Atipične karakteristike albino embrija psa tupana Carcharhinus plumbeus (Chondrichthyes: Carcharhinidae) u Gabeškom zaljevu (južni Tunis, centralni Mediteran)

An abnormal partially-albino embryo with atypical characteristics was removed from a pregnant female sandbar shark, Carcharhinus plumbeus, caught in the Gulf of Gabès in southern Tunisian, central Mediterranean. The specimen is described and atypical characteristics and albinism in shark species is reviewed.Neuobičajeni embrio s atipičnim obilježjima, djelomično albino, koji je odstranjen iz skotne ženke psa tupana, Carcharhinus plumbeus uhvaćen je u Gabeškom zaljevu (južni Tunis), centralni Mediteran. U ovom radu opisan je nađeni primjerak. Dat je pregled atipičnih obilježja i albinizma ove vrste morskog psa

Estudio taxonómico de Squalus megalops (Macleay, 1881) y Squalus blainvillei (Risso, 1827) (Chondrichthyes: Squalidae) en aguas de Túnez (Mediterráneo central)

Two species of spurdog of the genus Squalus occur in the Gulf of Gabès (southern Tunisia, central Mediterranean): the longnose spurdog Squalus blainvillei (Risso, 1827) and a short-snout spurdog of the Squalus megalops-cubensis group. Morphometric and meristic data as well as a genetic analyses (DNA inter-simple sequence repeat markers and molecular barcoding methods) support the assignation of this short-snout spurdog to Squalus megalops (Macleay, 1881). Squalus megalops occurs commonly in temperate and tropical Australian waters, and is also thought to occur in the eastern Atlantic, southern Indian Ocean and western North Pacific although these records need to be confirmed. Our study confirms that it occurs in the Mediterranean Sea. Populations of both S. blainvillei and S. megalops are described based on Tunisian material.En el golfo de Gabès (sur de Túnez, Mediterráneo central) se encuentran dos especies del género Squalus: el galludo Squalus blainvillei (Risso, 1827) y otra de morro más corto perteneciente al grupo Squalus megalops-cubensis. Los datos morfométricos y merísticos junto con el análisis genético (ADN Inter Simple Sequence Repeats markers y métodos moleculares Barcoding) apoyan la identificación de esta última especie como Squalus megalops (Macleay, 1881). Squalus megalops se encuentra en aguas australianas templadas y tropicales, y se piensa que habita también en el Atlántico este, en el océano Índico sur y en el Pacífico noroccidental, aunque estos registros deben ser confirmados. Nuestro estudio confirma su presencia en el mar Mediterráneo. La descripción tanto de S. blainvillei como de S. megalops está basada en especímenes capturados en aguas tunecinas

Overview of the Genus <em>Squalus</em> in the Mediterranean Sea

In the Mediterranean Sea, in addition to the two historically known species belonging to the Squalus genus (Squalus blainville and Squalus acanthias), a third species, Squalus megalops, has been reported. This last specie is a subject of debate between authors. S. acanthias is quite distinct from the other species of the genus Squalus, while S. blainville and S. megalops are very similar morphologically. This similarity has resulted in considerable confusion over their taxonomy. The lack of a well-preserved holotype for S. blainville, misidentifications in databases and in the literature, description, and figure of Risso (1827) not conforming to any known species of Squalus are impediments to the proper taxonomic identification and the potential revision of the genus. This chapter aims to clarify the state of the species of the genus Squalus in the Mediterranean Sea, taking into account all the studies carried out on this subject

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

WOS:000353595500015The age, growth, longevity, mortality and reproductive parameters were estimated for Dipturus oxyrinchus from the Gulf of Gabes (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 (T-L)) and 280 males (15.5-95 cm T-L) were examined to study the reproductive cycle. A subsample of 285 specimens (175 females and 110 males, ranging from 15.5 to 105 cm T-L) were analysed to study the age and growth. The oldest female in this study was 25 yr and 105 cm T-L, 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 were L-infinity = 123.9 +/- 2.56 cm, K = 0.08 +/- 0.004 yr(-1) and t(0) = -1.26 +/- 0.04 10(-1) yr for females and L-infinity = 102.1 +/- 3.23 cm, K = 0.12 +/- 0.007 10(-3) yr(-1) and t(0) = -1.18 +/- 0.03 10(-1) yr 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(-1) for females and 0.41 yr(-1) for males