Rivista Italiana di Paleontologia e Stratigrafia volume 104 numero 2 r*ole 1-2 pagrne 279-286 Agosto 1998

NOA BREVE

SPIRORBID AS BOREAL GUESTS IN THE MEDITERRANEAN PLEISTOCENE

ROSSANA SANFILIPPO

Received January 1, 1988; accEted April 17, 1998

Keytaords: Spirorbidae, Boreal Guests, Pleistocene, Mediterra- During cold phases the BGs funnelled inro the nean, North Atlantic. Mediterranean, superimposing on the Mediterranean au- Riassunto. Sono stati trovati numerosi tubi di policheti spiror- tochthonous temperate faunas. Their migration occurred bidi attribuibili alle specie spirorbis (Linnaeus, 1758) e Spí in successive, cumulative, increasingly cold floods, rorbis corallinae de Silva 6c Knight-Jones, 1962, provenienti vari depo- which correspond in part to the chronostratigraphic re- siti del Pleistocene freddo della Sicilia, nonché da sedimenti wiirmia- partition of the Early Pleistocene (Raffi, 1986). ni del Mar Tirreno. Tali spirorbidi vivono lungo le coste dell'Atlanti- BG species, used as (N4ars co settentrionale, in acque basse della piattaforma continentale, e early strarigraphic markers sono assenti nell'attuale Mediterraneo. Nei sedimenti pleistocenici 1963; Ruggieri et al. t976), were employed subsequently as questi sono invece associati a faune di media piattaforma ed epibatia- palaeoclimatic tools (Di Geronimo, 1974; Malatesta & li, probabilmente perché spiazzati da biotopi pirì superficiali. Viene Zarlenga, 1986; Raffi, 1986; Taviani et al., 1997). attribuito a S, spirorbis e S. corallinae un significato paleobiogeografi- co e paleoclimatico, in base alla loro attuale distribuzione biogeogra- Deposits rich in BGs have been studied since the fica. Tali specie, entrate in Mediterraneo durante una o più fasi fredde last century and crop out extensively in southern kaly. del Pleistocene, assumono quindi il significato di Ospiti Nordici. Spe- Records of boreal species are known from the colder pe- ciale attenzione è stata, infine, rivolta alla morfologia e struttura del riods of both the Mediterranean and tubo, le quali hanno ponato all'individuazione di caratteri diagnostici the Atlantic Ocean a livello specifico. (Taviani et al., 1991). Nevertheless, BGs are quire poor- ly documented within the East Atlantic Pleistocene se- Abstract. A first report of Spirorbis spirorbis (Linnaeus, 1758) diments (submerged thanatocoenoses) and are recorded tnd Spirorbis coralLinae (de Silva & Knight-Jones, 1962) from Early mainly from the Mediterranean and Middle Pleistocene deposits in Sicily and submerged Late Glacial Quaternary. sediments in the \Western Mediterranean is presented. Today both spe- Most BGs are molluscs, such as the bivalve Arctica cies live on shores and very shallow bottoms in the Nonh Atlantic islandica, the best known North Atlantic species in rhe and are unknown from the Recent Mediterranean, Such differences in Mediterranean, which is now regarded as a marker for the their present and past biogeographic distributions suggest that these Plio-Pleistocene species were Boreal Guests (BGs) in the Mediterranean Pleistocene. boundary @uggieri er al., 1984). Other ta- Special attention ìs paid to tube morphology and structure, which xonomic benthic groups, nohbly serpulids (Zibrowius, bear some diagnostic features for species identification. 1979; Zlbrowius & ten Hove, 1987) have been considered sporadically as palaeoclimatic-oceanographic tools. How- lntroduction. ever, these Plio-Pieistocene taxa, are more widely distribu- ted, belong to the deep-sea Mediterranean benthos and The appearance in the Mediterranean of boreal have an Atlantic or more generally oceanic affinity. shelf species, together with the progressive disappearance In the present work, the first Mediterranean fossil (since the Piacenzian) of warm-temperate taxa is a di- records of two North Atlantic spirorbid species are di- stinctive element of the cold Pleistocene phases (Raffi, scussed, together with an account of their present-day 1986; Raffi & Marasti, 1982). geographic distributions and ecology. These cold-water species are currently known as "Northern Guests" or "Boreal Guests" (BGs) as they Material and methods. spread mainly in the North Atlantic Ocean, from Arc- tic latitudes southward to the southern British Isles and The material examined (Fig. 1) originates from the Bav of Biscav. Early to Middle Pleistocene sandy deposits, cropping

