Resumen.-Se describen algunos parámetros biológicos de la bacoreta Euthynnus alletteratus en el Golfo de Gabes (sur de Túnez), tales como la proporción de sexos, el Índice Gonado-Somático (IGS), el Índice Hepato-Somático (IHS), la longitud de primera madurez sexual, y la relación longitud-peso. Se analizó un total de 397 specímenes (244 hembras y 153 machos) entre los 36,7 y 97,8 cm de longitud, con un promedio 52,29 ± 5,87 cm. Las muestras se recolectaron mensualmente, entre enero de 2008 y diciembre de 2009. El 61% de los ejemplares fueron hembras. El periodo de desove se extiende de junio a septiembre, calculado a partir de los altos valores de IGS. Las relaciones longitud-peso revelaron que la bacoreta presenta una alometría negativa. La longitud promedio de primera madurez de las muestras tomadas en el Golfo de Gabes fue de 44,8 cm de longitud de horquilla para las hembras y 42,8 cm para los machos.
Molecular data have shown that jellyfishes are more geographically restricted and evolutionarily divergent than previously thought. We examined genetic variation and divergence within the meroplanktonic barrel jellyfish Rhizostoma pulmo in the Mediterranean Sea; specific sampling areas were the northern Adriatic, western Mediterranean and Tunisian coast. A total of 19 sampling sites and 68 sequences of the mtDNA cytochrome c oxidase subunit I (COI) gene were used. Of the 68 COI sequences, 45 were newly collected specimens which originated from nine sampling sites along the Tunisian coast. A total of 24 haplotypes were obtained and the specimens sampled were characterised by relatively high levels of haplotype diversity (h = 0.866) and low levels of nucleotide diversity (Ï\u80 = 0.004). Haplotype network analysis showed the presence of three distinct phylogenetic lineages (populations), with separate geographic ranges in the northern Adriatic, western Mediterranean and Tunisian coast. The observed genetic differentiation between these three lineages was supported by the presence of significant genetic differentiation between the 19 populations (FST = 0.757, p < 0.001). The high level of genetic differentiation detected in the barrel jellyfish investigated could be attributed to either intrinsic and/or extrinsic barriers to genetic exchange between different populations that may have adapted to different environmental conditions
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