Introduction
Terebellidae are a diverse family of tubiculous polychaete annelids commonly found in shallow and deep waters in the world's oceans (Nogueira and Hutchings, Reference Nogueira and Hutchings2007; Hutchings et al., Reference Hutchings, Nogueira, Carrerette, Purschke, Böggemann and Westheide2021). The definition and coverage of the family is still under debate (Grube, Reference Grube1851; Malmgren, Reference Malmgren1866; Hessle, Reference Hessle1917; Holthe, Reference Holthe1986; McHugh, Reference Mchugh1995; Nogueira et al., Reference Nogueira, Fitzhugh and Hutchings2013; Stiller et al., Reference Stiller, Tilic, Rousset, Pleijel and Rouse2020). The traditional subfamilies used by Day (Reference Day1967), Fauchald (Reference Fauchald1977), and Holthe (Reference Holthe1986) were later raised to the family level (Nogueira et al., Reference Nogueira, Fitzhugh and Hutchings2013) and, together with the Trichobranchidae, constituted the Terebellidae sensu lato (Hutchings et al., Reference Hutchings, Nogueira, Carrerette, Purschke, Böggemann and Westheide2021; Lavesque et al., Reference Lavesque, Hutchings, Londoño-Mesa, Nogueira, Daffe, Nygren, Blanchet, Bonifácio, Broudin, Dauvin, Droual, Gouillieux, Grall, Guyonnet, Houbin, Humbert, Janson, Jourde, Labrune, Lamarque, Latry, Le Garrec, Pelaprat, Pezy, Sauriau and De Montaudouin2021). More recently, however, they have been replaced as subfamilies or tribes within Terebellidae (Stiller et al., Reference Stiller, Tilic, Rousset, Pleijel and Rouse2020).
Within Terebellinae, the genera, Baffinia Wesenberg-Lund, 1950, Hutchingsiella Londoño-Mesa, Reference Londoño-Mesa2003, Lanassa Malmgren, Reference Malmgren1866, Laphania Malmgren, Reference Malmgren1866, Leaena Malmgren, Reference Malmgren1866, Phisidia Saint-Joseph, 1894, Proclea Saint-Joseph, 1894, Pseudoproclea Hutchings & Glasby, 1990, Spinosphaera Hessle, Reference Hessle1917, and Stschapovella Levenstein, 1957 include species lacking branchiae and having double rows of uncini on some chaetigers. Spinosphaera, first described for Spinosphaera pacifica Hessle, Reference Hessle1917, lacks branchiae as well as lateral lappets, has short-handled avicular uncini in double rows and bears the so-called Spinosphaera-chaetae (Hessle, Reference Hessle1917). The genus contains six species, none of which are known to inhabit Mediterranean and European coasts: Spinosphaera barega Nogueira & Hutchings, Reference Nogueira and Hutchings2007 (Western Australia); Spinosphaera carrerai Londoño-Mesa, Reference Londoño-Mesa2003 and Spinosphaera hutchingsae Londoño-Mesa (Caribbean Sea); Spinosphaera harrisae Londoño-Mesa, Reference Londoño-Mesa2003 and Spinosphaera oculata Hartman, Reference Hartman1944 (California); and Spinosphaera pacifica Hessle, Reference Hessle1917 (Japan).
This study formally describes the first known Mediterranean species of Spinosphaera, compares it with its closely related species, and provides a dichotomous key to all species.
Materials and methods
The specimens of the new species were collected along the Aegean Sea coast of Türkiye and in the Çanakkale Strait (Sea of Marmara) at 27–80 m depth on sandy mud bottoms from 2005 to 2023. Sites were sampled using a van Veen grab, which sampled a total area of 0.1 m2 (Figure 1, Table 1).
Figure 1. Study area showing the sampling sites.
Table 1. Sampling date, coordinates, habitat structure and depth of the stations
Samples were sieved through a 0.5 mm mesh, fixed with 5% formalin, and transferred to a laboratory, where they were washed with tap water through a 0.5 mm mesh, sorted under a stereomicroscope, and preserved in 70% ethanol. Specimens were measured with an ocular micrometer, and some were stained with Shirlastain A or methyl green to increase the contrast of the key morphological features and to highlight glandular structures. Photographs were taken with a digital camera (Olympus OM-D E-M5 Mirrorless) mounted on stereo- and binocular microscopes.
