1
|
Brown ME, Pukazhenthi B, Olsen GH, Crowe C, Lynch W, Wildt DE, Songsasen N. Low estradiol production of non-laying whooping cranes (Grus americana) is associated with the failure of small follicles to enter follicular hierarchy. Gen Comp Endocrinol 2023; 338:114280. [PMID: 37011766 DOI: 10.1016/j.ygcen.2023.114280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/26/2023] [Accepted: 03/30/2023] [Indexed: 04/04/2023]
Abstract
For endangered species managed ex situ, production of offspring is a key factor to ensure healthy and self-sustaining populations. However, current breeding goals for the whooping crane (Grus americana) are impeded by poor reproduction. Our study sought to better understand mechanisms regulating ovarian function in ex situ managed whooping cranes and the regulatory function of the hypothalamic-pituitary-gonadal (HPG) axis in relation to follicle formation and egg laying. To characterize hormonal regulation of follicular development and ovulation, we collected weekly blood samples from six female whooping cranes during two breeding seasons, for a total of 11 reproductive cycles. The plasma samples were assessed for follicle stimulating hormone, luteinizing hormone, estradiol, and progesterone and the yolk precursors vitellogenin and very low-density lipoprotein. Ultrasonographic examination of the ovary was conducted at the time of blood collection. Preovulatory follicles (>12 mm) were present in laying cycles (n = 6) but absent in non-laying cycles (n = 5). The patterns of plasma hormone and yolk precursor concentrations corresponded to the stage of follicle development. Specifically, gonadotropin and yolk precursors concentrations increased as follicles transitioned from the non-yolky to yolky stage but did not increase further as the follicle advanced to preovulatory and ovulatory stages. Estrogen and progesterone concentrations increased as follicle size increased and reached peak concentrations (P < 0.05) when follicles developed to ovulatory and preovulatory stages, respectively. While overall mean circulating gonadotropin, progesterone, and yolk precursor concentrations did not differ for laying versus non-laying cycles, mean plasma estradiol in laying cycles was significantly higher than that in non-laying cycles. In summary, the findings suggested that disruption of mechanisms regulating follicle recruitment is likely responsible for the oviposition failure of the captive female whooping crane.
Collapse
|
2
|
Digby A, Eason D, Catalina A, Lierz M, Galla S, Urban L, Le Lec MF, Guhlin J, Steeves TE, Dearden PK, Joustra T, Lees C, Davis T, Vercoe D. Hidden impacts of conservation management on fertility of the critically endangered kākāpō. PeerJ 2023; 11:e14675. [PMID: 36755872 PMCID: PMC9901309 DOI: 10.7717/peerj.14675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Accepted: 12/11/2022] [Indexed: 02/05/2023] Open
Abstract
Background Animal conservation often requires intensive management actions to improve reproductive output, yet any adverse effects of these may not be immediately apparent, particularly in threatened species with small populations and long lifespans. Hand-rearing is an example of a conservation management strategy which, while boosting populations, can cause long-term demographic and behavioural problems. It is used in the recovery of the critically endangered kākāpō (Strigops habroptilus), a flightless parrot endemic to New Zealand, to improve the slow population growth that is due to infrequent breeding, low fertility and low hatching success. Methods We applied Bayesian mixed models to examine whether hand-rearing and other factors were associated with clutch fertility in kākāpō. We used projection predictive variable selection to compare the relative contributions to fertility from the parents' rearing environment, their age and previous copulation experience, the parental kinship, and the number of mates and copulations for each clutch. We also explored how the incidence of repeated copulations and multiple mates varied with kākāpō density. Results The rearing status of the clutch father and the number of mates and copulations of the clutch mother were the dominant factors in predicting fertility. Clutches were less likely to be fertile if the father was hand-reared compared to wild-reared, but there was no similar effect for mothers. Clutches produced by females copulating with different males were more likely to be fertile than those from repeated copulations with one male, which in turn had a higher probability of fertility than those from a single copulation. The likelihood of multiple copulations and mates increased with female:male adult sex ratio, perhaps as a result of mate guarding by females. Parental kinship, copulation experience and age all had negligible associations with clutch fertility. Conclusions These results provide a rare assessment of factors affecting fertility in a wild threatened bird species, with implications for conservation management. The increased fertility due to multiple mates and copulations, combined with the evidence for mate guarding and previous results of kākāpō sperm morphology, suggests that an evolutionary mechanism exists to optimise fertility through sperm competition in kākāpō. The high frequency of clutches produced from single copulations in the contemporary population may therefore represent an unnatural state, perhaps due to too few females. This suggests that opportunity for sperm competition should be maximised by increasing population densities, optimising sex ratios, and using artificial insemination. The lower fertility of hand-reared males may result from behavioural defects due to lack of exposure to conspecifics at critical development stages, as seen in other taxa. This potential negative impact of hand-rearing must be balanced against the short-term benefits it provides.
