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Brammer-Robbins E, Cowart JR, Calderon M, Burgess EA, Larkin IV, Martyniuk CJ. Sirenian (manatees and dugongs) reproductive endocrinology. Gen Comp Endocrinol 2024; 356:114575. [PMID: 38908455 DOI: 10.1016/j.ygcen.2024.114575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 06/19/2024] [Indexed: 06/24/2024]
Abstract
Reproductive hormones are essential to mating systems, behavior, fertility, gestation, parturition, and lactation in mammals and understanding the role of hormones in these processes is essential for species conservation. Sirenia is a unique order of marine mammals that include manatees, dugongs, and the extinct Steller's sea cow. Extant Sirenian species are all listed as vulnerable due to habitat loss, cold stress, boat strike trauma, harmful algal bloom toxicity, entanglements, and illegal hunting. Therefore, successful reproduction is essential to maintaining and increasing Sirenian populations. Understanding Sirenian reproductive behavior, endocrinology, and mating strategies will aid conservation and management efforts to protect and provide the proper conditions for successful reproduction. The objectives of this review were to synthesize the current knowledge regarding reproductive cycles and endocrinology of Sirenians and identify knowledge gaps for future investigation. The current literature on Sirenian reproductive physiology reports reproductive seasonality, sexual maturation, estrous cyclicity and acyclicity, pregnancy, and sex differences. However, there remain significant knowledge gaps on the cyclicity and pulsatile release of gonadotropins, maturation in females, and characterization of pregnancy hormone profiles throughout gestation. To date, there is no explanation for confirmed pattern for ovarian acyclicity, nor understanding of the function of the numerous accessory corpus luteum described in manatees. Research including a greater number of longitudinal and postmortem studies on a wider variety of wild manatee populations are important first steps. Taken together, understanding the reproductive endocrinology of these vulnerable and threatened species is critical for policy and management decisions to better inform protection initiatives.
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Affiliation(s)
- Elizabeth Brammer-Robbins
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA; Center for Environmental and Human Toxicology, University of Florida, Gainesville, FL, USA; Aquatic Animal Health Program, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA.
| | - Jonathan R Cowart
- Aquatic Animal Health Program, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Monica Calderon
- Aquatic Animal Health Program, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | | | - Iskande V Larkin
- Aquatic Animal Health Program, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA
| | - Christopher J Martyniuk
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA; Center for Environmental and Human Toxicology, University of Florida, Gainesville, FL, USA
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Lanyon JM, Burgess EA. Methods to examine reproductive biology in free-ranging, fully-marine mammals. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 753:241-74. [PMID: 25091913 DOI: 10.1007/978-1-4939-0820-2_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Historical overexploitation of marine mammals, combined with present-day pressures, has resulted in severely depleted populations, with many species listed as threatened or endangered. Understanding breeding patterns of threatened marine mammals is crucial to assessing population viability, potential recovery and conservation actions. However, determining reproductive parameters of wild fully-marine mammals (cetaceans and sirenians) is challenging due to their wide distributions, high mobility, inaccessible habitats, cryptic lifestyles and in many cases, large body size and intractability. Consequently, reproductive biologists employ an innovative suite of methods to collect useful information from these species. This chapter reviews historic, recent and state-of-the-art methods to examine diverse aspects of reproduction in fully-aquatic mammals.
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Affiliation(s)
- Janet M Lanyon
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, 4072, Australia,
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