GENET archive


5-Animals: Status of development of GE aquatic animals

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SOURCE: ISB News Report, USA, by Eric Hallerman
DATE:   April 2003

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Atlantic salmon expressing a growth hormone (GH) transgene may become the
first genetically engineered animal approved for commercial food
production1. With 4-6 times the growth rate and a 10-20% improvement in
feed conversion efficiency relative to non-transgenic salmon, production
of the transgenic line offers shorter production times, reduced costs,
and improved profitability to aquaculturists2. However, the transgenic
salmon also pose food safety and environmental concerns3-5. With other
transgenic fish likely to enter the regulatory system within the
foreseeable future, a review of issues posed by development of transgenic
aquatic species is timely.

Scope of research and development effort The AquaBounty Atlantic salmon
is the most widely publicized example of a large international effort
aimed at developing transgenic aquatic and marine organisms (Table 1).

Table 1. Scope of effort for development of transgenic aquatic animals.

The most frequent application is for food production; GH genes have been
inserted into over a dozen species4. Cecropin6, interferon, and other
genes have been introduced to increase non-specific immunity to disease.
Transgenic zebrafish, medaka, and other species are used as model systems
for research on gene expression and embryological development. In a
recent application, tilapia were engineered for use as bioreactors to
express human coagulation factor VII in their blood7. Transgenic fish are
under development for environmental biomonitoring, for example, for
detecting environmental mutagens8. Several research groups are
experimenting with transgenesis as a means of achieving reproductive
confinement9. Development of transgenic mollusks and crustaceans is
complicated by the inability of many P0 founders to transmit the
transgene5, although some progress has been achieved10.

Most transgenic lines are still in the development stage, although
several are nearing readiness for possible commercialization. In addition
to their possible benefits, the commercialization of transgenic aquatic
organisms also poses a range of controversial issues, including food
safety, environmental safety, and public policy.

Food safety Foremost to many prospective consumers is the issue of food
safety3,4. Although cooking and digestion would break down most transgene
products, three types of food safety concerns must be considered. First,
bioactivity of the transgene product may pose concern, especially for
pharmaceutical proteins. Second, allergenicity may prove hard to assess
if the transgene comes from a non-food organism. Allergenicity assessment
will be somewhat easier if the transgene comes from an organism
representing known allergenic food groups, including fish and shellfish.
In that case, the transgene product can be tested for reactivity against
antisera from individuals with known food allergies. Third, toxicity
potential is relatively easy to assess, and toxin genes would not be
candidates for gene transfer.

The National Research Council (NRC) found that the level of food safety
concern posed by products of animal biotechnology varies with the
application3. For fish expressing a GH transgene, neither GH, GH
fragments, nor hormones secreted in response to GH pose a risk to the
human consumer. Hence, GH salmon likely pose little or no food safety
risk. A comparative analysis of composition of products from GH and non-
transgenic salmon is ongoing2. The NRC has a broader study ongoing on
unintended health effects of genetically engineered foods.

Environmental safety A second set of issues concerns the environmental
safety of aquatic GMOs. Escape from production facilities, such as
floating net pens used for production of salmon, is likely. Interbreeding
with wild populations poses genetic and evolutionary risks. Ecological
risks are posed with a variety of species in the receiving ecosystem. The
NRC attached a high level of concern to possible environmental impacts of
transgenic fish3.

If transgenic individuals were to escape from confinement and interbreed
with wild fish, would the transgene be purged from the population or
would it persist? Empirical observations of particular transgenic
lines3,5 show higher oxygen consumption rate, lower critical swimming
speed, higher willingness to risk exposure to predators, and lower
viability of young. These observations suggest that transgenic
individuals are less fit than non-transgenic individuals, that selection
would remove the transgene from the receiving population, and that
genetic impacts would be minor. However, some researchers question
whether selection would remove the transgene from the population rapidly
enough that impacts would be minor, and question the impact of recurrent
introduction of transgenes into the population. Further, some researchers
argue that single-trait models are simplistic, and that we must consider
how the transgene affects fitness through the entire life cycle. For
example, would a gain in mating success due to large size of a GH
transgenic fish come at the cost of juvenile viability11? Two net fitness
models11,12 predict that when there are tradeoffs in fitness traits
through the life cycle, the transgene could spread through the population
and, under certain conditions, threaten the viability of the population.
Other possible tradeoffs would include: increased male mating success and
reduced adult viability; increased adult viability, and reduced male
fertility; and increased male mating success and adult viability but
reduced male fertility. Current knowledge of possible genetic impacts of
transgenic aquatic species is such that we cannot predict the outcome
should a transgene be introduced into a wild population.

Since possible genetic impacts are plausible, reproductive confinement is
appropriate. The proponents of the transgenic Atlantic salmon suggest
production of all-female triploid stocks2. This raises questions of
whether 100% triploidy can be reliably achieved at the scale of
commercial production and the level of sampling needed to assure that
production stocks are indeed all triploid. The NRC is conducting a study
of bioconfinement that should be helpful in addressing these questions.

