NEWS108
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opportunity todisplay toa female.Themo-
mentamalestarts todisplay in frontofa fe-
male then his neighbor comes shooting
over to steal the female. Because the two
males thenhave eyes only for their oppo-
nent, theoppressed lady has the ideal op-
portunity to make herself scarce in the
event that she isn't really ready tomate.
Anexcessofmales isagood thing!
But there isanadditional reasonwhyanex-
cess of males is an advantage: a single
male can afford to be prodigal with his
sperm, as he can inseminate several fema-
leswithina short timewithoutproblem.
There is noneed tobe fussy about choice
of partner.As a result every femalewithin
reach is courted as a rule andno selection
takesplace.
Mattersarequitedifferent in thecaseof the
females, which can bring only a limited
number of young into theworldevery4-6
weeks. Inaddition theproductionof eggs
abstracts energy and nutrients from the
bodyof themother.
The female must thus make a precise
choice as towho is going tobe the father
of her offspring. If possible thiswill always
be the largest,most beautiful, and stron-
gestmale,toprovideheroffspringwith the
bestpossiblegenetic inheritance.
Only large,strong,andhealthymalesareca-
pable of outcompeting a large number of
competitors. Because these characteristics
arepassedon to theoffspring,suchamale
is,of course, theoptimal choice inorder to
producevigorousoffspring that are,above
all, likely to survive.
.
Inorder to keep a strainof livebearers he-
althy and vital in the aquarium for a long
time, it isbest toplace the largest possible
number of males in the tank. (The actual
numberwill dependon the tank size.)And
that way the best genes will prevail. The
weakermales, by contrast,will hardly ever
get to breed. The females will produce
strong,vital young.
Speciesawareness required
The livebearers regularly found in the trade
belong to several species, and knowledge
about these is important, as each species
has its own specific behavior and that too
mustbe taken intoconsiderationwhende-
cidingon thenumbersofmalesand fema-
les.
The species-specific dorsal-fin forms of adult
Mollymales.
Poeciliasphenops
Poecilia latipinna
Poeciliavelifera
Guppies
All theguppies in the aquariumbelong to
the species
Poecilia reticulata
and
P.wingei
,
aswell ashybridsbetween them.Whathas
beensaidaboveappliesunreservedly toall
guppies: anexcessofmaleshasverybene-
ficial effectson the strain.
Platies
Theplatiesmaintained in theaquariumbe-
long to twospecies:
Xiphophorusmaculatus
and
X.variatus
.They aren't hybridized and
both speciesbreed true,at least as regards
behavior.Again, there is anunreserved re-
commendationapplying tobothplatyspe-
cies:theyshouldbekept inpairsorwithan
excessofmales.
Swordtails
Platies and swordtails belong to the same
genus,
Xiphophorus
,which contains a total
of 28 species.But theonly swordtail in the
trade is
Xiphophorushellerii
, theother spe-
cies are so seldommaintained as to count
as rarities. Swordtail males are, unlike the
guppiesandplaties,veryaggressiveamong
themselves.Dominantmales canoppress
subordinate individuals to such an extent
that they die as a result. For this reason
only onemale shouldbe kept in standard
sizes of aquariaup to60 cm in length,but
cangenerallybecombinedwithseveral fe-
males. Perhaps this is the sourceof the in-
correct blanket recommendation of kee-
ping livebearers in the ratio 1:3. In suffi-
ciently largeaquaria thatpermit themain-
tenance of 10-15 individuals, however, the
Swordtail toocanbekeptwith fiveormore
males together.But there shouldnever be
fewer than fivemales,asotherwise thedo-
minant individual will seriously harass
membersofhisown sex,even invery large
aquaria.
Mollies
Essentially,mollies trace theirancestryback
to three original species: the Common or
ShortfinMolly
Poeciliasphenops
,theSailfin
Molly
P.latipinna
,and theGiantSailfinMolly
P. velifera
.While the ShortfinMolly should
