Your email address is used to log in and will not be shared or sold. Read our privacy policy. If you are a Zinio, Nook, Kindle, Apple, or Google Play subscriber, you can enter your website access code to gain subscriber access. Your website access code is located in the upper right corner of the Table of Contents page of your digital edition. Sign up for our email newsletter for the latest science news. Guppies are extremely popular aquarium fish that give birth rather than lay eggs and have been used for much behavioral research, including on breeding behaviors. Males have a modified anal fin, the gonopodium, that is similar in function to a penis. When breeding, the male approaches and thrusts his gonopodium into a female, ejecting one or more balls of sperm. Male guppies also have claw-like appendages on their gonopodia.
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February 14, Male guppies pay a high cost for their sexual harassment of female guppies — including much higher mortality rates — a new study from Macquarie University has found. Sexual harassment in guppies, or unwanted male attention, is a product of males attempting to mate as many times as possible due to the low energy cost of sperm production. In the study published in the journal Ethology , males spent more than 45 per cent of their day chasing females , and their mortality rate was more than three times higher when housed with females compared to being housed with males.
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Sex chromosomes regularly evolve suppressed recombination, distinguishing them from other chromosomes, and the reason for this has been debated for many years. It is now clear that non-recombining sex-linked regions have arisen in different ways in different organisms. A major hypothesis is that a sex-determining gene arises on a chromosome and that sexually antagonistic SA selection sometimes called intra-locus sexual conflict acting at a linked gene has led to the evolution of recombination suppression in the region, to reduce the frequency of low fitness recombinant genotypes produced. The sex chromosome system of the guppy Poecilia reticulata is often cited as supporting this hypothesis because SA selection has been demonstrated to act on male coloration in natural populations of this fish, and probably contributes to maintaining polymorphisms for the genetic factors involved. I review classical genetic and new molecular genetic results from the guppy, and other fish, including approaches for identifying the genome regions carrying sex-determining loci, and suggest that the guppy may exemplify a recently proposed route to sex chromosome evolution. A major question concerning sex chromosome evolution is what has led to the lack of recombination between such chromosome pairs, or between sex-linked regions of these chromosomes. This requires inhibition of recombination between the differentiated segments of the X or Z and Y or W chromosomes. Today, these two aspects are generally distinguished, although both are likely to be involved in recombination suppression. A first process that may explain non-recombining fully sex-linked regions of genomes is that evolution of a genetic sex determination system from an ancestor that does not have separate sexes probably often involves two or more genes. A genetic sex determination system cannot evolve from an ancestrally hermaphrodite or monoecious state by a single mutation: at least two mutations are needed, one generating females and one males [ 2 , 3 ].
We've seen in our simulations that the more brightly colored a male guppy is, the more likely he will be seen -- and eaten -- by a predator. In a simulation or in the wild, where predators are plentiful, male guppies become increasingly drab over generations, pushed by predation pressure toward greater camouflage. So if camouflage confers such an obvious survival benefit to prey species like guppies when it comes to predator avoidance, what possible advantage could there be to sporting colors and patterns that make an individual more conspicuous? The answer lies in the fact that guppies have to do more than just survive. They also have to reproduce -- and to do that, they have to attract mates. The "flashier" a male guppy is, the more likely a female guppy will choose him as a mate, giving him the opportunity to pass his genes along to the next generation. This is sexual selection at work, and it is the force that pushes guppy coloration toward conspicuousness just as hard as predation pushes coloration toward drabness.
