Neuroendocrine control of reproduction
The hypothalamo-pituitary-ovary and hypothalamo-pituitary-testes axes are the hormonal messaging systems controlling reproduction. We need to know the critical players for fertility control, understanding cancer, farm animal production, aquaculture and captive breeding of endangered species. One of our most compelling recent discoveries is the fundamental role of a peptide called secretoneurin. Based on work in goldfish, zebrafish and mice, we have made the proposal that it is a new reproductive hormone. We also study similar hormonal control systems of reproduction in frogs. Comparing fish and frogs gives insight into the evolution of hormone systems, so what we find in one species can help us to understand others, including humans.
The zebrafish Danio rerio (family Cyprinidae) is an example of a gonochoristic teleost. Zebrafish, also known as the zebra danio, originates from Pakistan, India, Bangladesh, Nepal and Myanmar. It is a common aquarium species and is an important model species for scientific research on the mechanisms of development and reproduction in vertebrates. A: Sexually mature adult female. B: Sexually mature adult male. C: Dissection of the sexually mature adult female showing the large ovary outlined with the white line. D: Dissection of the sexually mature adult male showing the testis outlined with the white line. Modified from Trudeau, V.L. 2018. Reproduction in Osteichthyes. In M. K. Skinner (Ed.), Encyclopedia of Reproduction (Second ed., Vol. 6) (pp. 60–566). Academic Press: Elsevier.
Generalized depiction of the teleost pituitary gland. During the teleost radiation, extensive development of the direct innervation mode of hypothalamo-pituitary communication was accompanied by loss of the median eminence typical of mammals. Cells secreting follicle stimulating hormone, luteinizing hormone, and other hormones are directly innervated. These pituitary hormones are released into the blood and control ovarian and testicular function in females and males, respectively. See Trudeau, V.L. 2022. Annu. Rev. Anim. Biosci. 2022. 10:107–30 for more details.
Proposed model for neuroendocrine control of reproduction in teleosts. This is a composite and simplified view of neuroendocrine control pathways and does not represent a single teleost species. The main focus is on the control of luteinizing hormone (LH). See Trudeau, V.L. 2022. Annu. Rev. Anim. Biosci. 2022. 10:107–30 for more details.
Endocrine disruption and ecotoxicology
Our work on the transgenerational effects of Prozac- a significant pollutant in the aquatic environment are the first demonstrations that an antidepressant can have long-lasting negative effects on endocrine systems up to 4 generations after a single treatment in the zebrafish model. Studies on pesticides and industrial effluents including oil sands tailings ponds are at the leading edge to endocrine disruption research in frogs. Our work has shown that the brain is a major target for the actions of contaminants and that these disrupt normal development and reproduction. Such research has helped to shape the emerging field of “neuroendocrine disruption”.
Vera-Chang MN, St-Jacques AD, Gagné R, Martyniuk CJ, Yauk CL, Moon TW, Trudeau VL. Transgenerational hypocortisolism and behavioral disruption are induced by the antidepressant fluoxetine in male zebrafish Danio rerio. Proc Natl Acad Sci U S A. 2018 Dec 26;115(52):E12435-E12442. doi: 10.1073/pnas.1811695115. Epub 2018 Dec 10. PMID: 30530669; PMCID: PMC6310822.
Trudeau VL, Thomson P, Zhang WS, Reynaud S, Navarro-Martin L, Langlois VS. Agrochemicals disrupt multiple endocrine axes in amphibians. Mol Cell Endocrinol. 2020 Aug 1;513:110861. doi: 10.1016/j.mce.2020.110861. Epub 2020 May 22. PMID: 32450283.
Reproductive technologies for amphibians
Unprecedented rates of species decline have resulted in the sixth mass extinction currently threatening global biodiversity and ecosystem functioning. All vertebrate classes have been affected, though amphibians are exhibiting the most dramatic declines, with an estimated 40% of species threatened with extinction. Reproductive technologies are increasingly being adopted to enhance the propagation and genetic management of amphibian conservation breeding programs. Our contribution is the development of a highly effecting injectable hormone mixture to induce spawning. We call it the AMPHIPLEX method, combining the words amphibian and amplexus referring to the typical frog sexual behaviour. We are now on the search for new hormones that may be useful for spawning induction.
Trudeau V.L., Raven, B., Pahuja, H. & Narayan, E. 2022. Chapter 4. Hormonal Control of Amphibian Reproduction. In Aimee Silla, Harold Heathwole, and Andrew Kouba (Eds.), In: Reproductive Technologies and Biobanking as Tools for the Conservation of Amphibians (pp. 248). CSIRO and CRC; ISBN: 9781486313334.