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Accepted by P. Hutchings: 17 Oct. 2007; published: 30 Nov. 2007 41

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A collection of Sabellidae (Polychaeta) from Carrie Bow Cay (Belize, western Caribbean Sea) with the description of two new species

ADRIANA GIANGRANDE1,3, MARGHERITA LICCIANO1,4 & MARIA CRISTINA GAMBI2

1DiSTeBA Department of Biological and Environmental Sciences and Technologies. University of Lecce, Via Prov.le Lecce-Monteron, Complesso Ecotekne, 73100 Lecce, Italy. E-mail: [email protected], [email protected] Zoologica “Anton Dohrn”- Laboratorio di ecologia del benthos, Ischia (Naples), P.ta S. Pietro 80077 Ischia Naples, Italy. E-mail: [email protected] author

Abstract

In the framework of a research on taxonomy and ecology of selected families of polychaetes conducted at the field sta-tion of the Smithsonian Institution (Washington DC, USA) at Carrie Bow Cay (Belize, Western Caribbean Sea) onNovember 2005, several qualitative benthic samples from different habitats and substrate types (Thalassia testudinumshoots, fragments of dead hard corals, sponges) have been analyzed. In some of these samples, specimens of Sabellidaewere found, revealing, together with some taxa already known for the area, the presence of two new species, Megalommafauchaldi sp. nov., and Pseudoaugeneriella spongicola sp. nov., this latter representing a genus newly reported from theCaribbean. Sabellidae biodiversity and systematics between Caribbean and Mediterranean regions is also compared.

Key words: Caribbean Sea, polychaetes, Sabellidae, taxonomy, biogeography, Mediterranean Sea, Megalommafauchaldi, Pseudoaugeneriella spongicola

Introduction

According to Tovar-Hernández and Salazar-Vallejo (2006), Sabellidae from the Gran Caribbean region havebeen poorly studied in the past. At present, however, recent revisions of some genera have led to an increasein the number of species for the area: this is the case for Branchiomma, with the description of two new spe-cies and records of other species new for the area (Tovar-Hernández and Knight-Jones, 2006); as well as forChone with the description of five new species and record of other species new for the area (Tovar-Hernández,2005). The Caribbean region represents, therefore, an area that gives a good opportunity for sabellid systemat-ics and biodiversity studies.

In the framework of a research on taxonomic revision and ecology of selected families of polychaetesconducted at the Carrie Bow Cay field station (Western Caribbean, Belize) of the Smithsonian Institution(Washington DC, USA), several qualitative benthic samples from different habitats and substrate types havebeen analysed. In some of these samples, specimens of Sabellidae were found, two of which belong to newspecies here described. Due to the high importance of the Carrie Bow Cay field station to maintain inventoriesfor scientific marine studies in the Caribbean Sea (Ruetzler and Macintyre, 1982), we consider important toinclude in this report, together with the description of these new taxa, also the species already known for thegeographic area. In fact, up to now, only six species of sabellids have been reported for Carrie Bow Cay, allbeing descriptions of new species (Fitzhugh 1983; Rouse 1993, 1994; Rouse and Gambi, 1997). Four fabriciinworms: Fabriciola flammula Rouse, 1993, F. parvus Rouse, 1993, Novafabricia infratorquata (Fitzhugh,

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GIANGRANDE ET AL.42 · Zootaxa 1650 © 2007 Magnolia Press

1983), and Fabricinuda trilobata (Fitzhugh, 1983) and two small sabellins Amphicorina androgynae Rouse,1994 and Amphiglena lindae Rouse and Gambi, 1997.

Material and methods

The study was carried out in the framework of the Caribbean Coral Reef Ecosystem (CCRE) programme,funded by the Smithsonian Museum of Natural History (Washington D.C., USA) and conducted at the Smith-sonian field station located at Carrie Bow Cay (16° 48'N and 88° 05'W) (Belize, Western Caribbean) (CCREReport, 2005).

