Antipodean white sharks on a Mediterranean walkabout? Historical dispersal leads to genetic discontinuity and an endangered anomalous population.

The provenance of white sharks (Carcharodon carcharias) in the Mediterranean is both a conundrum and an important conservation issue. Considering this species's propensity for natal philopatry, any evidence that the Mediterranean stock has little or no contemporary immigration from the Atlantic would suggest that it is extraordinarily vulnerable. To address this issue we sequenced the mitochondrial control region of four rare Mediterranean white sharks. Unexpectedly, the juvenile sequences were identical although collected at different locations and times, showing little genetic differentiation from Indo-Pacific lineages, but strong separation from geographically closer Atlantic/western Indian Ocean haplotypes. Historical long-distance dispersal (probably a consequence of navigational error during past climatic oscillations) and potential founder effects are invoked to explain the anomalous relationships of this isolated 'sink' population, highlighting the present vulnerability of its nursery grounds.

Dasyatispora levantinae gen. et sp. nov., a new microsporidian parasite from the common stingray Dasyatis pastinaca in the eastern Mediterranean.

A new microsporidian infecting the Mediterranean common stingray Dasyatis pastinaca (Linnaeus, 1758) is described from Iskenderun Bay, Turkey. The parasite invades the disc muscles, producing slender, spindle-shaped subcutaneous swellings that develop into massive, elongated, tumor-like protuberances measuring up to 11 x 4 cm. Severity of the infection may vary from light (1 or 2 small lesions) to intense, with large parts of the dorsal surface covered with lumps and protrusions. These masses contained a yellowish-white caseous substance consisting of degraded host tissue and microsporidian sporophorous vesicles, which in turn contained developing sporonts, sporoblasts and spores. The ripe spore contained a uni-nucleate sporoplasm and large posterior vacuole, and measured 3.8-4.3 x 2.6-2.8 microm. Infection prevalence was 21% in a sample of 143 host individuals examined. All the infected stingray individuals were within the weight class of 300 to 800 g (200 to 305 mm disc width). Phylogenetic analyses of rDNA sequences indicate that this microsporidian belongs to the Pleistophoridae and clusters with species of the genera Ovipleistophora Pekkarinen, Lom & Nilsen, 2002 and Heterosporis Schubert, 1969. However, the morphology, development and host differ distinctly from all reported species, including those belonging to these 2 genera, and it is thus assigned to a newly erected genus and named Dasyatispora levantinae gen. et sp. nov. This is the first record of a microsporidian infection in a batoid. It is also the first microsporidian species to be formally described from an elasmobranch.