Tilapia fish engineered for transgenic expression of growth hormone
had deformed heads and backs, atrophied gonads, and lower mineral content.
Manipulated Organism:
Tilapia (Oreochromis niloticus).
Inserted Transgenes:
Tilapia growth hormone gene, with expression controlled by the beta-actin
promoter from medaka fish.
Goal of This Study:
Compare the growth of tilapia expressing the growth hormone transgene with
their non-GM siblings.
Intended Effect:
At 87 days post hatching, the average body weight of the GM fish
was nearly 3 times that of the non-GM fish. By 147 days, the GM fish
had reached market weight (165 g), while the non-GM fish required an
additional 90 days to reach that size.
Results of This Study:
Numerous morphological and compositional differences were observed when
the fish were harvested (at the same weight but months apart), including:
-
The GM fish had larger heads and wider bodies. Some had deformed, even
fractured, backs and heads.
-
The viscera of the GM fish were 8% of their total body weight compared
with 6% for the non-GM fish (p < 0.01).
-
The gonads of the GM fish were strongly atrophied, comprising only 0.05%
of the total body weight compared with 1.0% for the non-GM fish.
-
The GM fish had a higher moisture content (77% versus 70%) and contained
significantly less calcium (Ca) and phosphorus (P). On a dry weight
basis, the GM fish had only 72% and 86% of the Ca and P, respectively,
of the non-GM fish at market weight. The authors interpret this fact
as indicating incomplete bone mineralization, which is consistent with
the observation of bone fractures in the GM fish.
Source:
Lu, J., J. Li, Y. Furuya, G. Yoshizaki et al. (2009). "Efficient
Productivity and Lowered Nitrogen and Phosphorus Discharge Load
from GH-Transgenic Tilapia (Oreochromis niloticus) under Visual
Satiation Feeding," Aquaculture vol. 293, pp. 241-7.
Author Affiliations:
Tokyo University of Marine Science and Technology, Japan.
Funding:
Japanese Ministry of Education, Science, Sport and Culture.
Product Status:
Not on the market as of 2009.
Copyright 2009 The Nature
Institute.
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