Samples were collected by two of the authors (MCG and AG) in November 2005 by SCUBA diving atvarious sites around the Carrie Bow Cay area (see Table 1) (Macintyre and Aronson, 1997). Various habitatsand substrate types were considered, such as shoots of the seagrass Thalassia testudinum, fragments of deadhard corals (coral rubble) and living sponges (Ircinia spp., Tedania insignis), and sampled from 0.5 m to 21 mdepth (Table 1). After collection the material was stored for a few hours in the running seawater aquaria of theCBC field station. Sponges were cut in small pieces and placed in a solution of seawater and formalin(approx. 1%) for 30 min to force the fauna living inside the tissue to crawl outside. Fragments of dead hardcorals were left overnight inside buckets in still seawater to produce anoxic conditions and force the animalsout of their habitats. Finally, Thalassia shoots were checked for both leaf and sheath-rhizome epibionts thatwere gently removed. Polychaetes sorted from the sampled materials were fixed in 4% formalin in seawater.Sabellidae were separated, identified and drawn directly at the CBC station. Identifications were confirmed atthe Lecce University, after comparison with the literature.

For the newly described species holotypes are deposited at the Museum Nacional de Ciencias Naturalesde Madrid, Spain (MNCN). Paratypes are deposited at the Smithsonian Institution National Museum of Natu-ral History, Washington D.C., USA (USMN), and at the Author’s personal collection of the Laboratory ofZoology of Lecce, Italy (PCZL). All the other species of sabellid collected are deposited at the PCZL.

For the comparative analysis between Caribbean and Mediterranean areas, the paper from Tovar-Hernán-dez and Salazar-Vallejo (2006) has been utilized as a base for Caribbean list complemented with some otherpapers dealing with single families (Tovar-Hernández, 2005; Tovar-Hernández and Knight-Jones, 2006), ordescription of species (Fitzhugh 1983; Rouse 1993, 1994; Rouse and Gambi, 1997). The check-list of the ital-ian fauna (Castelli et al., 1995) was instead utilized for Mediterranean area complemented with some otherpapers (Giangrande et al., 1999; Knight-Jones and Giangrande, 2003; López and Tena, 1999; Giangrande, etal., 2006; Licciano and Giangrande, 2006; Giangrande and Licciano, 2006; Tovar-Hernández et al., 2007;Giangrande and Licciano, in press).

Results

Subfamily Sabellinae

Anamobaea Krøyer, 1856

Anamobaea oerstedii Krøyer, 1856Figure 1A

Anamobaea oerstedii Krøyer, 1856; San Martin et al., 1994; Humann, 1992; Tovar-Hernández and Salazar-Vallejo, 2006.

Material examined. Two specimens inside dead stony corals at 3 m N-W Wee Wee Cay (sample CBC-KF1015).


Zootaxa 1650 © 2007 Magnolia Press · 43A COLLECTION OF SABELLIDAE

Remarks. This genus, characterized by unusual abdominal chaetae (Fig. 1A), also present in the closelyrelated genera Notaulax and Hypsicomus, is represented in the area by two species. The more common is A.oerstedii reported for Mexican Caribbean, British Virgin Islands, Jamaica, Antilles, and Puerto Rico, typicallyinhabiting rocky bottom. This species reaches a large size (13 cm length). A good description of A. oerstedii isavailable in Tovar-Hernández and Salazar-Vallejo (2006), who also described A. phyllisae from British VirginIslands, found on sandy substrates.

FIGURE 1. A) Anamoboea oerstedii. abdominal chaetae, B) Bispira melanostigma. thoracic uncinus with companion

chaeta, C) Demonax jamaicensis. thoracic uncinus with companion chaeta.

Bispira Krøyer, 1856

Bispira brunnea (Treadwell, 1917)

Metalaonome brunnea Treadwell, 1917; Sabella bahamensis Augener, 1922; Bispira brunnea Knight-Jones and Perkins,1998; Tovar-Hernández and Salazar-Vallejo, 2006.





Material examined. Several specimens on dead coral rubble at 7 m (sample CBC-KF 1011) (PCZL). Remarks. This is a gregarious species very common in the Caribbean, reaching about 30 mm in length, of

which more than half is represented by the crown. The species seems to be confined to the West Indies andCaribbean. Good descriptions and figures are available in Knight-Jones and Perkins (1998) and Tovar-Hernández and Salazar-Vallejo (2006).

Bispira melanostigma (Schmarda, 1861)Figure 1B

Sabella melanostigma Schmarda, 1861 (36, pl. 22, Fig. 190); Uebelacker, 1984 (54-42, 54-43, Gulf of Mexico, part);Sabella variegata Kroyer, 1856; Sabella thoracica Kroyer, 1856; Sabella bipunctata Baird, 1865; Bispira mel-anostigma Knight-Jones and Perkins, 1998 (415–419, Figs 11, 12).

