Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 454 DISCOVERY REPORTS Variation of fertility with age It has been shown that the female fin whale experiences a seasonally monoestrous sexual cycle. If this is true then variations in the rate of production of ova will be mainly related to the incidence of multiple ovulations, or to the percentage of females ovulating at each ovulatory period, rather than to variations in the number of dioestrous cycles in each ovulatory period. Multiple ovulations The varying incidence of multiple ovulations with age in the present
Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 454 DISCOVERY REPORTS Variation of fertility with age It has been shown that the female fin whale experiences a seasonally monoestrous sexual cycle. If this is true then variations in the rate of production of ova will be mainly related to the incidence of multiple ovulations, or to the percentage of females ovulating at each ovulatory period, rather than to variations in the number of dioestrous cycles in each ovulatory period. Multiple ovulations The varying incidence of multiple ovulations with age in the present material is shown in Table 26. For different numbers of corpora albicantia are shown the numbers of females with more than one corpus luteum in the ovaries. The incidence of multiple ovulations appears to increase with increasing numbers of corpora albicantia (and therefore with increasing age), but there is a significant difference only between the first two groups. It seems probable that there is a real increase in the occurrence of multiple ovulations, because Kimura (1957, fig. 10) shows, for a much larger sample, that the frequency of dizygotic twins similarly increases with age from about o-i (at 1-5 corpora) to 6-25 (at 30-35 corpora). The average incidence of multiple ovulations in the present material is 2-i6±o-82. So far we have not considered the variations in actual numbers of ovulations in cases of multiple ovulation. In different cases of multiple ovulations the number of corpora lutea produced varies from 2 to 13 (in the present material). There are 22 females with 2 corpora lutea, 3 with 3 corpora lutea, 1 with 4 corpora lutea and 1 with 13 corpora lutea. Table 26. No. of corpora albicantia 0-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 5°-54 Total Variation in incidence of multiple ovulations with age (number of corpora albicantia) Total ovaries with corpora lutea 490 281 178 128 76 49 29 15 3 2 Multiple ovulations 1 7 5 6 5 1 Percentage multipl
Size: 1425px × 1404px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