Istituto Policattedra di Oceanologia e Paleoecologia, Università di Catania, Corso ltalia 55,I-95L29, Catania, Italy, e-mail: [email protected] 280 R. Sanfi.lippo

Fio I Fossil (closed symbol$ and Recent (open symbols) records of Spirorbis spirorbis (triangle$ and, Spirorbis corallinae (circle$. 1) Augu- sta; 2) Valle del Belice; 3) Salice; 4) Canyon del "Toro".

.western out in (Valle del Belice) and eastern (Augusta des noroegicus, Spirobrancbus po/ytrema, Serpula concha- and Salice) Sicily, and from submerged Late Glacial sedi- rum and Pomatoceros triqueter. Most S. corallinae tubes ments in the Tyrrhenian Sea (canyon "del Toro"). show a concave attachment surface, indicating grorÀ/th The Valle del Belice section crops out along the on articulate coralÌine stems (P1. 1, Fig. Z, 8), while right side of the Belice river, in south'western Sicily (Fig. some S. spirorbis tubes have flat attachment surfaces, 1). It consists of a biogenic sandy succession, ca.3.5 m suggesting that they may have been attached to kelp thick, within a clayey sequence of uppermost Eariy fronds. Pleistocene age. The sands are highly fossiliferous, with The Augusta outcrop is located along the left side corallinaceous algae, rhodoliths and molluscs. The spi- of the Marcellino river (SE Sicily), ca.7 km S\l of Au- rorbid tubes were found in a bed with Arctica islandica. gusta (Fig. 1). It consists of an organogenic sequence of Palaeoecologic indications inferred from the benthic ma- muddy-gravelly sands of uppermost Early Pleistocene crofaunistic assemblages, suggest an upper-circalittorai age (Di Geronimo et al., in press), over 1 m thick, con- soft bottom (ca. 35-40 m depth) (Di Geronimo et al., tained in bluish sandy muds. Palaeoecologic observa- 1994). Several species of North Atlantic origin are pre- tions from the sandy levels indicate a mid-shelf area (up- sent. S. spirorbis (10 specimens) and S. corallinae (21 spe- per Circalittoral) with palaeocommunities characterized cimens) are associated with other serpulids, i.e. Hydroi- by North Atlantic immigrant species, among which ,4.

PLATE 1

Scale bar : 400 pm

Fig. 1 - Spirorbis spirorbis (Linnaeus, 1758). Augusta, Early Pleistocene. Fig. 2 - Spirorbis spirorbis. Valle del Belice, Early Pleistocene. Fig.3 - Spirorbis coralLinae de Silva Ec Knight-Jones (1962), forming irregular ascending coils. Salice, Early Pleisrocene Fig. 4 - Spirorbis corallinae, with regularly flat coìls. Valle del Belice, Early Pleistocene. Fig. 5 Tube of Sptrorbis corallinae on a Corallina stem. Valle del Belice, Early Pleistocene. Fig. 6 - Tube of Spirorbis coraLlinae, attached on Corallina stem. Belice, Early Pleistocene. Frg.7 - Bioimmuration of Corallina stem lry Spirorbis corallinae. Augusta, Early Pleistocene. Fig. 8 - Detail of Frg. 7 showing casts of sporangiae. Pleistocene Soirorbid Pohchaetes in the Mediterranean 281 282 R. Sanfilippo

