Brachidontes Pharaonis Research Articles

The impact of climate change on mediterranean intertidal communities: losses in coastal ecosystem integrity and services

As has been shown for other ecosystems, the ecological and socio-economic impacts of climate change on Mediterranean intertidal habitats are highly variable in space and time. We conducted field and laboratory mea- surements of cellular, ecophysiological and behavioural responses of selected intertidal invertebrates (mussels, gastropods and sponges) and completed a literature review to determine what is known of socio-economic consequences of these biological changes. Results suggest significant gaps in our knowledge that may impede a complete understanding of likely impacts (physical, bio- logical and socio-economic) and that sufficient data for such an analysis are available only for mussels. Application of ecological models for native mussels Mytilaster minimus and invasive Brachidontes pharaonis bivalves indicates that the current distribution of these species is linked to the availability of food and local temperature. Choosing Israel as a case study, the study focused on the identification of ecosystem services and goods provided by the Mediterranean rocky intertidal and on the assessment of conservation approaches. Intertidal systems were poorly represented in the socio-economic literature, and there was low awareness of the value of these ecosystems among stakeholders. Subsequently, conservation efforts for intertidal communities were minimal. While climate change will very likely continue

Biological aspects and ecological effects of a bed of the invasive non-indigenous mussel Brachidontes pharaonis (Fischer P., 1870) in Malta

No mussel beds were known to occur in the Maltese Islands previous to 2009, when a single bed of the Lessepsian immigrant Brachidontes pharaonis, first recorded from the islands in 1970, was discovered in Birzebbugia Bay. The population structure of B. pharaonis was investigated to assess its potential to spread and colonise new shores, while the biotic community at the mussel bed was compared to that present on uncolonised substratum to determine the effects of mussel bed establishment on the associated biota. Results indicate a lower species richness and slightly different community structure with greater small-scale heterogeneity at the mussel bed site compared to the adjacent rocky shore where mussels are present but where there is no bed formation. The B. pharaonis population had a peak density of 16550 ± 2051 ind.m-2 within the mussel bed and included recent recruits. These data suggest that the B. pharaonis population has the potential to expand. Establishment of extensive beds by this invasive mussel could change the structure of native rocky shore assemblages around the Maltese Islands and elsewhere in the Mediterranean.

Branching out: mapping the spatial expansion of the lessepsian invader mytilid Brachidontes pharaonis around the Maltese Islands

One of the several lessepsian species colonizing areas of the Mediterranean is Brachidontes pharaonis, a bivalve with the ability to form dense mytilid mats over a range of different mediolittoral substrata. Since its initial observation from the Maltese Islands in the early 1970s, the species has consolidated its presence all over the archipelago. Close examination of the entire length of the Maltese shoreline was conducted to collect quantitative and qualitative data on the mytilid and on dominant accompanying macrofaunal and macrofloral species, in what represents the first comprehensive mapping of an allochthonous species within an island territory. Brachidontes pharaonis was found to have colonized most of the northern and eastern coastal stretches of the island of Malta, preferring limestone substrata in inlets with limited wave exposure and affected by high marine concentrations of hydrocarbons and other pollutants, where it reached individual abundances exceeding 1000 individuals per square metre.

Settlement of the alien mollusc Brachidontes pharaonis in a Mediterranean industrial plant: Bioassays for antifouling treatment optimization and management

In this work, we investigated the efficacy of three new biocides (77351, 73532, 73503 – NALCO®) as specific antifouling products against adult organisms of the bivalve Brachidontes pharaonis (Fischer P., 1870), a Lessepsian species introduced in the Mediterranean Sea by sea transport (ballast water), and which has recently shown invasive behaviour in an industrial plant in Southern Italy (Sicily). These biocides were tested to verify their efficacy, as well as their environmental compatibility at discharge point, using the crustacean belonging to the genus Artemia (Leach, 1819) as model organism, according to Government Decree (D. Lgs) No. 152/06. Biocides were also tested using alternative crustaceans, Amphibalanus amphitrite (Darwin, 1854), and Tigriopus fulvus (Fischer, 1860), in order to check whether their introduction as model species in the national regulation could affect discharge limit concentrations (DLC) due to their different sensitivity, with likely economic and technical repercussions in the industrial water treatment sector.

