Scolelepis (Scolelepis) neglecta, Surugiu, Victor, 2016

Surugiu, Victor, 2016, On the taxonomic status of the European Scolelepis (Scolelepis) squamata (Polychaeta: Spionidae), with description of a new species from southern Europe, Zootaxa 4161 (2), pp. 151-176 : 161-168

Scolelepis (Scolelepis) neglecta , new species

Figures 5–8

Scolecolepis squammata [sic].— Dörjes 1971: 213, 215, fig. 4. Partim. Not Abildgaard, in O.F. Müller, 1806. Nerinides cantabra .— Viéitez 1976: 240. Not Rioja, 1918.

Pseudomalacoceros cantabra .— Viéitez 1981: 247, 254, tab. 1. Not Rioja, 1918.

Scolelepis squamata .— Parapar 1991: 188 –189, 990. Partim. Not Abildgaard, in O.F. Müller, 1806.

Material examined. Type material. Holotype: ATLANTIC OCEAN: SPAIN: Cantábria, Asturias, sedimentary area between Cabo Vidio and Cabo de Peñas, st. 6 D 27, 25 m depth, fine sand, 1998, leg. R. Acuña Castroviejo, MNCN 16.01 /3852 (1 af).

Paratypes: same data as holotype, st. 2 D 59, 25.6 m depth, MNCN 16.01 /3851 (1 af); st. D 84, MNCN 16.01 /3854 (1 af); st. 7 D 53, 32 m depth, MNCN 16.01 /3855 partim (1 af on SEM stub); st. 4 D 72 , 8.4 m depth, MNCN 16.01/3856 (1 af); st. 9 D 16, 28 m depth, MNCN 16.01/3857 (1 af); st. 8 D 18, 32 m depth, MNCN 16.01/ 3858 (1 af, 1 mf); st. 7 D 53, 32 m depth, MNCN 16.01/3859 (2 rehydrated af); st. 8 D 19, MNCN 16.01/3860 (2 af); Galicia, Pontevedra, Ría de Vigo, beach of Meira , Oct 1975, leg. J.M. Viéitez, MNCN 16.01 /17364 (2 af) ; Galicia, Coruña, Ría de Ferrol, Laxe , intertidal, coarse sand, 22 Jan 1988, leg. J. Parapar, MNCN 16.01 /12568 partim (4 af).

Non-type material. ATLANTIC OCEAN: SPAIN: Gulf of Biscaya, Cantabrian coast, Santander , Peña Vieja , Oct 1891, coll. Estación Biológica, MNCN 16.01 /370 partim (2 af) ; Galicia, Pontevedra, Ría de Vigo, Playa de Meira , St. 13, 42°17'04"N, 8°43'08"W, Aug 1972, leg. J.M. Viéitez, MNCN 16.01 /373 (1 dehydrated af).

MEDITERRANEAN SEA: TYRRHENIAN SEA: ITALY: Campania, N. of Napoli, Gulf of Gaeta, Licola, 1966–1968, leg. J. Dörjes, SMF 12914 partim (~30 af, juveniles only).

BLACK SEA: ROMANIA: Năvodari—Digul de Sud, 44°19'25.4"N, 28°38'21.4"E, 0.5–0.8 m, fine sand with shells, 29 Jun 2014, leg. V. Surugiu, MNINGA PLY 0 0 59 (1 af, in good condition).

Diagnosis. Prostomium anteriorly with medial portion elongated into an acute point and with rounded anterolateral lobes; prostomium with transverse furrow at level of palp insertions; caruncle subtriangular, slightly inflated, attached to dorsum. Occipital antenna absent. Peristomium short, separated from prostomium by distinct groove, forming well-developed dorso-lateral wings. Palps short, with smooth basal sheaths and with two widely spaced longitudinal bands of elevated lobes bearing transverse rows of cilia. Low dorsal, segmentally arranged, transverse ciliated bands present throughout body. Chaetiger 1 with foliaceous notopodial postchaetal lamellae, with chaetae in both rami. Anterior chaetigers with obtuse, subtriangular prechaetal notopodial lamellae. Branchial tips always free from notopodial postchaetal lamellae. Bidentate neuropodial hooded hooks from chaetiger 19–49; shafts of hooks strongly curved and slightly constricted at bend.

Type locality. SPAIN, Cantabria, Asturias, sedimentary area between Cabo Vidio and Cabo de Peñas, 25 m.

