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Xiphophorus and Poecilia spp.
April 23, 2012
7:27 am
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Matt
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Are members of these two genera able to hybridise with one another?

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April 23, 2012
5:29 pm
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coelacanth
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I have seen pictures of purpoted intergeneric hybrids in the Poeciliidae, can't remember which book it was in though.

April 24, 2012
7:10 am
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Matt
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Specifically Xiphophorus x Poecilia Pete?

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April 24, 2012
11:12 am
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ricefish
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There are always stories going round about livebearer hybrids but I have seen little or no proof of them,It is regarded as almost nil that a Xiph x poecilia would cross and produce offspring

April 24, 2012
11:12 am
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coelacanth
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Foudn this partial reference "Genetics of an intergeneric hybrid: Xiphophorus helleri x
Molliensia sphenops. J. Genet, (in the press)". Of course if you'd asked this 80 years ago it would have been easier, as you had Xiphophorus and Platypoecilus. The book that listed some hybrids was I think "Livebearing Aquarium Fishes", by Kurt Jacobs, but I'm not sure where my copy ended up.

April 24, 2012
1:29 pm
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paul thompson
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Interestingly, Xiphophorus (certainly helleri) doesn't have X Y (sex) chromasomes. The sex of swordtails is determined by autosomes. The old TFH booklet on Genetics has some fascinating info on this . . .

Can't give you any more info as I'm working overseas and the book is at home in the UK - worth a read if you can get hold of an old copy.

April 24, 2012
1:59 pm
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Bojan Dolenc
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This article is interesting:
Conservation of Synteny between Guppy and Xiphophorus Genomes

http://cgi.sfu.ca/~fabstar/htd.....394329.pdf

April 24, 2012
7:05 pm
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plesner
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QUOTE (paul thompson @ Apr 24 2012, 03:12 PM) < {POST_SNAPBACK}>
Interestingly, Xiphophorus (certainly helleri) doesn't have X Y (sex) chromasomes. The sex of swordtails is determined by autosomes. The old TFH booklet on Genetics has some fascinating info on this . . .

Can't give you any more info as I'm working overseas and the book is at home in the UK - worth a read if you can get hold of an old copy.

Which book are you referring to? This one by any chance:

Genetics for Aquarists
Author Dr. J. Schroder
Published by TFH, 1975, 125 pages
(and I think it was possibly re-published in 1991?)

Whether this is the book you are referring to or not, I do now know that I'm missing a book in my collection. I do find stuff like that rather fascinating and would love to read it.

April 25, 2012
2:09 am
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paul thompson
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Yes that sounds right (Genetics for Aquarists, Schroder), bought my copy in the 1970's. The chapter relating to swordtails contained some real surprises.

April 25, 2012
7:05 am
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Bojan Dolenc
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QUOTE (paul thompson @ Apr 25 2012, 03:52 AM) < {POST_SNAPBACK}>
Yes that sounds right (Genetics for Aquarists, Schroder), bought my copy in the 1970's. The chapter relating to swordtails contained some real surprises.

I have this interesting Book; very instructive is chapter 14. called HARMFUL EFFECTS OF GENES FROM A DIFFERENT SPECIES... author says there:
"In recent years a whole series of dominant color genes have been discovered in family Poeciliidae; these lead to cancerous growths when crossed into a species possessing a higher concentration of free amino acids than the species receiving the color gene originated. Conversely, if the species receiving the color gene has a lower concentration of free amino acids in its tissue fluids than the donor species, the effect of the color gene may even be absent from the phenotype of the backcross hybrids.
This shows that other genetic factors are involved which determine the level of amino acids and co-determine whether a color gene finds its normal expression or its presence results in the formation of melanomas instead. In this way natural selection can prevent the interbreeding between species since the species hybrids are killed by pigment cell tumors."

April 25, 2012
7:36 am
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paul thompson
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QUOTE (Bojan Dolenc @ Apr 25 2012, 06:48 AM) < {POST_SNAPBACK}>
I have this interesting Book; very instructive is chapter 14. called HARMFUL EFFECTS OF GENES FROM A DIFFERENT SPECIES... author says there:
"In recent years a whole series of dominant color genes have been discovered in family Poeciliidae; these lead to cancerous growths when crossed into a species possessing a higher concentration of free amino acids than the species receiving the color gene originated. Conversely, if the species receiving the color gene has a lower concentration of free amino acids in its tissue fluids than the donor species, the effect of the color gene may even be absent from the phenotype of the backcross hybrids.
This shows that other genetic factors are involved which determine the level of amino acids and co-determine whether a color gene finds its normal expression or its presence results in the formation of melanomas instead. In this way natural selection can prevent the interbreeding between species since the species hybrids are killed by pigment cell tumors."

Cancerous (malignant melanomas) in certain colour strains of swords have been known about for quite some time (I was aware of this in the late 1960s). Red tuxedo helleri (sometimes called Berlin Swords), if memory serves me right, were particulary prone to melanomas a number of years ago. Interestingly, the 'pure black' strain of helleri (black body with green iridescent scales) doesn't appear to suffer from this problem. The black colouration on these 'black' swords doesn't extend into their fins . . .

