UC San Diego

Like many in Southern California during the 2015/16 El Niño event, I was struck by the presence of thousands of bright red tuna crabs (Pleuroncodes planipes) abundant at sea and washing ashore. Their sudden prevalence inspired me to learn more about these fascinating animals. Despite drawing so much attention, basic details related to their feeding behaviors and life history remain unknown. P. planipes have long been thought, but never confirmed, to experience a unique life history among crustaceans during which they undergo a sequential habitat shift from pelagic to benthic as adults. In this dissertation research, I applied contemporary methods of stable isotope ecology in combination with ecomorphology to examine aspects of their life history relevant to their pelagic and benthic life stages. We further assessed their vulnerability to the climate change stressors of ocean acidification and ocean warming through a long-term experiment. Through this work, we uncovered morphological differences and an ontogenetic diet shift between pelagic and benthic adult stages as well as significant impacts of temperature, but not pCO2/pH on molting and growth in pelagic adults. These results provide the first evidence in support of the hypothesis that P. planipes adult pelagic and benthic stages are distinct and yield important insight into how this transition could be impacted as the oceans continue to change.