Material examined. Several specimens occurring as epiphytes on Thalassia leaves collected at 0.5 m in themain channel of the Twin Cays (sample CBC-TC Chan, others from a meadow off the N-E external side ofTwin Cays entrance (sample CBC-KF 1019).

Remarks. This species, commonly reported in the Caribbean area (Tovar-Hernández and Salazar-Vallejo,2006) is similar in size to B. brunnea, apart from the smaller length of its crown. This species is characterizedby asexual reproduction as seen in B. brunnea (Knight-Jones and Perkins, 1998) and can be found in aggrega-tions of individuals. The shape of the companion chaetae of the thorax is unusual for the genus in that they arenot geniculate (Fig. 1B). The distribution seems to be centered in the Caribbean and in the Gulf of Mexico,extending northward as far as North Carolina and Bermuda. Good descriptions and figures are available inKnight-Jones and Perkins (1998) and Tovar-Hernández and Salazar-Vallejo (2006).

Demonax Kinberg, 1867

Demonax jamaicensis (Augener, 1922)Figure 1C

Parasabella jamaicensis Augener, 1922Demonax jamaicensis Johansson, 1927; Perkins, 1984; Tovar-Hernández, 2005.

Material examined. Three specimens on dead coral rubble at 18 m from the outer coral reef in front of CarrieBow Cay (sample CBC-KF 1018), 1 specimen on dead corals rubble at 7–10 m from the outer reef in front ofCarrie Bow Cay (sample CBC-KF 1011).

Remarks. This species, endemic to the Caribbean, is about 13 mm long, with 10 pairs of radioles showingfive yellow-red cross-bands on pinnules. The companion chaetae are characterized by their stout handles (Fig.1C). Good descriptions and figures of this species are available in Perkins (1984) and Tovar-Hernández andSalazar-Vallejo (2006).

Branchiomma Kolliker, 1858

Branchiomma nigromaculatum (Baird, 1865)

Sabella crispa Kroyer, 1856; Sabella nigromaculata Baird, 1865; Dasychone nigromaculatum McIntosh, 1885 (PlateXXXI, Figs 4, 6), Branchiomma nigromaculata Johansson, 1927; San Martin et al., 1994; Knight-Jones, 1994;Tovar-Hernández and Salazar-Vallejo, 2006.



Material examined. One specimen collected at 0.5 m as an epibiont on dead shell of Strombus (Tricornis)gigas collected within Thalassia in the Carrie Bow Cay shallow lagoon between the island and the outer reef(not listed in Table 1); 1 specimen on dead coral rubble at 7 m off the W entrance of Twin Cays (sample CBC-KF 1007); 2 specimens on dead coral rubble at 18 m (CBC-KF 1018); 1 specimen in Thalassia at 4 m on theN-E external side of Twin Cays (sample CBC-KF 1019).

Remarks. Collected specimens are small, about 15 mm in length, compared to sizes reported in the liter-ature of up to 60 mm reported for this species. Radioles with dark brown bands alternating with white andorange bands, two pairs of macrostylods twice as long as their neighboring pairs, alternate along the radioleswith small sub-digitiform stylodes.

The species is endemic of the Caribbean Sea region. A recent redescription is available in Tovar-Hernán-dez and Salazar-Vallejo (2006) who clarified the complex synonymies and geographical distribution of thisspecies.