Scanning electron microscope (SEM) observations were carried out at the Central Research Test and Analysis Laboratory Application and Research Centre (EGE-MATAL, Ege University, Izmir, Turkey). Specimens were dehydrated in a graded ethanol series (70, 80, and 96%), transferred to absolute ethanol for 30 min, critical-point-dried with liquid CO2 in a Leica EM CPD300, coated with gold (80%)–palladium (20%) in a Leica EM ACE600 sputter, and observed using a Thermo Scientific Apreo SEM.
All specimens were deposited at the Museum of the Faculty of Fisheries (ESFM) of the Ege University, at Izmir, Türkiye.
Result
Taxonomic account
Family TEREBELLIDAE Grube, 1850
Genus Spinosphaera Hessle, Reference Hessle1917
Type species: Spinosphaera pacifica Hessle, Reference Hessle1917, by monotypy
Spinosphaera latachaeta sp. nov.
Zoobank: LSIDurn:lsid:zoobank.org:act:892CC552-192F-4D65-9618-90B2FB8637EC
(Figures 2–5, Table 2)
Figure 2. Spinosphaera latachaeta sp. nov. Holotype (ESFM-POL/2017-219): (A) lateral view; (B) saw-like chaeta of segment 6; (C) bilimbate chaeta of segment 6; (D) saw-like chaeta of segment 10; (E) Spinosphaera-chaeta of segment 10; (F) uncinus of segment 13; (G) Spinosphaera-like chaetae of segment 20. ap, anterior process; mf, main fang; n, notch; pp, posterior process; sa, subrostral appendix; sp, subrostral process. Scale bar: A, 850 μm; B, 57 μm; C, 22 μm; D, 57 μm; E, 57 μm; F, 20 μm; G, 67 μm.
Figure 3. Spinosphaera latachaeta sp. nov. (A) ventral view, methyl green stained (ESFM-POL/2005-3255); (B) antero-lateral view, Shirlastain A stained (ESFM-POL/2017-216), arrows point to thickening; (C) antero-dorsal view of body stained with Shirlastain A (ESFM-POL/2017-219), arrows pointing to thickening; (D) uncini of segment 6 (ESFM-POL/2023-001); (E) uncini of segment 25 (ESFM-POL/2017-216); (F) Notochaetae of segment 6 (ESFM-POL/2023-001); (G) Notochaetae of segment 12 (ESFM-POL/2017-216); (H) Spinosphaera-like chaetae of segment 20 (ESFM-POL/2017-216). Roman numbers: segment numbers. aw, asymmetrical wings; bp, basal part of prostomium; dp, distal part of prostomium; es, eye spots; ll, lower lip; up, upper lip; po, pharyngeal organ; lc, limbate chaeta; slc, saw-like chaeta; spc, Spinosphaera-chaetae before chaetiger 18; spc*, Spinosphaera-like chaetae from chaetiger 18 and after; SG: segment. Scale bar: A, 550 μm; B, 450 μm; C, 650 μm; D, 21 μm; E, 28 μm; F, 90 μm; G, 105 μm; H, 76 μm.
Figure 4. Spinosphaera latachaeta sp. nov. (ESFM-POL/2005-3255): (A) antero-ventral view; (B) antero-dorsal view; (C) segments containing last notopodia; Uncini: (D) segment 7; (E) segment 11; (F) segment 21; (G) segment 23; Uncinus: (H) segment 15; (I) segment 23. Roman numbers: segment numbers. bp, basal part of prostomium; dp, distal part of prostomium; ll, lower lip; ul, upper lip; po, pharyngeal organ; dun, double rows of uncini; oun, one row of uncini; lc, limbate chaeta; slc, saw-like chaeta; spc, Spinosphaera-chaetae before chaetiger 18; spc*, Spinosphaera-like chaetae chaetiger from 18 and after; SG: segment. Scale bar: A, 550 μm; B, 276 μm; C, 597 μm; D, 28 μm; E, 43 μm; F, 36 μm; G, 30 μm; H, 11 μm; I, 7 μm.
Figure 5. Spinosphaera latachaeta sp. nov. (ESFM-POL/2021-003). Notopodia: (A) chaetigers 1–3; (B) chaetigers 4–6; (C) chaetigers 7 and 8; (D) Notochaetae of chaetiger 10; (E) parapodium of chaetiger 12; (F) Notochaetae of chaetigers 14 and 15; (G) Spinosphaera-chaetae of chaetiger 12. Spinosphaera-like chaetae: (H) of chaetiger 15; (I) of chaetiger 16; (J) of chaetiger 17; (K) enlargement of the spiny region. Roman numbers: segment numbers. lc, limbate chaeta; slc, saw-like chaeta; spc, Spinosphaera-chaetae before chaetiger 18; spc*, Spinosphaera-like chaetae on chaetiger 18 and after; SG: segment. Scale bar: A, 128 μm; B, 157 μm; C, 117 μm; D, 68 μm; E, 108 μm; F, 34 μm; G, 93 μm; H, 40 μm; I, 69 μm; J, 30 μm; K, 10 μm.