Description. All specimens incomplete; longest anterior fragment 51 mm for 93 chaetigers and widest 2.75 mm. Holotype 24 mm long, 1.42 mm wide (at chaetiger 15) for 61+ chaetigers, widest anteriorly (around chaetigers 7–21), then gradually tapering to posterior end; body suboval in cross section. Colour in alcohol yellowbrown, without pigmentation.

Prostomium anteriorly trilobate, medially acuminate, antero-laterally rounded, posteriorly extended as a short, bluntly rounded, attached, slightly raised caruncle, extending to posterior margin of chaetiger 1 ( Figs. 5 A, 6A), with transverse constriction in posterior third. Occipital antenna absent. Eyes usually absent, but four faded, subcuticular eyes in a trapezoidal arrangement observed in a few specimens. Nuchal organs a J-shaped inconspicuous structure, on posterior lateral margins of caruncle, just behind bases of palps ( Fig. 5 A).

Peristomium short, distinctly separated from prostomium by a shallow groove, forming well-developed dorsolateral wings, indistinctly separated from chaetiger 1 ( Fig. 5 A–B). Eversible proboscis sac-like, inflated. Palps deciduous, present only in six examined specimens; when present, palps very short, tapering ( Figs. 5 B, 6B), reaching at most to chaetiger 5; ciliation of palps consisting of two frontal longitudinal distinctly separated bands of transverse rows of short, non-motile cilia, both on elevated 12-µm-tall lobes of approximately equal width, those on medial side approximately 14–14.3 µm wide, those on lateral side subdivided into two closely applied rows of approximately 7 µm wide each (14 µm in total with a distance less than 1 µm between them) ( Fig. 7 A–B). Ratio of long to short rows approximately 1.20–1.25 with a distance of 11–15 µm separating them. Palp sheaths rounded, short, smooth, tightly adhering to lateral and abfrontal bases of palps ( Fig. 7 C). Holotype with only left palp present (fell off during the study), reaching back chaetiger 4.

Branchiae from chaetiger 2 to end of fragments, best developed by chaetigers 5–20; ciliation along inner edge of branchiae; tips of branchiae acuminate, glandular, devoid of cilia. In anterior chaetigers, branchiae fused to notopodial postchaetal lamellae for approximately half of their length ( Figs. 5 A, B, D, E, 7E); on last chaetigers, branchiae fused only basally to postchaetal lamellae ( Figs. 5 F–H, 7F).

Chaetiger 1 well developed, capillary chaetae present in both rami, fewer than in following chaetigers; notopodial lamellae elongate, digitiform, tapered subdistally; neuropodial lamellae shorter, acute-ovate ( Fig. 5 B– C); notopodial capillaries with indistinct double rows and a dorsal superior tuft of thin and long capillaries numbering up to 10, longer than ventral ones and as long as, or slightly shorter than those of dorsal superior tuft on following chaetigers; neuropodial capillaries more numerous, arranged in two distinct rows, 7–9 per row, plus a ventral inferior tuft, all shorter than those of following chaetigers.

Dorsal transverse ciliation as primary ciliary bands on mid-part of each chaetiger (nototrochs), continuous with ciliation of branchiae; additional short row of cilia on outer edge of branchiae between tips of notopodial lamellae and subdistal portion of branchiae. In anterior chaetigers (to about chaetiger 26–30) secondary dorsal transverse rows of cilia located on anterior part of chaetigers also present ( Fig. 5 A). In middle and posterior chaetigers dorsal surface smooth with low transverse folds uniting branchiae (from about chaetiger 25). Ventral surface smooth with a shallow median groove ( Fig. 7 D).

Notopodial postchaetal lamellae well-developed from chaetiger 2 ( Fig. 5 A–B, D), on anterior chaetigers elongated, narrow, attached to branchiae, with outer margin smooth, entire, with free tips acuminate ( Fig. 5 D–E), in middle and posterior chaetigers becoming gradually shorter, wider and attached only at base of branchiae, with lower portion directed ventrally towards neuropodial postchaetal lamella ( Figs. 5 F–H, 7F). Notopodial prechaetal lamellae subtriangular, with stubby (subobtuse) tip, best developed from chaetiger 2 to around chaetiger 29 ( Fig. 5 B, 7D), then becoming lower and broader inconspicuous folds.