Megalomma Johansson, 1927

Megalomma fauchaldi sp. nov. Figure 2

Material examined. Type material: Holotype, on Thalassia at 3 m, on lagoon side of CBC, collected inNovember 2005, MNCN 16.01/11018 (sample CBC-KF 1012). Paratypes, one specimen from the same local-ity USNM 1102753; two specimens from the same locality PCZL. Description. Holotype specimen complete with 8 thoracic and 58 abdominal chaetigers. Body length 20mm, width 3 mm. Crown length 7 mm; 14–15 pairs of radioles in each lobe with three brown bands. Subter-minal compound eyes on seven pairs of radioles. Dorsalmost radioles bearing larger eyes and small tip beyondthe eye spot (Fig. 2D). The others with smaller eyes and longer tips (Fig. 2E). Dorsal lips long with broadbase, with brown pigment (Fig. 2A), radiolar appendage present, long, 1/4 of length of radioles. Ventral lipswith parallel lamellae. Dorsal margin of collar fused to faecal groove and forming two very deep pockets,clearly visible. Base of collar dorsally completely enveloping first chaetiger and extending to second chaetiger(Fig. 2A, B). Collar slightly higher ventrally with poorly developed lappets (Fig. 2C). Ventral shield of firstchaetiger quadrangular, following shields rectangular (Fig. 2C). Chaetiger 3 with four superior thoracicnotochaetae elongate narrowly hooded. Inferior thoracic notochaetae broadly-hooded, resembling paleate cha-etae and arranged in two rows, 10 present in chaetiger 3 (Fig. 2F). Thoracic neuropodia widely separated fromventral shield (Fig. 2C), neurochaetae avicular with well developed breast (Fig. 2G), up to 20 uncini on chae-tiger 1, and 14 on last thoracic neuropodia. Companion chaetae with roughly symmetrical tips, with teardrop-shaped membrane (Fig. 2H). Abdominal neurochaetae arranged in two rows, anterior row with elongate, nar-rowly hooded chaetae and modified, elongate, narrowly-hooded chaetae in posterior row, about 7 per row.Abdominal uncini avicular with manubrium shorter than present on thoracic uncini, about 14 present per toruson mid abdominal segments. Tube encrusted with shell and sand. Remarks. The number of chaetae and neurochaetal uncini is variable along the body of all material exam-ined. The number of superior thoracic chaetae ranges from 4 to 7, the number of inferior thoracic chaetae from3 to 10, the number of thoracic uncini from 14 to 20, and the number of abdominal chaetae from 5 to 7, in eachrow.

Megalomma species are usually placed into 5 artificial groups on the basis of whether the mid-dorsal col-lar margins are fused to the faecal groove or are unattached, whether the dorso-lateral collar margin formspockets or not, and the distribution and abundance of eyes on the radioles (Knight-Jones, 1997). Althoughartificial, these groups have been useful for species comparison (Nishi, 1998; Fitzhugh, 2002, 2003). Thenewly described species belongs to the group “1A”, which is defined by the dorsal margin of the collar being



fused to the faecal grove, the presence of dorso-lateral pockets, and the occurrence of eyes on most radioles.Among the sabellid species previously listed from the Carribean (Tovar-Hernández and Salazar-Vallejo, 2006)including M. vesiculosum (Montagu, 1815), M. lobiferum (Ehlers, 1887), M. pacificum Johansson, 1927, M.heterops Perkins, 1984, M. bioculatum (Ehlers, 1887), M. pigmentum (Reish, 1963), and M. perkinsi Tovar-Hernández and Salazar-Vallejo, 2006, only M. vesiculosum, M. lobiferum and M. pacificum belong to thisgroup. Megalomma fauchaldi n. sp., can be distinguished from M. lobiferum by lacking the “caruncle”, a dis-tinctive feature which is present also in M. pigmentum, and in other two species from the Caribbean area, pre-viously described as M. pigmentum by Perkins (1984), and Megalomma sp. 2 (Tovar-Hernández and Salazar-Vallejo, 2006), but probably belonging to different species for the moment indicated as Megalomma sp. 1 andMegalomma sp 2. Megalomma fauchaldi n. sp., differs from M. pacificum, and M. vesiculosum, whose pres-ence within the Caribbean region needs confirmation, especially with regards to the presence of the broadly-hooded inferior thoracic chaetae. This is particularly relevant for records of M. vesiculosum from the Carib-bean, following the recent revision of Mediterranean species which limits the distribution of this taxon to highlatitudes (Giangrande and Licciano, in press). Finally, the collar features of M. fauchaldi n. sp. clearly distin-guish this taxon from all the other worldwide distributed species belonging to group “1A”, as it has chaetae ofsimilar shape to those present in M. fauchaldi n. sp., M. claparedei (Gravier, 1908) from the Red Sea, M. cir-cumspectum (Moore, 1923) from California, M. multioculatum Fitzhugh, 2002 from Thailand and M. sus-piciens (Ehlers, 1904) from New Zealand. The shape of the collar of M. fauchaldi, with the ventral pocketsextending to the second chaetiger, appears unique within Megalomma. Among the species of the group “1A”,a similar feature is also present in M circumspectum (Moore, 1923) and M. lanigera (Grube, 1846) in which,however, the pocket base does not reach the second chaetiger.

