leica Wild microscope and Helicon Focus™ software and used to document methyl green staining patterns, including the glandular region on chaetiger 3, and gross morphology. Body staining patterns were classified according to Schüller and Hutchings, Reference Schüller and Hutchings2010, Reference SCHÜLLER and HUTCHINGS2013 and Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022. Other key characters examined were branchial type (sensu Parapar et al., Reference Parapar, Moreira and O’reilly2016), abdominal uncini type (sensu Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a), and thoracic uncini type (sensu Parapar et al., Reference Parapar, Martin and Moreira2020b; Lavesque et al., Reference Lavesque, Nogueira, Daffe and Hutchings2024), as well as additional characters relating to branchial papillae and filaments, notopodial and dorsal projections, and geniculate chaetae. The staining agent Shirlastain A was particularly useful in highlighting elements such as the branchial papillae.
Sequencing of six specimens was undertaken for both cytochrome c oxidase subunit I (COI) and mitochondrial 16SrRNA. Details of primers, protocols, and sequences generated, including GenBank accession numbers, are provided in supplementary materials S2 and S3.
Results
Figure 1 shows the distribution and identification of all nominal species identified within the AC-MW collection. Table 1 provides geographic, bathymetric, and biometric data for each of the species identified. A large number of the specimens (around half) could only be identified as ‘juvenile’ or ‘indeterminate’ due to essential branchial characters, such as the papillae, being undeveloped or, in many cases, branchiae being damaged or missing altogether. The majority (>90%) of the specimens collected from the Outer Bristol Channel, between Wales and England, were juveniles. Figure 2 illustrates the major characters (methyl green staining patterns of the anteroventral and glandular regions and branchial morphology) of each of the five species identified during the project. Scanning electron micrographs of the thoracic and abdominal uncini (where available – abdominal uncini not available for imaging from T. europaea) are provided in Figure 3.
Map showing the geographic distribution of specimens and their identification. Grey shading represents the UK Exclusive Economic Zone. Species identified only as ‘spp.’ are those where enough characters were present to distinguish specimens from those other nominal species identified, but no positive identification to any other currently known species could be made. For clarity, localities with specimens only identified as juvenile or indeterminate (n = 99) are not included.
Images of the diagnostic characters of methyl green staining of anterior body segments (a, d, g, j, and m), glandular region and anterior segment morphology (b, e, h, k, and n), and branchial morphology (stained with Shirlastain A; c, f, i, l, and o) for each of the nominal species identified. (a–c) Terebellides bonifi Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 (a, b NMW.Z.1987.067.1470; c NMW.Z.2011.020.109); (d–f) Terebellides europaea Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 (NMW.Z.2003.065.105); (g–i) Terebellides gentili Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 (NMW.Z.2003.013.200); (j–l) Terebellides scotica Parapar, Capa, Nygren & Moreira, 2020 (j, k NMW.Z.2008.071.69; l NMW.Z.2003.065.104); (m–o) Terebellides shetlandica. Parapar, Moreira & O’Reilly, 2016 (NMW.Z.1989.104.1685). Arrows indicate the glandular region, where present, for each species. Scale bars: (a) 2.5 mm; (b, d, e, i, and l–n) 1 mm; (c, f, and o) 0.5 mm; (g and h) 5 mm; (j and k) 10 mm.
Scanning electron microscope images of thoracic (a, c, d, f, and h) and abdominal (b, e, g, and i) –uncini for each of the nominal species identified, abdominal uncini not available for T. europaea. (a, b) Terebellides bonifi Lavesque, Hutchings, Daffe, Nygren, & Londoño-Mesa, 2019 (NMW.Z.1987.067.1470); (c) Terebellides europaea Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 (NMW.Z.2003.065.105); (d, e) Terebellides gentili Lavesque, Hutchings, Daffe, Nygren & Londoño-Mesa, 2019 (NMW.Z.2003.013.201); (f, g) Terebellides scotica Parapar, Capa, Nygren & Moreira, 2020 (NMW.Z.2008.071.69); (h, i) Terebellides shetlandica. Parapar, Moreira & O’Reilly, 2016 (NMW.Z.2008.059.64). Scale bars: (a, b, d–h) 10 µm; (c and i) 5 µm.
