Marine Gastrotricha from the coasts of Sardinia (Italy)

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1 Bolletino di zoologia ISSN: (Print) (Online) Journal homepage: Marine Gastrotricha from the coasts of Sardinia (Italy) Maria Balsamo, Elena Fregni & Paolo Tongiorgi To cite this article: Maria Balsamo, Elena Fregni & Paolo Tongiorgi (1995) Marine Gastrotricha from the coasts of Sardinia (Italy), Bolletino di zoologia, 62:3, , DOI: / To link to this article: Copyright Taylor and Francis Group, LLC Published online: 28 Jan Submit your article to this journal Article views: 120 View related articles Citing articles: 10 View citing articles Full Terms & Conditions of access and use can be found at Download by: [ ] Date: 06 January 2018, At: 01:13

2 Boll. Zool. 62: (1995) Marine Gastrotricha from the coasts of Sardinia (Italy) MARIA BALSAMO Dipartimento di Scienze della Produzione animale, via S. Mauro 2, I Pagnacco (Udine, Italy) ELENA FREGNI PAOLO TONGIORGI Dipartimento di Biologia animale, Università di Modena, via Università 4, Modena (Italy) ABSTRACT Twenty-eight macrodasyid and twenty-eight chaetonotid species of marine Gastrotricha are reported. Of these species, two - Halichaetonotus clavicornis and H. genatus - are new, and three are described for the first time for to the Italian fauna. The influence of various physical and chemical environmental factors on gastrotrich distribution along the peninsular and island coasts of the Tyrrhenian Sea are analysed and discussed. KEY WORDS: Gastrotricha - Marine meiofauna - Mediterranean fauna - Sardinia - Italy. ACKNOWLEDGEMENTS We wish to thank Prof. Marco Curini-Galletti and Prof. Alberto Castelli for their collaboration in collecting samples. Thanks are also due to Dr. Wayne Evans (Ohio University, Athens, USA) who provided the computer software for the calculation of grain size parameters and to Mr. Donato Giannetti for the drawings. This research was supported by grants from the Italian Consiglio Nazionale delle Ricerche (C.N.R., CT04 to P. Tongiorgi) and the Ministero dell'università e della Ricerca Scientifica e Tecnológica (within the research M.U.R.S.T. 40% Programme «Popolamento animale del Mediterráneo Occidentale»). (Received 5 April Accepted 24 May 1995) INTRODUCTION The programme of faunistic and taxonomic research of the Gastrotricha of the Italian seas which has been underway for several years is now concerned with the fauna of the coasts of Sardinia. Knowledge of gastrotrichs from the Ligurian Sea (Gerlach, 1953, and unpublished data), from the coasts of Tuscany and Latium (Luporini et al., 1971, 1973; Hummon et al., 1992, 1993), from the Tuscan archipelago (Balsamo et al., 1992, 1994; Todaro et al., 1992) and from the island of Ponza (Todaro, 1992) is fairly extensive, while there is little data on Sardinia, where to date only two species have been recorded (Todaro et al., 1988). The central position in the Mediterranean basin of this major Italian island, its substantial distance from the continental coast, the considerable diversity of its substrates, and, particularly, the still limited anthropic impact make Sardinia an ideal source of faunistic and Zoogeographie data, especially with regards a better understanding of the origin and nature of Mediterranean fauna. MATERIALS AND METHODS Collecting time and sites Marine sediments were sampled during three collecting campaigns carried out in 1993 at the 26 localities listed below and illustrated in Figure 1. The first trip (May 1993) regarded ten sites on the northern coast of the island, from Olbia to Alghero; the second trip (June 1993) touched nine sites on the western and southern coast between Alghero and Cagliari, and the last trip (October 1993) reached other nine sites on the southern and eastern coast. At most localities, two samples were taken, one from the water-line (littoral samples) and the other from a depth varying between 1 and 8 m (sublittoral samples). The water depth of sublittoral samples and the nature of the sediment at the collecting sites are given in parentheses. 1. Porto Rotondo (2-3 m depth, coarse siliceous sand within a field of Posidonia); 2. Porto Sardinia (littoral sample, medium siliceous sand; 1-2 m depth, coarse siliceous sand); 3. The island of Caprera (1-2 m depth, fine siliceous sand mixed with silt and abundant organic detritus); 4. Cala Capra (1-3 m depth, medium sand); 5. Conca Verde (1-2 m depth, coarse sand); 6. Baia di Santa Reparata (1-2 m depth, very coarse siliceous sand with organic detritus); 7. Castelsardo (2-3 m depth, very coarse siliceous sand and gravel); 8. Spiaggia Pelosa (2-3 m depth, medium carbonaceous sand); 9. Golfo di Dragunara (littoral sample, medium carbonaceous sand; 2-3 m depth, coarse carbonaceous sand with organic detritus; 7-8 m depth, coarse sand mixed with silt); 10. Fertilia (1-2 m depth, medium carbonaceous-siliceous sand); 11. Bosa Marina (littoral sample, medium siliceous sand; 2-3 m depth, medium sand); 12. Is Arenas (1-2 m depth, fine sand); 13. Torre Corsari (littoral sample, medium carbonaceous-siliceous sand; 2-3 m depth, coarse sand); 14. Masua (littoral sample, medium carbonaceous-siliceous sand; 2-3 m depth, medium carbonaceous-siliceous sand); 15. Calasetta, the island of S. Antioco (littoral sample, medium carbonaceous-siliceous sand; 2-3 m depth, medium carbonaceous-siliceous sand within a field of Posidonia); 16. Capo Turri, the island of S. Antioco (2-3 m depth, fine siliceous sand); 17. Capo Spartivento (1-2 m depth, fine siliceous sand mixed with silt); 18. Poetto (1-2 m depth, fine siliceous sand within a field oí Posidonia); 19. Solanas (littoral sample, fine siliceous sand; 1-2 m depth, coarse siliceous sand); 20. Simius (2-3 m depth, medium siliceous sand); 21. Piscina Rei (2-3 m depth, medium siliceous sand); 22. Costa Rei (littoral sample, fine siliceous sand; 1-2 m depth, medium sand); 23. Marina di Gairo (2-3