Neuropodial postchaetal lamellae in anteriormost 2–5 chaetigers acute, with a small median knob (mammilate), as long as wide, in following chaetigers becoming progressively more rounded, semicircular, entire, wider than long ( Fig. 5 B, D); slight notch developing in inferior 1/3 of lamella on chaetigers 14–41, in adults (usually wider than 1.5 mm) on chaetigers 35–41 ( Figs. 5 F, 8); notch becoming deeper in middle chaetigers, dividing lamella into two separate lobes, upper lobe being more than twice as large as lower subtriangular lobe, lower lobe located at level of ventral inferior bundle of capillaries ( Fig. 5 F–H). In posteriormost chaetigers gap between lobes wider, setting lobes further apart, upper lobe becoming narrow, rounded, with upper portion elongated and directed towards ventral portion of notopodial postchaetal lamella, lower part reduced to triangular cirrus ( Fig. 5 G–H). Neuropodial prechaetal lamellae absent.

Anterior chaetigers with capillaries only, arranged in three distinct groups in both noto- and neuropodia. Notopodial capillary chaetae elongate, narrow, arranged in double rows (7–11 per row) and a dorsal superior tuft of 2–10 longer (up to ~twice the branchiae length) and thinner capillaries; capillaries of anterior row unilimbate, with fibrose cores, of approximately same length and width as those of posterior row; capillaries of posterior row unilimbate, with uniformly granulated cores ( Fig. 6 C). Number and length of notopodial capillaries gradually decreasing towards posterior end.

Neuropodial capillaries similar in morphology to those of notopodia, although shorter and broader, with narrow limbation, with granulated cores (when viewed in direct light) or appearing fibrous (when viewed in reflected light), also arranged in double vertical rows (6–16 per row) plus a ventral inferior bundle of 1–4 long, unilimbate capillaries in position of sabre chaetae ( Fig. 6 E); capillaries of anterior row ( Fig. 6 D) slightly shorter and broader than those of posterior row.

Neuropodial hooded hooks first present in posterior row of chaetigers 19–49, in adults in chaetigers 40–49 ( Fig. 8 ), up to 13 per fascicle, accompanied in middle and posterior chaetigers by 0–4 alternating slender capillary chaetae and by 0–7 shorter slender limbate capillaries in ventral inferior tuft. Hooded hooks with bluntly rounded main fang surmounted by a smaller bluntly rounded apical tooth, angle between main tooth and shaft 85–95°; shaft long, with small constriction and bend just below hood insertion ( Fig. 6 F–G). Hood elongate, more than 5 times length of main fang, with apical-rostral slit-like opening. Ventral sabre setae absent.

Notopodial hooded hooks not observed.

Pygidium unknown.

Methyl green staining pattern. Most intense blue staining on peristomial wings, on margins of both notopodial and neuropodial postchaetal lamellae, on tips of notopodial prechaetal lamellae, on tips of branchiae and on superior margins of basal sheaths of palps ( Fig. 6 A–B). Prostomium and peristomium with uniformly dispersed speckles forming indistinct longitudinal stripes. Ventral side uniformly speckled on each chaetiger, with unclear transversal stripes.

Remarks. Scolelepis (S.) neglecta sp. nov. most closely resembles S. (S.) kudenovi Hartmann-Schröder, 1981 , described from Western Australia, and S. (S.) angulata Zhou, 2014 , recently described from the South China Sea and the Yellow Sea. The three species are morphologically similar in the following characteristics: the shape of the prostomium (somewhat truncate, with a conical medial tip and subdistal lateral angles anteriorly and with a transversal constriction in the posterior third), the caruncle extending to the posterior margin of chaetiger 1, short palps (never exceeding chaetiger 5), the presence of anterior prechaetal notopodial lamellae, and bidentate hooded hooks.

With regard to palp ciliation pattern, the new species is somewhat similar to S. (S.) hutchingsae Dauer, 1985 in having distinctly separated long and short rows, with the short rows on elevated lobes ( Williams 2007). However, S. (S.) neglecta sp. nov. presents a new pattern in having both rows on elevated lobes. Thus, for those eleven species of Scolelepis that have been so far examined with SEM for the palp ciliary pattern, six distinct morphological types have been recognized ( Williams 2007; Zhou 2014; present study). It is likely that further investigation of palp morphology for other species will greatly increase the number of morphological types to which they belong.

The new species is similar to the Australian specimens of S. (S.) kudenovi . However, S. (S.) neglecta sp. nov. differs from S. (S.) kudenovi by the shape of subdistal anterolateral lobes on prostomium, which are broadly rounded in the former and bluntly tapered in the latter, the presence of well-developed peristomial wings in the former, and the shape of the neuropodial hooded hooks, which have smaller, bluntly rounded teeth instead of sharp teeth with an upright apical tooth. Also, specimens of S. (S.) kudenovi appear to be much more slender than those of S. (S.) neglecta sp. nov. ( Table 1 ). Specimens of S. (S.) kudenovi reported by Imajima (1992) from Japan seem to belong to a species distinct from the Australian material (Meißner & Götting 2015).

