Tunisian Waters Research Articles

Morphology, seasonality and phylogeny of Zschokkella trachini n. sp. (Myxozoa, Myxosporea) infecting the gallbladder of greater weever Trachinus draco (L.) from Tunisian waters.

We describe a new myxosporean species, Zschokkella trachini n. sp., infecting the gallbladder of greater weever Trachinus draco Linnaeus 1758 from Tunisia. This is the first record of Zschokkella species in T. draco. Plasmodia were polysporic producing six to eight mature spores; they were attached to the gallbladder epithelium or free floating in the bile. Mature spores were sub-ovoid in the frontal view, measured 15.2 ± 0.6 (14.4-16.0) μm in length and 9.8 ± 0.7 (9.0-10.8) μm in width. Two equal spherical polar capsules 4.0 ± 0.4 (3.6-4.5) μm in diameter, were located separately at the spore's extremities. The prevalence of infection ranged from 23.5 to 87.7%. Morphological data and molecular analysis of the small subunit rDNA gene identified this parasite as a new species of Zschokkella. Neighbour joining clustered the parasite in a sub-clade containing other Zschokkella species parasiting the gallbladder of marine fish hosts, located within the coelozoic clade of the major freshwater clade. This is the second Zschokkella species reported from Tunisia.

Unusual record of bluemouth rockfish Helicolenus dactylopterus (Osteichthyes: Scorpaenidae) in Tunis Southern Lagoon (Northern Tunisia, Central Mediterranean)

The record of bluemouth rockfish Helicolenus dactylopterus (Delaroche, 1809) at low depth suggests that the species is prone to large vertical migrations. This capture confirms the occurrence of the species in the Tunisian waters where it is known as very rare. It confirms also the success of ecological restoration of Tunis Southern Lagoon and the possible establishment of fish populations, mainly due to a favourable biological environment, mostly constituted by crustacean species among them, species belonging to the genus Sphaeroma Latreille, 1802 play an important role.

Morphometric and Meristic Characters of Greater Amberjack <i>Seriola dumerili</i> (Pisces: Carangidae) from the Gulf of Gabes, Tunisia

Morphometric and meristic characters of Greater amberjack Seriola dumerili have been studied from Gulf of Gabes, Tunisia, Eastern Mediterranean. Samples of S. dumerili were collected in the period June 2004 to May 2006 for this study. Eleven morphometric in percentage of total fish length and seven meristic characters have been studied. No significant differences were observed between male and female fish. Isometric and both positive and negative allometric growth of morphometric characters of Seriola dumerili were observed. Therefore, the present study gives information to fishery biologists about morphometric and meristic characters of the fish, Seriola dumerili from the Tunisian waters. This will help to plan further conservation strategy for this fish.

Population genetic structure of Epinephelus marginatus in the Central Mediterranean Sea (Gulf of Gabès and the coast of Libya)

In the present study, mitochondrial DNA sequences from the cytochrome b (cytb) gene and seven nuclear microsatellites were examined to assess the genetic diversity of Epinephelus marginatus inhabiting Tunisian and Libyan coastal waters. Based on 940 base pairs of the cytochrome b segment, we found low level of genetic variability for the two samples analysed (h = 0.294 ± 0.097and h = 0.274± 0.142 respectively in Tunisia and Libya). An analysis of molecular variance (AMOVA) showed significant pattern of genetic structure based on nuclear data (7 microsatellite loci) (ΦST= 0.28487; P < 0.001). Conversely, no genetic structuring was found for mtDNA (ΦST = -0.0121). In summary, this study provides preliminary assessment of geographical patterns of differentiation of E. marginatus in this region for conservation, management and stock identification.

Additional and unusual captures of elasmobranch species from the northern coast of Tunisia (central Mediterranean)

The present paper reports occurrences of six elasmobranch species previously considered as rare and/or unknown in northern Tunisian waters. Captures of sharpnose seven-gill shark, Heptranchias perlo (Bonnaterre, 1788) and bluntnose six gills shark, Hexanchus griseus (Bonnaterre, 1788) showed that both species although they are threatened are not totally exctincted in the area. A new record of a juvenile great white shark, Carcharodon carcharias (Linnaeus, 1758) confirms one again that the central Mediterranean could be considered as a possible nursery area for this species. Additionally, captures of sandbar shark, Carcharhinus plumbeus (Nardo, 1827) and blackchin guitarfish Rhinobatos cemiculus E. Geoffroy Saint-Hilaire, 1817 are due to migrations from southern toward northern areas as a consequence of the warming of the latter areas. It may be also the case for blue shark, Prionace glauca (Linnaeus, 1758), from Algerian waters where the species is rather abundant.

