Abstract:
BACKGROUND
Follicle numbers and developing ovarian morphology, particularly with reference to the
presence of interstitial tissue, are intimately linked within the ovary of the African elephant
during the period spanning mid-gestation to puberty. These have not been previously
quantified in any studies. The collection of 7 sets of elephant fetal ovaries between 11.2 and
20.2 months of gestation, and 29 pairs of prepubertal calf ovaries between 2 months and 9
years of age during routine management off-takes of complete family groups in private
conservancies in Zimbabwe provided an opportunity for a detailed study of this period.
RESULTS
The changing morphology of the ovary is described as the presumptive cortex and medulla
components of the fetal ovary settled into their adult form. Interstitial tissue dominated the
ovary in late fetal life and these cells stained strongly for 3β–hydroxysteroid dehydrogenase.
This staining continued postnatally through to 4.5 years of age suggesting continued secretion
of progestagens by the ovary during this period. The considerable growth of antral follicles
peaked at 28% of ovarian volume at around 16.7 months of fetal age. The numbers of small
follicles (primordial, early primary and true primary), counted in the cortex using stereological protocols, revealed fewer small follicles in the ovaries of animals aged 0 to 4.5
years of age than during either late fetal life or prepubertal life.
CONCLUSIONS
The small follicle populations of the late-fetal and prepubertal ovaries of the African elephant
were described along with the changing morphology of these organs. The changes noted
represent a series of events that have been recorded only in the elephant and the giraffe
species to date. The expansion of the interstitial tissue of the fetal ovary and its continued
presence in early post natal life may well contribute to the control of follicle development in
these early years. Further research is required to determine the reasons behind the variation of
numbers of small follicles in the ovaries of prepubertal calves.
