Bizerte Lagoon Research Articles

Locomotor behaviour in males, females and groups of Orchestia montagui (Amphipoda, Talitridae) in the supralittoral zone of Bizerte lagoon

Locomotor activity rhythm of Orchestia montagui was investigated under constant darkness in a population collected in spring from the supralittoral zone of Bizerte lagoon (northern region of Tunisia) at Menzel Jmil in spring. This rhythm was recorded in individual and groups of animal by infrared actography every 20 min by multichannel data loggers, at a constant temperature of 18 ± 0.5 °C. According to double-plotted actograms, wave forms and periodogram analysis, results revealed different locomotor pattern. However, locomotor activity rhythm of males was more stable than females. Furthermore, the mortality was statistically higher in unmixed groups than in mixed groups.

Spatial and temporal variation of biochemical biomarkers in Gobius niger (Gobiidae) from a southern Mediterranean lagoon (Bizerta lagoon, Tunisia): Influence of biotic and abiotic factors

This study aims at evaluating both the influence of natural and some anthropogenic pressures on spatio-temporal variations on biomarker responses in sedentary benthic fish Gobius niger. For this purpose, variability of biotransformation enzymes and oxidative stress parameters response were studied in six stations from Bizerta lagoon as well as a reference station located in Ghar El Melh lagoon. Biomarker responses were shown to vary according to both physico-chemical parameters and anthropogenic pressures, but no influence of sex was reported. Based on multivariate analyses, the responses of biomarkers, obtained after covariate analysis in order to weigh the effect of physico-chemical parameters, allowed us to discriminate all stations, with a good classification rate for those that are highly contaminated. Altogether, this study shows the usefulness of G. niger as a sentinel species and stresses the necessity of integrating natural variables for data interpretation.

Validation of an Adapted QuEChERS Method for the Simultaneous Analysis of Polycyclic Aromatic Hydrocarbons, Polychlorinated Biphenyls and Organochlorine Pesticides in Sediment by Gas Chromatography-Mass Spectrometry.

A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method has been adapted and validated for the simultaneous analysis of 16 PAHs, 12 PCBs and 9 OCPs in sediment. The sample preparation was adapted by modifying the nature of the extraction solvent, the extraction technique and the amount of sediment. The analytical performances were evaluated in terms of accuracy, linearity and quantification limits. The method was validated by the analysis of a reference marine sediment material (SRM 1941b). The obtained concentrations are in good agreement with the certified values with recoveries ranging 60 %-103 % for most of PAHs. Acceptable recoveries are obtained for PCBs, ranging 76 %-131 %, and for OCPs ranging 81 %-137 %. The method was applied to the analysis of sediments from the hydro-system Bizerte Lagoon/Ichkeul Lake (Tunisia). The Bizerte lagoon is mainly contaminated by PAHs whereas the Ichkeul lake is mainly by OCPs.

Organic matter quantity and quality, metals availability and foraminiferal assemblages as environmental proxy applied to the Bizerte Lagoon (Tunisia)

This study analyzes the benthic trophic state of Bizerte Lagoon (Tunisia) based on the total organic matter and the bioavailability of biopolymeric carbon including proteins (PTN), carbohydrates (CHO), lipids (LIP), chlorophyll a, as well as bacteria counts. The overall simultaneously extracted metals (SEM), and acid volatile sulfides (AVS) as well as the SEM/AVS ratio indicative of the toxicity of the sediments also were analyzed aiming to study their impact in the dimension, composition and structure of both dead and living benthic foraminiferal assemblages.In the studied sites TOC content is relatively high and the PTN/CHO values indicate that they can be considered as meso-eutrophic environments. The CHO/TOC and C/N values suggest that the OM which accumulated on the sediments surface has mainly natural origin despite the introduction of municipal and industrial effluents in the lagoon and the large bacterial pool.The living assemblages of benthic foraminifera of Bizerte Lagoon are quite different to other Mediterranean transitional systems studied until now. They are composed of typical lagoonal species but also include several marine and opportunistic species including significant numbers of bolivinids, buliminids, Nonionella/Nonionoides spp. and Cassidulina/Globocassidulina spp. These assemblages seem to benefitfrom the physicochemical parameters and the sediment stability. They may however face environmental stress in the lagoon related to the AVS production as a result of the organic matter degradation and toxicity in some areas due to the available concentrations of metals. Nonetheless statistical results evidence that the structure and dimension of assemblages are being controlled mostly by OM quantity and quality related mainly to the availability of PTN, CHO and chlorophyll a. Results of this work support the importance of considering OM quantity and quality in studies of environmental impact in coastal systems.