Table 2. Diagnostic features of all species of Spinosphaera
Material examined
Holotype: ESFM-POL/2017-219, station 8, Güllük Bay, 05.05.2017, 80 m. Paratypes: ESFM-POL/2005-3255, station 7, off Kuşadası, 08.10.2005, 50 m, 2 specimens (mounted for SEM); ESFM-POL/2013-1431, station 1, Çanakkale Strait, 06.06.2013, 50 m, 1 specimen; ESFM-POL/2017-216, station 6, Ildırı Bay, 13.10.2017, 60 m, 1 specimen; ESFM-POL/2017-217, station 8, Güllük Bay, 05.05.2017, 80 m, 3 specimens; ESFM-POL/2017-218, station 2, off Gökçeada, 14.05.2017, 45 m, 2 specimens; ESFM-POL/2021-003, station 4, off Karaburun, 19.08.2021, 71 m, 3 specimens (mounted for SEM); ESFM-POL/2021-004, station 5, Gülbahçe Bay, 22.08.2021, 27 m, 1 specimen; ESFM-POL/2023-001, station 3, off Foça, 4.10.2023, 58 m, 2 specimens; ESFM-POL/2023-002, station 4, off Karaburun, 27.09.2023, 70 m, 1 specimen.
Description
All specimens incomplete anterior fragments. Holotype: 6.3 mm long (4–18 mm in paratypes), 0.4 mm wide at chaetiger 7 (excluding parapodia) (0.4–1.2 mm in paratypes), with 29 chaetigers (16–43 in paratypes). Body yellowish in alcohol, lacking markings, elongate. Anterior segments dorsally inflated, slightly expanded laterally from chaetigers 7–9, weakly tessellated dorsally and ventrally, becoming smooth posteriorly after chaetigers lacking neuropodia (Figures 2A & 3A–C). Prostomium one basal annulation at base of upper lip, with many small brownish eye spots irregularly scattered laterally, and one distal annulation, smooth, semicircular, with buccal tentacles of one type, thick, cylindrical, weakly grooved, not annulated (Figure 3B, C).
Peristomium ventrally distinct, with a short, smooth, crescent-shaped upper lip with grooves leading to mouth, a swollen, oblong, longer than wide lower lip and a semicircular pharyngeal organ (Figures 3A, B & 4A). Segment 1 visible dorsally, ventrally, and laterally, forming ventral lobe below lower lip (Figures 3A–C & 4B). Lateral lobes absent. Segments 2 and 3 slightly thickened laterally (Figure 3B, C). Ventral shields from segments 2 to 22, one on each segment, oblong, wider than long, with smooth surfaces; shields on segments 2 and 3 shorter than subsequent ones (Figures 3A & 4A). Mid-ventral groove not observed. Branchiae absent.
Notopodia from segments 4 to 21 (Figures 2A & 4B), short, more or less triangular. Notochaetae in two rows of three types: bilimbate capillaries, saw-like, and Spinosphaera-chaetae (Figure 2B–E, G). Chaetigers 1–7 with bilimbate capillaries and saw-like only; bilimbate capillaries in posterior row, with asymmetrical wings, minutely serrated alimbate tip and alimbate proximal region (Figure 2C). Eight to ten saw-like in anterior row of chaetiger 1, until last parapodia; sickle-shaped on chaetigers 1–7, with serrated cutting edge, perpendicular to bilimbate shaft (Figure 2B), from chaetiger 8 to posterior end with serrated cutting edge (distal part) abruptly widening and bending at about 90° angle to shaft (Figures 2D; 3G; & 5A–F). From chaetigers 8–14, limbate capillaries suddenly change to Spinosphaera-chaetae; limbation limited to short middle part on chaetigers 7–14, with indistinct, colourless transverse spines and distal part with serrated cutting edge, slightly curved (Figures 2E; 3G; & 5D–G); from chaetigers 15 to 18, Spinosphaera-chaetae suddenly change to Spinosphaera-like chaetae, limbate and distal part completely fused, middle part greatly expanded, covered with distinct, orange spines and distal part abruptly bent at 90° angle, with serrated cutting edge convex, more or less triangular, largely expanded and a bulbous swelling at base of serration (Figures 2G; 3H; 4C; & 5F, H–K).