3 274 M. BALSAMO, E. FREGNI, P. TONGIORGI TAXONOMIC ACCOUNT OB 1 / O{ 3 /stand o/ f Caprera The sediment of 22 of the 26 localities sampled yielded 55 species, 28 Macrodasyida belonging to 15 genera and 27 Chaetonotida of 7 genera (Tables I, II). In four species, only the genus could be identified due to the limited number of specimens found. 9( ^AIghero X1*25 TABLE I - Macrodasyida found along the coasts sampled during the three collecting trips. MEDIT ERRANE/VN SEA \ As Island t\r*\ S. Antioco V A " ^ Fig. 1 - Location of sampling sites. Caqliari 0 20?24? TYRRIHENIAN SEA m depth, medium and very coarse siliceous sand); 24. Santa Maria Navarrese (5-6 m depth, fine siliceous sand within a field of Posidonia); 25. Cala Liberotto (littoral sample, medium siliceous sand; 3-4 m depth, medium siliceous sand); 26. La Caletta (littoral sample, medium siliceous sand; 3-4 m depth, medium siliceous sand). Methods Sampling and study methods are described in Todaro et al. (1992). Grain size analysis of sediments was carried out according to Giere et al. (1988) using sieves with mesh sizes of 4, 2, 1, 0.500, 0.250, and mm. Parameters were calculated by a specially designed computer software programme based on the Seward-Thompson & Hails (1973) equation. The total organic matter in the sediment was measured according to Giere et al. (1988). Morphometric parameters, which are the basis of the taxonomy at species level, are given for those species new to Italian fauna, while for others they are indicated only where they contrast with data in the literature. Photographic negatives of the two new species have been deposited as holotypes at the Museo Cívico di Storia Naturale, Verona, Italy. Since most gastrotrich species have a broad geographic distribution, we chose to limit our indications to that along the Italian coasts. Details on the presence of species on the islands of Ischia and Procida have been kindly provided by W. D. Hummon, M. R. Hummon and M. A. Todaro. Macrodasyida North South-West South-East DACTYLOPODOLIDAE Dactylopodola D. typhle LEPIDODASYIDAE Dolichodasys D. elongatus Megadasys M. minor Mesodasys M. adenotubulatus M. laticaudatus M. sp. MACRODASYIDAE Macrodasys M. caudatus Urodasys U. viviparus THAUMASTODERMATIDAE Acanthodasys A. aculeatus Diplodasys D. ankeli Platydasys P. sp. Pseudostomella P. etrusca Ptychostomella P. mediterránea P. sp. Tetranchyroderma T. cirrophorum T. papii T. polypodium T. quadritentaculatum T. sardum T. thysanogaster T. thysanophorum Thaumastoderma T. mediterraneum T. ramuliferum TURBANELLIDAE Paraturbanella P. dohrni P. pallida P. teissieri Turbanella T. ambronensis T. cornuta Abbreviations: TL, total length; PhL, pharynx length; FuL, furca length. Total

4 GASTROTRICHA FROM THE COASTS OF SARDINIA 275 Two species, Halichaetonotus clavicornis and H. genatus, are new to science. Megadasys minor, Chaetonotus inaequidentatus and Heteroxenotrichula arcassonensis are reported for the first time along the Italian coastline. TABLE II - Chaetonotida found along the coasts sampled during the three collecting trips. Chaetonotida North South-West South-East Order Macrodasyida Rao & Clausen, 1970 Family DACTYLOPODOLIDAE Strand, 1929 Genus Dactylopodola Strand, 1929 Dactylopodola typhle (Remane, 1927) Castelsardo, 2-3 m; Torre Corsari, 2-3 m; Piscina Rei, 2-3 m; Marina di Gairo, 2-3 m; Cala Liberotto 3-4 m. Many specimens were collected from medium and coarse sediments of the sublittoral zone. Characteristic features of the specimens were the consistency of the main metric parameters (TL xm, PhL [im, FuL 13.5 um) and of the number and arrangement of the ventral adhesive tubes (3 cephalic, 4 lateral and 3 caudal per side), among the lower values reported for the species. Dactylopodola typhle is quite a variable species, probably comprising two different but closely related taxa (Hummon, personal communication). The species has previously only been found in medium sand along the coast of Tuscany and Sicily. Family LEPIDODASYIDAE Remane, 1927 Genus Dolichodasys Gagne, 1977 Dolichodasys elongatus Gagne, 1977 Calasetta (the island of S. Antioco), 2-3 m. Three specimens were collected in medium sand, but only one was adult. Body length, 1400 [im, was much shorter than the average reported for the species, \im. Dolichodasys elongatus is present along the Tuscan coast and widespread in the Adriatic Sea (the coasts of Apulia, the Marches, Véneto and Friuli), generally in fine sands. Genus Megadasys Schmidt, 1974 Megadasys minor Kisielewski, 1987 The island of Caprera, 2-3 m. This is the first record in the Mediterranean of the genus Megadasys, otherwise only reported in the English Channel. The species was collected in sediments rich in organic detritus, as is the case in all the species of this CHAETONO TIDAE Aspidiophorus A. mediterraneus A. paramediterraneus A. polystictos Chaetonotus Euchaetonotus C. (E.) aegilonensis C. (E.) apechochaetus C. (E.) siciliensis C. (E.) sp. Hystricochaetonotus C. (H.) lacunosus C. (H.) variosquamatus Schizochaetonotus C. (S.) atrox C. (S.) dispar C. (S.) inaequidentatus C. (S.) neptuni Halichaetonotus H. aculifer H. atlanticus H. clavicornis n. sp. H. genatus n. sp. H. jucundus H. margaretae H. spinosus H. thalassopais Heterolepidoderma H. loricatum XENOTRICHULIDAE Draculiciteria D. tesselata Heteroxenotrichula H. arcassonensis H. squamosa Xenotrichula X. intermedia X. pygmaea X. punctata Total speciez only found in 1987 (Todaro et al., 1988) genus observed by other authors (Fenchel & Riedl, 1970; Boaden, 1974; Kisielewski, 1987). Genus Mesodasys Remane, 1951 Mesodasys adenotubulatus Hummon, Todaro & Tongiorgi, 1993 Torre Corsari, 2-3 m; Capo Turri (the island of S. Antioco), 1-2 m; Simius, 2-3 m; Piscina Rei, 2-3 m; Cala Liberotto, 3-4 m; La Caletta, 3-4 m.