Predation by the polyclad flatworm Imogine mediterranea on the cultivated mussel Mytilus galloprovincialis in Bizerta Lagoon (northern Tunisia)

This study was carried out to investigate a paradigm of predation under natural conditions in Bizerta lagoon. The free-living marine polyclad flatworm Imogine mediterranea was found to feed on the commercial mussel Mytilus galloprovincialis. Such predation could represent a real threat to mytiliculture at this site. Our field experiments have shown that the mortality of the commercial mussel as a result of active predation by this polyclad is approximately 52% when one polyclad and one prey were placed together in a same experimental container. We found a statistically significant relationship between the size of the polyclad and the extent to which the mussels were disabled or completely eaten. Moreover, in our field experiments, the times required for predation-caused decreases of populations of the bivalves, that is, LT10, LT25 and LT50, decreased significantly with increases in the size of the polyclad. The time, LT50, required for polyclads to kill half of the bivalve population in field experiments was approximately 4.5 days. A simple disabling (an attack by the polyclad on the adductor muscle of the mussel) was shown to be sufficient to cause irreversible changes leading to mortality. Furthermore, disabling and mortality were found to be linearly correlated. The importance of mucous secretions, pharyngeal type and body musculature in supporting predation by polyclads is discussed. We suggest that measures to control the polyclad pest could incorporate the control of this flatworm's embryonic and postembryonic developmental stages.

Impact of the biocide Irgarol on meiofauna and prokaryotes from the sediments of the Bizerte lagoon-an experimental study.

The biocide Irgarol 1051 has been reported to have negative effects on a large number of living components including non-target organisms, but information on its impact on the marine meiofauna and benthic prokaryotes is completely lacking. Here, we report the results of long-term experimental studies in which we determined the effects of increasing Irgarol concentrations (from 11.5 to 315ngg(-1) sediment dry weight) on meiofauna and benthic prokaryotes. We found that this biocide had a significant impact on meiofauna abundance, even at the lowest concentrations, causing a drastic decline in the abundance of nematodes (the dominant meiofaunal taxon) and an increase of the relative importance of oligochaetes. Even if no direct effects of Irgarol were found on prokaryotic abundance and biomass, the molecular fingerprinting analyses (automated ribosomal intergenic spacer analysis) showed that the prokaryotic diversity was significantly altered by the biocide. The results of the present study indicate that Irgarol 1051 in marine sediments has a significant impact on the smallest eukaryotic and microbial components also at very low concentrations (ca 12ngg(-1)).

The Influence of Environmental Factors on the Population Structure and Reproductive Biology of <i>Idotea balthica basteri</i> (Isopoda, Valvifera) of the Bizerte Lagoon (Northern Tunisia)

The reproductive biology of a natural population of Idotea balthica basteri (Pallas, 1772) collected from Menzel Jemil (Bizerte lagoon, Tunisia) was monthly studied from October 2009 to October 2010. Besides water temperature, salinity, turbidity, pH, and dissolved oxygen were measured. Based on the state of differentiation of individuals, the population was divided into 8 categories. Their numbers depend on the one hand to intrinsic factors imposed by the specimens and the structure of the population themselves, and to extrinsic factors due to the variability of environmental conditions on the other hand. Females were morphologically recognisable at smaller size than males. Reproductive activity, which was reflected through the presence of ovigerous females and juveniles, underwent fluctuations throughout the year, but it was continuous. Moreover, salinity, temperature, nitrates, and plant biomass have a noticeable effect on the fecundity and fertility. The Principal Component Analysis also confirmed that the richness of the water in nitrates would be favorable to fecundity and fertility of Idotea balthica basteri. However, higher phosphate concentrations, in April and May seem to have a positive effect on the sex ratio. Otherwise, the temperature would be responsible for increasing the percentage of ovigerous females.

