It’s not every day that catching up on scientific literature causes you to almost do a spit-take on your laptop screen.  This happened to me recently due to the weird and wild world of aquaculture.  Aquaculture is the practice of growing aquatic animals such as fish and shellfish for the purpose of food, and has been held up as both a savior and destroyer of the marine ecosystem.  To get an idea of what this generally looks like (at least here in the U.S.), Amy has a whole series of posts on aquaculture operations in North Carolina.

As with land-based farming, aquaculturists are motivated to find ways to increase the food value of their stock.  The methods used are varied, from high-protein feed mixes to genetic manipulation.  Recently, farmed salmon genetically-modified to grow larger and faster than their wild conspecifics have been approved for human consumption by the FDA, though not without debate.  This man-made subspecies was created by modifying the already-existing DNA of the fish, but what if it turned out that simply injecting DNA from a different species could improve the growth and protein output of farmed fish?  And what if that foreign DNA came from sharks?

This is exactly what a researchers in the Middle East are trying out.  In two separate papers published this year, El-Zaaeem (2012) and El-Zaaeem et al. (2012) (try to keep those two straight), describe the use of DNA extracted from the mighty spiny dogfish shark and injected into the muscle tissue of two popular aquaculture species to improve size, growth, and feeding efficiency in those fish.  The goal is to make a higher-quality and hopefully better-selling product.  According to these papers, it seems to have worked.  Perhaps frighteningly well.

El-Zaaeem (2012) compared grey mullet injected with either dogfish DNA or DNA from African catfish with those simply raised using normal methods.  Both types of DNA-injected mullet showed improved feed-to-protein efficiency, and shark DNA blew the catfish DNA out of the water in terms of improvement in growth and body composition.

For their next trick, El-Zaaeem et al. (2012) injected shark DNA into red tilapia and compared six dietary treatments between the injected and non-injected fish.  Across all feeding trials, tilapia carrying shark DNA outperformed the standard fish in feeding efficiency, growth, and condition factors.

In both cases the shark DNA was centrifuged out of samples of spiny dogfish liver, and injected into fingerlings.  This means the fish were already well-developed when they were injected, as opposed to in the egg or larval stages where genetic modification typically happens.  It’s the aquaculture equivalent of the bull shark testosterone meme, except it apparently works.

My reaction to these papers was probably the same you’re having right now.  Is this for real?  Is it really as simple as just injecting shark DNA into a different species, causing them to become superfish?  How many times has this happened in the kind of movie shown on the SyFy Channel during the day on a Saturday, usually with tragic consequences?  The titles practically write themselves: Killapia!

I don’t consider myself anti-aquaculture or necessarily anti-GM food, provided it’s done ethically, but this seems a little bizarre to me.  I’m also only a knuckle-dragging ecologist so I may be missing something in the genetic portion.  If anyone more familiar with DNA wants to take a look at these papers, feel free to offer your likely more-informed opinion in the comments.  In the meantime, I’ll be wondering what pan-fried killapia tastes like.

References

Samy Yehya El-Zaeem, . (2012). Extraordinary mullet growth through direct injection of foreign DNA AFRICAN JOURNAL OF BIOTECHNOLOGY, 11 (33) DOI: 10.5897/AJB11.4085

Samy Yehya El-Zaaeem, Talaat Nagy Amer, & Nader Azzat El-Tawil (2012). Evaluation of the productive performance characteristics of red tilapia (Oreochromis sp.) injected with shark DNA into skeletal muscles and maintained diets containing different levels of probiotic and amino
yeast African Journal of Biotechnology, 28, 7286-7293 : 10.5897/AJB12.332