5 276 M. BALSAMO, E. FREGNI, P. TONGIORGI Mesodasys adenotubulatus is quite common along the Tyrrhenian coast of Sardinia in fine and medium sediments of the sublittoral zone (1-4 m depth). It is also known in Tuscany, Latium, Campania, the island of Ischia, Sicily and the Adriatic coast of the Marches. Mesodasys laticaudatus Remane, 1951 Golfo di Dragunara, 2-3 m, 7-8 m; Bosa Marina, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m. The species is generally found in sublittoral medium and coarse sediments with some organic detritus, as well as in organogenic fine sands. Other than in Sardinia, M. laticaudatus is present along the Ligurian and Tyrrhenian coasts (Tuscany, the Tuscan archipelago, Latium, the island of Ponza, Campania, the island of Ischia, and Lucania) and on the Adriatic coast of Apulia. Bosa Marina, 2-3 m. Mesodasys sp. A single specimen, 1150 urn in length and presenting 22 postoral adhesive tubes and about 50 lateral tubes per side, was found in medium sand. It is not possible to assign the specimen to any specific taxon, even though it certainly differed morphologically from M. laticaudatus. Family MACRODASYIDAE Remane, 1926 Genus Macrodasys Remane, 1924 Macrodasys caudatus Remane, 1927 Golfo di Dragunara, 2-3 m, 7-8 m; Marina di Gairo, 2-3 m; Cala Liberotto, 3-4 m; La Caletta, 3-4 m. All the specimens collected were subadult and thus small ( urn body length) and with a total number of lateral and caudal adhesive tubes lower than that reported in the literature. This species colonizes both fine and coarse sand, mainly with detritus. The species is cosmopolite and has been found in many localities on the Italian coast and on the islands of Elba, Giglio and Capraia in the Tuscan archipelago. Genus Urodasys Remane, 1926 Urodasys viviparus Wilke, 1954 Golfo di Dragunara, 2-3 m. One specimen was found in coarse sublittoral sand. This is the only species of this genus known for the Italian fauna and is widespread along the Tyrrhenian peninsular coasts. Family THAUMASTODERMATIDAE Remane, 1926 Genus Acanthodasys Remane, 1927 Acanthodasys aculeatus Remane, 1927 Bosa Marina, 2-3 m; Masua, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m; Capo Turri (the island of S. Antioco) 1-2 m, Piscina Rei, 2-3 m; Marina di Gairo, 2-3 m; Cala Liberotto, 3-4 m; La Caletta, 3-4 m. Many specimens were found, all with a body length slightly shorter than that typical of this species, vs 800 urn. Acanthodasys aculeatus is common along the peninsular coast, on the islands of the Tuscan archipelago and in Sicily. This species, which is present in medium and coarse and Amphyoxus sand, shows a marked preference for fine sand, even when rich in detritus. Genus Diplodasys Remane, 1927 Diplodasys ankeli Wilke, 1954 Castelsardo, 2-3 m; Golfo di Dragunara, 2-3 m; Torre Corsari, 2-3 m; Piscina Rei, 2-3 m; Marina di Gairo, 2-3 m; Cala Liberotto 3-4 m. The single specimen collected from Piscina Rei showed remarkably large dimensions: 358 urn body length and 79-6 urn pharynx length vs um and \im respectively reported for this species. Diplodasys ankeli is common in sublittoral, even deep, sediments, especially in coarse sand mixed with shell fragments, as well as in biogenic and Amphyoxus sand. The species has previously been found in the Tuscan archipelago, the island of Ponza, the Gulf of Naples, in Sicily, and along the Ionian coasts of Calabria and Apulia. Torre Corsari, 2-3 m. Genus Platydasys Remane, 1927 Platydasys sp. Several specimens of an unidentified species belonging to the genus Platydasys were collected from coarse sublittoral sand. The body was stout and flattened, and between 362 and 455 urn in length. The head and trunk were similar in width, 115 and 125 M.m, respectively. Many tactile bristles, urn long, were arranged in a row on the anterior edge of the mouth and in a longitudinal row on each side of the body. The whole body was covered with cuticular conic papillae. Each side of the body showed a longitudinal row of 3-8 lateral adhesive tubes, urn in length, and another of ventrolateral adhesive tubes of urn. The first 2-6 tubes of the ventrolateral rows were urn long and anterior to the pharyngo-intestinal junction. The edge of the caudal end presented 8-22 adhesive tubes of um arranged in a single transversal row.

6 GASTROTRICHA FROM THE COASTS OF SARDINIA 277 The ventral edge of the mouth was surrounded by adhesive tubes arranged in two lateral groups, each of 6-12 tubes, and a transversal row of 18 tubes. The length of the tubes ranged from 5.5 um for medial ones to 8.0 [im for the lateral ones. The ventral ciliary field was uniform. The (im long, funnel-shaped mouth opened into a cylindrical pharynx of um. The reproductive system consisted of two lateral ovaries and the right testicle which opened into the right part of the caudal organ. The morphology of these specimens greatly differed from that of all the other species of this genus. With regard to the species so far recorded along the Italian coasts, they differed from P. maximus, P. styliferus and P. tentaculatus in that they lacked the cephalic tentacles and showed quite a different number of adhesive tubes. P. phacellatus is close to Platydasys sp. in body size and number and length of the lateral adhesive tubes, but differs in presenting a larger number of ventrolateral and caudal tubes, 70 and 40 respectively and two longer caudal tubes, as well as some ventral cirri, which have otherwise never been observed in the Sardinian specimens. These specimens certainly belong to a new taxon; however, the description is incomplete and the species therefore cannot be named. Genus Pseudostomella Swedmark, 1956 Pseudostomella etrusca Hummon, Todaro & Tongiorgi, 1993 Bosa Marina, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m; Capo Turn (the island of S. Antioco), 1-2 m; Piscina Rei, 2-3 m; Cala Liberotto, 3-4 m. Pseudostomella etrusca is abundant in all the localities, preferring fine sand in the sublittoral zone, and has been found in Italy along the Ligurian and Tuscan coasts, on the islands of the Tuscan archipelago (Elba and Giglio), in Latium, Campania, on the Tyrrhenian coasts of Calabria and in Sicily. A single specimen, certainly belonging to this genus, was collected in coarse sand. However, the insufficient data recorded did not allow the specimen to be assigned to a specific taxon. Genus Tetranchyroderma Remane, 1926 Tetranchyroderma cirrophorum Levi, 1950 Cala Liberotto, 3-4 m; La Caletta, 3-4 m. Numerous specimens were present in both localities. The SEM study of the individuals from Cala Liberotto revealed the expansion of the ventrolateral spines into lamellar structures similar to the hydrofoil scales of many marine chetonotids (Fig. 2). Tetranchyroderma cirrophorum is already known in the coarse sublittoral sand of the islands of Elba and Capraia (Tuscan archipelago) and of many localities along the Italian coasts. Tetranchyroderma papii Gerlach, 1953 Bosa Marina, 2-3 m; Torre Corsari, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m; Simius, 2-3 m; Cala Liberotto, 3-4 m; La Caletta, 3-4 m. Tetranchyroderma papii was abundant in medium and coarse sand in all localities. This widespread species has been recorded in Italy on the Tyrrhenian (Tuscany, Latium, Campania) and Adriatic (Apulia, Friuli) coasts and in Sicily. Tetranchyroderma polypodium Luporini, Magagnini & Tongiorgi, 1973 Porto Sardinia, 1-2 m; Castelsardo, 2-3 m; Spiaggia Pelosa, 2-3 m. Genus Ptychostomella Remane, 1926 Ptychostomella mediterránea Remane, 1927 Marina di Gairo, 2-3 m; Cala Liberotto, 3-4 m; Torre Corsari, 2-3 m. This uncommon species is generally found in medium and coarse and Amphyoxus sand of the sublittoral zone. It was very abundant in the very coarse sand of Marina di Gairo. In Italy, P. mediterránea has been reported in Tuscany, the Tuscan archipelago, Latium, the island of Ponza, Campania and Sicily. Torre Corsari, 2-3 m. Ptychostomella sp. Fig. 2 - Tetranchyroderma cirrophorum. Detail of the ventral side. The ventrolateral tetrancres have a branch extended in a hydrofoil lamella S.E.M., xl900.