Heart beat rate adaptations to varying salinity of two intertidal Mediterranean bivalves: The invasive Brachidontes pharaonis and the native Mytilaster minimus

Changes in heart beat rates (HBR) of Brachidontes pharaonis (an invasive Lessepsian species) and Mytilaster minimus (a native Mediterranean species) in response to changes in salinity values from brackish (20) to extreme hyper-saline (75) were investigated both in situ and in the laboratory. The two species displayed different responses to varying salinity, with clear differences in HBR observed between groups investigated at different salinities and between groups originating from different environments. The native species, adapted to narrow salinity changes as those observed in the superficial waters of the Mediterranean Sea, showed signs of stress at salinities slightly above 37 (in the range 37–45). On the other hand, the invasive species displayed clear signs of stress only at salinities over 45 and exhibited heart activity even under hyper-saline conditions (i.e. salinity = 75). These results indicate that the Lessepsian species has the potential to invade most of the transitional environments across the entire Mediterranean basin. We therefore stress the need of including Brachidontes pharaonis in all coastal monitoring programmes assessing the actual and potential spreading of alien species in the Mediterranean region.

Inventory of alien marine species of Cyprus (2009)

An updated inventory of alien marine species from coastal and offshore waters of Cyprus is presented. Records were compiled based on the existing scientific and grey literature, including HCMR database of Mediterranean alien species, technical reports, scientific congresses, academic dissertations, and websites, as well as on unpublished/personal observations. The listed species were classified in one of five categories: established, invasive, casual, cryptogenic, and questionable. The mode of introduction and the year of first sighting were also reported for each species. Eight new records based on personal observations of the authors were reported (Chondria coerulescens, Neosiphonia sphaerocarpa, Enchelycore anatina, Lagocephalus spadiceus, Lagocephalus suezensis, Scomberomorus commerson, Sillago sihama, and Sphoeroides pachygaster). Nine species, previously reported as aliens in Cypriot waters, were excluded from the inventory for various reasons. Ten established species were characterized as invasive (Caulerpa racemosa var. cylindracea, Cerithium scabridum, Strombus persicus, Trochus erythraeus, Brachidontes pharaonis, Pinctada radiata, Fistularia commersonii, Lagocephalus sceleratus, Siganus luridus, and Siganus rivulatus) as they have a substantial impact on biodiversity and/or local economy. The impact of alien marine species in Cyprus is expected to grow in the close future, and further effort directed towards recording alien invasions and their impact will be needed.

New distributional and ecological data of some marine alien molluscs along the southern Italian coasts

A large number of Red Sea species are colonizing the eastern Mediterranean Sea after the opening of the sea-level Suez Canal in 1869, mainly following the Levantine and Anatolian coasts and then spreading westwards, at least in part, by shipping transport of larvae, juveniles, or adult specimens. Two of them are Cerithium scabridum and Fulvia fragilis , well established along the Italian coasts, where new large and stable populations have formed. Some other species, such as Anadara demiri , were accidentally introduced through shipping in our seas and have found good conditions to survive and develop. New distributional and ecological data about these alien molluscs are given and all the species found in association are listed to improve understanding of their living biocoenosis. The presence of a further lessepsian mollusc and of an intentionally introduced species, Brachidontes pharaonis and Ruditapes philippinarum , was also confirmed respectively from Vibo Valentia harbour and from the Gulf of Naples and the Gulf of Taranto. The nomenclature used is based on the CLEMAM Database (last research on 9 January 2008).