April 25, 2012
7:41 am
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Bojan Dolenc
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QUOTE (paul thompson @ Apr 25 2012, 03:52 AM) < {POST_SNAPBACK}>
Yes that sounds right (Genetics for Aquarists, Schroder), bought my copy in the 1970's. The chapter relating to swordtails contained some real surprises.

Yes, in Chapter 10. POLYGENIC SEX DETERMINATION author says there are 2 types of males in the swordtails with polygenic autosomal sex determination mechanism: earyl males ("strong" males) and larger late males ("weak" males), which become sexually mature much more later.
Guppies and even platies from the same genus Xiphophorus possess a sex determination mechanism based on the pressence of sex chromosomes (gonosomes). There are XX males and XY females, for instance, which in turn produce offspring that deviate from the norm. If we cross an XX female with an XX variation male, the progeny consist of nothing but daughters (XX). Conversely, if an XY variation female is mated to a normal XY male, then daughters (XX) and sons (XY, YY) at ratio 1:3 are produced. As would be expected, YY males mated to normal females (XX) produce only male descendants (XY).

April 25, 2012
3:12 pm
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Byron Hosking
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I have the Jacobs book mentioned earlier by coelacanth; in the chapter on Reproduction he writes:

In 1903 Johannes Peter pointed out that no one had succeeded in producing a hybrid between two genera "because such a cross would be prevented by the differing structure of the sexual organs." In 1912 there was a report of a hybrid between a male Poecilia mexicana and a female Molliensia latipinna and this was hailed as the first intergeneric cross. According to modern ideas on systematics this does not appear so wonderful, because both these species are now classified in the genus Poecilia. [note below]
Nowadays one can state that the livebearers will hybridize in aquarium tanks and the crosses are, in general, interspecific or at the most intergeneric. By applying the Mendelian rules of heredity it is possible to produce some very beautiful forms within the genus Xiphophorus and also in the Guppy.
[There then follows some discussion on sperm differences and so forth.]
Successful hybridization can only be achieved if one to three females are put together with only a single male of the other species. Even then it is necessary to experiment. ... If this male does not mate with the females within 10-14 days, the attempt must be repeated using a different male. This experiment must be patiently continued until a male does finally mate with a female.

A note on the Poecilia species: Some ichthyologists have recently proposed that the guppy does not share certain specific traits with the other molly species and should be separated. Poeser et al. (2005) suggested re-validating Acanthophacelus, originally erected by Eigenmann in 1907 and subsequently deemed a synonym for Poecilia, as a subgenus, and Schories et al. (2009) follows this but proposes that the entire genus Poecilia is in need of revision.

I initially asked the question of Matt, so thought I should try to offer something to the discussion.

Byron.

Byron Hosking, BMus, MA Vancouver, BC Canada
April 26, 2012
8:08 am
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Bojan Dolenc
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Of course we today know, that each platy has 2 or 3 sex chromosomes (X, Y or W), so their offspring is of five different gender (3 female and 2 male gender).

April 27, 2012
1:33 am
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paul thompson
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QUOTE (Bojan Dolenc @ Apr 26 2012, 08:51 AM) < {POST_SNAPBACK}>
Of course we today know, that each platy has 2 or 3 sex chromosomes (X, Y or W), so their offspring is of five different gender (3 female and 2 male gender).

Yes - all the more surprising that platy x sword crosses have produced fertile hybrids. Fascinating subject area . . .

April 27, 2012
8:00 am
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Matt
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QUOTE (kermit58 @ Apr 25 2012, 02:55 PM) < {POST_SNAPBACK}>
I initially asked the question of Matt, so thought I should try to offer something to the discussion.

Think you're getting much more valuable input from everyone else than you would've from me Byron. /thumbs_up.gif" style="vertical-align:middle" emoid=":thumbsup:" border="0" alt="thumbs_up.gif" />

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April 27, 2012
9:55 am
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retro_gk
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Wischnath's Atlas of livebearers of the world has a picture of P. reticulata x P. latipinna hybrids on page 274. The author mentions such crosses are "mostly infertile".

I don't think there ever has been a successful Poecilia x Xiphophorus cross, although reports surface from time to time.

April 27, 2012
10:16 am
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Graham Ramsay
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QUOTE (paul thompson @ Apr 27 2012, 02:16 AM) < {POST_SNAPBACK}>
Yes - all the more surprising that platy x sword crosses have produced fertile hybrids. Fascinating subject area . . .

Which species are we talking about here? The words platy and swordtail are not well defined.

April 27, 2012
10:40 am
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paul thompson
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QUOTE (mummymonkey @ Apr 27 2012, 10:59 AM) < {POST_SNAPBACK}>
Which species are we talking about here? The words platy and swordtail are not well defined.

X. Maculatus crossed with X. Helleri

April 27, 2012
11:00 am
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Bojan Dolenc
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Looking say platys and swordtails (Xiphophorus genus) are practically all that are for sale in petshops, hybrids between three species: X. maculatus, X. variegatus and X. helleri.

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