The ovaries and reproduction in Pontoporia blainvillei (Cetacea: Platanistidae)

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Abstract
The ovaries of 113 Pontoporia blainvillei (Franciscana dolphin) were examined and their characteristics related to season, body length of the animals and, in some individuals, foetal length. The following conclusions were drawn from the results: most females attain sexual maturity when they reach 136–146 cm body length; most conceptions occur in the period December to February, with a peak in the first half of January; usually only one ovulation occurs, and no animal ovulated more than twice, in a season; postpartum ovulation may occur, and evidence is presented that this is probably followed by conception and that animals may breed once a year but most females breed every other year; body length at birth is greater than 70 cm and less than 85 cm, and probably nearer the smaller figure; the gestation period is 10.5–12 months (depending on what is the actual figure for length at birth, but probably less than 11 months); lactation lasts at least nine months; the corpus luteum contains two morphologically distinct, but apparently functional cell types; there is no apparent morphological difference between corpora lutea which are not associated with pregnancy, and corpora lutea of pregnancy; corpora albicantia may persist for a maximum of four years before being reabsorbed completely.