Effect of salinity and temperature on feeding physiology and scope for growth of an invasive species ( Brachidontes pharaonis - MOLLUSCA: BIVALVIA) within the Mediterranean sea

The Indo-Pacific mytilid Brachidontes pharaonis (Bivalvia, Fischer 1870) offers an excellent model for the study of “Lessepsian migration” and the successive colonization at new Mediterranean locations. This species in out competing indigenous bivalves is particularly well adapted to Mediterranean conditions and this is likely due to biological characteristics and physio-ecological plasticity. In the present paper, we report on clearance rate (CR), respiration rate (RR) and Scope for Growth (SFG) of B. pharaonis collected from a Western Sicilian pond (Southern Tyrrhenian, MED). Physiological variables were determined in response to a range of temperatures from 11 ° to 20 °C and a broad range of salinities from 15 to 60 psu. Salinity and temperature had a significant influence on CR of B. pharaonis as there was a general reduction in CR with a decline in temperature from 20 °C to 11 °C and declining salinity from 37 to 15 psu. RR showed a general temperature dependent relationship with highest RR at 20 °C. SFG showed negative values at lowest salinity of 15 psu at all tested temperatures. SFG values were generally the highest at 45 psu (at 11 °C and 20 °C), although SFG showed a maximum at 37 psu at 15 °C. SFG values were positive over the broadest range of salinities (25 to 60 psu) at 20 °C. The plasticity of the physiological rates demonstrated that B. pharaonis had the capacity to maintain positive SFG and tolerate a wide range of temperature/salinity conditions. Possible implications of high physiological plasticity of B. pharaonis in competing against indigenous bivalves are discussed.

Controlling factors of recent clastic coastal sediments (Viransehir, Mersin bay, S Turkey)

The Plio-Quaternary conglomeratic sets within the marine environment of the Viransehir coast (W Mersin, S Turkey) are responsible for the evolution of sandy and gravely beaches due to their control on various factors such as sea floor irregularity, wave energy, and organic activity. The conglomeratic sets close to the shoreline (50–150 cm) act as wave breakers, creating hard substratum and high energy, well-oxygenated environment for organisms like Patella sp., Phoronida worms and Brachidontes pharaonis (Fischer P. 1870). The boring activities of these organisms have disintegrated the sandy matrix of these sets. Finer-grained matrix sediments have been transported to the interset and open sea, while cobble–pebbles have been carried landwards and have created imbricated gravely beach deposits without matrix. Sandy beach is evolving where the conglomeratic sets away from the shoreline (5.0–10.0 m). In this example, sets form a bar; causing fivefold division as backshore, berm, surf zone, bar and offshore from land to sea. Poorly sorted, cobbles-pebbles cobbles and pebbles are found associated with the high-energy environments of bars, whilst well-sorted sands are observed in low energetic environments on shore. The sets and recent shell fragments are the main sources of coastal sediments in Viransehir. However, the amount of shell fragments decrease towards the active river mouth. This is due to sediment and fresh water influx from the river causing deteriorated temperature, salinity and light penetration of the marine environment resulting in less organic diversity.

A new lessepsian species in the western Mediterranean ( Brachidontes pharaonis Bivalvia: Mytilidae): density, resource allocation and biomass

The present study reports on population dynamics and growth performance relative to a lesser known exotic invasive species ( Brachidontes pharaonis ) inhabiting the southern Mediterranean. The study was carried out in western Sicily, where B. pharaonis is present on both the submerged and emerged surfaces of a hyperhaline saltpan. Individuals were scraped, counted and measured for shell length, total weight, somatic, gonadic and shell biomass. Brachidontes pharaonis intensively colonized all hard substrates of the saltpan with annual average densities of 375 ± 293 ind. 400 cm −2 with density peaks in autumn as a function of habitat. The occurrence of juveniles was different for mediolittoral and infralittoral populations as was mean size, spawning periods and annual organic matter biomass. Organic matter allocated to the shells represented 56.4% (of the total), gonad allocation was 7.3%, while somatic allocation averaged 36.3% for both populations. Brachidontes pharaonis reached high individual density, rare among temperate members of the genus Mytilus in Mediterranean and European waters, but common in tropical dense mussel beds. Considering its invasive potential and the recent warming trend of the Mediterranean, in the future B. pharaonis may actively invade more habitats, threatening indigenous bivalve species which may be unable to compete with B. pharaonis in terms of reproductive effort and density.