islandica is dominant (Di Geronimo et al., in press). they had been attached to comparatively thin srems of Some layers of the sequence supplied tubes of S. spiror- algae, hydroids or bryozoans. Als (6 specimens) and S. corallinae (14 specimen$. They A stock of living specimens of S. spirorbls from are mostly detached from the original substrata, proba- Iceland, collected by Drs. P. and E.\L Knight-Jones, was bly coming from neighbouring shallower biotopes. used for observations and comparison of tube structu- Among the associated serpulids, Hydroides noraegicus is res. They are densely settled on a blade of. Fwcus serratus. the more abundant species. Moreover, several tubes of For SEM observations, before coating with gold an undetermined Circeis species occur. palladium, fossil and Recent tubes were cleaned with The Salice section crops out near the town of Sali- FIzOz. Some tubes were broken to investigate the wall ce, ca. 15 km W of Messina (Fig. 1). The Middle Pleisto- slructure. cene outcrop (Di Stefano & Lentini, 1996) is an organo- genic sandy sequence, 13 m thick, overlying in uncon- Tube morphology and structure. formity limestones with bathyal corals. The sands are often cross-bedded and increase in muddy fraction Differences between the tubes of S. spirorbi.s and S. upwards. The same two spirorbid species (13 S. spirorbis corallinae are seemingly slight, both tubes being sini- and 25 S. corallinae specimens) were obtained within strally coiled, smooth and similar in shape. Neverthe- some layers of the sands, becoming more abundant in less, careful observations of tube morphology allow a their upper part. The associated benthic assemblages in- distinction at the species level to be made, even when dicate an epibathyal palaeoenvironment swept by cur- only fossil material is available. rents, with infra- and circaiittoral elements transported Size is also similar, the outer coil diameter being down from shallower biotopes located on top of the ca. 2-3 mm in S. spirorbrs and 2-2.5 mm in S. corallinae. steep sides of the palaeobasin. Faunas are characterised The opening is simple, without peristomes, in both spe- by species with a markedly Atlantic affinity (such as cies (Pl. 1, Figs. 1,,2,4). Neouermilia falcigera among serpulids). Placostegus tri- A weak sculpture occurs oniy in S. corallinae, dentatus and Serpula lobiancoi are the dominant associa- consisting of wide-spaced rounded gros/th ridges, indica- ted serpulids. Some tubes of Circeis sp. are also present. ting the previous openings (P1. 1, fig. a). S. corallinae tubes are usually detached from the substra- In S. spirorbls the outer edge of the tube spreads te, showing a concave area of attachment, suggesting an out to form a more or less evident peripheral flange (Pl. originai settlement on cylindrical substrata \ke Coralli- 1, Figs. 1,2). This feature is distinctive for S. spirorbis na. sÍems, (see Rzhavsky, 7994), but lacking in S. corallinae, the S. spirorbis and S. corallinae were found also in a cross section of which is regularly circular (Pl. 1, Figs. sample dredged from "del Toro" canyon, off southwe- 3,4,5). stern Sardinia (Stn. DG03, 38o43.28'N, 8o20.59'8, I95 When attached to the small and convex fronds of m). The sample consists of muds rich in oyster shells Corallina, a tube of S. corallinae grows often as irregular and scleractinians, indicating a Late Glacial age. S. spiror- ascending coils (P1. 1, Figs. 3, 5, 6). On fronds of larger bis and S. corallinae (both with 6 specimens) occur toget- algae it is regularly flat and planispirally coiled. The her with deep circaiittoral and bathyal serprlids (Meu- tube diameter of the external coii does not increase ro- verrnilia rnultioistau, Semioermilia agglutinaa, Hyalopo- ward the opening (Pl. 1, Fig. a). The outer coil of S. matus oariorugosus and Filogranula stellau). As in the spirorbis, however, lies partly over the inner ones and the previous sample, spirorbids seem to have been displaced tube diameter increases more rapidiy with growth (P1. 1, from the infralittoral environment, down to epibathyal Figs. 1, 2). On the attachment surface of S. corallinae, depths. Some specimens of spirorbids are free in the on casts of Corallina stems and sporangia are often visi- mud, showing limited areas of attachment, as though ble (Pl. 1, fig. 7, 8).

