Eurasian otter populations strongly declined and partially disappeared due to global and local causes (habitat destruction, water pollution, human persecution) in parts of their continental range. Conservation strategies, based on reintroduction projects or restoration of dispersal corridors, should rely on sound knowledge of the historical or recent consequences of population genetic structuring. Here we present the results of a survey performed on 616 samples, collected from 19 European countries, genotyped at the mtDNA control-region and 11 autosomal microsatellites. The mtDNA variability was low (nucleotide diversity = 0.0014; average number of pairwise differences = 2.25), suggesting that extant otter mtDNA lineages originated recently. A star-shaped mtDNA network did not allow outlining any phylogeographic inference. Microsatellites were only moderately variable (H o = 0.50; H e = 0.58, on average across populations), the average allele number was low (observed A o = 4.9, range 2.5-6.8; effective A e = 2.8; range 1.6-3.7), suggesting small historical effective population size. Extant otters likely originated from the expansion of a single refugial population. Bayesian clustering and landscape genetic analyses however indicate that local populations are genetically differentiated, perhaps as consequence of post-glacial demographic fluctuations and recent isolation. These results delineate a framework that should be used for implementing conservation programs in Europe, particularly if they are based on the reintroduction of wild or captive-reproduced otters.

In most mammalian species the cardiac skeleton is composed of coarse collagen fibres, fibrocartilage, and pieces of hyaline cartilage. Bone, the os cordis, is a regular constituent of the ruminant heart. The cardiac skeleton of the otter (Lutra lutra) has not previously been described. The skeleton in 30 otter hearts was studied by -ray analysis and light microscopy. Serial sections were cut parallel to the atrioventricular plane and histochemical staining methods were performed to identify connective tissue fibres, glycosaminoglycans, mineral deposits, and bone. Age and sex of the animals under investigation were considered. The otter heart skeleton was composed of coarse collagen fibres with intercalated pieces of fibrous and\or hyaline cartilage, calcified cartilage, and lamellar bone with red or white marrow. Pieces of hyaline cartilage were not clearly defined : a perichondrial layer was missing and coarse connective tissue continuously transformed into fibrous and hyaline cartilage. In both sexes the amount of cartilage and bone were found to increase with age.Our results establish the presence of bony material in the heart skeleton of the otter, a small mammalian species. This finding indicates that differentiation of bone is not exclusively related to the size of the organ. Increasing amounts of calcified cartilage and bone correlated with increasing age.Key words : Cardiac skeleton ; os cordis ; cartilage ; extracellular matrix. The musculature of the atrial and ventricular walls is inserted into the cardiac skeleton, which comprises the fibrous rings (annuli fibrosi) and the fibrous trigone (trigona fibrosa). The fibrous rings are mainly composed of interwoven bundles of collagen fibres with a few elastic fibres surrounding the atrioventricular openings and the openings of aorta and pulmonary artery. The fibrous trigones consist of areas of dense connective tissue between the aorta and the atrioventricular openings and are connected by the aortic-mitral curtain. The right trigone, together with the membranous septum, constitutes the central fibrous body (Gray, 1995). In certain mammalian species, the trigones contain fibrocartilage, hyaline cartilage, and even bony material. The latter forms a right and left cardiac bone (os cordis) related to the trigone between atrioventricular ostia and the aortic Correspondence to Dr M. Egerbacher,

Data obtained from the dissection of 1067 otters Lutra lutra were used to compare the causes of mortality in relation to age composition, time trends, and regions. Age determination was based on the analysis of incremental cementum lines in teeth. Major causes of mortality of otters were traf®c accidents (69.9%), followed by natural deaths (6.6%), deaths in ®sh-traps (6%), hunting (4.1%), and other violent events (4.4%). No signi®cant differences in mortality structure between the sexes were found. Resulting from a log-linear and a contrast analysis, signi®cant differences in frequencies of mortality causes in relation to different time periods, regions and age classes of otters were observed. The frequency of otters dying from hunting or diseases was highest in youngest (AC I) and oldest (AC V) otters. Generally, the greatest differences between age classes resulted from comparison of frequencies of traf®c-mortality, hunting, and ®sh-traps. Concerning time trends, the greatest differences were found in the periods before and after 1990. In addition to the increase of traf®c-mortality, hunting and deaths in ®sh-traps in¯uenced the distribution of mortality in different time periods. In eastern Germany, there is a clear difference in mortality between northern and southern regions. This results mainly from commercial ®sh-trapping being more common at the northern coast and lakes. However, in all different subsamples of time, region or age-class, traf®c-killed otters amounted to > 50% of all otters found dead.

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