Distribution and biometric data for specimens examined in the study
Table 1 Long description
Columns list species or authority, number of specimens out of 1606, distribution in this study, depth range in meters, length in millimeters, and number of chaetigers. T. bonifi has 16 specimens from Scotland Shetland and southwest Norway, at 120 to 163 m depth, length 7.3 to 22.3 mm, and 39 to 50 chaetigers. T. europaea has 1 specimen from Scotland Loch Creran, at 22 m depth, length 11 mm noted as incomplete, and no chaetiger count given. T. scotica has 4 specimens from Scotland Loch Creran, Firth of Clyde, and Campbeltown Loch, at 15 to 49 m depth, length 32 to 58 mm, and 51 to 53 chaetigers. A combined row for T. europaea and T. scotica with morphological identification only has 264 specimens from Wales Bristol Channel, Celtic Sea, and Irish Sea, Scotland all round, and England Bristol Channel and Scilly Isles, at 3 to 95 m depth, length 4.0 to 59.2 mm, and 29 to 53 chaetigers. T. gentili has 3 specimens from Dart Estuary in Devon, at 6 m depth, length 37 to 52 mm, and 52 to 55 chaetigers. T. shetlandica has 419 specimens from Wales St Georges Channel and Celtic Sea, Northern Ireland outer Belfast Lough marked with an asterisk, Scotland Shetland and North Sea, and southwest Norway, at 24 to 225 m depth, length 1.6 to 25.7 mm, and 34 to 50 chaetigers, with a note that 74 percent are deeper than 90 m. Terebellides juvenile or indeterminate has 885 specimens with no distribution listed, depth 0.7 to 160 m, length 1 to 28 mm, and no chaetiger count given. Terebellides species unidentified has 14 specimens with no distribution listed, depth 5 to 143 m, length 6.3 to 13.1 mm, and no chaetiger count given.
* identification confirmed through genetic sequencing
In the northern North Sea region, T. shetlandica and T. bonifi co-occurred in deep water (120–163 m) between the Shetland Islands and Norway (Figure 1). This area and one site slightly further south were the only localities from which T. bonifi was identified and represent the first records of the species outside of the Mediterranean from where it was described. The size range for specimens examined in the original description is unknown, but the 16 specimens recorded here were smaller than reported for the holotype, although characters were well developed and clear (Figures 2a–c and 3a,b). The North Sea specimens were collected from fine sandy sediments at deeper depths than originally reported (mud, ∼90 m: Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019).
The majority of named specimens (n = 419) were T. shetlandica (Figure 2m–o, 3h–i) and were present in offshore samples from the central and northern North Sea, Shetland Islands, and the Celtic Sea; one outlying point, in the outer Belfast Lough (Figure 1), was the only one confirmed through sequencing (16S and COI). Most were recorded in depths of 90 m or greater; all specimens recorded from shallower depths, except one, were collected from the Sullom Voe area of the Shetland Islands (Figure 1). The specimen collected from Belfast Lough was recorded at a depth of only 24 m, marginally extending the previous shallowest recorded depth for the species (25 m: Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022). A greater variability in habitat was noted, with specimens recorded from sandy habitats, ranging from very fine to medium and coarse, although soft sediments were still a predominant habitat feature. The size range for the species was also significantly extended, with the largest specimen being recorded at 25.7 mm, more than 50% longer than previously reported (16 mm: Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022).
T. europaea (Figures 2d–f and 3c) and T. scotica (Figures 2j–l and 3f–g) have been reported as being only distinguishable through genetics. Five specimens sequenced in this study were attributable to one or the other of these species, four as T. scotica (COI only, no other 16S sequences available for comparison), and one as T. europaea (16S and COI) (Figure 1). All sequenced specimens were from two localities on the west coast of Scotland, with one locality (Loch Creran) having both species present, albeit from different stations in similar depths (15–22 m). The rest of the specimens used in the study could only be identified as a combined T. europaea/scotica form and formed the next largest (n = 264) named group after T. shetlandica. This group was distributed all around Scotland, the west coast of Ireland, Wales and the Bristol Channel, and the Scilly Isles off the southwest coast of the UK. All sites were inshore, mostly shallower than 50 m, except for three offshore sites in the Celtic Sea at a depth of 95 m (Figure 1). T. europaea/scotica occurred sympatrically with T. shetlandica at only two sites: Sullom Voe in the Shetland Islands and one site in the Celtic Sea, the deepest record for T. europaea/scotica. Over 90% of the records were from depths of less than 53 m. Specimens ranged in size up to a maximum of 59.2 mm, around 30% longer than previously reported for either species (Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a).
