Induction of cetacean cytochrome P4501A1 by beta-naphthoflavone exposure of skin biopsy slices.

Marine mammals can accumulate environmental contaminants in their blubber at concentrations harmful to laboratory animals. Induction of the cytochrome P450 1A1 (CYP1A1) enzyme is widely used as a biomarker of exposure and molecular effects in animal species, yet the validity of this biomarker has not been established in marine mammals. In vivo studies are generally precluded in these protected species, but skin biopsies (epidermis and dermis) can be collected in a minimally invasive way. We developed an in vitro assay using skin biopsy slices to examine CYP1A1 protein induction in marine mammals in response to chemical exposure. Skin biopsies from sperm whale (Physeter macrocephalus) were exposed for 24 h to beta-naphthoflavone (BNF), a prototypical CYP1A1 inducer, and CYP1A1 induction was detected by immunohistochemical staining in endothelial cells, smooth muscle cells, and fibroblasts. Biopsy slices were exposed to a range of BNF concentrations (0.6-600 microM), and a significant concentration-effect relationship was observed in both endothelial and smooth muscle cells (p = 0.05). This is the first study using skin biopsy slices to examine exposure of cetacean tissue to a CYP1A1 inducer. It demonstrates a causal relationship between chemical exposure and CYP1A1 induction and therefore validates the use of CYP1A1 expression in skin biopsies as a biomarker in cetaceans. Our protocol can be adapted to the investigation of chemicals, mixtures, concentrations, incubation times, or biological endpoints of choice. This should prove particularly relevant for these and other protected species that cannot be studied in the laboratory.

Mitochondrial DNA diversity and population structure among southern right whales (Eubalaena australis).

The population structure and mitochondrial (mt) DNA diversity of southern right whales (Eubalaena australis) are described from 146 individuals sampled on 4 winter calving grounds (Argentina, South Africa, Western Australia, and the New Zealand sub-Antarctic) and 2 summer feeding grounds (South Georgia and south of Western Australia). Based on a consensus region of 275 base pairs of the mtDNA control region, 37 variable sites defined 37 unique haplotypes, of which only one was shared between regional samples of the Indo-Pacific and South Atlantic Oceans. Phylogenetic reconstruction of the southern right whale haplotypes revealed 2 distinct clades that differed significantly in frequencies between oceans. An analysis of molecular variance confirmed significant overall differentiation among the 4 calving grounds at both the haplotype and the nucleotype levels (F(ST) = 0.159; Phi(ST) = 0.238; P < 0.001). Haplotype diversity was significantly lower in the Indo-Pacific (h = 0.701 +/- 0.037) compared with the South Atlantic (h = 0.948 +/- 0.013), despite a longer history of exploitation and larger catches in the South Atlantic. In fact, the haplotype diversity in the Indo-Pacific basin was similar to that of the North Atlantic right whale that currently numbers about 300 animals. Multidimensional scaling of genetic differentiation suggests that gene flow occurred primarily between adjacent calving grounds within an ocean basin, with mixing of lineages from different calving grounds occurring on feeding grounds.