SYSTEMATICS

DIAGNOSIS (AFTER AGUIRREZABALAGA & CEBERIO, Reference Aguirrezabalaga and Ceberio2005, AMENDED)

Prostomium anteriorly rounded or with short anterolateral projections, narrowing posteriorly, with caruncle. Nuchal organs absent. Two chevron-shaped chitinous plates or single chitinous plate surrounding anterior part of prostomium. Eyes absent. Peristomium well developed forming posteriorly open collar that surrounds prostomium. Branchiae absent. Parapodia of first chaetiger reduced, lacking notopodial postchaetal lobe and with small neuropodial postchaetal lobe. Subsequent parapodia larger, well-developed with rounded noto- and neuropodial postchaetal lobes. Posterior notopodial lobes connected by low dorsal ridge or ridges absent. Notopodial chaetae all capillary or capillaries and multidentate hooded hooks on posterior chaetigers. Posterior neuropodia with long-shafted, multidentate hooded hooks, with complete hood. Sabre chaetae present. Pygidium morphology uncertain, possibly rounded with a pair of small anal cirri.

Spiogalea capixaba sp. nov.
(Figures 2–5)

Fig. 2. Spiogalea capixaba sp. nov., holotype: anterior region, dorsal view. Scale bar: 400 µm.

Fig. 3. Spiogalea capixaba sp. nov., holotype: close-up of the prostomium, dorsal view: Scale bar: 200 µm.

Fig. 4. Spiogalea capixaba sp. nov., holotype: (A) Left notopodium of chaetiger 8, dorsal view; (B) Left neuropodium of chaetiger 9, ventral view; (C) Left neuropodium of chaetiger 16, ventral view. Scale bars: 70 µm.

Fig. 5. Spiogalea capixaba sp. nov., holotype: (A) sabre chaeta from neuropodium of chaetiger 14; (B) short limbate capillary chaetae; (C) long non-limbate capillary chaetae; (D) hooded hook. Scale bars: 20 µm.

TYPE MATERIAL

Holotype: Incomplete specimen, 0.8 mm wide, palps missing. AMBES Project, Station Amb 3 CAND6R2 (19°37′49.14″S, 39°3′59.7″W), 950 m depth (MNRJP 1220); coll. V. Veloso/PETROBRAS, 11/12/2011.

Paratypes: two incomplete specimens, 0.3 and 0.7 mm wide, palps missing (MNRJP 1221). Collection details as for holotype.

COMPARATIVE MATERIAL EXAMINED

Spiogalea vieitezi Aguirrezabalaga & Ceberio, Reference Aguirrezabalaga and Ceberio2005. Paratype: Incomplete specimen, palps missing. (Aguirrezabalaga's personal collection; not deposited in MNHN), Capbreton Canyon, Bay of Biscay, Station KF 50 (43°35′35″N 18°55′15″W); collected with Flusha Box corer, 1000 m depth, 14/09/1989.

DESCRIPTION

Three specimens examined, all incomplete. Holotype with 44 chaetigers; 4 mm long, 0.8 mm wide at chaetiger 4 (excluding parapodia).

Body elongate, dorsoventrally flattened, without regionalization. Anterior portion wide, tapering from middle body region onwards (Figure 2).

Prostomium bearing short anterolateral projections, posteriorly narrowing to an inconspicuous caruncle reaching posterior margin of first chaetiger. Nuchal organs absent. Single large chitinous plate present on the dorsal and ventral sides of anterior part of the prostomium. Eyes absent (Figure 3).

Peristomium large, well developed, separated from chaetiger 1, encircling the prostomium. Peristomium biannulated, overlapping the first chaetiger on posterior margin. Palps lost. Branchiae absent throughout the body.

First chaetiger reduced. Notopodial postchaetal lobe absent, bearing few long non-limbate capillaries. Neuropodial postchaetal lobe thick and rounded, reduced, bearing few long non-limbate capillaries.

Parapodial lamellae well developed starting on chaetiger 2. Notopodial postchaetal lamellae rounded from chaetigers 2–5, being progressively smaller between chaetiger 6–9 and reduced from chaetiger 10 onwards. Dorsal ridges absent. Neuropodial postchaetal lamellae from chaetigers 2–7 short, slender and cirriform, progressively smaller from chaetiger 4 and strongly reduced from chaetiger 8 onwards (Figure 4).