T. gentili (Figures 2g–i and 3d, e) was first described from three localities on the north coast of France, almost directly across the English Channel from Devon, on the south coast of England, from where the three specimens here were recorded. The UK specimens fit well into the general parameters known for T. gentili, being recorded from shallow waters (France: 2–17 m; UK: 6 m) and large-bodied, although the UK specimens were substantially larger than those recorded from France (France: 20–32 mm; UK: 37–52 mm).
A further 14 specimens from various localities were large enough to have developed diagnostic features, but the combination of features present could not definitely be attributed to any currently described species.
Discussion
Museum collections are important repositories for benthic specimens from monitoring programmes and can provide an invaluable source of distributional data (Bakker et al., Reference Bakker, Antonelli, Clarke, Cook, Edwards, Ericson, Faurby, Ferrand, Gelang, Gillespie, Irestedt, Lundin, Larsson, Matos-Maraví, Müller, Von Proschwitz, Roderick, Schliep, Wahlberg, Wiedenhoeft and Källersjö2020; Hutchings and Lavesque, Reference Hutchings and Lavesque2020; IUCN SSC, 2026), particularly as taxonomic knowledge advances and species descriptions are modified, or new species are described. Unfortunately, museum curators rarely have time to re-identify specimens in their collections unless specific projects or enquiries arise, and therefore, data from those collections can become misleading over time and if taxonomy of species changes. Open repository databases such as GBIF, OBIS, BOLD, and GenBank can only be as accurate as the data supplied to them. An investigation into identification errors present in BOLD and GenBank (Pentinsaari et al., Reference Pentinsaari, Ratnasingham, Miller and Hebert2020) highlighted misidentification of museum specimens as a significant issue for some groups in natural history museum collections and a source of errors in the database. An analysis of Myxicola infundibulum (Montagu, Reference Montagu1808) sequences present in GenBank compared with sequences from a newly designated neotype (Darbyshire, Reference Darbyshire2023) found several lineages that clearly represented species other than M. infundibulum. Although databases such as GBIF and OBIS update taxonomic changes when a single species is revised with respect to changes to family, genus, or specific name, they cannot account for a species being split into multiple new ones or, as in the case herein, where a species is no longer believed to occur in a particular area and specimens previously identified as such are referred to multiple others. These changes can only be managed at the source, for example, by a sequence author updating the names attached to their submitted sequences on BOLD or GenBank, or a museum curator or other researcher re-identifying the specimens in a museum collection, as was done in this project. In another example, a review of Eunicida from the Falkland Islands region (Darbyshire and Cameron, Reference Darbyshire and Cameron2024) found that the 10 species reported in that study had previously been represented by 17 other names that were either incorrect or no longer valid. Although some of those changes could have been accounted for through simple taxonomic updates such as GBIF or OBIS might perform, others were a case of misidentification or of new species being designated sometime after a species was originally identified, situations that can only be corrected through hands-on examination of the specimens and only possible for specimens that have been officially deposited in publicly accessible (generally museum) collections. Users of data repositories must therefore be vigilant to consider how old the data are that they are accessing and what taxonomic changes may have occurred since that time that could affect their analysis or planning.
For this project, over 1600 specimens of Terebellides from a single museum collection were re-examined with the aim of improving knowledge of the distribution of Terebellides species around the UK following the description of many new species over the last 10–15 years. Many of the specimens originated from oilfield reference collections, but also from AC-MW’s own benthic survey work, and were therefore particularly focussed around Wales and the southern Irish Sea, inshore coasts of Scotland and the central and northern North Sea region.
T. shetlandica was already known to be present over a wide area with localities in Norway, Sweden, and eastern Scotland (Parapar et al., Reference Parapar, Moreira and O’reilly2016; Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022), but there were few confirmed points between those regions. The records presented here fill several gaps within this coverage, confirming the species’ presence further south into the central North Sea on the east and off Northern Ireland on the west, as well as demonstrating a strong presence in the soft sediments of the St George’s Channel and Celtic Deep between Wales and Ireland.
T. europaea and T. scotica could only be definitely identified for a small number of specimens (one and four specimens, respectively) that were sequenced, but these confirmed the presence of both species, individually and sympatrically, at sites on the western coast of Scotland. Both species have been recorded from the northeastern reaches of the UK (and further for T. europaea) and south to northern France (T. scotica) or Spain (T. europaea) but with little recorded presence between those extremities (Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019; Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a; Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022) and not previously from the same locality. Their combined presence from a single location on the Scottish west coast supports the approach taken by the most recent identification key for northeast Atlantic species (Barroso et al., Reference Barroso, Moreira, Capa, Nygren and Parapar2022), whereby the two species key out together, over that taken in earlier keys where they were separated on a geographical basis (Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a). As a combined entity, T. europaea/scotica was recorded from inshore sites around Scotland and was the dominant form recorded off the Welsh coast. However, the data highlight the need for more specimens that can be both sequenced and examined morphologically to potentially highlight consistent differences between them – small variations in the morphology of the glandular region and branchiae were noted during the project, but without molecular confirmation, it was not possible to determine whether these were natural variation within a single species or consistent differences between more than one.
