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Behavioural Endocrinology ا : Introduction and Case Study

Behavioural Endocrinology ا : Introduction and Case Study. Text Chapter 8. Contents. Basic review of the endocrine system Hormone types, modes of action and categories of influence Case study: Growth hormone and salmonid fishes Darek’s research – An ecological assessment. Definitions.

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Behavioural Endocrinology ا : Introduction and Case Study

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  1. Behavioural Endocrinology ا:Introduction and Case Study Text Chapter 8

  2. Contents • Basic review of the endocrine system • Hormone types, modes of action and categories of influence • Case study: Growth hormone and salmonid fishes • Darek’s research – An ecological assessment

  3. Definitions Behavioural Endocrinology: The study of hormonal influence on behaviour and the behavioural influence on hormone expression Hormone: Organic chemical substance produced by an endocrine gland, exocrine gland or neurosecretory cell (neurohormone) that may alter the physiology and/or behaviour of an organism Physiological/Behavioural Change Target Tissue Neuroseretory Cell CNS Endocrine/Exocrine Gland

  4. Endocrine System Features Neurosecretory Cells: • Modified nerve cells • Secrete neurohormones into bloodstream • Direct and indirect actions Exocrine Glands: • release hormones via ducts or tubes • Affect adjacent organs or external environment Eckert 2000 Nelson 1995

  5. Nelson 1995 Endocrine System Features EndocrineGlands: • highly vascularized, ductless • Secrete hormones into bloodstream • Attach to specific binding sites called hormone receptors • Affect any cell with receptors

  6. Hormone Types 1) Amines: • small, amino acid-derived • include catecholamines and thyroid hormones 2) Prostaglandins: • synthesized in membranes • cyclic unsaturated hydroxy fatty acids • include thromboxane

  7. Hormone Types 3) Steroid Hormones: • cyclic hydrocarbon derivatives synthesized from steroid cholesterols • include testosterone and estrogen 4) Peptide/Protein Hormones: • largest, most complex • includes insulin, growth hormone

  8. ExamplePathways…

  9. Feedback Loops • Feedback loops help regulate the secretion of many hormones • 1) Negative Feedback - Control of secretion of adrenocortical steroids • 2) Positive Feedback - Estrogen and LH during LH surge

  10. Synergism and Antagonism • Synergy and permissive effects : •  Epinephrine and nor-epinepherine both increase the heart rate singly, but together effect is greater • One hormone can also increase the responsiveness of a tissue to a second hormone (Exposure of the uterus to estrogen increases its response to progesterone) • Small amounts of one hormone may assist in the maturation of receptors for a second hormone, known as up regulation

  11. Synergism and Antagonism • Antagonistic Effects : • Insulin and glucagon, have antagonistic effects on blood glucose levels and on the cellular uptake and use of glucose • Prolonged exposure to polypeptide hormones desensitize target cells and promote receptor down regulation • (i.e. release of FSH and LH in the ovulatory cycle)

  12. Categories of Influence • Organizational effects versus activational effects Organizational Effects: result in long-term changes in body tissues manifested during critical periods of development (i.e. sex determination) Activational Effects: relative expression of a hormone correlates with the behavioural response (i.e. testosterone level and aggression)

  13. Case Study: GH and Salmonids • Growth Hormone: • Polypeptide hormone • Involved in somatic growth, metabolism, energy utilization and osmoregulation

  14. 1 2193 2897 4061 M N 2653 2654 815 F 1559 R 534 bp 207 bp A-F D-R Oppro-F 841 R 1963 F B 745 bp 331 bp 826 bp 972 bp Ocean Pout AFP 5’ promoter region Ocean Pout AFP 3’ region Chinook salmon GH cDNA What is a transgenic fish? opAFPGHc2 • Transgenic: Any organism containing stable foreign DNA within its genome • Genetically heritable Modified from Du et al. 1992

  15. Pros Increased productivity ( profits and/or market value) Increased food supply Cons Ecological implications Human health implications Transgenic Debate

  16. Ecological Concerns Gross 1998

  17. Ecologically Risky Physiology? • growth rates • rate of energy reserve loss (Cook et al. 2000) • Intrinsic metabolism? AQUA Bounty Inc.

  18. External stimuli Positive Feedback Animal Conditioned Future Response (G+E+I)+(A+P) Behaviour(s) Consequences Internal stimuli (Proximate & Ultimate) Negativefeedback Modified from Lehner 1996 • GH transgenesis directly alters the genetic, anatomonic, and physiological components of internal stimuli • Behavioural consequences may impact fitness

  19. Peripheral GH Injection Behavioural Responses: spontaneous activity appetite aggression antipredator behaviour

  20. Table 1. Highlighted behavioural differences between growth hormone transgenic and non-transgenic Coho (Oncorhynchus kisutch) and Atlantic (Salmo salar) salmon juveniles.

  21. Nelson 1995 • Hormones can act on all the behavioural components of an organism • Change the probability that certain behaviours will be emitted indirectly by acting on one or more of these three systems

  22. Bjornsson et al 2004

  23. CNS and Hormones • Hormones may act on the CNS directly or indirectly • GH receptors exist in salmonid brain, but direct mechanism unknown • Monoamine neurotransmitters influence agonistic behaviour and stress reactions in teleosts • Dopaminergic system: positively correlated to aggression and swimming activity • Serotonergic system: negatively correlated with aggression and swimming activity

  24. GreaterMetabolic Requirement Direct CNS Influence Increased Appetite Increased Spontaneous Activity Jonsson et al. 2003 Greater Feeding Motivation Reduced Antipredator Behaviour Increased Aggression Dominance

  25. Bottlenecks of survival: • Reproductive success • Early freshwater phase • (survival from egg to smolt)

  26. Redd Emergence N. Giles N. Giles • Establish foraging territories (McNichol and Noakes 1981) • Unsuccessful fry displaced downstream (Bujold et al. 2004) • Physiological costs and predation risks may be incurred

  27. Fry Competition • Body size • Prior experience • Aggression • Prior residence Factors influencing territory recruitment/retention: (Deverill et al. 1999) N. Giles

  28. Prior Residence • Competitive advantage held by existing occupants over a contested space • Prior residence > aggression (O’Connor et al. 2000) • Prior residence > body size (Metcalfe et al. 2003)

  29. Behavioural Asymmetries? Will early territorial relationships involving transgenics differ? • Aggression vs. prior residency How will increased aggression in GHT parr influence territory size and competitive interactions in a naturalized stream environment? • Quantify territory size and aggressive interactions

  30. Physiological Asymmetries? Deitch et al.(unpublished): Intrinsic in post-smolt transgenic Atlantic salmon • Alevin respiratory metabolism • Endogenous phase characteristics

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