[ibon] COMING SOON: TRANSGENIC FISH FOR SALE
IBONRED
COMMENTARY
COMING SOON: TRANSGENIC FISH FOR SALE
Genetically modified fish such as the 'glofish' and the transgenic
salmon, trout, carp, and tilapia pose extreme risk, but there is a
regulatory vacuum behind the rush for their commercial release
By Joe Cummins
The tiny zebra fish, a popular laboratory and aquarium animal, was
genetically modified to produce a flourescent red pigment. Today,
it is being promoted as the "glofish", a household aquarium pet.
The glofish caused a stir in the United States because regulation
of such transgenic pets is murky and none of the major regulatory
agencies-the Food and Drug Administration (FDA), the United States
Department of Agriculture (USDA) or the Environmental Protection
Agency (EPA)-is willing to take the lead in regulating the glofish
(even though USDA does deal with pet animals).
The glofish was set to go on sale last January, even without
regulatory approval.
The FDA announced: "Because tropical aquarim fish are not used for
food purposes, they pose no threat to the food supply. There is no
evidence that these genetically engineered zebra danio fish pose
any more threat to the environment that their unmodified counterparts,
which have long been widely sold in the United States. In the absence
of a clear risk to the public health, the FDA finds no reason to
regulate these particular fish."
The FDA position that transgenic glofish are substantially equivalent
to unmodified fish is hypothetical and no effort has been made to
test the transgenic fish in contained, but wild-like environments.
Fish pigmentation with "poster" colors is an aphrodisiac to wild
fish and may even provide protection from predators in certain light
conditions. The pigment flourescence may also signal toxic defense-as
in the stinging sea anemone from which glofish transgene was prepared,
and that way, discourages predators.
The FDA was presumptuous in washing its hands of the regulation of
the transgenic zebra fish, which is likely to become a major pest
of warm water areas.
The release of glofish may signal relaxation of the regulation of
transgenic fish now being promoted for commercial release. To ensure
that transgenic fish do not empower or seriously pollute the gene
pool, both promoters and regulators stress the safety of "sterile"
transgenic fish released to bodies of water.
Previously, "sterile" fish are produced using synthetic triploid
strains of fish produced from treatment of eggs with pressure or
temperature shock and with sex horomones. The sterile triploids
were "leaky" and tend to produce a few fertile progeny, which can
establish transgenic populations.
In spite of these problems, the transgenic fish are being promoted
as the first marketable transgenic animals for human consumption.
More effort seems to have been spent on promoting the existing
defective transgenenic fish that on improving them so they can be
safely released for commercial production.
Muir and Howard defined conditions under which transgenic can cause
rapid extinction to wild fish stock, thus posing extreme risk; but
this has been ignored in the rush to commercialization.
Development of transgenic fish has focused on a few species including
salmon, trout, carp, tilapia, and a few others. Salmon and trout
are cash crops while the others primarily provide sources of protein.
The salmon nearest to commercial release is Atlantic salmon engineered
with a pacific salmon growth hormone driven by the arctic antifreeze
promoter gene.
The rapid growth of that transgenic salmon is achieved not so much
by the transgenic growth hormone as by the antifreeze gene promoter
that fucntions in the cool water desirable for salmon flavor. The
commecial release of transgenic salmon, even in somewhat contained
fish farms, is likely to lead to problems similar to those experienced
in the Atlantic salmon farms of the northwest Pacific.
A number of studies indicate that salmon produced in sea pens escape
and breed with native species, introducing new disease and spreading
pollution from the culture pens. These problems will probably be
amplified in the fast-growing transgenic stocks.
Tilapia fish, native to Africa, are cultured woldwide as "poor man's
food", second only to carp as warm water food fish, and exceeding
the production of Atlantic salmon (whose market value is twice that
of tilapia). Tilapia has been extensively genetically modified and
promoted as a transgenic fish exclusive for isolated or contained
production.
Transgenic tilapia, modified with pig growth hormone, is three times
larger than its non-transgenic siblings. Tilapia genetically modified
with human insulin grew faster than non-transgenic siblings, and
could also serve as a source of islet cells for transplantation to
human subjects.
Trout growth hormone was used to produce transgenic carp with
improved dressing properties. Such transgenic carp is recommended
for production in earthen ponds.
Giant mud loach was produced by linking the mud loach growth hormone
with its actin promoter. These giant fish are not, technically
speaking, transgenic, as they contain no foreign genes-even though
the inserted construct is artificial, and poses a paradox for
regulators.
Silk moth genes were introduced into Medaka fish to create resistance
to bacterial pathogens. Some commercially desirable fish and
crustaceans have been difficult to genetically engineer because
embryonic tissue is difficult to manipulate. But it has been found
that the parental gonads of such animals could be modified, using
replication-defective pantropic retroviral vectors.
Pantropic vectors can transform an array of species-they are modified
forms of the Moloney mouse leukaemia virus used extensively in gene
therapy. Such vectors have proven useful in modification of a range
of edible marine animals, including mollusks.
Animals produced using modified mammalin leukaemia viruses will
require extensive testing and long-term evaluation prior to release
for human consumption. This is particularly important in view of
the leukaemia cases found among the handful of successes in human
gene therapy, which were done with a retroviral vector.
The current generation of transgenic fish has not passed the test
of complete sterility if released (or if it escapes) to the
environment. Fish production in inland earthen ponds may prove
acceptable for contained transgenic fish culture. But such facility
should be provided with fail-safe destruction of the pond animals
in the event of flooding, and adequate protection from theft.
Aquaculture can help feed the world without diminishing ocean
resources, but premature releases of transgenic fish stocks will
do more harm than good. Bad decisions have plagued aquaculture,
resulting in pollution and extensive damage to native stocks.
International agencies such as the World Bank, International
Development Bank, and the Food and Agriculture Organization of the
United Nations have created harm by ill-advised projects that led
to pollution and damage to native resources.
Scientists Julio E. Perez and Mauro Nirchio of Venezuela, along
with Juan A.
Gomez of Panama, commented, "If the aquaculture industry is going
to reduce the pressure on wild fish stocks and provide food for the
world's growing population, substantial changes must be made by
governments, the private sector and internaitonal funding agencies.
They must protect coastal ecosystems, promote research and development
of native species, and encourage farming of low-trophic-level
fish-those low on the food chain."
Without such constructive thinking, the aquaculture industry poses
a threat, not only to ocean fisheries but also to itself. Third
World Network Features/IBON Features