Crustacea Decapoda associated with Brachidontes pharaonis (P. Fischer, 1870) (Mollusca, Bivalvia) beds from the Levantine coasts of Turkey

[The spatial distribution of the decapod crustacean fauna associated with Brachidontes pharaonis (Mollusca, Bivalvia) beds from the Levantine coasts of Turkey was studied in September 2005. Triplicate samples were collected by means of a quadrate sampler covering 400 cm2 at nine intertidal stations located between Iskenderun Bay and Antalya Bay. A total of 13 species, represented by 61 individuals was identified. Among these, Pachygrapsus marmoratus was the most dominant species represented with 19 individuals. P. marmoratus and Pilumnus hirtellus were the most frequent decapod species on the mussel beds with 25.9% occurrence. La repartition spatiale de la faune de crustaces decapodes associee aux moulieres de Brachidontes pharaonis (Mollusca, Bivalvia) des cotes levantines de Turquie a ete etudiee en septembre 2005. Des echantillons en triple ont ete collectes au moyen d'un echantillonneur carre couvrant 400 cm2 dans neuf stations intertidales situees entre la baie d'Iskenderun et la baie d'Antalya. Un total de treize especes, represente par 61 individus a ete identifie. Parmi ceux-ci, Pachygrapsus marmoratus etait l'espece dominante avec 19 individus. P. marmoratus et Pilumnus hirtellus etaient les especes de decapodes les plus souvent presentes dans les moulieres avec une frequence de 25,9%., The spatial distribution of the decapod crustacean fauna associated with Brachidontes pharaonis (Mollusca, Bivalvia) beds from the Levantine coasts of Turkey was studied in September 2005. Triplicate samples were collected by means of a quadrate sampler covering 400 cm2 at nine intertidal stations located between Iskenderun Bay and Antalya Bay. A total of 13 species, represented by 61 individuals was identified. Among these, Pachygrapsus marmoratus was the most dominant species represented with 19 individuals. P. marmoratus and Pilumnus hirtellus were the most frequent decapod species on the mussel beds with 25.9% occurrence. La repartition spatiale de la faune de crustaces decapodes associee aux moulieres de Brachidontes pharaonis (Mollusca, Bivalvia) des cotes levantines de Turquie a ete etudiee en septembre 2005. Des echantillons en triple ont ete collectes au moyen d'un echantillonneur carre couvrant 400 cm2 dans neuf stations intertidales situees entre la baie d'Iskenderun et la baie d'Antalya. Un total de treize especes, represente par 61 individus a ete identifie. Parmi ceux-ci, Pachygrapsus marmoratus etait l'espece dominante avec 19 individus. P. marmoratus et Pilumnus hirtellus etaient les especes de decapodes les plus souvent presentes dans les moulieres avec une frequence de 25,9%.]

A new record of the invasive Red Sea mussel Brachidontes pharaonis (Fischer P., 1870) (Bivalvia: Mytilidae) from the Turkish coasts

A specimen of the invasive mytilid mussel Brachidontes pharaonis (Fischer P., 1870) was collected on 18 April 2007 in Karaburun Peninsula, Izmir. This record represents the northernmost occurrence of the species along the Aegean coast of Turkey. Information on the distribution of the species along the Mediterranean coast of Turkey is provided.

Biodegradation effects over different types of coastal rocks

Modern coastal areas have natural and transported rocks (armourstone) on which various types of organisms live. Burrowing, boring and feeding by these organisms can destroy or modify the coastal rocks and hence change the coastal morphology. Two rock types and three dominant types of organisms have been studied in Mersin Bay, Eastern Mediterranean of southern Turkey. In this study area, Plio-Quaternary conglomerates and variously aged limestone armourplates have been affected by Phoronida worms, bivalve Brachidontes pharaonis (Fischer P. 1870) and the limpet Patella sp. Phoronida colonies were found covering the hard substratum as a mat and form tubular endolithes of 35.0 mm depth and 1.5 mm diameter, whilst Brachidontes pharaonis (Fischer P. 1870) form 44 mm deep vase-shaped gastrochaenolites. The bioerosive activity of Limpet Patella sp., found intertidal and within the spray zone, cannot be significantly observed on the rocks over short time periods. The soft sandy matrix of the conglomerates present were found to disintegrate by bioerosional processes, with the released gravels being transported and deposited onto the beach. Within the armourstone limestone blocks, a maximum of 44.0 mm deep holes developed after 50–60 years. However, these biological activities do not threaten the stability of the blocks due to their hard and homogeneous internal structure. Furthermore, the organism colonies that cover these rocks as a strong mat (maximum 29.0 mm) act to protect their surfaces from further biological attack and wave action.

