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Re: Hybrid sunnies

Some very good and interesting points.  I wasn't aware that the male did
contrubute anything at all in teh Amazon Molly.  However, it makes sense,
since only some species of males (erm, you know what I mean) will "work."
Many, many, species will hybridize in captivity that just don't seem to
"want to" in the wild.  Its interesting, but, in cichlids I've bred, I've
often had an individual refuse a mate of his own kind and instead take
another.  Mind you, the other species was not introduced before the
prospective mate.  Weird. :) 
I was aware that hermpahrodites are not uncommon.  However, simultanious
hermpahrodites in the fish world are very uncommon. AFAIK, the two
rivulines are teh only ones which can do it.  Also.. I don't believe that
R. marmaratus ever fertilizes its own eggs...  I just thought it exchanged
gametes with another.... I'd like to hear any other info you may have on
Another weirdo in the fish kingdom I thought of:  The four eyed fish:
Which can only mate with individuals of the other orientation.  The fishes
sexual organs are located one one side.. so a left orientated male can
only mate with a right orientated female.  Truly odd order.

J. L. Wiegert
 Dubotchugh yIpummoH.                      bI'IQchugh Yivang!
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On Sat, 3 Oct 1998, David E. Boruchowitz wrote:

> Date: Sat, 03 Oct 1998 19:41:29 -0400
> From: David E. Boruchowitz <editor at tfh_com>
> To: nfc at actwin_com
> Subject: Re: Hybrid sunnies
> Hi, all!
> I usually lurk here, but this is one of my favorite topics.  Hybrids almost
> always grow faster/bigger than either parent species. This is true for
> strains within a species, too, and is called "hybrid vigor" or heterosis.
> It's one reason Americans tend to be taller than Europeans or
> Asians---there's a lot of genetic mixing going on in the States!
> As for the species concept, it is partly a human construct. Birds and fish
> especially are prone to hybridization between species---usually in
> captivity, where all the normal behavioral and territorial controls are
> absent, but occasionally in the wild. When the parent species are close,
> the offspring are often fertile. There are even some bird hybrids where
> only one sex is fertile in the F1!
> >   The best breaks to the Bioloigcal Species Concept truly come in the
> >fishes.  Think of Rivulus marmoratus: A "hermaphrodite" fish.  Or again,
> >to invoke the livebearers, the Amazon Molly... which will only breed with
> >males of another speies, and has no males in its own!  A truly bizzare
> >species, indeed.  
> Hermaphrodite species are not really a problem for the species concept.
> Many fish species are hermaphrodites which change sex at different stages
> of life--very common in coral reef fishes. The marmoratus is the only one I
> know of that is both sexes at the same time and fertilizes its own eggs.
> Parthenogenetic species, like the Amazon molly, are almost always the
> result of an interspecies cross. There are a few among the reptiles, too.
> BTW recent evidence suggests that the sperm of the other species male MIGHT
> make some genetic contribution to the Amazon molly fry. Up until now it was
> believed that the sperm was only necessary to "jump start" the egg into
> developing. Parthenogenetic species are typically short-lived (in
> evolutionary timescales).
> There are a few hybrids whose parent species are not definitely known. The
> society finch is a combination of at least two mannikin species, and its
> origin is lost in antiquity--it exists only in captivity. The domestic goat
> is another domestic-only species with uncertain hybrid origin. Domestic
> platies and swordtails, which were already mentioned, are a mix of at least
> three species, often more, and they do not normally occur in the wild.
> A very common hybrid in captivity is the convict cichlid with the blue-eye
> (Archocentrus nigrofasciatum x A. spilurum). It does not usually occur,
> however, in nature, even where both species inhabit the exact same locales.
> This is surprising, since in captivity convicts will hybridize with quite
> distant relatives--I've heard it said they'll mate with a can of tuna!  :)
> A question for everyone collecting Lepomis. Just how frequent are these
> hybrids? One in a 1000? More? Less?
> David.
> --
> David E. Boruchowitz
> Editor, TFH Magazine
> editor at tfh_com