Utilization of stored energy reserves during fasting varies by age and season in Steller sea lions

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Abstract:

Nine captive Steller sea lions (Eumetopias jubatus (Schreber, 1776), 1.75–6years of age) were fasted for 7–14d to test the effect of short-term fasting on changes in body mass and body condition. Trials were repeated during both the summer breeding season and the nonbreeding season in seven animals to elucidate whether there was a seasonal component to the ability of Steller sea lions to adapt to limited food resources. Mean percent mass loss per day was higher during the breeding season in juveniles (1.8%± 0.2%·d–1) than in subadults (1.2%± 0.1%·d–1), but there were no significant age-related differences during the nonbreeding season (juveniles, 1.5%± 0.3%·d–1; subadults, 1.7%± 0.3%·d–1). A decrease in the rate of mass loss occurred after the first 3d of fasting only in subadults during the breeding season. Percent total body lipid ranged from 11% to 28% of total body mass at the initiation of fasting trials. Animals with lower initial percent total body lipid exhibited higher subsequent rates of mass loss and a lower percentage of tissue catabolism derived from lipid reserves. There was no evidence of metabolic adaptation to fasting in juveniles, which suggests that juvenile sea lions would be more negatively impacted by food limitation during the breeding season than would subadults.

Neuf lions de mer de Steller (Eumetopias jubatus (Schreber, 1776), âgés de 1,75–6 ans) ont été soumis à un jeûne de 7 à 14 j afin de vérifier l’effet d’un jeûne de courte durée sur les changements de masse et de condition corporelles. Nous avons repris les expériences à la fois durant la saison de reproduction et durant la période non reproductive chez sept animaux afin de voir s’il y avait une composante saisonnière à l’aptitude des lions de mer de Steller de s’adapter à des ressources alimentaires réduites. La perte moyenne de masse en pourcentage par jour est plus importante durant la saison de reproduction chez les jeunes (1,8%± 0,2%·j–1) que chez les subadultes (1,2%± 0,1%·j–1), mais il n’y a pas de différence significative en fonction de l’âge durant la période non reproductive (jeunes 1,5%± 0,2%·j–1; subadultes 1,7%± 0,3%·j–1). Une diminution du taux de perte de masse se produit après les 3 premiers jours de jeûne, mais seulement chez les subadultes durant la saison de reproduction. Le pourcentage des lipides corporels totaux variait de 11% à 28% de la masse corporelle totale au début des expériences de jeûne. Les animaux ayant un lipide corporel total initial plus faible ont subi des taux subséquents de perte de masse plus importants et ont connu un pourcentage plus faible de catabolisme tissulaire dérivé des réserves de lipides. Il n’y a aucune indication d’une adaptation métabolique des jeunes au jeûne, ce qui indique que les jeunes lions de mer subiraient un impact négatif plus important lors d’une pénurie de nourriture durant BS que les subadultes.

Document Type: Research Article

Publication date: February 1, 2007

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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