A mitochondrial phylogeography of Brachidontes variabilis (Bivalvia: Mytilidae) reveals three cryptic species

This study examined genetic variation across the range of Brachidontes variabilis to produce a molecular phylogeography. Neighbour joining (NJ), minimum evolution (ME) and maximum parsimony (MP) trees based on partial mitochondrial DNA sequences of 16S-rDNA and cytochrome oxidase (COI) genes revealed three monophyletic clades: (1) Brachidontes pharaonis s.l. from the Mediterranean Sea and the Red Sea; (2) B. variabilis from the Indian Ocean; (3) B. variabilis from the western Pacific Ocean. Although the three clades have never been differentiated by malacologists employing conventional morphological keys, they should be ascribed to the taxonomic rank of species. The nucleotide divergences between Brachidontes lineages (between 10.3% and 23.2%) were substantially higher than the divergence between congeneric Mytilus species (2.3–6.7%) and corresponded to interspecific divergences found in other bivalvia, indicating that they should be considered three different species. Analysis of the 16S-rDNA sequences revealed heteroplasmy, indicating dual uniparental inheritance (DUI) of mtDNA in the species of Brachidontes collected in the Indian Ocean, but not in the species in the Pacific nor in the species in the Red Sea and the Mediterranean Sea. When we employed the conventional estimate of the rate of mitochondrial sequence divergence (2% per million years), the divergence times for the three monophyletic lineages were 6–11 Myr for the Indian Ocean and Pacific Ocean Brachidontes sp. and 6.5–9 Myr for the Red Sea and Indian Ocean Brachidontes sp. Thus, these species diverged from one another during the Miocene (23.8–5.3 Myr). We infer that a common ancestor of the three Brachidontes species probably had an Indo-Pacific distribution and that vicariance events, linked to Pleistocene glaciations first and then to the opening of the Red Sea, produced three monophyletic lineages.

Seasonal Variation in Copper, Zinc, Chromium, Lead and Cadmium Levels in Hepatopancreas, Gill and Muscle Tissues of the Mussel Brachidontes pharaonis Fischer, Collected along the Mersin Coast, Turkey

Levels of copper, zinc, cadmium, chromium and lead were determined in the gill, hepatopancreas and muscle tissues of Brachidontes pharaonis collected from the Mersin coasts of Turkey. Water and animal samples were collected monthly from the four stations between June 2002 and May 2003 for metal determinations. Metal levels in water samples of Mersin coasts were higher than those measured in other parts of Turkish coasts. Levels of metals in soft tissues of B. pharaonis showed an increase towards autumn and winter months which exceeded the levels that are recommended by Turkish Standart Institute's food codex.

Population structure of Brachidontes pharaonis (P. Fisher, 1870) (Bivalvia, Mytilidae) in the Mediterranean Sea, and evolution of a novel mtDNA polymorphism

Brachidontes pharaonis (Fisher P, 1870) is an Indo-Pacific mussel that has colonized the Mediterranean Sea via the Suez Canal. Mussels may have migrated by natural dispersal of pelagic larvae, or they may have been transported on the hulls of ships, or in ballast water, or by some combination of these. Mitochondrial COI sequences (618 bp) from 101 mussels from six localities in the central and eastern Mediterranean Sea and from one site in the Red Sea were used to describe population structure. Analysis of molecular variance indicated that frequencies differed among populations, and that 92% of the variation resided within populations. The majority of haplotypes were private alleles. No simple pattern of longitudinal variation was detected for haplotype frequencies, haplotype diversity, or nucleotide diversity. A variety of tree-building algorithms (NJ, MP, ME) gave consistent results, showing two sister groups. One clade had a leucine (L-form) and the other one a methionine (M-form) at the 30th amino acid. These sympatric forms were detected within all localities and they had similar frequencies in males and females. The M- and L-form were separated by a 7.3% sequence divergence, indicating that this is an ancient polymorphism. Closely related species of mussels had exclusively the L-form, so we infer that the M-form evolved from the L-form lineage of B. pharaonis, probably in the northern portion of the Red Sea. Neutrality tests detected an excess of rare mutations, a pattern of variation expected in expanding populations. Patterns of variation detected by Tajima’s D suggest that some form of balancing selection has maintained this polymorphism.