7 278 M. BALSAMO, E. FREGNI, P. TONGIORGI The Sardinian specimens, which were numerous only in the coarse sand of Porto Sardinia, differed from those described by Luporini et al. (1973) in that they presented fewer ventrolateral adhesive tubes (21-46 vs 60 per side) and caudal tubes (2 vs 3 per side). Tetranchyroderma polypodium is a rare species, found in Italy only on the Tuscan coast. Tetranchyroderma quadritentaculatum Balsamo & Tongiorgi, 1992 Todaro, Costa Rei, 1-2 m; Piscina Rei, 2-3 m; Cala Liberotto, 3-4 m. All the specimens were collected in medium sand and fully matched the original description of this species, previously found only on the island of Elba and along the coast of Latium. Tetranchyroderma sardum Todaro, Balsamo & Tongiorgi, 1988 Porto Sardinia, 2-3 m; Baia di Santa Reparata, 2-3 m. Tetranchyroderma sardum was found for the first time in Sardinia and later also on the island of Ischia and on the coast of Campania (Hummon & Todaro, unpublished data) and Sicily (Balsamo, Fregni & Tongiorgi, unpublished data) in medium and coarse sands. It is worth noting that in the type locality, Cala Liberotto, T. sardum was very abundant in 1988 but completely absent in Tetranchyroderma thysanogaster Boaden, 1965 Bosa Marina, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m; Capo Spartivento, 2-3 m. The Sardinian specimens showed smaller caudal appendages, urn as opposed to 25 um of the original description. In Italy this species has been reported in fine and medium sands in the Tuscan archipelago and on the coast of Campania. Tetranchyroderma thysanophorum Hummon, Todaro & Tongiorgi, 1993 Piscina Rei, 2-3 m; Castelsardo, 2-3 m; Bosa Marina, 2-3 m; Torre Corsari, 1-2 m; Capo Turri (the island of S. Antioco), 1-2 m; Santa Maria Navarrese, 5-6 m; Cala Liberotto, littoral. Although sexually mature, most specimens from Cala Liberotto presented fewer ventrolateral and caudal adhesive tubes, vs and 4 vs 6, respectively. Tetranchyroderma thysanophorum, which prefers fine and medium sand, even with detritus, has been found along the Tuscan coast, in the Tuscan archipelago (Elba, Giglio and Capraia) and in Sicily (Balsamo, Fregni & Tongiorgi, unpublished data). Genus Thaumastoderma Remane, 1927 Thaumastoderma mediterraneum Remane, 1927 Bosa Marina, 2-3 m. Few specimens of this uncommon species were collected in medium sand. Thaumastoderma mediterraneum is generally present in sediments of the sublittoral zone ranging from fine to coarse, even including those rich in detritus, in biogenic and in Amphyoxus sands. It has already been found along the Tyrrhenian and Ionian coasts of the Italian peninsula, as well as in the Tuscan archipelago (Elba, Giglio and Capraia), on the island of Ischia, and in Sicily. Thaumastoderma ramuliferum Clausen, 1965 Marina di Gairo, 2-3 m. Only one specimen was collected in coarse sand. Like the other species of this genus, T. ramuliferum lives in sediments of various grain size in the sublittoral zone and in Amphyoxus sand. It has been reported in Tuscany and the Tuscan archipelago (Elba and Capraia), on the islands of Ponza and Ischia, in Campania and Sicily, and on the Ionian coast of Apulia. Family TURBANELLIDAE Remane, 1925 Genus Paraturbanella Remane, 1927 Paraturbanella dohrni Remane, 1927 Calasetta (the island of S. Antioco), 2-3 m; Santa Maria Navarrese, 5-6 m; Cala Liberotto, 3-4 m. Many specimens were collected from fine and medium sediments. The species, which is very common, especially in fine sand, is widespread in Italy, being known on the Ligurian and Tyrrhenian (Tuscany and the Tuscan archipelago, Campania, Lucania, Calabria and Sicily), the Ionian (Apulia) and the Adriatic coasts (Molise, the Marches, Véneto and Friuli). Paraturbanella pallida Luporini, Magagnini & Tongiorgi, 1973 Porto Rotondo, 2-3 m; Golfo di Dragunara, 2-3 m, 7-8 m. The metric parameters of the specimens from both localities were slightly smaller than those reported for the species (TL urn, PhL um, FuL 46 xm), which is widespread along the Italian coasts (Liguria, Tuscany and the Tuscan archipelago, Campania, the island of Ischia, Sicily, Apulia, the Marches and Friuli).

8 GASTROTRICHA FROM THE COASTS OF SARDINIA 279 Paraturbanella teissieri Swedmark, 1954 Porto Sardinia, 1-2 m; Baia di Santa Reparata, 2-3 m; Castelsardo, 2-3 m; Bosa Marina, 2-3 m; Torre Corsari, 2-3 m; Piscina Rei, 2-3 m; Cala Liberotto, 3-4 m; La Caletta, littoral, 3-4 m. Many specimens were collected in medium to very coarse sand. Paraturbanella teissieri is one of the most common and numerous species in Italy, having been reported in Liguria, Tuscany and the Tuscan archipelago, Latium and the island of Ponza, Campania and the island of Ischia, Calabria, Sicily, Lucania, Apulia, the Marches and Friuli. Generally present in clean and oxygenated medium sands of the sublittoral zone, it has also been found in fine and Amphyoxus sand. Genus Turbanella Schültze, 1853 Turbanella ambronensis Remane, 1943 Porto Sardinia, littoral; Calasetta (the island of S. Antioco), littoral. All the Sardinian specimens were extracted from the littoral sand and had the ventral pair of adhesive tubes inserted at the height of the 5-6th lateral adhesive tube, as observed in some other populations of this species (Todaro et al., 1992). Turbanella ambronensis is widespread along the Ligurian and Tyrrhenian coasts (Tuscany, the Tuscan archipelago, Latium, Campania, the island of Ischia), and those of Sicily and the Adriatic regions (Apulia, the Marches, Emilia-Romagna and Friuli). Turbanella cornuta Remane, 1924 Cala Liberotto, 3-4 m; La Caletta, 3-4 m. This species was abundant in medium, sublittoral sand of both localities. Turbanella cornuta is known in sediments of various grain size in many localities on the Tyrrhenian coast (Tuscany, the Tuscan archipelago, Latium, Campania) and on those of Sicily and the Marches. Order Chaetonotida Rao & Clausen, 1970 Family CHAETONOTIDAE Zelinka, 1889 Genus Aspidiophorus Voigt, 1904 Aspidiophorus mediterraneus Remane, 1927 Baia di Santa Reparata, 2-3 m; Santa Maria Navarrese, 5-6 m; Cala Liberotto, 3-4 m. Numerous specimens were found in fine to very coarse sands. This cosmopolite species, which colonizes sediments of differing grain size, is present in Italy on the Ligurian and Tyrrhenian coasts (Tuscany, the Tuscan archipelago, Latium, Campania and the island of Ischia), in Sicily, and also along the Ionian coast of Apulia and the Adriatic coasts of Véneto and Friuli. Aspidiophorus paramediterraneus Hummon, 1974 Porto Sardinia, 2-3 m; Golfo di Dragunara, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m; Capo Turri (the island of S. Antioco), 1-2 m; Marina di Gairo 2-3 m; Santa Maria Navarrese, 5-6 m. A number of specimens consistent with the morphology of this species, which is closely related to A. mediterraneus, were collected at all sites. The species is known in Liguria, Tuscany and the Tuscan archipelago, Latium, the island of Ischia, Apulia, the Marches, Véneto and Friuli. Aspidiophorus polystictos Balsamo & Todaro, 1987 Porto Sardinia, littoral; Baia di Santa Reparata, 2-3 m. Aspidiophorus polystictos was first found along the Ionian coast of Apulia, and subsequently also reported on the Ligurian coast and in many Tyrrhenian and Adriatic localities (Tuscany and the Tuscan archipelago, Latium, the island of Ischia, Apulia, the Marches, Véneto and Friuli), proving to be one of the most common chaetonotid species in Italy. Genus Chaetonotus Ehrenberg, 1830 Subgenus Euchaetonotus Schwank, 1990 Chaetonotus (E.) aegilonensis Balsamo, Todaro & Tongiorgi, 1992 Santa Maria Navarrese, 5-6 m. The only two specimens extracted in Sardinia from fine sand were considerably smaller than those collected in the medium sediments of the island of Capraia (TL 128 vs 200 urn, PhL vs 41 y.m, FuL vs 36 um). At present, the geographic distribution of this chetonotid is restricted to the Tuscan coast, the Tuscan archipelago and Campania. Chaetonotus (E.) apechochaetus Hummon, Balsamo & Todaro, 1992 Baia di Santa Reparata, 2-3 m; Masua, 2-3 m. The total body length of the few specimens found in medium and coarse sands in Sardinia was slightly greater than that of the other Italian specimens observed, as opposed to 140 \im. Chaetonotus apechochaetus has recently been described in sublittoral fine sediments in Apulia, and subsequently reported in Liguria, Tuscany, the Tuscan archipelago, the island of Ischia and Sicily.