Type locality: Carrie Bow, Belize.Etymology: This species is named in honour of Kristian Fauchald as a tribute of his major contribution to

polychaete systematics, his kindness and long friendship with us, and facilitating our visit the CBC.

Subfamily Fabriciinae

Pseudoaugeneriella Fitzhugh 2003

Pseudoaugeneriella spongicola sp. nov. Figure 3

Material examined. Type material: Holotype, found inside the sponge Ircinia cf strobilina from 1 m, WestBay of Twin Cays (sample CBC-KF 1008) collected November, 2005. MNCN catalog number 16.01/11019.Paratypes: 2 specimens from the same site USNM catalog number 1102754. 8 specimens from the same site atPCZL.

Description. Holotype complete with 8 thoracic and 3 abdominal chaetigers. Branchial crown length0.80 mm, body length 2 mm, maximum width 0.35 mm at chaetiger 4. Body slightly inflated in the mid part(Fig. 3A). Branchial crown with 3 pairs of radioles, distal ends filamentous, same length as pinnules, all termi-nating slightly below level of radioles. Dorsal lip erect, broadly rounded, distinct from radioles (Fig. 3C); ven-tral lip-like process present at base of proximalmost pinnules of ventral radioles (Fig. 3C). Vascularizedventral filamentous appendages unbranched, shorter than radioles (about 0.20 mm), and wider than pinnules,surface slightly wrinkled and with large blood vessel inside (Fig. 3A, B ,C). Branchial hearts present. Anteriormargin of anterior peristomial ring, low ridge dorsally and laterally. Collar developed as ventral quadrangularlobe, about twice as long as remainder of anterior ring (Fig. 3A). Annulation visible only dorso-laterally. Mid-dorsal medial lobe dorsal to mouth, high, triangular (Fig. 3B).



One pair of small reniform eyes in anterior half of posterior peristomial ring. Pygidium with one pair oflarge reniform eyes.

FIGURE 2. Megalomma fauchaldi sp. nov. A) anterior end dorsal view from the holotype, with branchial crown open toshow the dorsal lips, B) anterior end dorsal view from paratype, C) anterior end ventral view from the holotype, D) tip ofthe dorsalmost radiole encircled by the eye, E) tip of one of the following radioles, F) inferior thoracic notochaetae fromthe third chaetigers, G) thoracic uncinus, H) companion chaeta. dl = dorsal lip

Superior thoracic notochaetae elongate, narrowly hooded, 2 per fascicle; inferior thoracic notochaetae inchaetiger 2 and 7–8 also narrowly-hooded, but shorter, 2 present (Fig. 3D). Chaetigers 3–6 with 2 pseu-dospathulate chaetae (Fig. 3E). Abdominal neuropodia of chaetiger 9–11 with elongate, narrowly-hooded cha-etae, 1–2 per fascicle (Fig. 3H). Thoracic acicular uncini with single large tooth over main fang, followed byseries of smaller teeth (Fig. 3F); hood present, 6 per fascicle in irregular single row. Abdominal uncini with 6rows of teeth in profile, 3–4 teeth per row, manubrium twice as long as dentate region (Fig, 3G). Uncini in



chaetiger 9 to 11 number 21, 18, 15 respectively. Branchial crown unpigmented in all specimens.

FIGURE 3. Pseudoaugeneriella spongicola sp. nov. A) entire worm ventral view, B) anterior end dorsal view, C) crownsection showing the dorsal and ventral lips, D) thoracic elongate narrowly hooded chaeta, E) pseudospatulate chaeta, F)thoracic uncinus, G) abdominal uncinus, profile and frontal view, H) abdominal chaeta. dl = dorsal lip; vl = ventral lip.



Remarks. The genus Pseudoaugeneriella was erected by Fitzhugh (1998), with the species P. uniramafrom Japan. The author pointed out that the genus is similar to Augeneriella Banse, 1957, and differs only inthe unbranched nature of the ventral appendages. These filaments, however, in Augeneriella are initiallyunbranched in the ontogeny (see for example A. hummelincki Banse, 1957). Therefore P. unirama could beconsidered as the most plesiomorphic taxon within the genus Augeneriella, but in order to maintain its mono-phyly, Fitzhugh preferred to erect a new genus.