Foot Abnormalities in Venericardia antiquata and Venus verrucosa from the Bizerte Lagoon Complex (Northern Tunisia): Hydrodynamics and Sediment Texture Inductions

The Examination of the soft part of the two bivalve species Venericardia antiquata (Linnaeus 1758) and Venus verrucosa (Linnaeus 1758), that occur together in northern coast of Tunisia, allowed us to discover for the first time the presence of morphological abnormalities affecting the foot of many individuals (annual rate of 31.6%). The presence of a developed byssus was also detected in some specimens of V. antiquata. A classification scale of this malformation, established depending on the degree of this anomaly, showed six initial types that evolve to form two or three feet, at the posterior and/or anterior sides of the animal. In order to determine the causes of this malformation, experiments of transplantation were carried out. Specimens of V. verrucosa collected from Zarzouna station were transplanted in Chaâra station which is characterized by low rate of malformations, low hydrodynamics and different sediment type and vice versa. Results revealed that foot malformations degree is highly correlated with both hydrodynamics and substrate type. This may be the main cause of foot malformations. The present study provides data on foot malformations in V. antiquata and V. verrucosa from the Tunisian coast that could be used as a starting point for future monitoring programs.

Assessment of the Water Quality of Bizerte Lagoon of Tunisia by Use of Statistical Analyses

The purpose of this study is to provide a better understanding of the impact of different sources of stress (natural and human related) on water quality in a coastal lagoon (Bizerte, Tunisia). Impacts have been assessed through both surface and bottom water samples that were analysed for a range of chemical parameters. Results indicate that nutrient concentrations were generally high throughout the column especially during the rainy season. This period generally corresponds to intensive vertical mixing and massive discharge from rivers inflows. Concentrations were generally relatively high at the surface. The data structure is identified by the first three principal components explaining 68% of the total variance. Cluster analysis showed two different groups of similarity between the sampling sites reflecting the different physico-chemical characteristics and pollution levels of the studied water.

First report of goniodomin A production by the dinoflagellate Alexandrium pseudogonyaulax developing in southern Mediterranean (Bizerte Lagoon, Tunisia)

The dinoflagellate Alexandrium pseudogonyaulax is widely distributed around the world including the Mediterranean waters. The objectives of this study were to determine the morphology and phylogenic affiliation of A. pseudogonyaulax strain isolated from Bizerte Lagoon (Mediterranean waters, Tunisia) and investigate its toxicity. Molecular analyses confirmed the morphological identification of the isolated strain (APBZ12) as A. pseudogonyaulax. Moreover, it showed that it is 100% identical with strains of this species found in New Zealand, Japan, China and North Sea (Norway and Denmark) suggesting that this species is cosmopolitan. Until now, no toxin studies have been conducted on fully characterized (morphologically and molecularly) A. pseudogonyaulax. Cellular toxin production was determined using high pressure liquid chromatography coupled to mass spectrometry (HPLC/MS). Results showed for the first time that A. pseudogonyaulax contains goniodomin A (GDA), a highly toxic macrolide polyether previously shown to be produced by two other dinoflagellate species Alexandrium monilatum (Hsia et al., 2006) and Alexandrium hiranoi (erroneously identified as A. pseudogonyaulax in Murakami et al., 1988) in American and Japanese waters, respectively. This biologically active toxin has been associated over decades with fish mortality. Our study showed that the cell extracts of APBZ12 showed an important bioactivity using GH4C1 rat pituitary cytotoxicity bioassay.

Morphology and molecular analysis of life-cycle stages of Proctoeces maculatus (Looss, 1901) (Digenea: Fellodistomidae) in the Bizerte Lagoon, Tunisia.

The life cycle of Proctoeces maculatus (Looss, 1901) (Digenea, Fellodistomidae) was studied in Bizerte Lagoon (Tunisia). Three sequential hosts appear to be involved: the Mediterranean mussel Mytilus galloprovincialis Lamarck, 1819 (Mytilidae) as the first intermediate host; the polychaete Sabella pavonina Savigny, 1822 (Sabellidae), as the second intermediate host; and fishes (Lithognathus mormyrus (Linnaeus, 1758) (Sparidae), Trachinotus ovatus (Linnaeus, 1758) (Carangidae) and Sparus aurata Linnaeus, 1758 (Sparidae) as the definitive hosts. It should be noted that S. pavonina was recorded as second intermediate host for P. maculatus for the first time. Molecular confirmation of the morphological identification of the life-cycle stages of this digenean was obtained using partial 28S rDNA sequences. Comparative sequences revealed that the sporocysts and the metacercariae are conspecific but they diverged by 0.3% from the adults. The present results raised the possibility of the existence of cryptic species within the different developmental stages. However, all the present isolates differed from material from Archosargus probatocephalus in the Gulf of Mexico identified as P. maculatus.