Modeling of Beta Diversity in Tunisian Waters: Predictions Using Generalized Dissimilarity Modeling and Bioregionalisation Using Fuzzy Clustering.

Spatial patterns of beta diversity are a major focus of ecology. They can be especially valuable in conservation planning. In this study, we used a generalized dissimilarity modeling approach to analyze and predict the spatial patterns of beta diversity for commercially exploited, demersal marine species assemblages along the Tunisian coasts. For this study, we used a presence/absence dataset which included information on 174 species (invertebrates and fishes) and 9 environmental variables. We first performed the modeling analyses and assessed beta diversity using the turnover component of the Jaccard’s dissimilarity index. We then performed nonmetric multidimensional scaling to map predicted beta diversity. To delineate the biogeographical regions, we used fuzzy cluster analysis. Finally, we also identified a set of indicator species which characterized the species assemblages in each identified biogeographical region. The predicted beta diversity map revealed two patterns: an inshore-offshore gradient and a south-north latitudinal gradient. Three biogeographical regions were identified and 14 indicator species. These results constitute a first contribution of the bioregionalisation of the Tunisian waters and highlight the issues associated with current fisheries management zones and conservation strategies. Results could be useful to follow an Ecosystem Based Management approach by proposing an objective spatial partitioning of the Tunisian waters. This partitioning could be used to prioritize the adjustment of the actual fisheries management entities, identify current data gaps, inform future scientific surveys and improve current MPA network.

First Mediterranean records of spinetail devil ray, Mobula japanica (Elasmobranchii: Rajiformes: Mobulidae)

Captures of 11 spinetail devil rays, Mobula japanica (M&#252;ller et Henle, 1841), from the northern coast of Tunisian (central Mediterranean) are reported in the present paper. Of these 11 specimens, five specimens were described. These captures constitute the first records of the species in the Tunisian waters, but also in the Mediterranean Sea, extending its distribution. This unusual occurrence of M. japanica is probably due to a migration from the eastern tropical Atlantic into the Mediterranean Sea through the Strait of Gibraltar.

First Mediterranean records of spinetail devil ray, Mobula japanica (Elasmobranchii: Rajiformes: Mobulidae)

Captures of 11 spinetail devil rays, Mobula japanica (Muller et Henle, 1841), from the northern coast of Tunisian (central Mediterranean) are reported in the present paper. Of these 11 specimens, fi ve specimens were described. These captures constitute the fi rst records of the species in the Tunisian waters, but also in the Mediterranean Sea, extending its distribution. This unusual occurrence of M. japanica is probably due to a migration from the eastern tropical Atlantic into the Mediterranean Sea through the Strait of Gibraltar.

Disparate past demographic histories of three small Scombridae (Actinopterygii) species in Tunisian waters

The bullet tuna Auxis rochei, the little tunny Euthynnus alletteratus, and the Atlantic Chub mackerel Scomber colias are three small Scombridae with similar life-history traits such as overlapping epipelagic distribution and a shared spawning area in Tunisian waters. In this study, we compared the phylogeography and demographic histories of these species by analyzing the sequence variability of the mitochondrial DNA control region. None of the species showed genetic differentiation in their Tunisian distribution; however, we inferred three completely different population histories. E. alletteratus showed a demographic history of a very recent bottleneck followed by sudden population expansion probably consequence of a population decline in the Last Glacial Maximum. S. colias also presented a population expansion after collapse but in this case about ten-fold older than that observed in E. alletteratus. Finally, A. rochei presented a history of demographic stability. These contrasting population histories were discussed based on their possible differences in life-history traits, but the hypothesis of stochastic factors affecting the demography of these species was also invoked.

Seasonal variation of reproductive traits of the caramote prawn in the Gulf of Tunis

The caramote prawn, Melicertus kerathurus , is a Penaeidae species inhabiting the Mediterranean Sea and the Est Atlantic Ocean. Caramote prawn represents a commercially important species in terms of both aquaculture and fishing; however, there is poor information on its reproductive biology in Mediterranean and, particularly, in Tunisian waters. To fulfil such a gap, monthly samples of caramote prawn were collected along the northern Tunisian coast throughout one year. Ovaries maturity data, obtained by histological analysis, together with reproductive and condition indices, indicated the main spawning season extends from April to August, with a clear peak in July–August. However, gonadic production still persists during September-December, although at lower levels. The seasonal patterns of somatic and gonadic conditions suggested that energy reserves, during the main spawning period, were invested both in gonadic and body production; but males and females appeared to devote differently such energy reserves. During the spawning peak, females revealed both good somatic and gonadic conditions simultaneously, while males displayed worse body conditions. Monthly sea surface temperature (SST) showed a high level of pattern correspondence with ovary maturity phase and gonadosomatic index (GSI); but a strong linear relationship between SST and GSI in the study area was observed only for males. Such results increased reproductive biology knowledge, therefore allowing to improve the management quality of both wild caramote prawn stocks and reared populations.

