Archived message board.
Baby Sword Tail
Badmans Tropical Fish Message Center: General
message area: Baby Sword Tail
|
David
|
Thursday,
January 17, 2002 - 06:38 pm
I just have a simple question (I hope)
My Female Sword tail just gave birth and all the fry are
the same color. They are sort of greyish. Does that mean
they are all female or do they change colors when they get
older. My male adult sword is red.
Any information would be helpful
|
|
Pandora
|
Thursday,
January 17, 2002 - 08:24 pm
Hey David,
You may have wanted a simple answer, but I'm afraid
that genetics is not always so =) First off, the fry
will sometimes change color hue a little, but usually the
base color of the fry will give you some idea of whether
or not they will be reddish or greyish, for example.
As for the genetics part, you have to know some things about
the pedigree of the parents to know for sure (in other
words, what color their grandparents were). But you
can usually assume that the ones sold by a dealer are pure
color strains (unless the strains are themselves hybrid,
but I won't get into that here). In most cases with
fish, the melanism gene is dominant over other colors. So,
calling the gene for dark (D) and the gene for red
(r), and assuming both parents are homozygotes (DD
X rr cross):
___D___D
r__Dr__Dr
r__Dr__Dr
You'll get 100% heterozygous "Dr" young. Because
D is dominant to r, this allele will mask the other, and
you *see* dark young if there is complete dominance
(you can't see their genes, after all). If you
were to breed these to each other (not that I'm
supporting inbreeding, but hypothetically), in the next
generation you should get 75% dark young (1/3 of those
homozygous dark, 2/3 heterozygous) and 25% red (all
homozygous).
Sorry if any of this is confusing, but actually I've
simplified quite a bit. You may want to look up actual genotypes
for swordtails, sometimes incomplete dominance, codominance,
multi-locus alleles, etc. can add even more complexity,
since there aren't just 2 alleles for color.
|
|
Pandora
|
Thursday,
January 17, 2002 - 08:33 pm
Oh, and one more thing... you asked if the fry were all
female BECAUSE they were all greyish like the mom. Color
is not a sex-linked trait, and the color of the young will
have nothing to do with their gender, the alleles assort
independently.
|
|
David
|
Thursday,
January 17, 2002 - 11:09 pm
Well alrighty then. So I guess I will tell the male by the
sword on the tail right?
|
|
Pandora
|
Sunday,
January 20, 2002 - 11:22 am
David, you won't see a sword in fry. This trait doesn't
develop in growing fish until well after primary sexual
maturation, which is often several several months... varying
time period. It's more reliable to look for the male
modified anal fin, the gonopodium, in livebearer fish...
this develops sooner, but even then not for more than 2
months, in most cases (until then, all your young will
look female).
|
|
William
|
Sunday,
January 20, 2002 - 11:27 pm
Wow, somebody knows their biology. Mendel and his pea plants
would be proud
|
|
Pandora
|
Monday,
January 21, 2002 - 11:24 am
LOL, William. Years of genetics & ecology, and here
I am back to (punnett) square one....
|
|
|