Scolelepis (S.) neglecta sp. nov. differs from S. (S.) angulata in the shape of the prostomium, the lack of pigmentation on the posterior caruncle, the shape of the peristomium, which has a smooth contour in S. (S.) neglecta sp. nov. and a wavy contour in S. (S.) angulata , the shape of the neuropodial postchaetal lamellae of anteriormost chaetigers, which are ovate in S. (S.) neglecta sp. nov. and rectangular in S. (S.) angulata , the extension of branchiae, which are present on at least 79 chaetigers (the longest anterior fragment), while in S. (S.) angulata the branchiae are limited to first 43–51 chaetigers, and by ciliation on palps (absent in S. (S.) angulata ). There are also differences in the habitat preferences: S. (S.) angulata mainly inhabits tidal flats with saltmarsh cordgrass ( Spartina alterniflora ), whilst S. (S.) neglecta sp. nov. mainly inhabits fine sublittoral sands.

Scolelepis (S.) neglecta sp. nov. has been confused in the past with S. (S.) squamata , S. (S.) mesnili , S. (Scolelepis) cantabra , and Dispio uncinata Harman, 1951 . Thus, individuals from Cantabria were identified by G. San Martín either as Dispio uncinata and subsequently revised by O. Díaz as Scolelepis mesnili (unpublished study by Centro de Investigaciones Submarinas, 1998, Guillermo San Martín, pers. comm., Dec 2015), or as Scolelepis squamata by G. San Martín and J.M. Viéitez. The material from Galicia was identified as Scolelepis cantabra by J.M. Viéitez (1976, 1981) or as Scolelepis squamata by Parapar (1991). Also, the material from Licola, the Mediterranean Sea, was identified as Scolelepis squamata by Dörjes (1971).

The new species differs from S. (S.) squamata by the shape of the prostomium (with anterolateral lobes and with a transverse furrow in front of the caruncle in S. (S.) neglecta sp. nov. and without anterolateral lobes and without a transverse furrow in front of the caruncle in S. (S.) squamata ), by having a shorter peristomium, by having well-developed lateral peristomial wings which are separated from the prostomium by a distinct grove, by the shape of basal sheaths (smooth in S. (S.) neglecta sp. nov. and slightly rugose in S. (S.) squamata ), by the ciliation pattern of palps, by the chaetiger 1 having much longer notopodial postchaetal lamellae and capillaries, by the shape of anterior postchaetal lamellae (with entire, smooth margins in S. (S.) neglecta sp. nov. and with folded, notched margins in S. (S.) squamata ), and by the presence of a distinct prechaetal lamellae. Also, in S. (S.) neglecta sp. nov., the branchiae on anterior chaetigers are less fused to the notopodial postchaetal lamellae (about 1/2 as against to 2/ 3 in S. (S.) squamata ). Palps are usually deciduous in S. (S.) neglecta sp. nov. and non-deciduous in S. (S.) squamata . The eggs in S. (S.) squamata are characterized by 12 peripheral vesicles ( Joyner 1962), whereas in Scolelepis (S.) neglecta sp. nov. the eggs have 27–31 peripheral vesicles.

The new species can be easily distinguished from S. (S.) cantabra by the absence of occipital antenna (which is present in S. cantabra fide Maciolek (1987)) , by the presence of notochaetae in chaetiger 1, and by the presence of a notch in the neuropodial postchaetal lamellae.

Scolelepis (S.) neglecta sp. nov. has been confused also with Dispio uncinata because of the large notopodial postchaetal lamellae on chaetiger 1, which resembles a lamella joined with branchia. At first glance it was difficult to discern whether on chaetiger 1 there is a large lamella or a small branchia completely fused to the notopodial lamella. However, the vascular core of the branchia, which can be detected on chaetiger 2, was not observed on chaetiger 1. Also, anterior notochaetae are very long, resembling those of Dispio uncinata . There are, however, major differences in most other characters between these two species.

Etymology. The species name “ neglecta ” (derived from the Latin nominative singular feminine adjective neglecta meaning disregarded, neglected, or ignored) refers to the fact that the species has in the past been misidentified and overlooked, without being recognized as a distinct species.

