Reproductive biology of male franciscanas (Pontoporia blainvillei) (Mammalia: Cetacea) from Rio Grande do Sul, southern Brazil
The reproductive biology of male franciscanas (Pontoporiablainvillei), based on 121 individuals collected in Rio Grande do Sul State, southern Brazil, was studied. Estimates on age, length, and weight at attainment of sexual maturity are presented. Data on the reproductiveseasonality and on the relationship between some testicular characteristics and age, size, and maturity status are provided. Sexual maturity was assessed by histological examination of the testes. Seasonality was determined by changes in relative and total testis weight, and in seminiferous tubule diameters. Testis weight, testicular index of maturity, and seminiferous tubule diameters werereliable indicators of sexual maturity, whereas testis length, age, length, and weight of the dolphin were not.Sexual maturity was estimated to be attained at 3.6 years (CI 95% =2.7–4.5) with the DeMaster method and 3.0 years with the logistic equation. Length and weight at attainment of sexual maturity were 128.2 cm (CI 95%=125.3–131.1 cm) and 26.4 kg (CI 95% =24.7–28.1 kg), respectively. It could not be verified that there was any seasonal change in the testis weight and in the seminiferous tubule diameters in mature males. It is suggested that at least some mature males may remain reproductively active throughout the year. The extremely low relative testis weight indicates that sperm competition does not occur in the species. On the other hand, the absence of secondary sexual characteristics,the reversed sexual size dimorphism, and the small numberof scars from intrassexual combats in males reinforce the hypothesis that male combats for female reproductive access may be rare for franciscana. It is hypothesized that P. blainvillei form temporary pairs (one male copulatingwith only one female) during the reproductive period.
| Main Authors: | , , , , |
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| Format: | article biblioteca |
| Language: | English |
| Published: |
2004
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| Subjects: | Ecology, Fisheries, |
| Online Access: | http://hdl.handle.net/1834/30938 |
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