Biology Reference
In-Depth Information
CHAPTER
6
Salmonid Smoltifi cation
Karine Rousseau,
1,a,
* Patrick Martin,
2
Gilles Boeuf
3
and
Sylvie Dufour
1,b
6.1 Introduction
The secondary metamorphosis is a non-classical metamorphosis occurring
during the juvenile period in opposition to the fi rst or “true” metamorphosis,
which is a typical indirect development involving a larval metamorphosis
leading to the juvenile period (Youson, 1988). Secondary metamorphosis,
which occurs after a juvenile period, involves various morphological,
physiological and behavioural modifi cations that pre-adapts the animal
to life in the next environment, but that is less drastic than that observed
during the larval metamorphosis. Two examples are found in Teleosts:
smoltifi cation (also called smolting or parr-smolt transformation) in salmon
(this Chapter) and silvering in eel (Chapter 7). They both concern extreme
migratory Teleosts and are related to their complex life cycles.
The Atlantic salmon (
Salmo salar
) spawns in freshwater (Fig. 1). The
embryos hatch and develop into alevins (yolk-sac fry), which live off
their nutrient rich yolk-sac that is attached to their underside. The young
alevins will emerge as fry from the gravel when they absorb their nutrient
rich yolk-sac and start actively searching for food. The small vulnerable
1
Research Unit BOREA “Biology of Aquatic Organisms and Ecosystems” Muséum National
d'Histoire Naturelle, CNRS 7208, IRD 207, UPMC, 7 rue Cuvier, CP32, 75231 Paris Cedex 05,
France.
a
E-mail: rousse@mnhn.fr
b
E-mail: dufour@mnhn.fr
2
Conservatoire National du Saumon Sauvage, 43 300 Chanteuges, France.
E-mail: pmartin@cnss.fr
3
Laboratoire Arago
,
Research Team « Models in cell and evolutionary biology”, University
Pierre and Marie Curie- Paris 6/CNRS, Banyuls-sur-mer
and Muséum national d'Histoire
naturelle, 57 rue Cuvier, 75231 Paris Cedex 05, Paris, France.
E-mail: boeuf@mnhn.fr
*Corresponding author