Neuropodia from segment 5 (chaetiger 2), as low ridges from body surface throughout. Uncini in single row on chaetigers 2–7, double rows (arranged face to face) on chaetigers 8–18, and single from chaetiger 19 to body end (Figures 2A & 4D–G). Uncini short-handled and similar on all segments; posterior process (i.e. heel) triangular with smooth tip; a downwardly directed anterior process broad and rounded (i.e. prow); a subrostral process (i.e. dorsal button) at about proximal third, between base of main fang and tip of anterior process; subrostral appendix brush-shaped, extending beyond main fang tip; a deep notch just below subrostral process, at around midway distance between base of main fang and tip of anterior process. Main fang surmounted by about five rows of pointed teeth; first row of secondary teeth in front of others in anterior body, then in the same line in posterior body (Figure 4H, I); minute teeth on lateral side of rostrum (Figures 2F; 3D,E; & 4H, I). Nephridial papillae not observed. Pygidium unknown.
Methyl green pattern
Posterior ventral margin of segment 1 stained with rectangular to trapezoidal shape. Ventral shields of segments 1–14 stained deeply (Figure 3A). Remaining structures lightly stained.
Reproduction
A specimen from Ildırı Bay in the Aegean Sea, collected in October, had coelomic oocytes (150–260 μm in diameter) from chaetiger 20 to the posterior body end.
Etymology
The species name refers to the broad (‘lata’ in Latin) shape of the Spinosphaera-like chaeta.
Type locality
Güllük Bay, Aegean Sea, eastern Mediterranean, Türkiye.
Ecology and distribution
Found on sandy mud bottoms and maerl beds in the Aegean Sea and the Sea of Marmara between 27 and 80 m depth.
Discussion
Spinosphaera latachaeta sp. nov. is mainly characterized by having 11 pairs of broad Spinosphaera chaetae and 18 pairs of notopodia ending on the last segment with the double rows of uncini. The new species resembles Spinosphaera carrerai, a Caribbean species, in that it has double rows of uncini, and notopodia are placed on the same segments, which distinguishes them from the other species such as Spinosphaera barega, Spinosphaera harrisae, and Spinosphaera pacifica (ending before the last notopodia), and Spinosphaera hutchingsae and Spinosphaera oculata (ending after the last notopodia) (Table 2). A notch below the subrostral process is present in S. latachaeta sp. nov. and S. barega, whereas it is absent in other species. Notopodia are 18 pairs in S. latachaeta sp. nov., in contrast 23 pairs in S. barega and S. pacifica, 15 pairs in S. carrerai, 20 pairs in S. harrisae, 22 pairs in S. hutchingsae, and 41 pairs in S. oculata. The Spinosphaera-like chaeta is present on 11 chaetigers in S. latachaeta sp. nov., whereas it is present on 16 chaetigers in S. barega, on 9 chaetigers in S. carrerai, on 13 chaetigers in S. harrisae, on 15 chaetigers in S. hutchingsae, on 34 chaetigers in S. oculata, and on 16 chaetigers in S. pacifica. The ventral shields are present on 21 segments in S. latachaeta sp. nov., whereas on 13 segments in S. barega and S. oculata, and on 10–11 segments in S. carrerai, S. hutchingsae, and S. harrisae (Table 2).
Spinosphaera contains only six species worldwide (Table 2), all characterized by having the Spinosphaera-chaetae first described by Hessle (Reference Hessle1917) and later in more detail by Nogueira et al. (Reference Nogueira, Hutchings and Fukuda2010). The transition from limbate to Spinosphaera-chaetae occurs suddenly at segment 11 (chaetiger 8) (Nogueira et al., Reference Nogueira, Hutchings and Fukuda2010) in all species, including S. latachaeta sp. nov., except in S. carrerai (chaetiger 7) (Table 2). Spinosphaera latachaeta sp. nov. has the saw-like chaeta sickle-shaped in the anterior-most chaetigers, with the serrated distal part perpendicular to the shaft, and then become broad, with the serrated distal part bending at almost 90° to the shaft in most posterior chaetigers (Figures 2B, D; 3G, H; 4C & 5C, I). However, the currently available information does not allow us to assess whether this is a unique feature of the new species or has been overlooked or undescribed in other species of the genus.
