Gill Morphometry in Growth Hormone Transgenic Atlantic Salmon

We show that many of the morphological features of the respiratory system of growth enhanced transgenic salmon are greater than those of similarly sized control salmon. Growth hormone transgenic Atlantic salmon, Salmo salar were the F₂ generation produced using eggs from a transgenic F₁ female and milt from a nontransgenic male. At the time the gill tissues were sampled, the transgenic salmon were growing 2.1 times more rapidly than the nontransgenic control salmon, and they had oxygen uptake rates that were about 1.6 times greater than control salmon. In the present study we show that the gill surface area available for respiratory exchange in the transgenic salmon is about 1.24 times that in control salmon which does not parallel the 1.6 elevation in oxygen uptake. The increase in gill exchange area was due largely to a relatively uniform increase in length of each gill filament.