Notopodial chaetae of three types: (1) anterior row of 3–6 wide, short, limbate chaetae, densely granulated throughout length, decreasing in number after chaetiger 8, being absent after chaetiger 13; (2) posterior row of 5–10 long (up to 1.5 times longer than limbate chaetae) non-limbate chaetae and (3) from chaetiger 25–27, 2–4 long-shafted multidentate (3–4 pairs of small teeth above main tooth) hooded hooks per rami, accompanied by 1–4 long non-limbate chaetae (Figure 5).

Neuropodial chaetae of four types: (1) anterior row of 2–5 wide, short, limbate chaetae, densely granulated throughout length, decreasing in number after chaetiger 8, being absent after chaetiger 13; (2) posterior row of 4–8 long (up to 2 times longer than limbate chaetae) non-limbate chaetae; (3) from chaetiger 12–16, 2–5 long-shafted multidentate (3–4 pairs of small teeth above main tooth) hooded hooks per rami, accompanied by 1–4 long non-limbate chaetae and (4) lightly granulated sabre chaetae from chaetiger 9–10, only one per rami, almost straight at chaetigers 9–10 and more curved on following chaetigers (Figure 5).

Gametes not observed. Pygidium unknown.

Methyl green staining pattern: Margins of postchaetal notopodial lamellae of chaetigers 2–10 and whole dorsal and ventral surfaces of chaetigers 15–20 intensely stained.

Etymology

‘Capixaba’ is the common denomination given to natives of the Espírito Santo State, in south-eastern Brazil, where the specimens were collected.

Distribution

Espírito Santo Basin, Doce Canyon, on muddy bottoms (mainly silt), 950 m depth.

The present record expands the geographic range of the genus to the Western Atlantic.

REMARKS

Spiogalea capixaba sp. nov. exhibited significant morphological differences from S. vieitezi, mainly the presence of a single prostomial chitinous plate instead of two, a T-shaped rather than bluntly rounded prostomium, biannulated peristomium, absence of low dorsal ridges, presence of notopodial hooded hooks and the position of neuropodial hooded hooks.

According to Aguirrezabalaga & Ceberio (Reference Aguirrezabalaga and Ceberio2005), long non-limbate notopodial capillaries are absent, although such chaetae could be observed on the first 9 chaetigers of the paratype. The fact that notopodial hooded hooks are present in S. capixaba sp. nov. and lacking in S. vieitezi, is quite unusual, since this character is usually constant among species of the same genus. While notopodial hooded hooks are not present on all Scolelepis species (Rocha & Paiva, Reference Rocha and Paiva2012) and absent on most Laonice species (Sikorski, Reference Sikorski2003), in Aurospio, notopodial hooded hooks may start after the 30th chaetiger (Maciolek, Reference Maciolek1981; Mincks et al., Reference Mincks, Dyal, Paterson, Smith and Glover2009; Paterson et al., Reference Paterson, Neal, Altamira, Soto, Smith, Menot, Billett, Cunha, Marchais-Laguionie and Glover2016). Based on the original illustrations of S. vieitezi, it is likely that the type-specimen was regenerating the posteriormost chaetigers and the pygidium, since the authors described a pygidium of uncertain morphology that could not be seen clearly. Furthermore, the holotype had only 19 chaetigers, against 44 in S. capixaba. Thus, the absence of notopodial hooded hooks in S. vieitezi is doubtful considering that type-specimens are likely to be not complete.

According to Aguirrezabalaga & Ceberio (Reference Aguirrezabalaga and Ceberio2005), the chitinous plates surrounding the anterior part of the prostomium are a feature that distinguishes Spiogalea from the remaining genera of Spionidae. Other features include the absence of branchiae, peristomium forming a posteriorly open collar encircling the prostomium, parapodia of the first chaetiger reduced and long-shafted multidentate neuropodial hooded hooks with complete hoods.