Biodiversity of cyanobacteria in Tunisian freshwater reservoirs: occurrence and potent toxicity – a review

In spite of the great environmental and sanitary importance of cyanobacteria, their biodiversity is little known in Tunisia. In this work, a review was carried out, based on literature data, of potentially toxic cyanobacteria occurrence in Tunisia. Microcystis, one of the most widely distributed toxic bloom-forming cyanobacteria genera, was represented by Microcytis wesenbergii, found only in Lebna water reservoir, and Microcytis aeruginosa recorded in different water bodies. The invasive potentially toxic cyanobacterium Cylindrospermopsis raciborskii , reported for the first time in Tunisia in October 2004, was observed in the semi-arid to arid areas. The harmful genus Planktothrix was represented in Tunisian freshwater by the green-pigmented species P. agardhii . The filamentous cyanobacteria dominance is increasingly reported in Tunisia in eutrophic water bodies. This dominance increases especially during the summer–autumn period. Recently, potentially toxic cyanobacteria blooms have been reported in some reservoirs in the north east of the country. These blooms were generated by the potentially toxic Chroococcale Microcystis aeruginosa. Harmful cyanobacteria tend to spatio-temporal expansion in the Tunisian inland waters. The toxicological potential evaluated by several methods showed that none of the Tunisian strains were proved to be cylindrospermopsin nor saxitoxin producers. However, the majority of Microcystis were able to synthesize microcystin.

Cumulative human threats on fish biodiversity components in Tunisian waters

Human activities are increasingly impacting biodiversity. To improve conservation planning measures in an ecosystem-based management context, we need to explore how the effects of these activities interact with different biodiversity components. In this study, we used a semi-quantitative method to assess the cumulative impacts of human activities on three biodiversity components (species richness, phylogenetic diversity, and functional diversity) in Tunisia’s exclusive economic zone. For each of the nine activities considered, we developed an understanding of their effects from local studies and the expert opinion of stakeholders with country-specific experience. We mapped the cumulative effects and the three biodiversity components and then assessed the degree to which these elements overlapped using an overlap index. This is the first time such an assessment has been made for Tunisia’s marine ecosystems and our assessment highlight the inappropriateness of current conservation measures. The results of this study have specific application for the prioritization of future management actions.

Update of alien fauna and new records from Tunisian marine waters

An updated inventory of alien marine fauna in coastal and offshore Tunisian waters is presented. Records were compiled from scientific and ‘grey’ publications, presentations at scientific meetings, theses presented in fulfillment of requirements towards MSc and PhD degrees, websites and personal observations. 136 alien species were recorded in Tunisian waters, 60 records in northern coasts, West Mediterranean and 76 in central and southern coasts, Central Mediterranean. Nearly half of the first sightings in Tunisian waters took place in the Gulf of Gabès. The dominant taxa are Crustancean (24%), Molluscs (23%), Fishes (19%) and Annelida (13%). Twenty one species previously reported as aliens, were upon consideration, reclassified as range-expanding Atlantic species. Amathia verticillata, previously considered native to the Mediterranean, is reclassified as pseudoindigenous. Twenty one alien species are newly recorded from Tunisia, including 5 fish species, 5 polychaetes, 4 crustaceans, 4 molluscs, and one each schyphozoan, bryozoan and tunicate. The findings of Gibberulus gibberulus albus, Morula aspera and Calcinus latens, three species new to the Mediterranean, and of Actaedoes tomentosus, reported for the second time in the basin, are described. Species were classified according to their establishment status and their origins. This contribution highlights the dual origin of biological invasion in Tunisian waters (Red Sea and Atlantic), with slightly more species of Red Sea and Indo-Pacific origin (61,76%). The impact of the alien species in Tunisian waters was discussed.

New observations on Myxozoa of the goldline sea bream Sarpa salpa L. 1758 (Teleostei : Sparidae) from the Mediterranean coast of Tunisia.

