Amphitrite figulus ( Dalyell, 1853 )

Lavesque, Nicolas, Pinsivy, Lucas, Daffe, Guillemine, Daramy, Flore, Grosse, Maël, Chauvaud, Laurent & Hutchings, Pat, 2025, A new species of the Thelepus cincinnatus complex from Saint-Pierre and Miquelon Archipelago (NW Atlantic) and genetic diversity of Amphitrite figulus (Dalyell, 1853) (Annelida, Terebelliformia), Zootaxa 5588 (2), pp. 250-268 : 256-259

Amphitrite figulus ( Dalyell, 1853)

Figures 2 and 3

Terebella figulus Dalyell, 1853: 191–197 , pl. XXVII, figs 1–2, pl. XXVIII, figs 1–2.

Amphitrite johnstoni Fauvel 1927: 248–249 , fig. 85a–e.

Neoamphitrite figulus Holthe 1986: 100–101 , fig. 42.— Hartmann-Schröder 1996: 515–516, fig. 251.

Amphitrite figulus Jirkov 2020: 330 , figs 1C, 14–15.

Amphitrite stimpsoni Meyer, 1912: 34–35 .

Material examined. MNHN-IA-2017-2211 , North Atlantic Ocean, Saint-Pierre and Miquelon Archipelago, Grande Miquelon Lake , 47.092622° N, 56.368040° W, intertidal, October 2023, one complete specimen, some parapodia used for molecular analysis. AM W.55317, North Atlantic Ocean, Saint-Pierre and Miquelon Archipelago, Saint-Pierre Harbour , 46.776196° N, 56.163452° W, intertidal, October 2023, one complete specimen, some parapodia used for molecular analysis, specimen mounted for SEM .

Description. Large-sized species with longest specimen 147.8 mm long and 11.4 mm wide, for about 112 segments.

Prostomium at base of upper lip, without eyespots, distal part forming shelf-like tentacular membrane from which filiform, wrinkled and deeply grooved buccal tentacles originate ( Figs 2A–C ; 3A ). Peristomium forming lips; upper lip thick, hood-like, convoluted, broader than high; lower lip swollen, broader than high ( Fig. 2C ). Segment I clearly visible, forming protruding lobe below lower lip ( Fig. 2C ). Segments II–III with small ventro-lateral lobes, SG IV with very small dorsal lobes, situated anteriorly and ventrally from the notopodia ( Figs 2A ; 3B ).

Three pairs of dichotomous branchiae, on SG II–IV, with wide medial gap; second pair inserted more laterally than first and third pairs; with numerous strongly annulated filaments, arising from short stems ( Figs 2A–B ; 3A ). Dorsum of anterior chaetigers tessellated ( Figs 2B ; 3A ). Thirteen-fourteen ventral shields, rectangular, broader than long, present on SG III–XV ( Fig. 2C ); absence of mid-ventral groove.

Notopodia short, rectangular, present on SG IV–XXVIII (n=25), one specimen with 24 notopodia on one side and 25 on the other one. Notochaetae almost straight, medially winged with wings of same width, and distally serrated; two rows of chaetae, those of anterior row less than half as long as those of posterior row ( Fig. 3B ).

Neuropodia beginning from SG V, with uncini arranged in single rows on SG V –X, uncini in double rows on SG XI–XXIX (second abdominal chaetiger), in a face-to-face arrangement, and in single rows again from SG XXX. One specimen with second abdominal neuropodia with uncini in double row dorsally, and in a single row ventrally. Thoracic neuropodia as low ridges, situated latero-ventrally ( Figs 2A, C , 3A–B ); abdominal neuropodia raised from body and displaced more laterally ( Figs 2D , 3E ). Uncini avicular, with short triangular heel, with distally pointed prow, large pointed to digitiform dorsal button inserted halfway between base of main fang and tip of prow, convex base; and crest with five rows of secondary teeth above main fang ( Fig. 3A–D ).

Seventeen pairs of very small nephridial and genital papillae present on SG III–V and VI–XIX respectively ( Figs 2A ; 3A–B ), first pair larger than the following ones, situated above base of second pair of branchiae, second pair below first notopodia and slightly displaced dorsally, subsequent pairs between noto- and neuropodia, slightly displaced dorsally, last pairs difficult to see.

Pygidium rounded and slightly crenulated ( Fig. 2D ).

Type locality. Probably North Sea coast of Scotland ( Gil 2011).

Type material. Could not be traced ( Holthe 1986, Jirkov 2020).

