Proximate and Ultimate Perspectives on Sperm Production and Mating Behavior in a Bisexual-Unisexual Mating System Between Sailfin (Poecilia Latipinna) and Atlantic (P. Mexicana) Mollies with Clonal Amazon Mollies (P. Formosa)




Ma, Jacqueline

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Hormonal regulation plays an important role in influencing mating behavior in vertebrate species. In mating systems where closely related species are sympatric, hormones may affect species recognition. I examined the potential role of hormones in mediating species recognition in a bisexual-unisexual mating system consisting of bisexual sailfin mollies (Poecilia latipinna) and Atlantic mollies (P. mexicana) with clonal Amazon mollies (P. formosa). 11-ketotestosterone (KT) is the dominant male androgen in teleosts that influence secondary sex characteristics and sperm production. Male and female sailfin mollies from a population sympatric with Amazon mollies both showed greater KT responsiveness (post-mating KT/pre-mating KT) after a mating with each other whereas this pattern was absent when males mated with Amazon mollies. In this study, I examined whether KT is important in species recognition for sailfin mollies that are from a population allopatric to Amazon mollies. Male sailfin mollies significantly preferred to mate with conspecific females over Amazon mollies. However, I found no significant difference in KT responsiveness of male or female sailfin mollies that mated. Amazon mollies also displayed no change in KT responsiveness. It is possible that the observed KT responsiveness in sailfin mollies from conspecific matings in sympatric populations is a derived trait, which is not present in the allopatric population. However, comparison of multiple sympatric and allopatric populations is needed to test this hypothesis. I also examined the role of KT production in sperm production of male Atlantic mollies when they were associated with either a female Atlantic molly or an Amazon molly for either seven days or for one hour. Pre-association KT levels were not correlated with pre-association sperm levels in male Atlantic mollies. Males that were paired with conspecific females for seven days showed a positive correlation between pre-association KT levels and the amount of sperm primed. There was no correlation between KT responsiveness and post-association sperm levels after one hour of association. Males also did not prime more sperm for conspecific females over Amazon mollies during the one hour association. Our results suggest KT is not involved with species recognition or sperm priming in Atlantic mollies



Behavioral ecology, Reproductive isolation, 11-ketotestosterone, Sperm priming, Mate choice, Mollies


Ma, J. (2011). <i>Proximate and ultimate perspectives on sperm production and mating behavior in a bisexual-unisexual mating system between Sailfin (Poecilia Latipinna) and atlantic (P. Mexicana) Mollies with Clonal Amazon Mollies (P. Formosa)</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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