Phenotypic plasticity in physiological status at emergence from nests as a response to temperature in Atlantic salmon (Salmo salar)

Successful transitions from relying on yolk to exogenous feeding may be strongly influenced by temperature conditions experienced both during embryonic development, through effects on juvenile phenotype, and during initiation of feeding. Here we simultaneously assess these two effects of temperature treatments (2, 5, 8, and 12°C) in Atlantic salmon (Salmo salar). Fry emerging from low incubation temperatures were smaller and had metabolized more energy prior to emergence, but had larger yolk sacs and higher mass specific energy levels, than those experiencing higher temperatures. After emergence, activity, feeding, and growth increased significantly with increasing temperature, but fry were able to initiate feeding and maintain positive growth at all four temperatures. Larger energy stores may provide an advantage when emerging at cold temperatures with a low potential for feeding activity, whereas having a large body size, which is primarily of importance in competitive interactions, may be less important owing to cryptic feeding and sheltering at low temperatures. However, the adaptive significance of the observed phenotypic response to incubation temperature remains untested. Le passage avec succes de la dependance du vitellus a l'alimentation exogene peut etre fortement influence par les conditions de temperature subies durant le developpement embryonnaire, a travers leurs effets sur le phenotype juvenile, ainsi que durant l'initiation de l'alimentation. Nous evaluons simultanement ici ces deux effets des traitements thermiques (2, 5, 8 et 12°C) chez le saumon atlantique (Salmo salar). Les alevins qui emergent de temperatures d'incubation basses sont plus petits et ont metabolise plus d'energie avant l'emergence, mais ils possedent des sacs vitellins plus gros et des niveau x d' energie specifiques a la masse plus grands que ceux qui ont connu des temperatures plus elevees. Apres l'emergence, l'activite, l'alimentation et la croissance augmentent significativement en fonction de la temperature croissante; cependant, les al evins sont capables de commencer a s' alimenter et de maintenir une croissance positive aux quatre temperatures. Les reserves plus importantes d'energie peuvent representer un avantage lors d'une emergence a basse temperature lorsque le potentiel d' acti vite alimentaire est faible; en revanche, une forte taille corporelle, qui est de premiere importance dans les interactions de competition, peut etre moins avantageuse pour l'alimentation cryptique et la mise a l'abri aux temperatures basses. Cependant, la valeur adaptative de la reponse phenotypique observee a la temperature d'incubation reste a tester. [Traduit par la Redaction]
Introduction The transition from relying on parentally provided resources to independent exogenous feeding represents a critical period of the life cycle in many organisms. Typically, a considerable amount of the [...]