Editing Amplexus (section)

== Physiological and hormonal function ==

=== Physiology ===
Amplexus has been found to involve different muscles in both male and female amphibians. The forelimb muscles in both males and females have been identified as the key muscles for amplexus that most species use.<ref name=":12" /> These forelimb muscles that are used during amplexus are typically larger in males than females, and for males these muscles contain more oxidative fibers, which could mean that amplexus involves an increased rate of aerobic metabolism.<ref name=":12" /> In addition to those forelimb muscles being larger in males, male frogs also typically have keratin pads or nuptial pads, which are located on their thumbs and contribute to the success of amplexus by assisting in gripping the female for the duration of amplexus.<ref>{{Cite journal|last1=Chakraborti|first1=S.|last2=Nag|first2=T.C.|last3=Das|first3=D.|last4=Sanyal Chatterjee|first4=T.|last5=De|first5=S.K.|date=2014|title=Cytokeratin localization in toe pads of the anuran amphibian Philautus annandalii (Boulenger, 1906)|journal=Tissue and Cell|volume=46|issue=3|pages=165–169|doi=10.1016/j.tice.2014.03.001|pmid=24698093|issn=0040-8166}}</ref> This amplexus behaviour allows the amphibians' cloacae to be in close contact, while gametes are released.<ref name=":2">{{Cite journal|last1=Propper|first1=Catherine R.|last2=Dixon|first2=Timothy B.|date=1997|title=Differential Effects of Arginine Vasotocin and Gonadotropin-Releasing Hormone on Sexual Behaviors in an Anuran Amphibian|journal=Hormones and Behavior|language=en|volume=32|issue=2|pages=99–104|doi=10.1006/hbeh.1997.1408|pmid=9367717|s2cid=41855944}}</ref> Additionally, amplexus is thought to help with the alignment of the reproductive tracts of both males and females, which furthermore contributes to successful fertilization.<ref name=":02">{{Cite journal|last1=Mollov|first1=Ivelin|last2=Popgeorgiev|first2=Georgi|last3=Naumov|first3=Borislav|last4=Tzankov|first4=Nikolay|last5=Stoyanov|first5=Andrei|date=2010|title=Cases of abnormal amplexus in anurans (Amphibia: Anura) from Bulgaria and Greece|journal=Biharean Biologist}}</ref> A female amphibian may not always be receptive to a male amphibian who is trying to initiate amplexus, as the female may not be ready to produce eggs.<ref name=":02" /> When the female is not ready to engage in amplexus, she will simply vibrate her body, which will then be felt by the male who is clasped to her and he will then stop the amplexus behaviour.<ref name=":02" />

=== Hormones ===
Two major hormones have been identified to be involved in amplexus. The hormone arginine vasotocin (AVT) has been identified as having an effect on the calling behaviours produced by these male amphibians when searching for a female mate, as AVT increased the amount of calling behaviour produced in male amphibians.<ref name=":2" /> Additionally, it is believed that the gonadotropin-releasing hormone (GnRH) has an influence on amplexus in amphibians, as it has been found to produce or initiate this behaviour in many anuran amphibians.<ref name=":2" /> Furthermore, both arginine vasotocin and gonadotropin-releasing hormone have been found to be involved in the sexual behaviour of male amphibians.<ref name=":2" /> The stress hormone corticosterone has also been identified as associated with the sexual behaviour of amplexus. A study conducted on red-spotted newts found an acute increase in corticosterone for both males and females who were engaged in the behaviour of amplexus.<ref name=":5">{{Cite journal|last1=Reedy|first1=Aaron M.|last2=Edwards|first2=Alex|last3=Pendlebury|first3=Chloe|last4=Murdaugh|first4=Laura|last5=Avery|first5=Ryan|last6=Seidenberg|first6=Jake|last7=Aspbury|first7=Andrea S.|last8=Gabor|first8=Caitlin R.|date=2014|title=An acute increase in the stress hormone corticosterone is associated with mating behavior in both male and female red-spotted newts, Notophthalmus viridescens|journal=General and Comparative Endocrinology|volume=208|pages=57–63|doi=10.1016/j.ygcen.2014.08.008|pmid=25157790|issn=0016-6480}}</ref> However, overall it was found that males have a higher level of corticosterone compared to females, as amplexus is seen as more energetically costly to males.<ref name=":5" /> The increase in corticosterone found in females could be attributed to amplexus preventing them from foraging for food.<ref name=":5" />