Assessment of reproductive status in male echidnas

Johnston, S. D.; Nicolson, V.; Madden, Cary T.; Pyne, Michael; Roser, Alice; Lisle, Allan; D’Occhio, Michael J.

doi:10.1016/j.anireprosci.2005.12.016

Cited by 17 publications

(6 citation statements)

References 6 publications

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“…The timing of the testosterone peak (60–90 min) following GnRHa injection is generally consistent with that reported for other avian species; for example, in a range of avian species the GnRH analogue (D‐Lys 6 ‐Gn‐RH‐EA) and synthetic mammalian GnRH administered in 0.5 to 20 µg/kg body weight doses are reported to elevate plasma testosterone levels after only 10 to 15 min and result in a maximum elevation within 60 to 120 min 16 . In the Japanese quail, doses of 0.8 and 8 µg/kg of chicken GnRH (GNRH‐1, GNRH‐II), corresponding analogues (D‐Tle 6 ‐cGnRH‐I, D‐Tle 6 ‐cGnRH‐II) and an agonist of mammalian GnRH (Supergestran) were all used to examine the dose/testosterone response relationship; not surprisingly, the higher the GnRH dose the greater the testosterone response 13 . Although further studies are required to determine what would represent a supramaximal dose of GnRHa in the cockatiel, the 8 µg/kg dose used in this study was sufficient to induce sustained testosterone secretion that enabled a clinical interpretation of reproductive status.…”

Section: Discussionsupporting

confidence: 83%

“…Administration results in the sustained release of luteinising hormone from the anterior pituitary and the production of Leydig cell enzymes capable of converting cholesterol into testosterone. The maximal testosterone concentration obtained after GnRH analogue injection has been used as a reliable index of testosterone secretion in a range of mammalian species, including the short‐beaked echidna, 6 koala, 7 sugar glider, 8 stallion 9 and human 10 . Exogenous GnRH has also been given to cockerels and was shown to overcome the suppressive effect of physical restraint on testosterone secretion 5 .…”

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confidence: 99%

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Using a GnRH agonist to obtain an index of testosterone secretory capacity in the cockatiel (Nymphicus hollandicus) and sulphur‐crested cockatoo (Cacatua galerita)

2010

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Section: Discussionsupporting

confidence: 83%

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confidence: 99%

Using a GnRH agonist to obtain an index of testosterone secretory capacity in the cockatiel (Nymphicus hollandicus) and sulphur‐crested cockatoo (Cacatua galerita)

2010

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“…Males in poor condition emerge later and are less likely to mate. As in other seasonal breeders, echidna testes atrophy after the breeding season, and in parts of Australia where the echidnas do not show extended deep hibernation testis recrudescence occurs in April‐May (Griffiths, ; Johnston et al, ). During the breeding season, the testes may exceed 1% of body mass, and the low metabolic rate of echidnas means that complete recrudescence requires 2‒3 months at euthermic T b (Morrow, Jones, & Nicol, ).…”

Section: Discussionmentioning

confidence: 94%

Energetics meets sexual conflict: The phenology of hibernation in Tasmanian echidnas

2019

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Echidnas are egg‐laying mammals found across Australia, and in Tasmania they hibernate, resulting in a most unusual mating system: males enter hibernation in late summer–early autumn and arouse in late autumn–early winter to mate, although females are still hibernating. Groups of males compete for matings and both males and females mate with multiple partners. Females that mate early return to hibernation even when pregnant, and males continue to mate with pregnant females. We asked to what extent can the bizarre combination of behavioural and physiological features that characterize reproduction of Tasmanian echidnas be attributed to their phylogeny, and how much is a consequence of their ecology? To understand the interaction between energetics and the echidna mating system in determining the timing of echidna hibernation, we analysed data from an 18‐year study of a wild population of Tasmanian echidnas (Tachyglossus aculeatus setosus) Males in best condition arouse earliest and seek out suitable females, and females that mate early in the mating season re‐enter hibernation while pregnant. Competition between males drives early mating and while mating with males in the best condition could be advantageous for females and their young, egg‐laying in winter is potentially disadvantageous, and post‐mating hibernation by females is a means of delaying hatching of young until environmental conditions are more favourable. This post‐mating hibernation by females is usually disrupted by males which mate with them although they are already pregnant. Comparisons with other echidna populations suggest that a decreased activity period due to hibernation has not increased male–male competition. Similar competition between groups of males for access to females is seen in chlamyphorid armadillos, which occupy a similar ecological niche to echidnas. A free Plain Language Summary can be found within the Supporting Information of this article.

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“…Monotremes, which diverged from therian mammals around 184 million years ago [Cúneo et al, 2013], have a number of reproductive characteristics that differ from the majority of therian mammals. They are the only mammalian order to retain the cloaca into adulthood; they are testicond with the testes being retained in the abdominal cavity, rather than descending to lie externally either in a scrotum or in the inguinal canal; their ejaculate contains bundles of sperm that swim cooperatively; and the monotreme penis is used purely as a reproductive organ, unlike therian mammals whose penile urethra is used for transport of both urine and semen [Owen, 1868;Griffiths, 1968;Johnston et al, 2007a].…”

Section: Introductionmentioning

confidence: 99%

The Unique Penile Morphology of the Short-Beaked Echidna, Tachyglossus aculeatus

Fenelon

McElrea

Shaw

et al. 2021

Sex Dev

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Monotremes diverged from therian mammal ancestors approximately 184 million years ago and have a number of novel reproductive characteristics. One in particular is their penile morphology. There are differences between echidna and platypus phalluses, but both are somewhat similar in structure to the reptilian phallus. The echidna penis consists of 4 rosette glans, each of which contains a termination of the quadrifurcate urethra, but it appears that only 2 of the 4 glans become erect at any one time. Despite this, only a few historical references describe the structure of the echidna penis and none provides an explanation for the mechanisms of unilateral ejaculation. This study confirmed that the echidna penis contains many of the same overall structures and morphology as other mammalian penises and a number of features homologous with reptiles. The corpus cavernosum is well supplied with blood, extends up to the base of the glans penis and is primarily responsible for erection. However, the echidna possesses 2 distinct corpora spongiosa separated by a septum, each of which surround the urethra only distal to the initial urethral bifurcation in the glans penis. Together with the bifurcation of the main penile artery, this provides a mechanism by which blood flow could be directed to only one corpus spongiosum at a time to maintain an open urethra that supplies 2 of the 4 glans to facilitate unilateral ejaculation.

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Assessment of reproductive status in male echidnas

Cited by 17 publications

References 6 publications

Using a GnRH agonist to obtain an index of testosterone secretory capacity in the cockatiel (Nymphicus hollandicus) and sulphur‐crested cockatoo (Cacatua galerita)

Using a GnRH agonist to obtain an index of testosterone secretory capacity in the cockatiel (Nymphicus hollandicus) and sulphur‐crested cockatoo (Cacatua galerita)

Energetics meets sexual conflict: The phenology of hibernation in Tasmanian echidnas

The Unique Penile Morphology of the Short-Beaked Echidna, Tachyglossus aculeatus

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