The Playful Platy
by Dr David Ford, Consultant
to Aquarian®, member of Halifax AS
A Fun Fish
the Platy could be bred to have the face of Mickey Mouse and sell like hot cakes
because of it! It is the dream fish for aquarists - pretty, active, peaceful,
eats anything, accepts all waters, many varieties and easy to breed, what more
can you ask of a tropical fish?
Even its name is funny. The original scientific
name was Platypoecilius and so it became Platy for short. This was in all languages
so the French, Germans, Spanish and others know the fish as the Platy too. When
books such as German Fish Encyclopedia are translated into American English, US
grammar rules are applied and the plural form makes the 'ys' become 'ies' - hence
a shoal will be Platies. But British English grammar would make this 'plate-is'
and the pronunciation is 'platt-is', so UK books use the (correct) term Platys,
American books write Platies (indeed they call them 'colorful Platies').
the fish is no longer Platypoecilius because the two different genera Platypoecilius
and Xiphophorus (Swordtails) within the family Poeciliidae, were found to be scientifically
the same (some can even crossbreed). Hence the Platy is now Xiphophorus too.
Xiphophorus means 'Sword Carrier' and aquarists say 'Why does the Platy have the
same name as a Swordtail, when it has no sword?'. The reason is that when the
Swordtail was first named, the Latin 'sword' was given not because of the tail
sword, but because the male's gonopodium (the anal fin) was wielded like a sword
during courtship! The Platy male certainly has one of these - and displays it
So Many Varieties
There are two species
chosen for the aquarium trade: X. variatus (Latin for variable) and X. maculatus
(Latin for speckled). Both species are very variable in both colour and patterning,
hence cross-breeding the fish has led to many different strains, chosen for their
potential sales by fish farmers and hobby breeders.
The fish can even be
crossed with Swordtails giving hybrids that are sold under invented names such
as the Sword Platy, Swordtail Platy and Marigold Platy.
Some of the colour
strains of Platys to be found in the aquarium trade:
Red Platy Red Moon
Platy Red Tuxedo Platy Red Wag Platy
Red Wagtail Platy Red-eyed Platy Red-tailed
Platy Red Twinbar Platy
Black Platy Black Variatus Platy Black and
Black Banded Platy Black and Red Platy
Blue Platy Blue
Variatus Platy Blue Mirror Platy
Gold Platy Gold Speckled Platy Gold Tuxedo
Platy Gold Moon Platy
Gold Comet Platy Gold Crescent Platy
Yellow Tail Platy White Ghost Platy Orange Spot Platy
The fish has
popular names not based on the colour name too. One is the Wagtail Platy - this
is a strain of X. maculatus that has black fins. The large tail fin is obviously
'wagging' as the fish dashes about the aquarium.
Another colour morph of
X. maculatus is as yellow as the moon and is known as the Moon Platy. However,
if the yellow is too orange, the fish becomes the Marigold Platy. If there is
an iridescence present the fish then becomes the Coral Platy. There is even a
Mirror Platy where the iridescence is pronounced.
There are also names that
describe the fin shape such as the Hi-fin and Sword. Some strange fin shapes can
be seen in Platy-Swordtail crosses known as Papagai and Spitz Platys (named after
German and American breeders).
The Scientist's Fish
fun fish has a dark side. The reason for the natural colour variation which breeders
exploit, is in the genes. The species has a genetic form that gives different
melanophores (the structures that contain colour pigments) in every individual
fish. These are so dominant that they can run riot and become a melanoma (skin
cancer). Cross breeding a Platy and a Swordtail that have strong black colours
will often give a hybrid with an obvious melanoma, an effect well known to breeders
Hence the fish is used in cancer research, particularly because
the fish can survive for years carrying the cancerous growth. Doctors need to
know: how can it survive with such a disease?
Being hardy and a livebearer with anything from 10 to 75 vigorous
fry born almost monthly, the fish is ideal for studies in fish nutrition. Hence
the Waltham® Aquacenter had the specimens on feeding trials when Aquarian®
was being developed.
From these trials I learnt that the fish needed 1/3rd
of its diet as a vegetable and 2/3rd as animal origins. The fish is obviously
an omnivore (can eat anything) but it is partly vegetarian; something is necessary
from plants that the fish has to digest to be healthy. These will be phytochemicals
- nutrients that derive from photosynthesis by plants in sunlight.
The fish originates from central America, as far North
as the USA-Mexican border (there is a 'Northern Platy'), through Guatemala, down
to Nicaragua, all on the Eastern Seaboard, in ponds, swamps and calm rivers.
from this sheltered, but variable waters, the fish obviously enjoys the calm life
of the aquarium. The fish I obtained however, were from Florida. Not wild species
but the popular Wagtails bred en mass in Florida fish farms. I found they liked
warm waters even though the books claim the fish will thrive in cool water (down
to 12ºC). I used 25ºC, but 27ºC for breeding.
It is known
the fish play in the sunlight in their natural home, so bright lights and floating
plants (e.g. Najas) were included in 36x12x12" (90x30x30cm) tanks. The water
was dechlorinated tapwater kept clear by gentle filtration (small powerfilters
with foam). Shoals of a dozen Platys in each tank soon gave a constant supply
of gravid females, obvious by their belly size.
These females were transferred
(gently via glass cups, not netting) to individual 18"/45cm polytanks where
they gave live births of immediately active fry. Each batch was raised on different
recipes of crushed flake foods and rates of growth measured via photography.
was in this research that the need for 1/3rd vegetable diet was discovered. Maximum
growth occurred when the flake was supplemented with frozen Algae, blanched lettuce,
squashed peas etc.
The fry grew rapidly and the males had to be removed
within just 3 months when gonopodium development of the anal fin was seen. If
left in the shoal, interbreeding started and the second generation fry were poor
because of sisterxbrother genetics. Some books claim that the fish will not breed
until about a year old - clearly this was wrong. Once the female was inseminated
she would drop that same father's young many times too.
There are many wild Platys still living in Mexican rivers
such as Rio Verde, Coy, Nautla and Atoyac - these range from cascading waterfalls
to narrow jungle streams but all have quiet pools where populations of Xiphophorus
species live out their lives.
Professional collectors and amateur breeders
collect these fishes, ranging from Museum Zoologists to conservationists hoping
to preserve endangered species. Even from the UK - the Viviparous Society have
members who visit Mexico to help with collection and maintenance of sites.
the constant supply of cheap fish from Florida, Hong Kong and Malaysian fish farms,
it is rare to see the wild forms of Platys on sale in aquarium shops. But if you
want to own a Central American River aquarium, the farmed fish look just as attractive
and are as hardy as the wild species - and all are still Xiphophorus, the sword
Fry are produced regularly,
of course, but these will not survive in the community aquarium. In a species
tank planted with (American) bushy species (e.g. Myriophyllum, Cabomba, Egeria
and Riccia) will give natural cover and food for the fry to survive.
Thanks to Dr David Ford, http://www.drdavidford.pwp.blueyonder.co.uk/