Understanding how new biological traits arise is a fundamental question in evolutionary biology, with broad implications for explaining the origins of biodiversity, predicting how organisms respond to environmental change, and advancing biotechnology innovation. Most research into evolutionary novelty has focused on traits that arise through the gain of new genes or pathways; far less is known about how the loss or modification of existing pathways can generate novelty. This project investigates the process of kleptocnidy, which is the theft and storage of microscopic stinging structures (nematocysts) from cnidarian prey, a striking natural example of biological innovation that has evolved independently multiple times. The research will determine whether this unique process evolved in nudibranch sea slugs through specialization of phagocytosis, an ancient cellular process used across animals for immune defense and intracellular digestion. By generating high-quality genomic, transcriptomic, and single-cell data resources for marine invertebrates, the project produces strategic biological data assets useful to the broader scientific community for biotechnology applications and the development of fundamental knowledge across evolutionary biology, comparative immunology, and cell biology. This project will also support the training of graduate and undergraduate students and postdoctoral researchers in genomics and computational analysis through research experiences and will broad