The presence of T. gentili on the south coast was not surprising given that the original records of the species were from the almost directly opposing coast along northern France (Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019). No other specimens were examined from the south coast of mainland England during the study, where it could be expected that more records of the species may occur. In contrast, the identification of T. bonifi from some of the most northern localities included in the study was particularly surprising, as the species was previously not known outside of its type locality in the Mediterranean (Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019). For this reason, it is essential that molecular confirmation be made in the future, although this will require new collections that retrieve and preserve specimens in a manner suitable for such analyses. Records here are confined to deeper offshore waters in the northern North Sea, which are similar to the depths and habitat originally reported for the species.
As records of the newer Terebellides species are still so few and far between, it is difficult to fully understand and analyse the distributions of each one, highlighting the need for more records and perhaps more re-examination of specimens from museum and consultancy reference collections. At the present time, it is apparent that while some Terebellides species appear to have very limited distributions, such as the type species, T. stroemii, itself (Nygren et al., Reference Nygren, Parapar, Pons, Meißner, Bakken, Kongsrud, Oug, Gaeva, Sikorski, Johansen, Hutchings, Lavesque and Capa2018; Parapar et al., Reference Parapar, Capa, Nygren and Moreira2020a), others are clearly present over wide geographic areas, such as T. europaea, shown to occur (so far) from Norway to northwest Spain (Nygren et al., Reference Nygren, Parapar, Pons, Meißner, Bakken, Kongsrud, Oug, Gaeva, Sikorski, Johansen, Hutchings, Lavesque and Capa2018; Lavesque et al., Reference Lavesque, Hutchings, Gullemine, Nygren and Londoño-Mesa2019). Equally, species can occur sympatrically, as shown in this study with T. europaea, T. scotica, and T. shetlandica and by Nygren et al. (Reference Nygren, Parapar, Pons, Meißner, Bakken, Kongsrud, Oug, Gaeva, Sikorski, Johansen, Hutchings, Lavesque and Capa2018), who found up to five species co-existing at a single site. No assumptions can therefore be made about the distribution of any Terebellides species unless wide-ranging samples are available that demonstrate geographic boundaries.
The large number of specimens examined resulted in several metrics for species being extended, particularly with regards to potential size (length) of species such as T. scotica, T. gentili, and T. europaea. As more records are published in the future, the true parameters for each species, in terms of geographic distribution and physical size, will be understood better.
In total, five named species were identified within the AC-MW collection, including two new to the UK fauna. This new data will improve awareness for consultancies and others working with benthic collections of both the confirmed and potential Terebellides species present in the region and, hopefully, stimulate the re-examination of other T. ‘stroemii’ specimens.
Supplementary material
The supplementary material for this article can be found at https://doi.org/10.1017/S0025315426101556.
Acknowledgements
This work was supported by Amgueddfa Cymru-Museum Wales through the provision of facilities and suitable time. Thanks also to Dr Nicolas Lavesque for reviewing images of Terebellides bonifi and confirming its likely identification for us. Finally, thanks to the two anonymous reviewers for giving their time to review this manuscript and provide comments to improve it.
Author contributions
T.D.: project concept and supervision, DNA sequencing and analysis, specimen identification and imaging, and manuscript preparation. M.H.: DNA sequencing, specimen identification and imaging, and manuscript preparation.
Declaration of interest
The authors declare none.
Data availability statement
The authors confirm that the data supporting the findings of this study are available within the article and/or its supplementary materials. Locality data and museum accession details are located in Supplementary Table S1. Primer and thermocycler protocols are available in Supplementary Table S2 and details of sequenced specimens, including GenBank accession numbers, can be found in Supplementary Table S3. In the case of any additional data being sought, then data are available from the corresponding author (T.D.), upon reasonable request.
Ethics and approach
No vertebrates or regulated invertebrates were involved in this study.
Funding statement
This research received no specific grant from any funding agency, commercial or not-for-profit sectors.