A member of the Sparidae family, the goldline sea bream Sarpa salpa (Linnaeus, 1758) collected from the Gulf of Tunis and the Bay of Bizerte in Northeast Tunisia, Western Mediterranean, were examined for the myxozoan parasites. During the parasitological exposure, a total of 7 myxosporean are found including 6 coelozoic species belong to the genus Ceratomyxa Thélohan, 1892 infected the gallbladder of their host of which 3 known species have been previously described, C. arcuata Thélohan, 1892, C. pallida Thélohan, 1895 and C. herouardi Georgévitch, 1916 and 3 species seem different in morphology to Ceratomyxa spp already known from Mediterranean Sea or from other localities in the wide world. These species are Ceratomyxa sp. 1, Ceratomyxa sp. 2 and Ceratomyxa sp. 3. Only one histozoic species belongs to the genus Henneguya Thélohan, 1892, Henneguya sp. identified for the first time infecting the mesentery vessels of S. salpa. The myxosporean parasite C. arcuata Thélohan, 1892 is reported for the first time in Tunisian waters from the goldline sea bream which represents as new host records. In addition to the Monoparasitism, the phenomenon of Polyparasitism was observed between the current species in both sampling sites with two types: Biparasitism and Triparasitism. The most frequent Polyparasitism was a Biparasitism-type between C. herouardi and C. pallida with frequency 16.97%. For all the species, no serious pathogenic changes have been recorded in the host organ or in the outward appearance of the fish. Morphological features, site of infection into the host, parasite prevalence and mean intensity of each myxosporean found during this survey are determined and their taxonomic affinities to other species are discussed.

First record and potential trophic impact of Phyllorhiza punctata (Cnidaria: Scyphozoa) along the north Tunisian coast (South Western Mediterranean Sea)

The Australian spotted scyphomedusa Phyllorhiza punctata was recorded for the first time in Tunisian waters in August 2012, in the lagoon of Bizerte (Tunisia). Metaephyrae and juveniles occurred simultaneously in August 2012. The occurrence of adult medusae was detected from September to November 2012, and from August to October 2013. This is the second record of a reproducing population of P. punctata in the Mediterranean Sea. The low abundance of mesozooplankton in summer and autumn 2012 coincides temporally with the highest density of P. punctata recorded in the lagoon, suggesting that predation by this alien jellyfish may have been a limiting factor for the mesozooplankton abundance on site.

Age, growth, longevity, mortality and reproductive biology ofDipturus oxyrinchus, (Chondrichthyes: Rajidae) off the Gulf of Gabès (Southern Tunisia, central Mediterranean)

The age, growth, longevity, mortality and reproductive parameters were estimated forDipturus oxyrinchusfrom the Gulf of Gabès (Southern Tunisia, central Mediterranean Sea), collected monthly during 2007 from commercial fisheries. The present study provides the first data on age and growth of this species in Tunisian waters, as well as additional data on its reproduction. A total of 240 females (16.5–105 cm total length (TL)) and 280 males (15.5–95 cmTL) were examined to study the reproductive cycle. A subsample of 285 specimens (175 females and 110 males, ranging from 15.5 to 105 cmTL) were analysed to study the age and growth. The oldest female in this study was 25 yr and 105 cmTL, whereas the oldest male was 22 yr and 95 cm. The annual deposition of growth bands was verified by marginal increment and edge analysis. The von Bertalanffy growth parameters wereL∞ = 123.9 ± 2.56 cm,K = 0.08 ± 0.004 yr−1andt0 = −1.26 ± 0.04 10−1yr for females andL∞ = 102.1 ± 3.23 cm,K = 0.12 ± 0.007 10−3yr−1andt0 = −1.18 ± 0.03 10−1yr for males. Growth was not significantly different between sexes. The maturity size was 72.05 cm for males and 82.1 cm for females. The maturity age was estimated to be 11.95 and 13.96 years, respectively, for males and females. Size and age at maturity were not significantly different between sexes. The estimated longevity was 26.18 and 38.84 yr for males and females, respectively. Based on life history parameters, natural mortality was estimated at 0.53 yr−1for females and 0.41 yr−1for males.