Subsequently, another two species were described as belonging to this genus, P. brevirama Fitzhugh, 1999and P. nigra (= Fabricia nigra) (Langerhans, 1880) from the Canary Islands. The difference among these spe-cies is mainly in the length of vascularized appendages, which are of the same length of radioles in P.unirama, about 50% of the length of radioles in P. brevirama, and about 25% in P. nigra (Bick, 2004). Thislatter author discussed the variability of the feature within P. nigra specimens, where the length ranges fromthe 18% to 38% of the length of radioles. This variability was also observed within the species here described,with the ventral filamentous appendage varying from 16% to 25% of the length of radioles, with a mediumlength of about of 20%. This means that ventral filamentous appendages are relatively shorter in P. spongicolathan in the other described species, including P. nigra. The new species can be distinguished from P. nigraalso by the absence of pigmentation, and in the number of thoracic and abdominal uncini, which, however,Bick (2004) found to be size dependent within the same species. Pseudoaugeneriella spongicola differs fromP. unirama and P. brevirama also in the shape of the ventral collar lobe and in the length of the manubrium ofthe abdominal uncini, which in this species is 1.5 times longer than the dentate region. Bick (2004) in his rede-scription of P. nigra, reports that the manubrium is twice as long as the dentate region, however he does notillustrate this. In contrast, Fitzhugh (1990), who examined Langerhans’ material of Fabricia nigra fromMadeira, records the manubrium of abdominal uncini being as long as the dentate region.

Lastly, it must be stressed that P. spongicola shows some similarities to Augeneriella hummelinki, espe-cially in the shape of ventral collar lobe, but differing in the number of teeth of abdominal uncini, which arelarger in A. hummelinki. As far as the nature of ventral filamentous appendages, it must be stressed that amongthe 11 P. spongicola specimens examined, some were large and ripe (including the holotype), but all, includ-ing the smaller ones, have unbranched appendages. The length of the unbranched appendages does not appearto be correlated to the size of the worms, and in addition some individuals are asymmetrical in their develop-ment, differing in length on the left and right hand side of the animal.

Type locality: Carrie Bow Cay, BelizeEtymology: The species was named after the habitat where it occurs.

Comparison between Caribbean and Mediterranean sabellid species and discussion

The Grand Caribbean, which includes Western and Southern Caribbean, Lesser and Greater Antilles, as wellas more broadly the Guyanas, Bahamas and the East coast of Florida, is an extended tropical region of theWestern Atlantic with a complex geological history which had a strong influence on the past and currentmarine biota (Salazar-Vallejo, 2000). The Mediterranean Sea, in contrast is a semi-closed, geographically welldefined temperate marine area of the eastern Atlantic, included in the Atlanto-Mediterranean region, with aunique geological history, especially during the late Miocene and the Quaternary, that resulted in a complexbiogeography (Taviani, 2002; 2004). Both areas are considered as “global areas of endemism” according toVan Soest and Hajdu (1997), and show a comparable degree of endemism of the polychaete fauna (Glasby,2006). The two regions show quite comparable extension, similar complex geological history and ancientgeological link, as well as past and present connections due to Gulf Stream current which can influence spe-cies distributions. In addition, although climatic differences of the two areas are relevant, both regions show ahighly diversified coastal marine habitats (e.g., although the Mediterranean lacks both coral reefs and man-



groves, it has Posidonia oceanica seagrass beds and coralligenous formations). In addition, recent climaticchanges, towards a general warming of the sea, have increased the tropical affinity of the Mediterraneancoastal waters, with increasing success of tropical introduced species, and geographic expansion of thermo-philous species, including those from the tropical Atlantic (see Zenetos et al., 2005; Bianchi, 2007). Lastly,several specialists on polychaete systematics are working in both areas, so the quality of identification formost of the species reported is reliable, including sabellids. Therefore, it would be interesting to comparebiodiversity and systematic make up of closely related groups of organisms in these two marine eco-regions.