The Spinosphaera-chaetae are divided into three regions: limbate, hirsute, and distal serrated blade (Nogueira et al., Reference Nogueira, Hutchings and Fukuda2010). Spinosphaera-chaetae that include all three regions are only present in S. barega, S. harrisae, and S. pacifica, while S. carrerai, S. hutchingsae, and S. oculata lack the limbate regions (Londoño-Mesa, Reference Londoño-Mesa2003). Nogueira et al. (Reference Nogueira, Hutchings and Fukuda2010) suggested that the last three species will need to be placed in another genus. However, the description of S. carrerai included an illustration of the Spinosphaera-like chaetae from segment 15, where only the hirsute and blade regions are present (see figure 2C in Londoño-Mesa, Reference Londoño-Mesa2003), as in S. latachaeta sp. nov. The Spinosphaera-like chaetae without the limbate region illustrated for S. hutchingsae was indicated as belonging to segment 11, but it might have belonged from a more posterior chaetiger, as shown in the SEM photograph (see figures 1D and 4D in Londoño-Mesa, Reference Londoño-Mesa2003). The chaetae described for S. oculata are from a posterior segment, which only have chaetae with hirsute and blade regions (see plate 22 and figures 33 and 34 in Hartman, Reference Hartman1944). However, a recent redescription of the paratype illustrates a chaeta from segment 20, which also lacks the limbate region (see figure 5D in Londoño-Mesa, Reference Londoño-Mesa2003). Therefore, the presence of Spinosphaera-chaetae with the limbate region in anterior chaetigers may have been overlooked for S. carrerai, S. hutchingsae, and S. oculata. In S. latachaeta sp. nov., the characteristic limbate region of Spinosphaera-chaetae disappears in posterior notopodia (chaetigers 15–18), where the limbation is not present as a separate region and the wings remain as thin structures at the margins within the broad spiny region (Figures 2G; 3H & 5H–K). In addition, the chaetigers have hirsute regions with orange-coloured spines that are significantly larger than those in the preceding chaetigers, while the blade tip is twice as wide as the spiny region (Figure 5J, K). The transformation of Spinosphaera-chaetae has not been described for any other species in the genus, and again further observations are required to confirm whether it is a species-specific characteristic or one that is widespread and previously overlooked character.
Key to all species of Spinosphaera
1. Double rows of uncini and notopodia ending on same segment2
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– Double rows of uncini and notopodia not ending on the same segment3
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2. 15 pairs of notopodia, Spinosphaera-chaetae on 9 segmentsS. carrerai Londoño-Mesa, Reference Londoño-Mesa2003
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– 18 pairs of notopodia, Spinosphaera-chaetae on 11 segmentsS. latachaeta sp. nov.
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3. Double rows of uncini ending before last notopodia 4
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– Double rows of uncini ending after last notopodia6
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4. 23 pairs of notopodia 5
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– 20 pairs of notopodia.S. harrisae Londoño-Mesa, Reference Londoño-Mesa2003
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5. Eyespots presentS. barega Nogueira & Hutchings, Reference Nogueira and Hutchings2007
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– Eyespots absent .S. pacifica Hessle, Reference Hessle1917
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6. 22 pairs of notopodia, Spinosphaera-chaetae on 15 segmentsS. hutchingsae Londoño-Mesa, Reference Londoño-Mesa2003
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– 41 pairs of notopodia, Spinosphaera-chaetae on 34 segmentsS. oculata Hartman, Reference Hartman1944
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Data
The data that support this study are available in the study.
Acknowledgements
The authors would like to express their gratitude to the crews of Research Vessels used during the sampling cruises, to the colleagues of the Benthology Laboratory at Ege University for their help in obtaining and sorting samples, to Dr Pınar Bahadır SÖZER (Ege University, MATAL) for her help in preparing material for SEM photography, and to the reviewers for critically reviewing and contributing to improving the original manuscript.
Author contributions
Deniz Erdoğan-Dereli: writing – original draft, investigation, data curation, and conceptualization. Melih Ertan Çinar: writing – original draft, investigation, methodology, validation, funding acquisition, and conceptualization.
Financial support
This study was partially supported by the following projects: DEN-İZ (Integrated Marine Pollution Monitoring), İZ-İZ (Oceanographic Monitoring Project in Izmir Bay, Yeni Foça and Akarcalar), and the TUBITAK Projects (codes: 104Y065 and 111Y268).
Competing interests
None.
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