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Response to gonadotropin-releasing hormone challenge: Seasonal variation in steroid production in a viviparous lizard, Tiliqua nigrolutea

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Edwards, A ORCID: 0000-0001-7268-9255 and Jones, SM ORCID: 0000-0001-8813-430X 2017 , 'Response to gonadotropin-releasing hormone challenge: Seasonal variation in steroid production in a viviparous lizard, Tiliqua nigrolutea' , General and Comparative Endocrinology, vol. 244 , pp. 70-76 , doi: 10.1016/j.ygcen.2015.11.002.

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Abstract

The hypothalamic–pituitary–gonadal axis plays a central role in the regulation of gamete maturation, sexsteroid production and the stimulation of reproductive behaviours in vertebrates. In seasonal breeders,the timely activation and deactivation of this control system is important to ensure successful reproduction:this process is not well understood in species which breed irregularly. Males of the viviparousblotched blue-tongued lizard, Tiliqua nigrolutea, breed annually, while females display a multiennialcycle. We investigated seasonal variation in hypothalamic–pituitary–gonadal axis responsiveness in bothsexes of T. nigrolutea. We measured changes in plasma concentrations of testosterone and estrogen inresponse to a single intraperitoneal injection of a GnRH agonist, chicken-II LH–RH, at three reproductivelydistinct times of year. Plasma testosterone concentrations in males were significantly increased duringgonadal quiescence, but not initial or final spermatogenesis. There was no estrogen response in malesat any time of year. Conversely, in females, there was an increase in plasma testosterone, but not estrogen,concentration, in reproductively quiescent females several months in advance of a successful pregnancy.These results indicate clear variation in HPG axis activity with sex, season and reproductivecondition in this seasonally breeding viviparous lizard. This study opens the way for further investigationinto the mechanisms by which internal (body condition) and external seasonal cues (temperature andphotoperiod) are coordinated to regulate reproduction in irregularly-breeding reptiles.

Item Type: Article
Authors/Creators:Edwards, A and Jones, SM
Keywords: estrogen, hypothalamic–pituitary–gonadal axis, reptile, seasonal reproduction, testosterone, regulation, steroids
Journal or Publication Title: General and Comparative Endocrinology
Publisher: Academic Press Inc Elsevier Science
ISSN: 0016-6480
DOI / ID Number: 10.1016/j.ygcen.2015.11.002
Copyright Information:

Copyright 2015 Elsevier Inc. All rights reserved.

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