Cloning and expression of MDR transporters from marine bivalves, and their potential use in biomonitoring

Multidrug resistance transporters (MDRs) are excellent candidates for molecular-level biomonitoring - they function in exporting xenobiotic compounds and their expression is inducible. However, currently available MDR sequence information from aquatic invertebrates is partial and mostly biased towards the conserved ATPase domain. In the present study, two genes belonging to the MDR/TAP (ABCB) family were cloned and characterized from the bivalve Brachidontes pharaonis, which thrives in rocky environments along the Israeli Mediterranean coast. One of these is a complete sequence of a 'half'ABCB, probably belonging to the ABCB10 subfamily, while the second is a 'full'ABCB1 transporter. A quantitative RT-PCR protocol for biomonitoring was tested in laboratory experiments. Bivalves exposed to diesel showed significant increase in B1 expression levels, while the expression of B10 was suppressed. These results suggest that B. pharaonis features an MDR1 homologue that is induced by pollution and may serve as a sentinel organism for routine biomonitoring programs. However, our findings also exemplify that not all MDRs are equally suitable for this purpose and sequence information must be expanded beyond the ATPase domain for correct classification of cloned genes.

Organometallic complexes with biological molecules. XVIII. Alkyltin(IV) cephalexinate complexes: synthesis, solid state and solution phase investigations

Dialkyltin(IV) and trialkyltin(IV) complexes of the deacetoxycephalo-sporin-antibiotic cephalexin [7-( d-2-amino-2-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid] (Hceph) have been synthesized and investigated both in solid and solution phase. Analytical and thermogravimetric data supported the general formula Alk 2SnOHceph · H 2O and Alk 3Snceph · H 2O (Alk=Me, n-Bu), while structural information has been gained by FT-IR, 119Sn Mössbauer and 1H, 13C, 119Sn NMR data. In particular, IR results suggested polymeric structures both for Alk 2SnOHceph · H 2O and Alk 3Snceph · H 2O. Moreover, cephalexin appears to behave as monoanionic tridentate ligand coordinating the tin(IV) atom through ester-type carboxylate, as well as through β-lactam carbonyl oxygen atoms and the amino nitrogen donor atoms in Alk 2SnOHceph · H 2O complexes. On the basis of 119Sn Mössbauer spectroscopy it could be inferred that tin(IV) was hexacoordinated in such complexes in the solid state, showing skew trapezoidal configuration. As far as Alk 3Sn(IV)ceph · H 2O derivatives are concerned, cephalexin coordinated the Alk 3Sn moiety through the carboxylate acting as a bridging bidentate monoanionic group. Again, 119Sn Mössbauer spectroscopy led us to propose a trigonal configuration around the tin(IV) atom, with R 3Sn equatorial disposition and bridging carboxylate oxygen atoms in the axial positions. The nature of the complexes in solution state was investigated by using 1H, 13C and 119Sn NMR spectroscopy. Finally, the cytotoxic activity of organotin(IV) cephalexinate derivatives has been tested using two different chromosome-staining techniques Giemsa and CMA 3, towards spermatocyte chromosomes of the mussel Brachidontes pharaonis (Mollusca: Bivalvia). Colchicinized-like mitoses (c-mitoses) on slides obtained from animals exposed to organotin(IV) cephalexinate compounds, demonstrated the high mitotic spindle-inhibiting potentiality of these chemicals. Moreover, structural damages such as ‘chromosome achromatic lesions’, ‘chromosome breakages’ and ‘chromosome fragments’ have been identified through a comparative analysis of spermatocyte chromosomes from untreated specimens (negative controls) and specimens treated with the organotin(IV) complexes.