PLATE 2 Scale bar : 400 pm (Fig. 1),20 pm (Figs. 2-7)

Fig. 1 - Spirorbis spirorbis on . Iceland, Recent, F;- , - T."-."-..- .-^'l^'1 of tube wall of Spirorbis spirorbis sho*ing an inner chitinous layer, a mid opaque and an outer glossy calcareous layer. Iceland, Recent. Fig. 3 - Microstructure of the two calcareous layers. Opaque layer with crystals arranged in a criss-cross pattern. Outer glossy with isorienta- ted crystals. Iceland, Recent. Fig. 4 Detaii of outer glossy layer. Needle-like crystals, perpendicular to the outer surface. Fig. 5 - Detail of mid opaque layer. Crystals of prismatic shape and criss-cross arrangement. Fig. 6 - Transverse wall section of fossil Spirorbis spirorbis, with homogeneous structure without layers. Augusta, Early Pleistocene. Fig.7 - Detail of Fig. 6. Crystals have lost the original shape structure and have crowded together. Pl.2 PLeistocene Spirorbid PoLychaetes in the Mediterranean 284 R. Sanfilippo

The tube wall of living S. spirorbis specimens has to the genus Spirorbls Daudin. S. rupestris, S. inornatus a glossy surface and is composed of two calcareous and S. tridentatus are exclusively boreal (Knight-Jones et layers (P1. 2, fig. 2,3). The inner layer is opaque, ca. 50 al., 1.991; Knight-Jones Ec Knight-Jones, 1995). S. striga- pm thick, and with crystals arranged in a criss-cross pat- tus, as well as the recently described S. (Wlorbis) gesae, tern (Pl. 2, Fíg. 5); the outer iayer is porcellaneous or live in the Atlantic at midlatitudes (off west Africa). almost vitreous, ca. 20 1tm thick, with larger crystals, Only three species live in the Mediterranean: S. infundi" showing a common axis orientation. At higher magnifi- bulum, which is probably endemic, S. cuneatus which cation, crystals appear needle-like and perpendicular to lives also in NE Atlantic, and the circumtropical S. (Spi the outer tube surface (Pl. 2, fig. 4). This kind of struc- rorbella) marioni, whose recent introduction into the ture results in transparency (Zlbrowius & ten Llove, Mediterranean was by ship transporr (Zibrowius & 1,987). A third chitinous layer rarely occurs around the Bianchi, 1981). The last species, and three other easrern lumen of the tube (Pl. 2, Fig. 2). Several burrows, proba- Pacific spirorbids (5. spatulatus, S. bifurcatus, S. rothlisber- bly by boring algae, are visible near the outer surface gi) are dextraily spiraled. Oniy two other Spirorbis are (P1. 2, Fig. 2). tropicai, S. placophora and S. bidentatus, the former Fossii tubes of both species are thick and rather known only from the Galapagos and the latter having a porcelaneous, with a glossy surface. They are always re- circumtropical distribution (Knight-Jones et al., 1991). crystallized. SEM micrographs show a unique homoge- In the fossil assemblage the associatio n of S. spiror- neous layer, 70 ptm thick, in which crystals are closely bis and S. corallinae with a deep water fauna can be ex- packed without a regular orientation (P1. 2, fig. 6, 7). plained easily by post-mortem down slope displacement The original wall structure is lost. from shallower bottoms. It is very unlikely that these shallow water spirorbids were fossilized within their ori- ginal environment, exposed to dispersing.wave Biogeography and ecology. action. The present geographic distribution of the two species investigated is Atlantic, north of latitude 40oN. Discussion. S. spirorbis is a boreal-arctic species (Fig. 1), ran- The present boreal and arctic distribution of S. ging from the Arctic Sea to the northeast coast of the spirorbis and S. corallinae, here reported as Pleistocene U.S. (Knight-Jones e/ a1.,1.99t).It is frequent in the Cel- fossils, suggests significantly colder conditions than to- tic and North Seas (Knight-Jones & Knight-Jones, 1,977; day. Their immigration into the Mediterranean Pleisto- Knight-Jones, pers. comm.). It was found also in the cene probably took place by a gradual southward expan- \X/hite and Barents Seas (Rzhavsky, 1,992). sion of their biogeographic range, in step with the pro- S. corallinae is boreal-arctic too, but less vzidely di- gressive cooling. The movement of their populations stributed, ranging from the Barents Sea (Rzhavsky, L992) into the Mediterranean would have been helped by their to southern Brittany (Fig. t). It is particularly common short planktonic larval phase and gregariousness during in the Celtic Sea, from Ireland to the Scilly Isles settlement. S. spirorbis and S. corallinae probably made a (Knight-Jones & Knight-Jones, 7977). relatively "late" appearance in the Mediterranean during In the southern area of distribution of both spe- cies (English Channel) the mean bottom water tempera- the cold Pleistocene. They are recorded from sediments not ture is 6-10o C in winter and does not exceed 16" C in older than the uppermost Early Pleistocene (Sicilian summer (Holmes, 1966). age), corresponding to the third molluscan migration Both species are mesolittoral to upper infralittoral, flood (Raffi, 1986). As already srressed by Buccheri occurring from rock pools to shallow depths (Knight-Jo- (1985) this age couid be correlated to the first cold Plei- nes et al., 1975; Knight-Jones & Knight-Jones, 7977; stocene peak recognised by Shackleton & Opdyke Rzhavsky, 1992). They are mainly epiphytic on fronds (lZe) at abour 0.8 Ma. of various algae. S. spirorbis typically settles on brown A similar southward movement of Spirorbis was fucoids (especially Fucus serratus) but may occur also on invoked to explain the recent finding of a species which kelps (Larninaria, Sacchorbiza) (Knight-Jones et may be endemic to Madeira, S. (Wlorbis) gesae Kníght- ^1., I975)" S. corallinae settles almost exclusively on Coralli- Jones & Knight-Jones (1,995). This is quite like S. spiror- na officinalis, and rarely on other red algae. Exceptional- bis, and the authors suggest that a common ancestor of ly it was found on the soft red alga Chondrus, in higher both species may have reached Madeira during an ice pools (Knight-Jones Er Knight-Jones, L977). Gregariou- age, and that S, (Wlorbts) gesae may be its modified de- sness is seen in both species and the larvae swim for no scendent. more than a few hours (Knight-Jones, 1951). As mentioned above, tubes of Circeis and of the The boreal distribution of S. spirorbis and S. coral- serpuiid H. noruegicui occur together with the fossil Spl- linae ís a character common to many species belonging rorbis snder study. Circeis is a circumboreal spirorbid Pleistocene Spirorbid Polychaetes in tbe Mediterranean 285

