Meeting Abstract
Individuals often do not grow at their maximal rates and are capable of undergoing rapid, compensatory growth following developmental setbacks. One reason that this might occur is that rapid growth induces costs that reduce longevity. However, mechanisms underlying this link are poorly understood. One mechanism that might be important in this regard is insulin-like growth factor 1 (IGF- 1). The IGF-1 signaling pathway is evolutionarily conserved and is positively related to growth and negatively related to lifespan across taxa. In this study, we experimentally manipulated growth rates in Franklin’s gull(Leucophaeus pipixcan) and examined the effects on circulating IGF-1 concentrations. In this system, chicks that hatch later in the season grow at a faster rate than early-hatched chicks. We collected first laid eggs from 20 early-nesting and 20 late-nesting females and incubated the eggs in the lab. After hatching, chicks were reared in captivity and randomly assigned to either a control treatment in which food was available ad libitum or experimental treatment in which food was restricted to 60% of ad libitum between days 7-17 post-hatch. Prior to and after this period of restriction food was available ad libitum. This experimental treatment altered growth rates. Both early season and late season birds had reduced growth during the period of restriction (P<.001) and accelerated, compensatory growth following restriction (P<.001). We also examined the influence of the treatment on IGF-1 levels and the results will be discussed within the context of life-history evolution.
