by Dr. Emil Javier
November 28, 2015
Since 1996 close to two billion hectares have been planted globally to GMO crops. However, to date no genetically engineered economic animal, whether poultry, livestock nor fish has been approved for release and commercialization.
This status is about to change with the approval last week by the US Federal Drug Administration (US-FDA) of a genetically engineered (GE) Atlantic salmon which grows almost twice as fast as regular Atlantic salmon under farmed conditions (i.e., aquaculture).
The US-FDA has determined that the nutrition profile of the GE salmon is no different from regular farmed salmon and is as safe to eat as food. Moreover, because of the sterility and lack of fitness of the GE salmon, it is unlikely to dominate salmon in the wild should they escape or be released in the open seas.
Salmons are valued not only for their good qualities as food fish but also for their low-saturated fat content and for their high contents of Omega-3 fatty acids and Vitamin D which reduce risk of heart disease and stroke.
Actually the family of Salmonidae is composed of many species found in the North Atlantic, North Pacific, Europe, Hawaii and Australia. Wild salmons are heavily fished and their populations have declined markedly in recent years so much so that a major species, the Atlantic Salmon is in the endangered list.
The total global production of salmon is about three million tons per year. However, only one-third of the total volume are caught in the wild, mainly in the Pacific Ocean. The majority (2/3) are Atlantic salmon which is 99% farmed or grown in aquaculture.
This new GE salmon, proprietarily called AquAdvantage Atlantic Salmon, grows very fast and attains market size at 16-18 months, instead of 30 months of the regular farmed salmon. The mature adult size of GE and regular farmed Atlantic salmon are about the same so the advantage of the GE salmon is more efficient use of aquaculture facilities and 25% reduction of feed required to produce the same fish biomass.
NATURE OF GENE CONSTRUCT
The advantage of faster growth of the GE Atlantic salmon is derived from an artificial gene construct inserted into the wild salmon. The gene construct consists of two parts, namely 1) a growth hormone gene from the Chinook salmon, and 2) a promoter gene from another fish, called ocean pout which switches on the growth gene all-year round instead of only during warm weather.
Chinook salmon is another popular salmon species, a native of the Pacific Ocean and belongs to the genus Onchorynchus. The Atlantic salmon on the other hand, belongs to the genus Salmo.
The ocean pout is unrelated to the salmon family. It is eel-like in appearance, a bottom-dwelling, cool-water fish which is edible but not commercially valuable. However, it has a special trait — ocean pout has “anti-freeze” proteins in its blood which enable it to survive near-freezing waters.
However, the high metabolic rate and high oxygen demand of the GE salmon which lead to faster growth rate is a liability for the GE salmon in the wild. These favorable conditions are artificially created in the farmed ponds but they do not obtain in the wild which make the GE salmon less fit to survive and dominate in the wild.
TRIPLOIDY AND SEX REVERSAL
There are two other genetic manipulation technologies embedded in the AquAdvantage Atlantic Salmon, namely: 1) triploidy, and 2) sex reversal. The final GE fish product contains not only the novel gene construct from chinook salmon and ocean pout fish but they are also triploids and they are all females.
Most organisms are diploids. They possess two sets of chromosomes — one set each from the male and female parents. Occasionally some have multiple sets e.g. triploids (3x). During cell division the chromosomes line up in pairs, regularly split and go to opposite poles. In triploids, the three sets of chromosomes get mixed up and the resulting reproductive cells end up with a mixed bag of variable chromosome numbers which make them sterile.
In plants, triploids produce bigger leaves, flowers and fruits which make them attractive specially for ornamental horticulture. However, in fish the advantage of triploids is that the energy for sexual reproduction is redirected to fish growth.
Besides since the offsprings are sterile this is how the animal breeder can biologically protect his innovation (intellectual property).
In fish, triploidy is easily induced by pressure and/or temperature shock on the fertilized eggs. In plants, the cells are chemically treated with colchicine.
Sex reversal is another popular technology in aquaculture. Sex reversal is achieved by feeding the fish fry with methyl testosterone. With all-males or all-females populations, the energy of the fish is again redirected to growth instead of sexual reproduction. Rafael D. Guerrero III of the National Academy of Science and Technology (NAST) had developed the sex reversal application on tilapia.
Usually, all-male populations are preferred because males grow faster but in this GE salmon the final product is all females because females are less competitive to the wild salmon should they escape or be released from confinement.
CONCLUSION
The world’s oceans are overfished and declining fisheries catch is a reality staring us in the face even now. The only way to arrest declining fisheries catch is by declaring no-fish seasons and no-catch zones to allow native fish populations to re-stock. These unpopular moves now being imposed by the Bureau of Fisheries and Aquatic Resources (BFAR) deserve our full support.
The other obvious approach to increase fish supply is by fish farming or aquaculture. Our domestic aquaculture sector grows mainly bangus, tilapia, prawns, carp and seaweeds, and increasingly more valuable fin fishes, crabs and mollusks.
This novel genetic engineering technology developed for GE salmon has far reaching implications for our aquaculture industry. This is a wake-up call to the Department of Agriculture (DA) and Department of Science and Technology (DOST) as well as the state universities and colleges to redouble our efforts in fish genetics, reproductive physiology, fish nutrition, fish pathology and related marine sciences; to understand our water environment better; master these technologies ourselves and share with the private sector to exploit these technologies to serve our national interests.
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Dr. Emil Q. Javier is a member of the National Academy of Science and Technology (NAST) and also Chair of the Coalition for Agriculture Modernization in the Philippines (CAMP).
For any feedback, email eqjavier@yahoo.com.
Source: http://www.mb.com.ph/genetic-engineering-for-salmon-and-fish/
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