genus, quite common in northeastern Atlantic infralitto- layer$. This suggests that at least in Recent materiai, ral waters, but not represented in the present-day Medi- not affected by diagenetic changes, tube microstructure terranean (Knight-Jones & Knight-Jones, 1977). It may can also be a diagnostic character at the species level. thus have the same palaeoclimatic significance as the two other spirorbids. H. noraegicus, still common in the Recent Mediterranean (Zibrowius, L972), appears more Achnouledgements. abundant in Pleistocene mid-shelf deposits. This could I am greatly indebted to P and E. W. Knìght-Jones also suggest lower Pleistocene temperatures. (Depanment of Zoology, Swansea) for constructive comments and The diagnostic value of shape and other morpho- loaned material. I also thank H. Zibrowius (Stat. Mar. Endoume, logic features of spirorbid tubes is demonstrated here. Marseille) for critical review of the manuscript, S. Di Geronimo Identification at the species level is possible only when (Istituto Policattedra dì Oceanologia e Paleoecologia, Catania) for useful suggestions and O" Torrisi (C.N.R., Catania) for assrstance rn or fossil tubes are available. SEM observations of empty SEM observations. the tube wail of S" spirorbis show a particular micro- This paper was supported financially by 40/o (Di Geronimo) structure, not observed in other spirorbids (two distinct M.U.R.S.T. erants.

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