001; and r = 0.8099, one-tailed P < 0.0001 respectively).

A comparison of corpora counts in three age groups of false killer whales from Japan (8–20, 20–32, and 32–44 yr) failed to demonstrate a significant difference in the mean numbers of corpora in pregnant and nonpregnant animals (3.8 vs. 3.9, t = 0.162, P = 0.437; 7 vs. 8.2, t = 0.569, P = 0.294; and 12.5 vs. 13.9, t = 0.771, P = 0.261 respectively), even though in all three age groups the means were lower in pregnant animals, albeit weakly so in the younger animals. These results do not support the resorption of CLs in false killer whales. The relationship between age and corpora count for both the South African and Japanese females is clearly non-linear and declines with check details age (Fig. 6), with South Roscovitine mw African females apparently ovulating less frequently than the Japanese false killer whales and ceasing to ovulate at an earlier age. Such a phenomenon would be consistent with the comparatively lower reproductive output of South African females suggested by the lower incidence of pregnant females and nursing age calves indicated earlier. An alternative explanation could be that the lower counts in South African females were a consequence of the poorer state of fixation of their ovaries, leading to some of the smaller corpora being overlooked. To test this hypothesis, the size distribution

of old CAs was compared between South African and Japanese females. The data were stratified into three age groups (6–20 yr, 20–45 yr, 45 +  yr), to control for the naturally 上海皓元医药股份有限公司 occurring decrease in corpus size with age. Overall the old CAs of the South African females ranged in diameter from 2.3 to 13.4 mm with

a mean of 5.8 mm (n = 177), while those of the Japanese females were significantly larger, ranging from 1.2 to 13.3 mm with a mean of 6.3 mm (n = 599, t = 2.85, two-tailed P = 0.0045). The mean corpus size was smaller in the South African sample for all three age groups (5.9 ± 1.2 vs. 7.5 ± 1.9 cm, 6.2 ± 1.7 vs. 6.4 ± 1.7 cm, and 5.3 ± 1.7 vs. 5.8 ± 1.9 cm, respectively), and significantly so in the 6–20 and 45 +  age groups (t-test, P = 0.0326 and 0.0155, respectively). Contrary to the prediction that a postmortem effect would result in smaller corpora not being as detectable, old CAs in the South African whales were consistently smaller than those from Japan across all age groupings. Accordingly, the hypothesis that the lower ovulation rate in the South African false killer whales is an artifact arising from poorer fixation was not supported by the results of this analysis. The generally larger size of the old corpora in the Japanese females could reflect their larger body size. Quantitative expression of the overall ovulation rate in both populations is complicated by the high individual variation, trend with age and (especially in South African whales) the relatively low sample size (Fig. 6).