Spontaneous neoplasms in harbour porpoises Phocoena phocoena.

Harbour porpoises are widely distributed in the North Atlantic and represent the most abundant cetacean species in the North and Baltic Seas. Spontaneous neoplasms are relatively rarely reported in cetaceans, and only little is known about neoplasia in harbour porpoises. Thus, archival material was reviewed for spontaneous neoplasms in harbour porpoises recorded during post-mortem examinations between 1999 and 2018. Neoplasms were identified in 7 adult porpoises: 6 animals originating from the North and Baltic Seas and investigated as part of German and Dutch systematic health monitoring programs, and 1 porpoise from Greenlandic waters. The tumours were of different histogenetic origins and further characterised by histology and immunohistochemistry. One individual had a neoplasia in the digestive tract (adenocarcinoma, n = 1); 4 animals, in the genital tract (Sertoli cell tumour, n = 1; genital leiomyoma/fibroleiomyoma, n = 3); and 2 porpoises, in endocrine organs (adrenal adenoma, n = 2). This is the first report of an adenocarcinoma in the liver, a testicular Sertoli cell tumour and adrenocortical adenomas in harbour porpoises. The cause of the tumorigenesis in examined cases remains undetermined. The involvement of endogenous factors, including mutation of cell cycle regulating genes, such as the tumour-suppressor gene p53, cannot be ruled out. The aetiopathogenetic significance of exogenous factors, such as infectious agents like liver flukes or anthropogenic factors, including persistent organic pollutants, should be the subject of future investigations.

Habitat selection and populations of Corynosoma (Acanthocephala) in the intestines of sea otters (Enhydra lutris) and seals.

Acanthocephalans are common intestinal parasites of marine mammals, the most widespread of which is the genus Corynosoma. In this study, parasite infrapopulations of two closely related species of Corynosoma were examined: Corynosoma enhydri from sea otters (Enhydra lutris) in Alaska (n = 12) and California (n = 19), and Corynosoma strumosum from seals in Germany (n = 22). Prevalence of C. enhydri was 100% in Californian otters, with a mean abundance of 30, and 83% in Alaskan otters, with a mean abundance of 232. In seals, C. strumosum had a prevalence of 65%, with a mean abundance of 33. Female C. enhydri dominated both Californian (82%) and Alaskan (79%) infections, while, in seals, female C. strumosum made up 68% of the parasite population. Reproduction rates for C. enhydri, with 16% (California) and 18% (Alaska) of females mated, were low compared to C. strumosum in seals, of which 40% of females were mated. Habitat selection also differed significantly between the two species. Corynosoma enhydri was found most frequently in the second and third fifths of the small intestine, while C. strumosum was found most frequently in the fourth. The differences in habitat selection and prevalence analysed in this study may be related to a trade-off between growth and reproduction between the two species.