Antibiotic resistance genes in bacterial and bacteriophage fractions of Tunisian and Spanish wastewaters as markers to compare the antibiotic resistance patterns in each population

The emergence and increased prevalence of antibiotic resistance genes (ARGs) in the environment may pose a serious global health concern. This study evaluates the abundance of several ARGs in bacterial and bacteriophage DNA via real-time qPCR in samples from five different sampling points in Tunisia; three wastewater treatment plants (WWTP 1, 2 and 3) and wastewater from two abattoirs slaughtering different animals. Results are compared with those obtained in the Barcelona area, in northeast Spain.Eight ARGs were quantified by qPCR from total and phage DNA fraction from the samples. Three β-lactamases (blaTEM, blaCTX-M cluster 1 and blaCTX-M cluster 9), two quinolone resistance genes (qnrA and qnrS), the mecA gene that confers resistance to methicillin in Staphylococcus aureus, the emerging armA gene, conferring resistance to aminoglycosides and sul1, the most extended gene conferring resistance to sulfonamides, were evaluated.Sul1 and blaTEM were the most prevalent ARGs detected at all five Tunisian sampling points, similarly with the observations in Barcelona. blaCTX-M-9 was more prevalent than blaCTX-M-1 both in bacterial and DNA within phage particles in all samples analysed. mecA and armA were almost absent in Tunisian waters from human or animal origin in contrast with Barcelona that showed a medium prevalence. qnrA was more prevalent than qnrS in bacterial and phage DNA from all sampling points.In conclusion, our study shows that ARGs are found in the bacterial and is reflected in the phage DNA fraction of human and animal wastewaters. The densities of each ARGs vary depending on the ARGs shed by each population and is determined by the characteristics of each area. Thus, the evaluation of ARGs in wastewaters seems to be suitable as marker reflecting the antibiotic resistance patterns of a population.

More than 35 years of studies on marine nematodes from Tunisia: a checklist of species and their distribution.

This work provides an inventory of species of free-living nematodes from Tunisian waters, based on samples collected from September 1977 until March 2013. Sediment samples were taken from 8 ecosystems: the Lagoons of Bizerte, Ghar El Melh and Bou Ghrara, Northern and Southern Lakes of Tunis, Old Harbor of Bizerte, Bizerte Bay and Ichkeul Lake. A total of 31 families, 133 genera, and 249 species of marine nematodes are currently known from Tunisia. The Xyalidae (with 30 species), Cyatholaimidae (25), Chromadoridae and Linhomoeidae (each 21) and Comesomatidae (20) are the richest families. Among them, Daptonema (with 9 species), Pomponema and Sabatieria (with 7 each) are the most species-rich genera. Some species were recovered only from a specific type of ecosystem. In detail, 109 species were recovered from lagoons, 56 species from sandy beaches and 6 species from mudflats. The 78 remaining species were widely distributed in Tunisian waters and four of these (Terschellingia longicaudata, Oncholaimus campylocercoides, Sabatieria pulchra and Theristus flevensis) were present in most of the 8 ecosystems studied.

Interspecific and geographical variations of trace metal concentrations in cephalopods from Tunisian waters

The concentrations of six metals (Ag, Cd, Cu, Hg, Pb, and Zn) were investigated and compared in three tissues (arms, digestive gland, and mantle) of three cephalopod species from the Tunisian waters: the common octopus (Octopus vulgaris), the common cuttlefish (Sepia officinalis), and the European squid (Loligo vulgaris). Whatever the species or the sites, the digestive gland displayed the highest concentrations of Ag, Cd, Cu, Pb, and Zn, highlighting its major role in their bioaccumulation and detoxification. This is also true for Hg but only for the digestive gland of O. vulgaris. Muscle from the arms and the mantle contained thus relatively low trace metal concentrations except for Hg in L. vulgaris and S. officinalis. Geographic comparison of metal concentrations in Tunisian cephalopods from three locations indicates that higher concentrations of Ag, Pb, and Hg were observed in cephalopods from northern and eastern coasts, whereas the highest Cd levels were detected in the southeastern, reflecting different conditions of exposure. Comparing the trace element concentrations between species, Ag, Cd, Cu, Hg, and Zn concentrations were the highest in the digestive gland of octopuses. This may be related to the differences in ecological features and swimming behavior among different cephalopod species. Effects of length and sex on metal levels were also considered, indicating a limited influence of sex on metal concentration.

First Record of Pampus argenteus (Euphrasen, 1788) (Osteichthyes: Stromateidae) in the Tunisian Coast (Mediterranean Sea)

First Record of Pampus argenteus (Euphrasen, 1788) (Osteichthyes: Stromateidae) in the Tunisian Coast (Mediterranean Sea) The second Mediterranean record of the silver pomfret, Pampus argenteus is reported, with the capture of four specimens in the Gulf of Hammamet (North-East Tunisia) on March 15th 2007. The species is a non-indigenous for the Mediterranean, being native to the Indo-West Pacific area. A short description of all these specimens is given and the presence of this species in the Mediterranean is critically discussed. This note describes the first record of the P. argenteus in the Tunisian waters (Southwestern Mediterranean Sea).