Prolonged Lag in Population Outbreak of an Invasive Mussel: A Shifting-Habitat Model

Biological invasions pose a great threat to the integrity of natural communities. Some invasive species demonstrate a population explosion shortly after arrival while in other cases a prolonged lag between arrival and population outbreak is evident. This paper describes a case of a prolonged lag and explores the possible mechanism for this lag. The Red Sea mussel Brachidontes pharaonis, a Lessepsian migrant, was first recorded in the Mediterranean seven years after the opening of the Suez Canal in 1869. Since then it spread along the Israeli coast and as far northwest as Sicily. Studies conducted in the late 1970s, when B. pharaonis was still rare, predicted that it would not establish dense populations along the Israeli coast and would not outcompete the indigenous mussel Mytilaster minimus, although it has strong negative effects on survival and growth of the native species. It was attributed to the invader’s low intrinsic rate of increase relative to that of the native species, and to strong density-independent mortality generated by exposure to high wave action and sedimentation. In contrast to these predictions, we found massive formations of B. pharaonis beds after lag of about 120 years. We looked for distributional patterns that may explain this lag and found no south–north gradient but a strong habitat-dependent colonization. Most apparent are dense B. pharaonis mussel beds (density >300 per 100 cm 2 ) on rocky platforms where mussel beds were absent in the past. These platforms lack the vermetid rim that is typical to this formation. In platforms protected by a biogenic rim, sediment accumulation is high and perennial algae flourish. None of the mussel species form beds in such habitats. We suggest that the delayed formation of B. pharaonis beds along the Israeli coast is a consequence of a recent shift in habitat conditions on some platforms. It is possible that receding of the biogenic rim at the edge of these platforms allowed more effective washing, reduced sediment accumulation, and reduced perennial algae cover making platforms more suitable for the mussels. Lower density-independent mortality allowed B. pharaonis to dominate on such platforms over the indigenous species. On beachrock, a habitat previously dominated by M. minimus, we recorded a rapid shift in numerical domination to B. pharaonis (from 1 : 7 to 1.4 : 1 Brachidontes/Mytilaster individuals) over a period of 4 years (1995–1999). This is probably a result of saturation of the habitat by B. pharaonis recruits originating from the established populations on platforms. Salinity changes and a potential genetic shift may also have contributed to the invasive mussel outbreak.

Sources of carbon and dietary habits of new Lessepsian entry Brachidontes pharaonis (Bivalvia, Mytilidae) in the western Mediterranean

The sources of carbon and the dietary habits of Brachidontes pharaonis (Mollusca, Bivalvia), a new Lessepsian entry in the western Mediterranean, living in a cooling vat of a saltworks system in western Sicily (MED), were assessed by estimating throughout a season the relative abundance of a stable carbon isotope (δ13C) in particulate organic matter (POM), sedimentary organic matter (SOM), primary organic matter sources (seagrasses, sand microflora, macroalgae), Brachidontes pharaonis and its biodeposition material. In the saltworks the most enriched primary food source potentially fuelling the saltworks food web was Cymodocea nodosa (seasonal average –7.9±0.6‰), Laurencia papillosa and Cystoseira sp., which represented the predominant macroalgae (seasonal average –19.0±1.0‰) and sand microflora δ13C (–14.7±0.11‰). POM annual mean δ13C was –17.4±0.9‰, and that of SOM was –17.0±2.3‰. The seasonal mean isotopic value of B. pharaonis was −14.7±0.7‰; while its faeces was more depleted (–17.7±2.4‰), while the pseudofaeces (–14.6±3.6‰) was similar to somatic B. pharaonis in composition. Our study showed that Brachidontes assimilated mostly mixed sedimentary organic carbon re-arranged via a detritus route dominated mainly by macroalgae and sand microflora and that it was able to exploit almost all the predominant carbon sources available in its colonised environment both directly (sand microflora) and indirectly via the POM/SOM detritus route. These carbon sources incorporated most of the environmental variability relative to the isotopic composition of primary producers (about –11‰ throughout the year).