Organohalogen concentrations and a gross and histologic ...

Also Pertoldi et al. (1997) investigated developmental stability in the Eurasian
otter (Lutra lutra) collected 1861-1994 (n=172). They measured three
metric traits of the skull and one on the lower jaw of which we measured the
one in the lower jaw and two of the three in the skull. Of these; FA in three
traits in females and two in males had increased significantly by time and it
was stated that this was probably due to lower genetic variations (bottle
necks) over time rather than toxic levels of contaminants (although levels of
contaminants was measured these were not reported; see section FA versus
contaminants). FA in skulls of the Yellowstone grizzly (Ursus arctos) has also
been associated with genetic isolation in 16 traits measured (Picton et al.,
1990) but this association is not likely in the present polar bear sample as a
relatively constant hunting has taken place over the last century (Sandell et
al., 2001).
FA is expected to be a result of in utero disturbances (e.g. Siegel and Doyle
1975a-c, Doyle et al., 1977, Siegel et al., 1977a-b). Therefore FA in polar bears
can be explained by environmental factors other than organohalogens.
Noise, temperature extremes and food availability are some environmental
factors impacting FA (e.g. Siegel and Doyle 1975a-c, Doyle et al., 1977, Siegel
et al., 1977a-b, Nilsson 1994, Carrascal et al., 1998). These results from controlled
studies of laboratory mammals (rats) have shown a significant correlation
between audiogenic and temperature stressors and dental and bone
fluctuating asymmetry. If these factors differ between the two periods 1892-
1960 and 1961-2002 it could explain that FA in the period before 1960 is
higher than in the period after 1960. Higher climatic fluctuations (temperature
extremes) in the first period could explain food availability and thereby
a high degree of developmental instability in the polar bears compared to
the second period. However, a temperature effect is not likely either as temperatures
above normal have been experienced in East Greenland during the
last two decades. Furthermore, an added complexity is that temperatures
were also relatively high in this area between ca. 1930 and ca. 1960 (Førland
2002). Finally genetic stress (bottleneck) could differ between the periods although
this is not likely as a relatively constant hunting has taken place over
the last century and no clear change has been observed in the number of
bears obtained or the areas where the hunt has taken place (Sandell et al.,
2001).
4.2 Age and sex differences
In general, FA was higher in adults than in subadults and was in the F-test
significant in 3 out of 14 traits for females and in 6 out of 14 traits for males
(both distance and teeth measurements). This result may be doubted as all
traits except 38 was not normal distributed and that the result was only supported
by the non-parametric Kruskall-Wallis in trait 38. Only for one trait
(28) FA were found higher in females compared to males and this result was
not significant in the Kruskall-Wallis test. The Kruskall-Wallis test found
that subadults were slightly significant higher than adults in trait 24 but as it
was not in accordance with the F-test the result may be doubted. In general
it may be postulated that it has resulted by chance due to the large (n=14)
number of traits examined between three groups (42 tests).
Although FA is thought to be a result of in utero disturbances (e.g. Siegel and
Doyle 1975a-c, Doyle et al., 1977, Siegel et al., 1977a-b) one may speculate
whether different age and sex groups have different FA. These results are in
accordance with the finding in harbour seals (Schandorff 1997a-b), where a
higher degree of fluctuating asymmetry in foramen FA (but not in teeth) was
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