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Vasconcelos Sampaio W, Leite Leão D, da Cunha Sousa P, Lima de Queiroz H, Farhayldes Souza Domingues S. Male fattening is related to increased seminal quality of squirrel monkeys (Saimiri collinsi): Implications for sperm competition. Am J Primatol 2021; 84:e23353. [PMID: 34855233 DOI: 10.1002/ajp.23353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 10/31/2021] [Accepted: 11/24/2021] [Indexed: 11/12/2022]
Abstract
Saimiri are neotropical primates with seasonal reproduction, males develop a seasonal fattening condition that has been suggested as a pre-copulatory sexual selection strategy. Furthermore, females mate with multiple males in the same season. This could also favor the evolution of a postcopulatory sexual strategy by sperm competition. In this study, we tested the hypothesis that there is a relationship between the fatted condition and advantageous seminal characteristics in Saimiri collinsi and evaluated its implications for sperm competition. Adult males (N = 10), aged 5-15 years, housed in mixed or only-male groups, were analyzed from June, 2015 to July, 2016. Measurements of weight, axilla, and arm skinfold, and testicular volume were taken monthly, and semen was collected by electroejaculation. A fattening index was developed to quantify and identify fatted males, biometrics, and seminal parameters were compared between the non-fatted and fatted conditions. The fatted males present a larger testicular volume. This is related to the increase in spermatogenic activity necessary to sustain a high ejaculation frequency during the mating season. An increase in seminal volume and in frequency of semen coagulation were detected in fatted males, advantages related to sperm protection in the female reproductive tract. Age and social context were not significant sources of variation for both morphological and seminal traits. A decrease in response from the fatted males in obtaining semen and an increase in the frequency of azoospermic ejaculates were observed. These unexpected results may be due to intense reproductive activities in a short period. The fattening phenomenon has many implications in the sexual selection of squirrel monkeys, and they are still not entirely unveiled. Our results corroborate the idea that, in S. collinsi, the fatted male condition is related to sexual selection, and we found evidence suggesting it may be also expressed by a post-copulatory component, sperm competition.
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Affiliation(s)
- Wlaisa Vasconcelos Sampaio
- Postgraduate Program in Animal Health and Production in the Amazon, Federal Rural University of the Amazon, Belém, Pará, Brazil.,Laboratory of Wild Animal Biotechnology and Medicine, Faculty of Veterinary Medicine, Federal University of Pará, Castanhal, Pará, Brazil
| | - Danuza Leite Leão
- Laboratory of Wild Animal Biotechnology and Medicine, Faculty of Veterinary Medicine, Federal University of Pará, Castanhal, Pará, Brazil.,Grupo de Pesquisa em Ecologia de Primatas Amazônicos do Instituto Mamirauá, Mamirauá Institute for Sustainable Development, Tefé, Amazonas, Brazil
| | - Patrícia da Cunha Sousa
- Laboratory of Wild Animal Biotechnology and Medicine, Faculty of Veterinary Medicine, Federal University of Pará, Castanhal, Pará, Brazil
| | - Helder Lima de Queiroz
- Grupo de Pesquisa em Ecologia de Primatas Amazônicos do Instituto Mamirauá, Mamirauá Institute for Sustainable Development, Tefé, Amazonas, Brazil
| | - Sheyla Farhayldes Souza Domingues
- Postgraduate Program in Animal Health and Production in the Amazon, Federal Rural University of the Amazon, Belém, Pará, Brazil.,Laboratory of Wild Animal Biotechnology and Medicine, Faculty of Veterinary Medicine, Federal University of Pará, Castanhal, Pará, Brazil.,Postgraduate Program in Animal Reproduction in the Amazon, Federal University of Pará, Belém, Pará, Brazil
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