Viability, growth and domoic acid toxicity of the diatom Nitzschia bizertensis following filtration by the mussel Mytilus sp.

The diatom Nitzschia bizertensis was recently discovered in Bizerte Lagoon (Tunisia, SW Mediterranean Sea), where it was shown to produce the amnesic shellfish poisoning toxin, domoic acid (DA). This diatom was previously found to be widespread in both time and space throughout the lagoon. The present study was carried out to test the hypothesis that N. bizertensis is able to survive after being filtered and ejected as biodeposits (faeces plus pseudofaeces) by mussels. N. bizertensis cultures (strains BD4 and BD8), at natural bloom concentrations, were fed to mussels (Mytilus sp.). The stomach contents (after 1 h) and biodeposits (after 48 h) were observed for the presence and viability of N. bizertensis cells. Light microscopy revealed intact and partial cells of N. bizertensis in both the stomach contents and biodeposits of the mussels. Incubation of the biodeposits resulted in the regrowth of N. bizertensis. This provides evidence that transplanted mussels have the potential to serve as vectors for the transport of N. bizertensis. Furthermore, cells regrown from the biodeposits contained DA, but at levels lower than those in pre-filtered cells (up to 11.9 fg cell−1). Thus, regrown cells remain toxigenic. The results suggest that one must guard against spreading N. bizertensis and other DA producers via the transfer of shellfish from contaminated to pristine areas.

Accumulation of trace metals in sediments in a Mediterranean Lagoon: Usefulness of metal sediment fractionation and elutriate toxicity assessment

The authors investigated sediment quality in Bizerte Lagoon (Tunisia) focusing on geochemical characteristics, metal sediment fractionation and elutriate toxicity assessment. Nickel, Cu, Zn, Pb, Cr and Cd partitioning in sediments was studied; accumulation and bioavailability were elucidated using enrichment factors, sequential extractions, redox potential, acid volatile sulfide and biotest procedures in toxicity evaluation. Results revealed an accumulation for Pb and Zn, reaching 99 and 460 mg kg−1 respectively. In addition, the acid volatile sulfide values were high in both eastern and western lagoon areas, thus affecting metal availability. Mean enrichment factor values for Pb and Zn were 4.8 and 4.9, respectively, with these elements as the main contributors to the lagoon's moderate enrichment level. Toxicity levels were influenced by accumulation of Zn in different surface sediment areas. Core sediments were investigated in areas with the highest metal concentrations; metal fractionation and biotest confirmed that Zn contributes to sediment toxicity.

Life history, excystment features, and growth characteristics of the Mediterranean harmful dinoflagellate Alexandrium pseudogonyaulax.

Studies considering the biology and ecology of the toxic bloom-forming species, Alexandrium pseudogonyaulax, are rare. Our results highlight five features not described before in A.pseudogonyaulax life cycle: (i) A.pseudogonyaulax gametes showed two modes of conjugation, anisogamy and isogamy, (ii) sexual conjugation occurs either in the dark or in the light phase by engulfment or a fusion process, (iii) the presence of planozygote and newly formed cysts in monoclonal culture suggests homothallism, (iv) newly formed cysts have very dark vesicular content and are mostly unparatabulated when observed under light microscope and (v) natural resting cysts are able to give either a planomeiocyte or two vegetative cells. Cyst viability was enhanced after 5months of cold storage (4°C), with excystment rate reaching 97% after 3d of incubation. Excystment rate was highest (43%-79%) in Enriched Natural Sea Water diluted culture medium, whereas few germling cells were able to survive without the culture medium (0%-13%). Salinity-irradiance experiments revealed that the highest cell concentrations occur at high irradiances for all the tested salinities. Vegetative growth rates generally increased with increasing irradiance, and were less dependent on salinity variations. The relatively low growth rate, low cell densities in the laboratory, and the notable capacity of producing cysts along growth phases of A.pseudogonyaulax could explain the occurrence of high resting cysts densities in the sediment of Bizerte lagoon and the relatively low abundances of vegetative cells in the water column.