Even with effective reproductive confinement, transgenic aquatic species
pose ecological impacts on receiving ecosystems. Two key concerns are
competition with and predation upon natural populations. Many
interactions among aquatic species are mediated by size, particularly
predation. We must determine for each case whether transgenics will
exhibit a larger size distribution than non-transgenics. Ecological
impacts can cascade through trophic levels in feeding webs. That is,
predation affects the interactions of many species and influences the
species structure of many aquatic communities. Aquaculture escapees can
outnumber wild fish. For example, should a medium-sized farm with 100,000
fish lose 3% of the stock, these 3,000 fish might outnumber the wild
population of the species, suggesting that competition and predation
could become important interactions between the sterile stock, the wild
stock, and prey populations. Recognition of these ecological risk
pathways has led to greater discussion of aquaculture in on-land, indoor
recirculating systems.

Public policy The discussions of food safety and environmental issues
posed by transgenic aquatic organisms have raised questions about the
adequacy of regulatory oversight3,4,13. Under the Coordinated Framework
for the Regulation of Biotechnology, a transgenic fish is regulated by
the Food and Drug Administration (FDA) as a "new animal drug" under the
Federal Food, Drug, and Cosmetics Act. This approach fosters rigorous
regulatory review of a product. Approval for marketing a product can be
contingent upon adhering to given methods of production (e.g., use of
all-female triploids or recirculating aquaculture systems).
Commercialization would be followed by food safety and environmental
monitoring, and approval for marketing could be withdrawn if found
appropriate. However, the regulatory process is not publicly transparent.
The existence and contents of a "new animal drug" application are
confidential unless disclosed by the applicant. At the conclusion of
regulatory review, FDA would publish its decision and rationale, without
having offered opportunity for public comment. The closed nature of the
procedure tends to decrease public acceptance of the regulatory process
and of the product of biotechnology. Regarding possible environmental
impacts of transgenic organisms, the Coordinated Framework invokes the
National Environmental Policy Act. However, the act is procedural,
requiring only that environmental impacts be formally assessed.
Furthermore, FDA has limited environmental expertise.

Other acts might be invoked to apply the authority and expertise of
federal agencies to issues posed by transgenic aquatic organisms4,13.
These include the Endangered Species Act (lead agencies are the U.S. Fish
and Wildlife Service [USFWS] and the National Marine Fisheries Service),
the Lacey Act (regarding injurious wildlife species, USFWS), the Non-
Indigenous Aquatic Nuisance Species Prevention and Control Act (USFWS),
Section 10 of the Rivers and Harbors Act (U.S. Army Corps of Engineers),
and the Toxic Substances Control Act (Environmental Protection Agency).
However, focusing only on the federal policy framework does not recognize
that the states generally have lead authority for management of aquatic
and marine resources to the three-mile limit offshore, plus valuable
expertise on the species and ecosystems at issue4.

Three recent reviews of public policy covering transgenic aquatic
organisms3,4,13 stopped short of recommending that public policies be
changed to strengthen regulatory oversight and improve transparency to
the public. The Pew Initiative of Food and Biotechnology has a
stakeholder forum that may make consensus recommendations14.

Conclusion AquaBounty, the company seeking regulatory approval for
commercialization of GH salmon, also has transgenic lines of rainbow
trout and tilapia2. Transgenic lines of GH tilapia and carp are under
regulatory review in Cuba and China, respectively4. Scientific and
regulatory issues posed by transgenic aquatic species will be debated for
years to come. 


1. Hallerman EM. 2000. ISB News Report, April 2000, http://
2. Entis E. 2003. Biotech at sea: Innovation required. http://
3. National Research Council 2002. Animal Biotechnology: Science-Based
4. Pew Initiative on Food and Biotechnology. 2003. Future Fish: Issues in
Science and Regulation of Transgenic Fish.
5. U.S. Department of Agriculture - Cooperative State Research Service,
Biotechnology Risk Assessment Research Program. 2002. Biotechnology risk
assessment data: Facts and conclusions.
6. Dunham RA et al. 2002. Marine Biotechnology 4:338-344.
7. Aquagene LLC. 2003.
8. Winn RN et al. 2000. Proceedings of the National Academy of Sciences
USA 93: 12655-12660.
9. Usbekova S et al. 2000. Journal of Molecular Endocrinology 25: 337-350.
10. Lu JK et al. 1996. Proceedings of the National Academy of Sciences
U.S.A. 98:3482-3486.
11. Muir WM and Howard RD. 1999. Proceedings of the National Academy of
Sciences U.S.A. 96: 13853-13856.
12. Hedrick PW. 2001. Canadian Journal of Fisheries and Aquatic Sciences
58: 841-844.
13. Council on Environmental Quality and Office of Science and Technology
Policy. 2001. Case studies of environmental regulation for biotechnology.
14. Michael Rodemeyer, Executive Director, Pew Initiative on Food and
Biotechnology, personal communication, January 31, 2003.

Eric Hallerman
Department of Fisheries and Wildlife Sciences
Virginia Polytechnic Institute and State University