Amphitrite figulus ( Dalyell, 1853 )

Lavesque, Nicolas, Daffe, Guillemine, Londoño-Mesa, Mario H. & Hutchings, Pat, 2021, Revision of the French Terebellidae sensu stricto (Annelida, Terebelliformia), with descriptions of nine new species, Zootaxa 5038 (1), pp. 1-63 : 13-16

Amphitrite figulus ( Dalyell, 1853)

Figure 4

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

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

Neoamphitrite figulus .— Holthe 1986: 100–101, fig. 42.

Amphitrite figulus .— Jirkov 2020: 330, fig. 1c, 14–15.

Other synonym. Amphitrite stimpsoni Meyer 1912 .

Material examined. MNHN-IA-PNT 127, posteriorly incomplete, English Channel, Dieppe, 49°55’5”N 1°04’28”E, intertidal, May 2020, posterior part used for molecular analysis. SMA-DIEP-Tere-02, posteriorly incomplete, English Channel, Dieppe, 49°55’5”N 1°04’28”E, intertidal, May 2020, posterior part used for molecular analysis. AM W.53324, complete, English Channel, Dieppe, 49°55’5”N 1°04’28”E, intertidal, May 2020, few parapodia used for SEM (plot SMA-DIEP-Tere-04) .

Description. Moderate-sized specimens, complete one being 47.9 mm long and 4.7 mm wide, for about 155 segments.

Prostomium at base of upper lip, without eyespots, distal part forming shelf-like tentacular membrane from which numerous filiform, wrinkled and deeply grooved buccal tentacles originate ( Fig. 4B, D ). Peristomium forming lips; upper lip thick, hood-like, convoluted, broader than high; lower lip swollen, broader than high ( Fig. 4D ). Segment I clearly visible, forming protruding lobe below lower lip. Segments II–III with small ventro-lateral lobes, SG IV without lateral lobes ( Fig. 4A–C ).

Three pairs of dichotomous branchiae, on SG II–IV, with wide medial gap; first pair the longest, situated slightly more dorsally; with numerous long filaments, arising from short stems ( Fig. 4A–C ). Dorsum of anterior chaetigers tessellated. Eleven ventral shields, rectangular, broader than long, present on SG III–XIII ( Fig. 4A ); absence of mid-ventral groove.

Notopodia short, rectangular, present on SG IV–XXVII (n=24). Notochaetae almost straight, medially winged with wings of same width, and distally serrated ( Fig. 4E–F ); two rows of chaetae, those of anterior row less than half as long as those of posterior row.

Neuropodia beginning from SG V, with uncini arranged in single rows on SG V–X, uncini in double rows on SG XI–XXV or XXVI, in a face-to-face arrangement, and in single rows again from SG XXVI–XXVII; thoracic neuropodia as low ridges, situated latero-ventrally ( Fig. 4B–C ); abdominal neuropodia raised from body and displaced more laterally ( Fig. 4A ). 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. 4G–H ).

Fifteen pairs of small globular nephridial and genital papillae present on SG III–XVII ( Fig. 4B–C ), first pair 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. Nephridial papillae (first three pairs) larger than genital ones (from SG VI), last pairs difficult to observe.

Pygidium rounded.

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

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

Distribution. In Europe, from Norwegian Sea to Aegan Sea ( Gil 2011) and White Sea (GenBank accession number: HM417784 ) ( Fig. 26 ). In France, from North Sea to Bay of Biscay ( Fauvel 1927; Jirkov 2020, this study, Resomar database). Also recorded from Canada, Japan, Gulf of Mexico and Sea of Okhotsk ( Gil 2011) but all these records have to be considered as doubtful. Mediterranean records could also correspond to misidentifications of Amphitrite rubra ( Risso, 1826) (see Jirkov 2020).

Habitat. In empty shells in deep water, 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 (this study), upper sublittoral to intertidal (this study, Jirkov 2020). This range of different habitats/depths suggests that these records may represent more than one species.

Remarks. The original description is not sufficiently informative according to current standards, consisting of a mixture of behavioural considerations and morphological data. Specimens examined in our study match those of the description provided by Fauvel (1927, specimens from French coasts), and the description of Amphitrite johnstoni Malmgren, 1866 , by Holthe (1986, specimens from Scandinavia) and by Jirkov (2020, specimens from White Sea and UK, and also from the Western Pacific). Obviously a detailed review of this species is required including the re-examination of material from all the above localities.

Genus Amphitritides Augener, 1922

Type-species: Terebella gracilis ( Grube, 1860) , by subsequent designation.

Diagnosis. (after Hutchings et al. 2021b). Transverse prostomium attached to dorsal surface of upper lip; basal part as a thick crest, eyespots may be present; distal part shelf-like. Buccal tentacles usually all uniformly cylindrical. Peristomium forming lips and continuing dorsally for a short extension, not forming a complete annulation; lips expanded, relatively short upper lip, hood-like, about as long as wide, distal margin rounded, slightly undulated; narrow, rectangular, mid-ventral lower lip. Segment I conspicuous all around, dorsally narrow, ventrally developed, with mid-ventral lobe marginal to mouth; additional lobes on anterior segments absent. Anterior segments highly glandular ventrally, with discrete, smooth to slightly corrugated, rectangular to trapezoidal shields. Two pairs of arborescent branchiae, on SG II–III, with short main stems. Rectangular to conical notopodia beginning on SG IV, extending for a variable number of segments; notochaetae all medially-winged and finely serrated distally, with basally bulbous wings. Neuropodia beginning on SG V, as low, sessile ridges throughout; neurochaetae as shorthandled avicular uncini, in completely separate double rows, beak to beak arrangement, from SG XI until posterior body. Nephridial papillae on SG III, genital papillae on some anterior segments, beginning from SG VI, between parapodial lobes or at anterior bases of notopodia.

Remarks. Recently, Jirkov (2020) proposed the synonymisation of Amphitritides with Amphitrite , arguing that characters such as the number of pairs of neuropodia with double rows of uncini is not unique to species of Amphitritides , but can be also present in species of Amphitrite . This is a character highly significant in terms of convergence in the family, and so it could be exhibited by some other genera besides these two. On the other hand, the structure of the lateral lobes is poorly understood in the whole family, and there is a great deal of misinterpretations regarding the shape, structure and orientation of the lateral lobes vs. the lateral ridges. Our suggestion is that Amphitritides has no lobes (except mid-ventral one on SGI, as described in the diagnosis), and which clearly differentiates it from Amphitrite , which has lobes on anterior segments, of variable length, usually on SG II–IV. It is clear, however, that the diagnosis of a genus is not based on a unique character that distinguishes it from the rest, but on a combination of characters, which defines the genus. It is also clear that a major revision of this group of genera, based on type material, if available, and fresh topotype material, is required in order to solve the relations within this group using both morphological and molecular data.

Figures

FIGURE 4. Amphitrite figulus (Dalyell, 1853) MNHN-IA-PNT 127. A. Anterior end, latero-ventral view; B. Anterior end, lateral view, MG staining; C. Anterior end, lateral view, MG staining; D. Anterior end, ventral view; E. Notochaetae, SG XVI; F. Tip of notochaetae, SG VII; G. Uncinus, SG VIII; H. Uncini, SG X. Abbreviations: GP, genital papillae; Ll, lower lip; NP, nephridial papilla; Ul, upper lip. Numbers referring to segments.

FIGURE 26. Majority-rule consensus tree from Bayesian analysis using COI. Asterisk indicates posterior probability> 80%. Text in red refers to specimens sequenced during this study.