Environmental Quality Assessment of Bizerte Lagoon (Tunisia) Using Living Foraminifera Assemblages and a Multiproxy Approach.

This study investigated the environmental quality of the Bizerte Lagoon (Tunisia) through an integrated approach that combined environmental, biogeochemical, and living benthic foraminiferal analyses. Specifically, we analyzed the physicochemical parameters of the water and sediment. The textural, mineralogical, and geochemical characteristics of the sediment, including total organic carbon, total nitrogen, simultaneously extracted metals (SEM), acid volatile sulfides (AVS), chlorophyll a, CaCO3, and changes in bacterial populations and carbon isotopes were measured. The SEM/AVS values indicated the presence of relatively high concentrations of toxic metals in only some areas. Foraminiferal assemblages were dominated by species such as A. parkinsoniana (20–91%), Bolivina striatula (<40%), Hopkinsina atlantica (<17%), and Bolivina ordinaria (<15%) that cannot be considered typical of impacted coastal lagoons both in Mediterranean and northeast Atlantic regions. The results of this work suggest that Bizerte Lagoon is a unique setting. This lagoon is populated by typical marine species that invaded this ecosystem, attracted not only by the prevailing favorable environmental conditions but also by the abundance and quality of food. The results indicate that the metal pollution found in some areas have a negative impact on the assemblages of foraminifera. At present, however, this negative impact is not highly alarming.

Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia, Southern Mediterranean Sea)

A high spatial resolution sampling of Alexandrium pacificum cysts, along with sediment characteristics (% H2O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotyping of cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum. The toxin profile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N-sulfocarbamoyl toxins C1 (9.82pgtoxincell−1), the GTX6 (3.26pgtoxincell−1) and the carbamoyl toxin Neo-STX (0.38pgtoxincell−1). The latter represented only 2.8% of the total toxins in this strain.High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63μm were examined as a favorable potential seedbed for initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.

Butyltin compounds in sediment and biota from the lagoon of Bizerte (northern Tunisia): Potential risk for consumers?

ABSTRACTLevels of butyltins (BTs) were monitored in sediment samples and in seven fish species (Boops boops, Diplodus sargus, Sarpa salpa, Serranus scriba, Spicara smaris, Trachurus draco, and Trachinus mediterraneus), five bivalve species (Cerastoderma glaucum, Chlamys flexuosa, Mytilus galloprovincialis, Pinna nobilis, and Ruditapes decussatus), two gastropod species (Bolinus brandaris and Hexaplex trunculus), cuttlefish (Sepia officinalis), and shrimp (Penaeus notialis), most of which are commonly consumed in Tunisia. Samples were collected from Bizerte lagoon during March 2012. Average concentrations of total BTs found in sediment and the muscle of fishes, bivalves, gastropods, cuttlefish, and shrimp were 17.7, 11.5, 31.8, 36.9, 8.1, and 9.4 ng Sn g−1 dw, respectively. The calculation of tolerable average residue levels and non-cancer hazard quotient for tributyltin (TBT) showed that daily exposure of these seafood to TBT is unlikely to cause any deleterious effects to humans, thus indicating that consumers may not be at risk through the inclusion of these species in their regular diet.

Locomotor activity patterns of two sympatric species Orchestia montagui and Orchestia gammarellus (Crustacea, Amphipoda)

Freshly adult individuals of two sympatric species, Orchestia gammarellus and Orchestia montagui, collected in spring from the supralittoral zone of Bizerte lagoon (Northern of Tunisia) at Menzel Jemil, were housed in a controlled environment cabinet. Locomotor activity rhythm was recorded in isolated individuals and groups by infrared actograph every 20 min by a data-logger, at a constant temperature of 18 ± 0.5 °C under constant darkness. According to double-plotted actograms and waveform curves, results showed the presence of two different locomotor patterns; in fact, individuals of O. gammarellus concentrated their activity during the hours of subjective night, whereas O. montagui were active during the subjective night and beyond the subjective dawn. Furthermore, whatever the species studied, periodogram analysis indicated a distinct circadian pattern of activity. Moreover, whatever the experiment condition is, the most clearly defined rhythms were found in O. gammarellus. In contrary to O. gammarellus, the group effect on the locomotor rhythm parameters seems to be less marked in O. montagui. On the other hand, a highly inter-individual variability was observed in the activity time for these two species and especially for O. montagui groups.