The presence, distribution and morphology of the branchiae are features of great taxonomic importance for spionids (Foster, Reference Foster1969, Reference Foster1971; Blake & Kudenov, Reference Blake and Kudenov1978; Johnson, Reference Johnson, Uebelacker and Johnson1984; Maciolek, Reference Maciolek1985; Blake, Reference Blake, Blake, Hilbig and Scott1996; Bick, Reference Bick2005; Delgado-Blas, Reference Delgado-Blas, de León- González, Bastida-Zavala, Carrera-Parra, García- Garza, Peña-Rivera, Salazar-Vallejo and Solís-Weiss2009; Radashevsky, Reference Radashevsky2012). Branchiae are also useful to access phylogenetic relationships of the family, as seen in Sigvaldadóttir et al. (Reference Sigvaldadóttir, Mackie and Pleijel1997), Sigvaldadóttir (Reference Sigvaldadóttir1998) and Blake & Arnofsky (Reference Blake and Arnofsky1999). Absence of branchiae is an unusual character that probably evolved independently among spionid genera. It is recorded only in the genera Spiophanes, Spiophanella, Glyphochaeta, some species of Polydorella Augener, 1914 (Williams, Reference Williams2004), and a single species of Aurospio Maciolek, Reference Maciolek1981 (Neal et al. in Paterson et al., Reference Paterson, Neal, Altamira, Soto, Smith, Menot, Billett, Cunha, Marchais-Laguionie and Glover2016).

Spiogalea can be distinguished from Spiophanes based on the presence of a chitinous prostomial plate, absence of nuchal organs, absence of crook-like chaetae on chaetiger 1, and presence of multidentate long-shafted neuropodial hooks. Spiogalea can be distinguished from Spiohanella, a monotypic and doubtful genus (Sigvaldadóttir et al., Reference Sigvaldadóttir, Mackie and Pleijel1997), based on the presence of a chitinous plate and by the shape of the peristomium, which is large, well-developed, separated from chaetiger 1, encircling the prostomium, and a reduced first chaetiger lacking notopodial postchaetal lobe and reduced postchaetal lobe. Spiophanella lacks notopodial multidentate hooded hooks, which are present at least in S. capixaba sp. nov.

Glyphochaeta is a recently described genus, which comprises only Glyphochaeta laudieni Bick, Reference Bick2005, described from Kongsfjorden, Spitsbergen. Spiogalea can be separated from G. laudieni based on the morphology of the prostomial projections, and the presence, in the former, of sabre chaetae, a chitinous plate and absence of grooved spines.

The genus Polydorella belongs to a complex of related genera informally called ‘Polydora-complex’ (Sigvaldadóttir et al., Reference Sigvaldadóttir, Mackie and Pleijel1997), ‘polydorids’ (Blake, Reference Blake, Blake, Hilbig and Scott1996) or ‘polydorins’ (Radashevsky, Reference Radashevsky2012), which comprises spionids with a modified 5th chaetiger bearing spines. According to Williams (Reference Williams2004), branchiae may be absent on some species, although Spiogalea species can be easily distinguished from Polydorella by the presence, in the former, of a chitinous plate and the absence of a modified 5th chaetiger bearing spines.

As for Aurospio, one of the main diagnostic characters are branchiae starting on chaetiger 3 (Maciolek, Reference Maciolek1981; Mincks et al., Reference Mincks, Dyal, Paterson, Smith and Glover2009), although a new species without branchiae, Aurospio abranchiata Neal, Paterson & Soto in Paterson et al., Reference Paterson, Neal, Altamira, Soto, Smith, Menot, Billett, Cunha, Marchais-Laguionie and Glover2016, was recently described in the North-east Atlantic, near Portugal. Spiogalea species can be easily separated from Aurospio abranchiata based on the presence of a chitinous plate, position of notopodial hooded hooks and morphology of the postchaetal notopodial lamella of chaetiger 3, that is rounded in Spiogalea and greatly enlarged and nearly square-shaped in A. abranchiata.

In conclusion, as both the lack of branchiae and presence of a prostomial chitinous plate are unusual features for the family Spionidae, the collection of more specimens of Spiogalea, including entire material suitable for morphological as well as molecular studies, would be of great relevance. The use of molecular techniques could provide valuable information on both the position of the genus and its relationships within Spionidae.