Abstracts (first author)
Ontogenescence and the Barnacle: an experimental examination of early life mortality in the estuarine barnacle Amphibalanus improvisus
Ontogenescence, the decrease in mortality rate experienced during early life, is a nearly universal life-history trait. Among aquatic organisms this high and declining early mortality is generally attributed to extrinsic risks to which developing individuals gradually become more robust through increasing size and speed (Acquisition of Robustness). We examined the stage-specific mortality patterns of larval estuarine barnacle Amphibalanus improvisus in the laboratory, and found that in the absence of the usual environmental risks (predation, washing away, rapid environmental changes), early mortality was still high and generally declining, but was focused around developmental transitions. We further found that even though individuals of these transitional stages are more likely to encounter certain environmental stressors (temperature and salinity shocks), these stages exhibited the lowest tolerance to these stressors. Our results, while not refuting the Acquisition of Robustness hypothesis, lend support to the Transitional Timing Hypothesis, which states that ontogenescence arises because biological transitions are dangerous, and are concentrated early in life. Our data illustrate several ways in which mortality can be concentrated around early-life transitions.