Inventory, Systematic and Biogeography of Brachyuran Crabs (Crustacea: Decapoda: Brachyura) on the Tunisian Coast

Several prospects on the northern, central and southern Tunisian coasts were carried out for the sake of a better interpretation of Brachyuran species distribution. Animals were either, captured by hand, caught with a fine mesh net or brought back by fishermen in nets or dredges. A total of 21 species belonging to twelve families and inhabiting different substrates were collected and divided into littoral species and species of depth. Five species were reported for the first time, in Tunisia. The littoral species are Carcinus aestuarii, Liocarcinus corrugatus, Liocarcinus vernalis, Pachygrapsus marmoratus, Pachygrapsus maurus, Brachynotus sexdentatus, Eriphia verrucosa, Maja squinado, Maja crispata, Acanthonyx lunulatus and Pisa tetraodon. The species of depths are Portunus hastatus, Euchirograpsus liguricus, Xantho granulicarpus, Ilia nucleus, Inachus dorsettensis, Lissa chiragra, Pisa corallina, Pisa armata, Calappa granulata and Dromia personata. All these species are reported in the Mediterranean. Some are reported for the first time in Tunisia: P. maurus, A. lunulatus, P. hastatus, E. liguricus, L. chiragra and P. corallina. In order to know the frequency of each species, the presence index was calculated. Carcinus aestuarii present in 91% of prospected stations is the most frequent and wide-distributed brachyuran species along Tunisian coasts.

Patterns of genetic and morphometric diversity in the marbled crab(Pachygrapsus marmoratus, Brachyura, Grapsidae)populations across the Tunisian coast

The present study reports on population structure analysis of the marbled crab Pachygrapsus marmoratus （Fabricius, 1787） from the Tunisian coast, an appropriate location to study biogeographical processes because of the presence of a well-known discontinuous biogeographic area （the Siculo-Tunisian Strait）. Patterns of morphological and genetic variation of this highly dispersive and continuously distributed decapod species were assessed among its geographically close populations which cover almost the entire Tunisian coastline. A total of 386 specimens from nine sites were collected and examined for morphometric variability at 14 morphometric traits. The results of multivariate analyses of linear morphometric traits showed the existence of sexual dimorphism in this species by PERMANOVA （Permutational multivariate analysis of variance）. In addition, both CDA （Canonical discriminant analysis） and NPMANOVA （Non parametric MANOVA test） analyses revealed statistically significant differences among the studied locations for both sexes. Overall, the outcome of CDA analysis showed that over 87% of individuals could be assigned correctly to three regional groups in both sexes （North, Center and South）. Specifically, SIMPER （Similarity Percentages） analysis showed that carapace length, carapace width and merus length were major contributors to the morphometric separation between populations. The pattern of phenotypic variation suggested by morphometric analyses was found to be highly discordant with that suggested by the analysis of a mitochondrial marker （cytochrome oxidase I, COI）. Indeed, the results inferred from restriction fragment analysis of the COI in 180 crabs, suggested high genetic homogeneity. Very low levels of haplotype diversity （h） were found in almost all the studied populations, associated with non significant genetic distances for nearly all population comparisons. Explanations to these morphometric and mtDNA patterns as well as the discrepancy between them are discussed.

Metazoan Parasites of the Mediterranean Garfish <i>Belone belone gracilis</i>(Teleostei: Belonidae) as a Tool for Stock Discrimination

The aim of the present study was to provide a current survey of metazoan parasites of the Mediterranean garfish Belone belone gracilis Lowe, 1839 off Tunisian coast and their potential use as biological tags for discriminate stocks. Parasitological analysis of 453 specimens of B. b. gracilis along the eastern Tunisian coast revealed the presence of ten species of metazoan parasites: one monogenean Axine belones Abildgaard, 1794;four digeneansLecithostaphylus retroflexus (Molin, 1859), Tergestia acanthocephala (Stossich, 1887) Stossich, 1899, Aponurus laguncula Looss, 1907 and Condylocotyla pilodora(metacercaria) Pearson et Prévot, 1985;one copepod Bomolochus bellonesBurmeister, 1835;two isopods Irona nana Schioedte et Meinert, 1884 andNerocila orbignyi (Guérin-Méneville, 1832);1 acanthocephalan Telosentis exiguus (Von Linstow, 1901) and one nematod Anisakid larvae. Discriminant analysis using parasites as biological tags, allowed identifying two stocks ofB. b. gracilis. Digenea L. retroflexus, A. laguncula and Anisakid larvae were the most important species in determining the position of sampled fishes from the central coast off Tunisia. Metacercaria C. pilodora characterized specimens from the Southern coast off Tunisia. These results were corroborated by comparing parameters of prevalence and mean abundance between zones. Discriminant analysis used for the separation of B. b. gracilis between seasons in both localities showed that a seasonal variation affected mainly specimens from the center suggesting seasonal move of fishes.