Distribution. Amphitrite figulus is present in Europe from the Norwegian Sea to the Aegean Sea ( Gil 2011, Jirkov 2020, Lavesque et al. 2021a), and in Canada ( Carr et al. 2011). This species is also reported from the North Atlantic, Arctic, North Sea, western Baltic ( Hartmann-Schröder 1996), Japan, the Gulf of Mexico and the Sea of Okhotsk ( Gil 2011) but all of these records should be regarded as doubtful, at least until molecular data are provided. Indeed, documenting species distributions using morphology alone has led to the popularization of the cosmopolitan species concept and a clear underestimation of biodiversity ( Hutchings & Kupriyanova 2018; Lavesque et al. 2019b; Hutchings & Lavesque 2020).

Habitat. This species lives in empty shells in deep water, and among rocks in shallow intertidal pools, on mud or sandy mud, among Zostera , Fucus or Laminaria , on mussel and oyster banks ( Gil 2011), in mud ( Lavesque et al. 2021a), in silted heterogeneous sediments in semi-enclosed lagoon (this study), in coarse gravels and shells ( Hardy et al. 2011) from 20 m to intertidal ( Hardy et al. 2011, Jirkov 2020, Lavesque et al. 2021a, this study).

In the original description, Dalyell (1853) considers this species to be an architect and calls it the “potter”. The worm selects mud or clay exclusively for the materials for its tube, which is thick and clumsy.

Remarks. As previously highlighted by Lavesque et al. (2021a), the species is poorly described in the original description which does not include important characters useful for the taxonomy of this genus. The specimens examined in this study match those of the French coasts ( Lavesque et al. 2021a), even if several morphological differences occur. Indeed, specimens observed from the French coasts were much smaller (48 mm) than specimens observed during this study (148 mm). Probably linked to the size of specimens, the number of genital papillae is higher in Saint-Pierre and Miquelon specimens (n=17) than in Normandy (n=15). Another difference concerns the presence of small lobes on SG 4 in some of the SPM specimens which are absent in specimens from Normandy. After re-examination of the specimen MNHN-IA-PNT 127, the right side shows a small lobe on SG4 (which is more difficult to observe on the left side, as illustrated in the Fig. 4 in Lavesque et al. 2021a). This lobe is also difficult to see on the specimen from St Pierre and Miquelon used for SEM ( Fig. 3B ). Jirkov (2020), who observed European specimens, also noted the presence of these small lobes on SG4. Morphological differences between small and large specimens of terebellid species have already been observed ( Martin et al. 2022; Hutchings et al. 2025).

The molecular analyses showed that Amphitrite figulus has a very wide distribution in the North Atlantic ( Fig. 4A ). However, genetic differences have been observed between specimens sampled in the north-east Atlantic ( France, Ireland, Russia, Norway) and those sampled in the west ( Canada) ( Fig. 4B ). More diversity is found in the Western Atlantic with four different haplotypes found whereas only one was found in the Eastern Atlantic. The genetic distances observed between the two populations (between 2.5 and 3%) could indicate that these populations belong to a single species with limited geneflow between populations. Large intraspecific distances in COI have previously been observed in polychaetes (e.g. Nygren et al. 2018) and are compatible with the large geographic distance between both populations. Alternatively, the two populations could represent different species. Recent speciation would explain the comparatively low interspecific distances. To test these hypotheses, new specimens need to be sampled in the geographical transition zones between the east and west of the Atlantic Ocean. In particular, it would be very interesting to obtain sequences of individuals from Greenland. At present, we conservatively consider both populations as belonging to a single species, but future studies will confirm or deny this hypothesis and more detailed genetic analyses must be performed.

Figures

FIGURE 2. Amphtrite figulus (Dalyell, 1853) MNHN-IA-2017-2211. A. Anterior end, lateral view; B. Anterior end, dorsal view; C. Anterior end, ventral view; D. Pygidium. Abbreviations. Numbers referring to segments. Abbreviations: Bf, branchial filaments; Bt, buccal tentacles; Gp genital papillae; Ll, lower lip; Ll4, lateral lobe SG4; Np, nephridial papillae; Py, pygidium; SG1, segment 1; Ul, upper lip.

FIGURE 3. Amphtrite figulus (Dalyell, 1853) AM W.55317, SEM. A. Anterior end, lateral view; B. Anterior end, lateral view; C. Uncini, segment 9. D. Uncini, segment 12; E.Abdominal neuropodia, segment 28; F. Uncini, segment 29. Abbreviations: Bf, branchial filaments; Bt, buccal tentacles; Ll4, lateral lobe SG4; Np, nephridial papillae; St, stem.

FIGURE 4.A. Maximum likelihood tree of Amphitrite species based on COI sequences.Asterisks indicate the bootstrap support values of the ML analysis>80%. B. Haplotype networks for COI for all specimens of A. figulus. Each haplotype is represented by a circle sized proportionally to the number of sequences. Colours indicate the geographic origin of the sequences. Hatched bars correspond to the number of mutational steps between haplotypes.