Pesticides in Ichkeul Lake-Bizerta Lagoon Watershed in Tunisia: use, occurrence, and effects on bacteria and free-living marine nematodes.

This study aimed to identify the most commonly used agricultural pesticides around Ichkeul Lake-Bizerta Lagoon watershed. First survey of pesticide use on agricultural watershed was performed with farmers, Regional Commissioner for Agricultural Development, and pesticide dealers. Then, sediment contamination by pesticides and response of benthic communities (bacteria and free-living marine nematode) were investigated. The analysis of 22 active organochlorine pesticides in sediments was performed according to quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, biodiversity of indigenous bacterial community sediment was determined by terminal restriction fragment length polymorphism (T-RFLP), and free-living marine nematodes were counted. The results of the field survey showed that iodosulfuron, mesosulfuron, 2,4-dichlorophenoxyacetic acid (2,4 D), glyphosate, and fenoxaprops were the most used herbicides, tebuconazole and epoxiconazole the most used fungicides, and deltamethrin the most used insecticide. Sixteen organochlorine pesticide compounds among the 22 examined were detected in sediments up to 2ppm in Ichkeul Lake, endrin, dieldrin, and hexachlorocyclohexane being the most detected molecules. The most pesticide-contaminated site in the lake presented the higher density of nematode, but when considering all sites, no clear correlation with organochlorine pesticide (OCP) content could be established. The bacterial community structure in the most contaminated site in the lake was characterized by the terminal restriction fragments (T-RFs) 97, 146, 258, 285, and 335 while the most contaminated site in the lagoon was characterized by the T-RFs 54, 263, 315, 403, and 428. Interestingly, T-RFs 38 and 143 were found in the most contaminated sites of both lake and lagoon ecosystems, indicating that they were resistant to OCPs and able to cope with environmental fluctuation of salinity. In contrast, the T-RFs 63, 100, 118, and 381 in the lake and the T-RFs 40, 60, 80, 158, 300, 321, and 357 in the lagoon were sensitive to OCPs. This study highlighted that the intensive use of pesticides in agriculture, through transfer to aquatic ecosystem, may disturb the benthic ecosystem functioning of the protected area. The free-living marine nematodes and bacterial communities represent useful proxy to follow the ecosystem health and its capacity of resilience.

Molecular evidence for the existence of species complexes within Macvicaria Gibson & Bray, 1982 (Digenea: Opecoelidae) in the western Mediterranean, with descriptions of two new species.

Morphological and molecular characterisation of specimens of Macvicaria spp. (Digenea: Opecoelidae) from five species of Mediterranean sparids (Teleostei: Sparidae) sampled in the Bizerte Lagoon and the Bay of Bizerte (Tunisia) revealed the presence of two species complexes designated as "obovata" and "crassigula" groups. Detailed comparative morphological and phylogenetic analyses revealed that two of the specimen sets, one from each complex, represent species new to science. M. maamouriae n. sp. from Sparus aurata L. and Lithognathus mormyrus (L.) appeared genetically similar to M. obovata (Molin, 1859) but differs in having a much larger ventral sucker relative to body width, a cirrus-sac extending dorsally to the posterior margin of the ventral sucker or more posterior, vitelline fields comprising distinctly more abundant vitelline follicles, reaching the level of the pharynx both ventrally and dorsally and confluent dorsally in the forebody, and an ovary contiguous with the anterior testis. Macvicaria bartolii n. sp. from Diplodus annularis (L.) and Spondyliosoma cantharus (L.) belongs to the "crassigula" group and is characterised by having almost exclusively dorsal vitelline follicles forming two non-confluent fields in the forebody. Additional morphological data are provided for Macvicaria dubia (Stossich, 1905), a poorly known parasite of Oblada melanura (L.). Morphological descriptions are associated with ITS1-5.8S-ITS2 and 28S rDNA sequences for the three Mediterranean species of Macvicaria Gibson & Bray, 1982. The results of our study suggest that further exploration of the species diversity within this genus should be based on both morphological and molecular data.