9 280 M. BALSAMO, E. FREGNI, P. TONGIORGI Chaetonotus (E.) siciliensis Hummon, Balsamo & Todaro, 1992 i» Porto Sardinia, 1-2 m; Capo Turri (the island of S. Antioco), 1-2 m; Cala Liberotto, 3-4 m. The Sardinian specimens were collected from fine to coarse sediments. Following the first report on the Tyrrhenian coast of Sicily, the species has also been found in sublittoral sands of various grain size in the Tuscan archipelago, on the island of Ponza, and along the coasts of Apulia and Molise. Golfo di Dragunara, 2-3 m. Chaetonotus (E.) sp. Only one individual of an unidentified species of the genus Chaetonotus (subgenus Euchaetonotus) was found in coarse sand. The total body length of the specimen was 142 \im, with a furca of 26 um and a pharynx of 33 \nm. It appeared very closely related to C. aegilonensis and C. apechochaetus, species described for Italian fauna, in that it presented numerous, short spines and two well developed parafurcal spines. However, the cuticular morphology of the furcal base and, especially, the presence of two very long (12.7 urn), thick spines at the dorsal posterior end distinguish the Sardinian specimen from both species. Even C. siciliensis, which shows a pair of long terminal spines, differs from the individual observed in the greater length of the dorsal spines, 20.0 vs 5.7 urn. Subgenus Hystricochaetonotus Schwank, 1990 Chaetonotus (H.) lacunosus Mock, 1979 Spiaggia Pelosa, 2-3 m; Fertilia, 2-3 m; Simius, 2-3 m; Piscina Rei, 2-3 m; Baia di Santa Reparata, 1-2 m. The Sardinian specimens were mainly extracted from medium sediments. The only individual from Spiaggia Pelosa showed two additional long spines at the ventral posterior end. The distribution of C. lacunosus includes the Ligurian, Tyrrhenian (Tuscany, the island of Ponza, Campania and the island of Ischia) and Adriatic (Apulia, the Marches, Friuli) coasts, and Sicily, generally in fine to medium sand. Chaetonotus (H.) variosquamatus Mock, 1979 (Fig. 3) Castelsardo, 2-3 m; La Caletta, littoral. All the specimens were extracted from medium to very coarse sediments of the littoral and sublittoral zones. The Fig. 3 - Chaetonotus variosquamatus. Ventral view of the posterior end. Nomarski optics, xl200. species has been reported in sediments of differing grain size in the Tuscan archipelago, on the Tyrrhenian coasts of Latium, Campania and the island of Ischia, in Lucania and in Sicily. Subgenus Schizochaetonotus Schwank, 1990 Chaetonotus (S.) atrox Wilke, 1954 Porto Sardinia, littoral; Calasetta (the island of S. Antioco), 2-3 m; Capo Turri (the island of S. Antioco), 1-2 m. Very abundant species in fine to coarse sands, even in the littoral zone. Chaetonotus atrox is a very common gastrotrich, reported in Liguria, Tuscany and the Tuscan archipelago, Campania and the island of Ischia, Calabria, Apulia, Molise and Friuli. Chaetonotus (S.) dispar Wilke, 1954 Golfo di Dragunara, 2-3 m, 7-8 m; Torre Corsari, 2-3 m. A few individuals were present in coarse sand at both sites. Like C. atrox, C. dispar is a common species in littoral and sublittoral sands of various grain size. In Italy, it is known in Tuscany, the Tuscan archipelago, Campania, the island of Ischia, on the Tyrrhenian coasts of Calabria, in Sicily, and on the Adriatic coasts of Apulia and Friuli.

10 GASTROTRICHA FROM THE COASTS OF SARDINIA 281 Chaetonotus (S.) inaequidentatus Kisielewski, 1988 (Fig. 4) Golfo di Dragunara, 2-3 m. Two specimens of this species were observed in a sample of coarse sand collected in the sublittoral zone. This is the first record of C. inaequidentatus in the Mediterranean, since it was previously known only in the English Channel (Kisielewski, 1988). Chaetonotus (S.) neptuni Wilke, 1954 Golfo di Dragunara, 2-3 m; Bosa Marina, 2-3 m; Calasetta (the island of S. Antioco), 2-3 m; Santa Maria Navarrese, 5-6 m; Cala Liberotto, 3-4 m. Numerous individuals were extracted from fine to coarse sands at all localities. Chaetonotus neptuni is very closely related to C. atrox and C. dispar and generally lives in fine to medium sediments and in Amphyoxus sand. It has previously been reported in Tuscany, the Tuscan archipelago, Campania, on the island of Ischia and in Apulia. Genus Halichaetonotus Schrom, 1972 Halichaetonotus aculifer Gerlach, 1953 Porto Sardinia, littoral; Spiaggia Pelosa, 1-2 m; Fertilia, 1-2 m; Bosa Marina, 2-3 m; Masua, 2-3 m; Capo Turri (the island of S. Antioco), 1-2 m; Simius, 2-3 m; Piscina Rei, 2-3 m; La Caletta, 3-4 m. Halichaetonotus aculifer is a widespread species, abundant in all localities and especially common in fine sand both from the littoral and sublittoral zones. In Italy it has been recorded at numerous sites along the peninsular (Liguria, Tuscany, Latium, Campania, Lucania, Apulia, the Marches, Véneto and Friuli) and on insular coasts (the island of Ponza, the island of Ischia and Sicily). Halichaetonotus atlanticus Kisielewski, 1988 Simius, 2-3 m. Only one individual was found in medium, sublittoral sand. This uncommon species, first reported on the Atlantic coast of Brittany, has already been found in Italy in the Tyrrhenian Sea (Tuscany, Latium and Campania). Halichaetonotus clavicornis n. sp. (Figs 5, 6) Porto Sardinia, littoral. Diagnosis Small size Halichaetonotus, ^m, with a 13 um long furca. Small cephalion and pleuria. Two ventrolateral, club-shaped tentacles, 7-9 \im long, beside the mouth. Seventeen longitudinal rows (13 dorsal) of Fig. 4 - Chaetonotus inaequidentatus. Dorsal view of the head. Nomarski optics, x!200. Fig. 5 - Halichaetonotus clavicornis n. sp. A, dorsal view; B, dorsal scale; C, ventral view. Dotting mimics the locomotory ciliature.