Habitat and ecology. The species inhabits fine sublittoral sands with an admixture of shells at depths ranging from 0.5 to 32 m. Short palps could indicate that this species is dependent on habitats rich in organic matter ( Dauer 2000). It usually occurs together with Aponuphis bilineata (Baird, 1870) , Goniada maculata Örsted, 1843 , Hilbigneris gracilis (Ehlers, 1868) , Magelona papillicornis F. Müller, 1858 , Nephtys cirrosa Ehlers, 1868 , Nephtys hombergii Savigny in Lamarck, 1818 , Nothria conchylega (Sars, 1835) , Onuphis eremita Audouin & Milne Edwards, 1833 , Owenia fusiformis Delle Chiaje, 1844 , Sigalion mathildae Audouin & Milne Edwards in Cuvier, 1830 , and Sthenelais limicola (Ehlers, 1864) ( Dörjes 1971; Viéitez 1976, 1981; Centro de Investigaciones Submarinas, unpublished study).

Reproduction. Oocytes were observed in the coelomic cavity from chaetiger 40 to the end of fragments. The eggs are ellipsoid, flattened disks, 200–230 µm × 150–170 µm in diameter. They have a thick papillated vitelline membrane, 27–31 peripheral vesicles, opaque yolky cytoplasm, and a centrally positioned hyaline nucleus ( Fig. 6 H–I).

Occurrence. Scolelepis (S.) neglecta sp. nov. is known so far only from the Cantabrian and Galician coasts of Spain ( Viéitez 1976, 1981, as Scolelepis cantabra ; Parapar 1991, as Scolelepis squamata ), from the Tyrrhenian Sea ( Dörjes 1971, as Scolelepis squamata ), and the Black Sea (present study).

Figures

FIGURE 5. Scolelepis (Scolelepis) neglecta sp. nov. A, B, holotype (MNCN 3852); C – H, paratype (MNCN 12568). A, anterior end, dorsal view (palps missing, left notopodial lamella and branchia of chaetiger 5 missing); B, anterior end, lateral view (left palp present only); C, parapodium of chaetiger 1, anterior view; D, parapodium of chaetiger 2, anterior view; E, parapodium of chaetiger 15, anterior view; F, parapodium of chaetiger 42, posterior view; G, parapodium of chaetiger 50, anterior view; H, parapodium of chaetiger 56, anterior view. Scale bars: A – H = 1 mm.

FIGURE 6. Scolelepis (Scolelepis) neglecta sp. nov., A, B, LM micrographs of formaldehyde-fixed specimens stained with a solution of methyl green in alcohol, H, I, LM micrographs. A, C – G, holotype (MNCN 3852); B, paratype (MNCN 3860); H, I, paratype (MNCN 12568). A, anterior end, dorsal view; B, anterior end, lateral view; C, capillary notochaeta from posterior row of chaetiger 9; D, capillary neurochaeta from anterior row of chaetiger 13; E, ventral inferior capillary from chaetiger 33. F, neuropodial hooded hook from chaetiger 50, lateral view; G, neuropodial hooded hook from chaetiger 59, front-on view; H, egg envelope ornamentation; I, coelomic egg with thick papillate membrane and peripheral vesicles. Scale bars: A – B = 1 mm; C – I = 0.1 mm.

FIGURE 7. Scolelepis (Scolelepis) neglecta sp. nov., SEM micrographs. A – F, paratype (MNCN 3855). A, distal tip of left palp with elevated lobes, frontal-lateral view (arrowheads indicate faint splitting of lateral rows into two smaller lobes); B, distal section of right palp, frontal view, showing elevated lobes; C, basal part of right palp, lateral view (arrowhead shows smooth basal palpal sheath); D, chaetigers 13 – 25 (from top right to bottom left), ventro-lateral view (arrowheads indicate prechaetal notopodial lamellae; arrow indicates ventral median groove); E, chaetigers 16 – 21 (from top right to bottom left), dorso-lateral view (arrowheads indicate lateral ciliated organs); F, chaetigers 29 – 32 (from right to left), lateral view (note ventrally directed inferior part of notopodial postchaetal lamella and dorsally directed superior part of neuropodial postchaetal lamella). Scale bars: A, B = 50 µm; C = 100 µm; D = 1 mm; E = 0.5 mm; F = 0.2 mm.

FIGURE 8. Scolelepis (Scolelepis) neglecta sp. nov., relationship between the body-size (referring to the maximum anterior width) and the first chaetiger on which a notch is present in the neuropodial postchaetal lamellae (triangles, holotype empty symbol, y = 13.28 + 10.106 x; r s = 0.931; P <0.0001; n = 36), and between the body-size (referring to the maximum anterior width) and the first chaetiger on which neuropodial hooded hooks are present (circles, holotype empty symbol, y = 15.673 + 11.97 x; r s = 0.846; P <0.0001; n = 36).