Page 140 - Cultural Studies of Science Education

8 Moral–Ethical Character and Science Education 117

predation on other species, and the introduction of diseases and parasites. If those
fish are genetically modified, then they may have adverse effects on native popula-
tions of the same species when modifying genes facilitate increased growth rates.
We see this phenomenon occurring within salmon populations for example. A
salmon that grows to adult size or larger in 18 months versus the normal 30 months
may swim slower but have more reproductive success because of its larger size. If
the larger salmon is an easier target for predators, then population declines may
result. This theory is called the Trojan Gene Effect (Muir and Howard 1999). The
most significant point for zebrafish, salmon, and other genetically modified fish, is
that genetic modifications can have serious and unintended consequences for native
populations and habitats – a detail worth considering before release.
But the FDA and others say that GloFish are not capable of living in US waters.
The reasoning for this conclusion is based on the idea that zebrafish have not been
found in US waters over the last 20 or more years they have been sold. However,
Cortemeglia and Beitinger (2005) conducted a study using wild-type and transgenic
GloFish to determine their lower and upper temperature tolerances. Although
Yorktown Technologies provides scientific letters specifically affirming that the
transgenic GloFish cannot withstand the temperatures of US waters, Cortemeglia
and Beitinger note that their “review located no published studies of thermal tolerance
of zebrafish” (p. 1434) – with one exception which does not cite supporting studies.
Although FDA notes they will not regulate GloFish because geographic distributions
will be the same as the wild-type zebrafish, Cortemeglia and Beitinger found
“statistically significant differences in both upper and lower thermal tolerance
between wild-type zebrafish and genetically modified zebrafish at two acclimation
temperatures” (p. 1435). While statistically significant, the standard deviations of
the fish groups examined were 0.54°C or less which means that the geographic
distribution will be similar for both wild type and GloFish. The authors recommend
that transgenic technology be more carefully scrutinized because temperature toler-
ance in different fish species could be affected differently by genetic modification,
which in turn, may lead to unintended consequences for native populations and
ecosystems. Their findings also suggest that both the wild type and transgenic
zebrafish can extend their lower temperature limits when acclimated to lower
temperatures. They note that the colder temperature tolerant zebrafish has a good
chance of being naturally selected, similar to the common carp (Cyprinus carpio)
which has a similar temperature tolerance to the zebrafish and yet has been successfully
introduced into most freshwaters of the USA. Based on their data, they suggest that
zebrafish have the potential to live and overwinter in Florida, southern California,
and Texas.
If zebrafish (wild type or transgenic) have a good chance of living and overwinter-
ing in some southern US states, then it follows that they would have at least an equal
potentiality in warmer waters south of the border. This idea refutes Yorktown and
Carolina Biological’s claims that the zebrafish cannot survive in North America,
assuming North America includes geographic locations south of the US border. Since
zebrafish have been introduced in places where they are banned (Bratspies 2005), it
follows that they will eventually make their way back toward native populations in