11 282 M. BALSAMO, E. FREGNI, P. TONGIORGI 10.0 x 2.5 um (hydrofoil scales) run along each ventral ciliary band. Two parallel, unconnected ciliary bands define a median bare area. Only two pairs of urn long elliptical scales with short spines are present one behind the other at the posterior end. Several small, rounded and spined scales (2.9 urn) cover the ventral base of the each furcal appendage (Fig. 5C). The mouth ring, 6.5 um in diameter, is thick and armed and opens on the ventral side. The pharynx ranges from 23.2 to 29-0 urn in length and shows an anterior bulbar swelling with two cuticular rods. Some of the specimens observed were sexually mature, with one or two large oocytes. Spermatozoa were not observed. Fig. 6 - Halichaetonotus clavicornis n. sp. Ventral view of the head. Nomarski optics, xlooo. elliptical keeled scales. Two rounded scales with a strong spine at the dorsal posterior end. Two ventrolateral rows of hydrofoil scales per side. Two pairs of keeled scales with short spines at the ventral posterior end. Pharynx [xm long, with two cuticular rods. Description Small size species, urn in body length. Slightly trilobate head, urn wide, presenting a small cephalion and two pairs of very small pleuria. A ventral hypostomion was not observed. Four tufts of cephalic cilia, the anterior tufts consisting of 3-4 cilia, 5-0 um in length, and a single much longer one (20 urn), and the posterior tufts consisting of 7-8 cilia of 15.0 um. Two peculiar, um long, club-like tentacles are inserted ventrolaterally near the mouth ring (Figs 5C, 6). The neck measures um in width and the trunk urn at its central region and 13-0 um at the furcal base. The caudal furca is 13-0 urn long, 8.0 urn belonging to the adhesive tubes. The body is covered with 17 longitudinal rows of scales (13 dorsal). Each row is composed of embricated scales, which are elliptical on the head and the trunk, and rounded on the neck. Each scale shows a prominent longitudinal keel (Fig. 5B). The scales measure x 2.5 um on the head, 3.0 x 3-0 urn on the neck, and * um on the trunk. Two rounded, double-keeled scales are located at the dorsal posterior end each bearing a 8.0 um tactile bristle. Three keeled scales cover the intrafurcal edge: the central scale is elliptical, while the two lateral are rounded and provided with a short (3 um), strong spine protruding into the intrafurcal space (Fig. 5A). The scales of the two lateral rows are similar to those located dorsally. Two longitudinal rows of scales provided with characteristic, sickle-shaped cuticular expansions measuring Remarks The elliptical shape and the number of the dorsolateral scales make these specimens similar to Halichaetonotus balticus, H. schromi, H. riedli and H. decipiens. However, the first two species are much greater in size, and urn, respectively, and have only 9 longitudinal rows of scales. H. riedli lacks terminal dorsal spines and any scaled cuticular covering on the ventral field. H. decipiens matches the Sardinian specimens in the morphology of the dorsal and ventral posterior ends, but has hydrofoil scales of a different shape. All the known Halichaetonotus species lack cephalic tentacles, which are the peculiar feature of the Sardinian specimens, and it is for this reason that we assign them to a new taxon, for which we propose the name Halichaetonotus clavicornis. Ecology Quite abundant only in the littoral zone in medium sand. Derivatio nominis Composed word from the Latin «clava» and «cornus», referring to the club-like shape of the cephalic tentacles. Halichaetonotus genatus n. sp. (Figs 7, 8) Porto Sardinia, littoral; Castelsardo, 2-3 m; Marina di Gairo, 2-3; Cala Liberotto, littoral; La Caletta, 3-4 m. Diagnosis Small size Halichaetonotus, urn, with trilobate head and furca urn i n length. Fifteen (13 dorsal) longitudinal rows of emielliptical scales with a prominent keel prolonged into a spiny process. The keel of the lateral scales forms a hook-like expansion. A series of six keeled scales along the dorsal intrafurcal edge, the lateral ones larger and provided with a short, strong spine. One ventrolateral longitudinal row of hydrofoil

12 GASTROTRICHA FROM THE COASTS OF SARDINIA 283 Fig. 7 - Halichaetonotus genatus n. sp. A, dorsal view; B, dorsal scale; C, ventral view. Dotting mimics the locomotory ciliature. Fig. 8 - Halichaetonotus genatus n. sp. Habitus. Nomarski optics, x800. scales per side. Interciliary field bare. Two pairs of elliptical keeled and spined scales at the ventral posterior end Jim long pharynx with two cuticular rods. Description The body, um in length, is rather stout, with a slightly trilobate head, urn wide, a faint, xm neck constriction, a trunk of (xm maximum width, decreasing posteriorly to um, and a urn long furca. The head is covered with a dorsally extended cephalion, two pairs of pleuria and a small ventral hypostomion. Both epipleuria and hypopleuria are evident and protruding (Fig. 7A, C). Two tufts of tactile cilia, urn in length, arise at the cephalion sides. The body is wholly covered with scales arranged in 15 longitudinal rows (13 dorsal) each of scales. The dorsal rows come together on the neck and on the posterior region of the trunk (Fig. 8). The keeled scales are emielliptical, with a truncated posterior edge (Fig. 7B); their length decreases from the head, utn, to the neck, xm, increasing again to um on the trunk. The keel of the dorsal scales is prominent and extends into a spiny process (1.5 ^m), while that of the lateral scales is particularly raised forming a hook-like expansion. At the dorsal posterior end, two rounded, double-keeled scales bear two 8 xm tactile bristles. A series of six, oval, keeled scales occurs along the intrafurcal edge, the two external ones being greater in size (5 l^m) and bearing a strong simple (im spine protruding into the intrafurcal space. The urn long furca has very long ( um) adhesive tubes. Ventrolaterally, only one longitudinal row of hydrofoil scales runs along each ciliary band. The hydrofoil expansions are well developed, 10.0 x 5.0 \xm, and subtriangular in shape (Fig. 7C). The two parallel ciliary bands are separate and wider in the anterior body region. The interciliary field is bare with the exception of two pairs of elliptical keeled plates with short spines at the posterior end. The two anterior plates are larger than the posterior ones, 10.0 x 6.6 xm as opposed to 5.0 x 2.5 (xm. Three small, round, and keeled scales, 2.0 \im, with a short spine are arranged in a row on the ventral base of each furcal appendage. The mouth opening is narrow and apical. The pharynx, which is weakly enlarged at the two extremities, is p.m long. Two cuticular rods are visible within the anterior pharyngeal swelling. All the specimens observed were in parthenogenetic phase. Spermatozoa were not seen. Remarks, I Within the genus Halichaetonotus, only H. margaretae, H. paradoxus and'//, spinosus share with the Sardinian specimens the emielliptical dorsal scales with a short spine, the large hydrofoil expansions and the scale arrangement of the ventral posterior end. However, H. margaretae has fewer rows of scales, 11 vs 15, and scale covering on the interciliary field. H. paradoxus has dorsal scales provided with lamellar keels and a different arrangement of the scales at the dorsal posterior end. H. spinosus shows a strong terminal.spine protruding in the intrafurcal space. Moreover all these species have very small pleuria. Therefore, these specimens are assigned to a new species, named Halichaetonotus genatus.

