Population genetics of Bursatella leachii (De Blainville, 1817) and implications for the origin of the Mediterranean population

Abstract The sea hare Bursatella leachii (de Blainville 1817) (Mollusca: Gastropoda: Heterobranchia: Aplysiidae) is a pantropical sea slug that has colonized the Mediterranean Sea in modern times. Because the initial records in the non-native range started in the Eastern Mediterranean, and its pattern of spread was relatively consistent with those observed in well-known Lessepsian invaders, B. leachii is commonly considered to be a migrant from the Red Sea. In this study, we investigate for the first time the origin of the Mediterranean populations of B. leachii inferring their population structure and assessing relatedness levels of different regional populations. Sequence data from the cytochrome oxidase I were used to conduct population genetic analyses on this species, particularly by investigating the genetic structure of Atlantic, Mediterranean, and Indo-Pacific populations. Our results confirm that B. leachii is a truly pantropical species which displays geographic structure among major ocean basins. More importantly, sequenced Mediterranean and Atlantic animals share similar or identical haplotypes, which are distinct in at least 5 substitutions from haplotypes recovered from Indo-Pacific specimens. The results suggest that the Mediterranean population of B. leachii here examined probably have an Atlantic origin, and for the first time casts doubts on the assumed primary pathway of migration into the Mediterranean Sea

Molecular and morphological systematics of Bursatella leachii de Blainville, 1817 and Stylocheilus striatus Quoy & Gaimard, 1832 reveal cryptic diversity in pantropically distributed taxa (Mollusca : Gastropoda : Heterobranchia)

he ragged sea hare (Bursatella leachii) and the long-tailed sea hare (Stylocheilus striatus) are two widely distributed species of benthic heterobranch sea slugs. In this paper, integrative taxonomic analyses have been conducted to detect possible cryptic diversity. Our results revealed that both nominal species are actually species complexes, consisting of five genetically distinct taxa. Two of them belong to the genus Bursatella and three to the genus Stylocheilus. The name B. leachii is retained for a widely distributed species, present in the Atlantic, the Mediterranean, and parts of the Indo-Pacific region. The name B. ocelligera is resurrected for the other species, restricted to the Indo-Pacific and co-occurring with B. leachii in that area. With the present data, it is not possible to test whether B. leachii and B. ocelligera have evolved allopatrically in the Atlantic and Indo-Pacific or sympatrically in the latter. Bursatella leachii has been able to maintain gene flow between the Atlantic and the Indo-Pacific Oceans, possibly because of a combined effect of the Agulhas Leakage process and the ability to survive the colder waters of South Africa. On the contrary, the three species of Stylocheilus are allopatric; the name S. striatus is retained for an Indo-Pacific species, while the names S. polyomma and S. rickettsi are resurrected for species inhabiting the Western Atlantic and the Eastern Pacific respectively. Finally, the discovery of a museum specimen mistakenly identified as B. leachii, but bearing a shell in its adult form, led to the resurrection of the genus Phycophila, previously synonymised with Aplysia. Phycophila euchlora, the only species described to date, is distributed in the Central and Western Pacific Ocean

Functional characterization of brain tumors: an overview of the potential clinical value.

Early detection and characterization are still challenging issues in the diagnostic approach to brain tumors. Among functional imaging techniques, a clinical role for positron emission tomography studies with [18F]-fluorodeoxyglucose and for single photon emission computed tomography studies with [201Tl]thallium-chloride has emerged. The clinical role of magnetic resonance spectroscopy is still being defined, whereas functional magnetic resonance imaging seems able to provide useful data for presurgical localization of critical cortical areas. Integration of morphostructural information provided by computed tomography and magnetic resonance imaging, with functional characterization and cyto-histologic evaluation of biologic markers, may assist in answering the open diagnostic questions concerning brain tumors