Mitochondrial DNA variability of the pipefish Syngnathus abaster.

This study provides data on the genetic structuring of the pipefish Syngnathus abaster in the western Mediterranean and Adriatic Seas. A total of 109 specimens were collected in brackish-water biotopes. The control region and three other regions of the mitochondrial genome were analysed. The most relevant result was the high genetic structuring found by Bayesian inference (BI), maximum likelihood (ML) and network analyses, which were consistent in showing three well-separated clusters of S. abaster populations. Furthermore, BI and ML did not support the monophyly of the taxon S. abaster. These results suggest the occurrence of a species complex in the study area, whose differentiation may have occurred since the Pleistocene. The results also show a very high genetic variability at the inter-population level, with no shared haplotypes among sites. Evolutionary forces due to the fragmented nature of the brackish-water habitats may account for the high genetic divergence found among the groups and populations. Finally, although dispersal by rafting over long distances may occasionally occur, this study suggests linear stepping-stone model of colonization to be most likely. The complexity of the results obtained suggests that further studies are needed to elucidate the phylogeny of S. abaster.

Molecular phylogeography of western Mediterranean dusky grouper Epinephelus marginatus.

Intraspecific sequence variation in a portion of the gene coding for cytochrome b in the dusky grouper (Epinephelus marginatus Lowe 1834), an endangered fish species in various regions of the Mediterranean sea, was examined in 29 individuals from the western Mediterranean sea. Sixty-four phylogenetically informative nucleotide positions were present in a 353-base pair cytochrome b sequence, amplified using the polymerase chain reaction. Statistical analysis of the sequence data using a variety of tree-building algorithms separated the taxa into one group of dusky groupers corresponding to some of the Algerian individuals and another regrouped set of fishes originating in France, Tunisia and the remaining Algerian specimens. Although, on the basis of their morphology, E. marginatus are now considered as a single species, our results suggest that a subgroup of the Algerian dusky grouper constitutes a cryptic (undescribed) species. These results suggest that morphological and genetic evolution may be uncoupled in dusky grouper, resulting in morphological similarity between species despite extensive genetic divergence. In addition, we cannot rule out the possibility of gene introgression with other species of grouper. A more in depth phylogenetic analysis (i.e. between and within the different Epinephelus species) would likely affect many conservation management decisions about this assemblage of groupers.

[Biology of Squalus blainvillei (Risso, 1826) (Pisces, Squalidae) from the Tunisian coast: relation of body, liver and gonadal weight. Relative coefficients of condition and of hepato and gonosomatic processes. Embryonic development]. / Recherches sur la biologie de Squalus blainvillei (Risso, 1826) (Pisces, Squalidae) des côtes tunisiennes: relations taille-poids du corps, du foie et des gonades. Coefficients de condition rapports hépato et gonosomatique. Croissance embryonnaire.

The relative increase of body-weight size, liver-weight size and gonad weight size relationships is pointed out in all individuals and chiefly in the young ones of Squalus blainvillei (Risso, 1826) of Tunisian coasts. The evolution of the cubic and relative coefficients of condition, and of hepato and gonosomatic relationships are depending of reproductive processes. During their growth, the embryos eat only vitellin reserves, the female uterin secretions interfere only on the ending gestation.