13 284 M. BALSAMO, E. FREGNI, P. TONGIORGI Ecology Usually found in medium to coarse sediment from both littoral and sublittoral zones. Derivatio nominis Derived from the Latin «gena», cheek, referring to the impression given to the head by the pleuria. Halichaetonotus jucundus (d'hondt, 1971) (Fig. 9) Porto Sardinia, littoral; Piscina Rei, 2-3 m; Costa Rei, 1-2 m; Cala Liberotto, littoral, 3-4 m. The Sardinian specimens, collected from medium sand of both the littoral and sublittoral zones, were slightly smaller than those described by d'hondt (1971) and Mock (1979), vs urn in body length, and showed two additional, longitudinal rows of dorsal scales, 11 as opposed to 9 (7 in Mock, 1979). However, on the basis of morphological features, and in particular of the presence of the characteristic fan-like expansions of all the dorsal and lateral spines, their identification with H. jucundus is almost certain. These spines were well developed even on the head scales, which in the descriptions of this species are indicated as presenting only curved spines. Most of the specimens observed were in parthenogenetic phase. Spermatozoa were not seen. In Italy, H. jucundus has already been recorded in medium, sublittoral sediments along the Tyrrhenian coast of Tuscany and Campania and on the Adriatic coast of Apulia and Friuli. Halichaetonotus margaretae Hummon, Balsamo & Todaro, 1992 Bosa Marina, 2-3 m. One specimen was extracted from medium sand. The geographical range of H. margaretae is restricted to the Italian seas, where to date it has been recorded in fine to coarse sediments in Liguria, Tuscany, the Tuscan archipelago, Campania, on the island of Ischia, in Apulia and Friuli. Halichaetonotus spinosus Mock, 1979 Porto Sardinia, littoral; Baia di Santa Reparata, 1-2 m. A few individuals were present in medium and very coarse sands of the littoral and sublittoral zones. Their metric parameters matched those of other Italian specimens, but were slightly smaller than those from the North Sea (Mock, 1979). The area of distribution of H. spinosus includes Liguria, Tuscany, the Tuscan archipelago, Latium, Campania, Apulia, Sicily, Véneto and Friuli, and it has usually been collected from fine sediments. Halichaetonotus thalassopais Hummon, Balsamo & Todaro, 1992 Porto Sardinia, littoral; Fertilia, 2-3 m. Very few specimens were found in medium sand, and all featured dorsal scales slightly longer than those reported in the original description: vs um. The species was described in the Tuscan archipelago and is now known in Liguria, Tuscany, Latium and Campania, on the island of Ischia, and in Sicily, Apulia and the Marches. It colonizes both littoral and sublittoral fine and medium sands. Genus Heterolepidoderma Remane, 1926 Heterolepidoderma loricatum Schrom, 1972 Marina di Gairo, 2-3 m. Unlike reports from other Italian localities, the two Sardinian specimens were collected from very coarse sand. The species is widely present in Italy along the peninsular (Liguria, Tuscany, Latium, Campania, Apulia, the Marches and Véneto) and island (the Tuscan archipelago, the island of Ponza, the island of Ischia, Sicily) coasts. Fig. 9 - Halichaetonotus jucundus. Habitus. Nomarski optics, x700. Family XENOTRICHULIDAE Remane, I927 Genus Draculiciteria Hummon, 1974 Draculiciteria tesselata Renaud-Mornant, 1968 Capo Turri (the island of S. Antioco), 2-3 m; Simius, 2-3 m; Cala Liberotto, 3-4 m; La Caletta, 3-4 m.

14 GASTROTRICHA FROM THE COASTS OF SARDINIA 285 Some specimens were collected from fine and medium sands of the sublittoral zone. Draculiciteria tesselata is known in fine sediments of the Tyrrhenian (Tuscany, Latium, the island of Ponza, Campania and the island of Ischia) and Adriatic (Apulia, the Marches, Véneto and Friuli) coasts. Genus Heteroxenotrichula Wilke, 1954 Heteroxenotrichula squamosa Wilke, 1954 Baia di Santa Reparata, 1-2 m; Torre Corsari, 2-3 m. Very few individuals were observed in coarse sand. The species is common and often abundant in fine and medium sand. In Italy, H. squamosa has been reported in Liguria, Tuscany (coast and archipelago), Latium, Campania, on the island of Ischia, in Sicily, on the Ionian coast of Calabria and Lucania and in Apulia. Heteroxenotrichula arcassonensis Ruppert, 1979 Baia di Santa Reparata, 1-2 m; Castelsardo, 2-3 m; Piscina Rei, 2-3 m. A few specimens were found in medium and very coarse sublittoral sand. Although some metric parameters slightly exceeded those reported in the literature (TL vs urn, FuL vs 48 ^m), the morphology of the Sardinian animals substantially agreed with that of H. arcassonensis, even in the presence of two evident openings dorsal to the X-cells. It should be noted that three of the specimens observed showed two short ( ^m) cuticular tubes, inserted dorsolaterally on the head at the height of the cephalic tentacles. This is the first record in the Mediterranean of this species, previously known on the French Atlantic coast, in fine to coarse, clean sediments (Kisielewski, 1988). Genus Xenotrichula Remane, 1927 Xenotrichula intermedia Remane, 1927 Golfo di Dragunara, 2-3 m; Fertilia, 2-3 m; Simius. 2-3 m; Cala Liberotto, littoral. A large number of specimens was extracted from medium sands sampled in littoral and sublittoral zones. Xenotrichula intermedia is a cosmopolite species recorded in numerous localities even along the Italian coastline, in the Tuscan archipelago and in Sicily. Xenotrichula punctata Wilke, 1954 Calasetta (the island of S. Antioco), 2-3 m; Capo Turri (the island of S. Antioco), 1-2 m; Cala Liberotto, 3-4 m; La Caletta, 3-4 m. All the Sardinia specimens were found in fine and medium sands. In Italy, the species has been recorded in Tuscany, Campania, on the island of Ischia, in Apulia and in Friuli. DISCUSSION The marine Gastrotrich fauna from Sardinia is rich and varied, and uniformly distributed along the coast (Tables I, II). The biodiversity in each locality varies, the number of species ranging from 1 to 15, with a peak of 22 species at Cala Liberotto. Nearly half of the species found (43%) are widely distributed, having been recorded in more than one site. Among the species collected from a single locality, the finding of Megadasys minor, Chaetonotus inaequidentatus and Heteroxenotrichula arcassonensis are especially interesting, since they were previously known only in the English Channel and on the Atlantic coast of France. Megadasys minor was found on the island of Caprera in very fine sand with mud and organic detritus, confirming that, unlike most marine gastrotrichs, species of this genus show a clear preference for sediments rich in organic matter (Fenchel & Riedl, 1970; Boaden, 1974; Kisielewski, 1987). The distribution of Chaetonotus inaequidentatus and two other unidentified taxa (Mesodasys sp. and Platydasys sp.) is restricted to the south-western coast of the island. This may be related to the direction of the sea currents, which in this part of the Mediterranean move anti-clockwise from Sardinia towards the French and Spanish coasts, not touching the Italian peninsula. The faunistic richness of Cala Liberotto, the only Sardinian locality to be previously sampled (Todaro et al., 1988) now differs considerably from the past, when only two species were reported (Tetranchyroderma sardum and Xenotrichula pygmaea). Indeed, we found 22 species at this site, but neither of the two collected five years before. The overall number of the species collected in Sardinia, 55 from 22 sites, is close to that for the facing Tyrrhenian coast of Tuscany and Latium, 51 from 22 sites. Sampling along the peninsular coast has been repeated many times, thus increasing the number of recordings and the number of species found. In contrast, each Sardinian locality was sampled only once, thus demonstrating the great richness and variety of the gastrotrich fauna of the island. The comparison with the faunistic situation of the minor islands of the Tuscan and Latium archipelagos (Balsamo et al., 1992; Hummon et al., 1992, 1993; Todaro, 1992; Todaro et al, 1992) confirms the interest of the insular sediments. Many more species are found than at peninsular ones, often including specimens new to science or to Italian fauna. It is worth noting that the gastrotrich fauna of the coast of Sicily, the other major Italian island, comprises only 42 species (25 macrodasyids and 17 chaetonotids) from 21 sites (Todaro & Balsamo, 1990; Balsamo, Fregni and Tongiorgi, unpublished data). The greater biodiversity of the Sardinian fauna is probably related both to the great