Collapse
Affiliation(s)
- Andrew Digby
- Kākāpō Recovery Programme, Department of Conservation, Invercargill, New Zealand
| | - Daryl Eason
- Kākāpō Recovery Programme, Department of Conservation, Invercargill, New Zealand
| | | | - Michael Lierz
- Clinic for Birds, Reptiles, Amphibians and Fish, Justus-Liebig University Giessen, Giessen, Germany
| | - Stephanie Galla
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand,Department of Biological Sciences, Boise State University, Boise, ID, United States of America
| | - Lara Urban
- Genomics Aotearoa, Dunedin, New Zealand,Department of Anatomy, University of Otago, Dunedin, New Zealand
| | - Marissa F. Le Lec
- Genomics Aotearoa, Dunedin, New Zealand,Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Joseph Guhlin
- Genomics Aotearoa, Dunedin, New Zealand,Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Tammy E. Steeves
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand,Genomics Aotearoa, Christchurch, New Zealand
| | - Peter K. Dearden
- Genomics Aotearoa, Dunedin, New Zealand,Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | | | - Caroline Lees
- IUCN SSC Conservation Planning Specialist Group, Auckland, New Zealand
| | - Tane Davis
- Te Rūnanga o Ngāi Tahu, Christchurch, New Zealand
| | - Deidre Vercoe
- Kākāpō Recovery Programme, Department of Conservation, Invercargill, New Zealand
| | | |
Collapse
|
3
|
Barker KJ, Xu W, Van Scoyoc A, Serota MW, Moravek JA, Shawler AL, Ryan RE, Middleton AD. Toward a new framework for restoring lost wildlife migrations. Conserv Lett 2021. [DOI: 10.1111/conl.12850] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Kristin J. Barker
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Wenjing Xu
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Amy Van Scoyoc
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Mitchell W. Serota
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Jessie A. Moravek
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Avery L. Shawler
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Rachael E. Ryan
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| | - Arthur D. Middleton
- Department of Environmental Science, Policy, and Management University of California—Berkeley Berkeley California
| |
Collapse
|
4
|
Edwards HA, Converse SJ, Swan KD, Moehrenschlager A. Trading off hatching success and cost in the captive breeding of Whooping Cranes. Anim Conserv 2021. [DOI: 10.1111/acv.12722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | - S. J. Converse
- U.S. Geological Survey Washington Cooperative Fish and Wildlife Research Unit School of Environmental and Forest Sciences & School of Aquatic and Fishery Sciences University of Washington Seattle Washington USA
| | - K. D. Swan
- The Calgary Zoo Foundation Calgary AB Canada
| | | |
Collapse
|
5
|
Assersohn K, Brekke P, Hemmings N. Physiological factors influencing female fertility in birds. ROYAL SOCIETY OPEN SCIENCE 2021; 8:202274. [PMID: 34350009 PMCID: PMC8316823 DOI: 10.1098/rsos.202274] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 07/12/2021] [Indexed: 05/30/2023]
Abstract
Fertility is fundamental to reproductive success, but not all copulation attempts result in a fertilized embryo. Fertilization failure is especially costly for females, but we still lack a clear understanding of the causes of variation in female fertility across taxa. Birds make a useful model system for fertility research, partly because their large eggs are easily studied outside of the female's body, but also because of the wealth of data available on the reproductive productivity of commercial birds. Here, we review the factors contributing to female infertility in birds, providing evidence that female fertility traits are understudied relative to male fertility traits, and that avian fertility research has been dominated by studies focused on Galliformes and captive (relative to wild) populations. We then discuss the key stages of the female reproductive cycle where fertility may be compromised, and make recommendations for future research. We particularly emphasize that studies must differentiate between infertility and embryo mortality as causes of hatching failure, and that non-breeding individuals should be monitored more routinely where possible. This review lays the groundwork for developing a clearer understanding of the causes of female infertility, with important consequences for multiple fields including reproductive science, conservation and commercial breeding.
Collapse
Affiliation(s)
- Katherine Assersohn
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Patricia Brekke
- Institute of Zoology, Zoological Society of London, Regents Park, London NW1 4RY, UK
| | - Nicola Hemmings
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| |
Collapse
|