Within the Caribbean area, 11 Fabriciinae and 72 Sabellinae are recorded, for a total of 83 species. Amongthem, 7 Fabriciinae and 28 Sabellinae are endemic (42% of endemism), and 25 genera are listed, withNotaulax, Branchiomma, Megalomma, and Chone as the most speciose ones. Within the Mediterranean 9Fabriciinae and 51 Sabellinae are recorded, for a total of 59 species. Among them 4 Fabriciinae and 12 Sabel-linae are endemic (26% of endemism), and 23 genera are listed, with Amphicorina, Chone, Euchone, Branchi-omma and Demonax, as the most speciose ones.

The genera Manayunkia, Fabricinuda, Augeneriella, Potamethus, Sabellastarte and Anamobaea occuronly in the Caribbean, while Notaulax, Branchiomma, Bispira and Megalomma, although present in bothregions, are more speciose in the Caribbean. In contrast, some genera such as Fabricia, Desdemona, andSabella, occur only in the Mediterranean region, and Amphicorina, and Euchone are better represented in thisarea. Only 5 species appear common to both regions.

Sabellid biodiversity exhibits a higher number of species together with a higher level of endemism in theCaribbean with respect to the Mediterranean. This confirms the previous hypothesis of the existence of a lati-tudinal gradient of sabellid diversity, with most of the species occurring in tropical areas (Giangrande and Lic-ciano, 2004). The Mediterranean biodiversity, however, appears relatively high for a non-tropical area(Giangrande and Licciano, 2004). This is probably due to geological events which occurred in the lateMiocene of the Quaternary (Bianchi and Morri, 2000), but also to the fact that the Mediterranean is histori-cally one of the best-studied areas in terms of biological diversity (Bianchi and Morri 2000). It must also bestressed that in both areas the genera with the highest number of species are those for which revisions havebeen recently outlined, reflecting the so called ‘author effect’ sensu Giangrande and Licciano (2004). Theseauthors, also pointed out a tropical affinity of the genera Fabricinuda, Augeneriella, Sabellastarte, Ana-mobaea, Notaulax, Branchiomma, and Megalomma. And this is in accordance with data from the presentpaper. Moreover, this tropical affinity can also be extended for the genus Pseudoaugeneriella. Other generaseem instead linked to higher latitudes (e.g. Fabricia and Sabella).

One of the clear outcomes is that the two areas show relatively few species in common and that, in addi-tion, can be of dubious identification. For some of them the taxonomic status has been recently solved, this isthe case for instance of Megalomma vesiculosum, up to now considered a cosmopolitan species present inboth areas, but actually a northern taxon not present in Mediterranean and probably also absent in the Carib-bean (Giangrande and Licciano, in press). Yet, among the common taxa, the recent finding in the Mediterra-nean of Novafabricia infratorquata by Bick and Rendal (2005) and Licciano and Giangrande (2006), whichwas described from Caribbean (Fitzhugh 1983) must be reconsidered, taking also into consideration the highvariability existing among populations of the two Mediterranean areas where the taxon was found.

Considering the ancient historical link between the two compared areas, which can be inferred from sometertiary relicts colonizing peculiar and restricted habitats within the Mediterranean basin (Minelli et al., 2005),it is not surprising that the two areas does not share many species. This is also consistent with a recent biogeo-graphic analysis, conducted on various polychaete taxa with a cladistic approach (Glasby, 2006), where thetwo areas are well separated in the cladogram. This recent approach has re-evaluated the potential biogeo-graphic utility of polychaetes, currently considered as poor biogeographic descriptors (see Glasby, 2006). Theincreased taxonomic knowledge on Sabellidae may lead us to consider this group of polychaetes as good bio-geographical indicators as showed recently by Syllidae (Musco and Giangrande, 2005).



Acknowledgements

We wish to thank Kristian Fauchald (Smithsonian Museum Natural History, Washington, USA) for the oppor-tunity he gave to MCG and AG to participate in the Caribbean Coral Reef Ecosystem (CCRE) program andvisit the Smithsonian Institution field station at Carrie Bow Cay (CBC, Belize). Thanks are also due to KlausRuetzler, Director of the CCRE program for funding the project. We had a great time while at CBC (notwithstanding tropical storm “Gamma”!), and we are grateful to GeoffW. Keel for support above- and underwater, Daniel Miller and Claudette DeCurley for assistance at sea andnice company on the Cay, and Michael Carpenter and Nadine for major support at the station and in thekitchen, respectively. Contribution #812 of the Caribbean Coral Reef Ecosystem Programme at CBC.

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