15 286 M. BALSAMO, E. FREGNI, P. TONGIORGI variety of the coastal environments, which favours the settlement of differently structured gastrotrich communities, and to the notable variations in grain size of sediments, as compared to the greater uniformity of Sicilian coastal sands. Most species found in Sardinia (81.3%) have also been recorded on the peninsular coasts and the minor Tyrrhenian islands. The remarkable similarity in the composition of Italian gastrotrich communities which are geographically far apart confirms the broad distribution of many marine species. A study of possible correlations between the gastrotrich fauna and various physical and chemical factors of the habitat at sampling time (sea condition, water temperature and salinity, depth, chemical composition and grain size of the sand, amount of organic matter) was carried out. Depth and grain size of the sediment, as well as the condition of the sea, exert a clear influence on the number of species and records. It is a fact that when the sea is rough, the number of the species collected decreases sharply. As observed in previous research, faunistic richness increases with depth. Littoral samples collected along the waterline are usually poor or even completely lacking in gastrotrichs. However, a qualitative difference between littoral and sublittoral sediments must be stressed, since several species were found in the littoral but not in the sublittoral zone of the same site. Gastrotrichs are present in sands of very different grain size, ranging from fine to very coarse, even if the highest mean number of species and records is in coarse and very coarse sand. Contrary to the observations by Evans et al., (1993), the multiple regression analysis of the grain size parameters indicates a significant correlation between the number of species and the parameters studied (F = 2.70; P < 0.01). As Hummon (1969) has already noted, the sorting coefficient (a v ) appears especially significant (F = 8.00; P < 0.01), indicating the level of heterogeneity of the sediment. The highest mean number of species and records occurs in poorly selected, heterogeneous sands. In all the samples with a significant amount of silt, such as Capo Spartivento (5.95%), the island of Caprera (3.40%) and the gulf of Dragunara (2.61%), a lower number of species and individuals were observed. This is certainly related to the smaller interstitial spaces and the consequent poorer oxygénation of the deeper sediment layers. The amount of organic matter was generally very scant in all the samples ( %), meaning that a correlation with the gastrotrich fauna cannot be calculated. On the other hand, data in the literature show that very few gastrotrich species are able to colonize habitats which are anoxic because rich in organic matter (Fenchel & Riedl, 1970; Reise & Ax, 1979, 1980; Boaden, 1974, 1977). The finding of just the single species Megadasys minor, in the only site characterized by abundant organic matter (Caprera) would appear to confirm this point. REFERENCES Balsamo M., Fregni E., Tongiorgi P., Marine and freshwater Gastrotricha from the island of Montecristo (Tuscan archipelago, Italy), with the description of new species. Boll. Zoll., 61: Balsamo M., Todaro M. A., Tongiorgi P., Marine gastrotrichs from the Tuscan archipelago (Tyrrhenian Sea). II. Chaetonotida, with description of three new species. Boll. Zool., 59: Boaden P. J. S., Three new thiobiotic Gastrotricha. Cah. Biol. mar., 11: Boaden P. J. S., Thiobiotic fact and fancies (Aspects of the distribution and evolution of anaerobic meiofauna). Mikrofauna Meeresbodens, 61: Evans W. D., Todaro M. A., Hummon W. D., Eutrophication and Gastrotrich diversity in the Northern Adriatic Sea. Mar. Pollut. Bull., 26: Fenchel T. M., Riedl J. M., The sulphide system: a new biotic community underneath the oxidised layer of marine sand bottom. Mar. Biol., 7: Gerlach S. A., Gastrotrichen aus dem Küstengrundwasser des Mittelmeeres. Zool. Anz., 150: Giere O., Eleftheriou A., Murison D. J., Abiotic factors. In: R. Higgins & H. Thiel (eds), Introduction to the study of meiofauna. Smithsonian Institution Press, Washington, pp d'hondt J. L., Documents sur les gastrotriches dulcicoles des eaux françaises. Ann. Lirnnol., 3: Hummon W. D., Distributional ecology of marine interstitial Gastrotricha from Woods Hole, Massachusetts, with taxonomic comments on previously described species. Unpublished Ph.D. Dissertation, University of Massachusetts. Hummon W. D., Balsamo M., Todaro M. A., Italian marine Gastrotricha. I. Six new and one redescribed species of Chaetonotida. Boll. Zool., 59: Hummon W. D., Todaro M. A., Tongiorgi P., Italian marine Gastrotricha: II. One new genus and ten new species of Macrodasyida. Boll. Zool., 60: Kisielewski J., New records of marine Gastrotricha from the coasts of Manche and Atlantic. I. Macrodasyida, with descriptions of seven new species. Bull. Mus. natl. Hist. nat., Paris, 4: Kisielewski J., New records of marine Gastrotricha from the French coast of Manche and Atlantic. II. Chaetonotida, with descriptions of four new species. Cah. Biol. mar., 29: Luporini P., Magagnini G., Tongiorgi P., Contribution à la connaissance des Gastrotriches des côtes de la Toscane. Cah. Biol. mar., 12: Luporini P., Magagnini G., Tongiorgi P., Gastrotrichi Macrodasioidei delle coste della Toscana. Pubbl. Staz. zool., Napoli, 38 (1970): Mock H., Chaetonotoidea (Gastrotricha) der Nordseeinsel Sylt. Mikrofauna Meeresbodens, 78: Reise K., Ax P., A meiofaunal «thiobios» limited to the anaerobic sulfide system of marine sand does not exist. Mar. Biol., 54: Reise K., Ax. P., Statement on the thiobios-hypothesis. Mar. Biol., 58: Seward-Thompson B. L., Hails J. R., An appraisal of the computation of statistical parameters in grain size analysis. Sedimentology, 20: Todaro M. A., Contribution to the study of the Mediterranean meiofauna Gastrotricha from the island of Ponza, Italy. Boll. Zool., 59: Todaro M. A., Balsamo M., First observations on marine gastrotrichs from Sicily. Proc. Congress on the Zoogeography and Ecology of Greece and adjacent regions, Iraklion (Crete). Todaro M. A., Balsamo M., Tongiorgi P., Marine gastrotrichs from the Tuscan archipelago (Tyrrhenian Sea). I. Macrodasyida, with description of three new species. Boll. Zool., 59: Todaro M. A., Tongiorgi P., Balsamo M., Tetranchyroderma sardum, a new species of the family Thaumastodermatidae (Gastrotricha, Macrodasyida). Boll. Zool., 55: