Influences of functional variation on venom expression in hydractiniid hydrozoans

Abstract

Cnidaria (jellyfish, hydra, sea anemones, etc) represent the earliest diverging venomous animal lineage. Cnidarians deploy venom for predation, defense, competition, and digestion. Recent evidence suggests venom composition can be influenced by age, diet, geography, and the presence of predators or prey. Although venom production and maintenance are central to the life history of cnidarians, little is known about their venom composition with respect to biological or ecological function. Hydractiniid hydrozoans are an ideal system for studying venom function and evolution due to their functionally specialized tissue types and complex life cycles. The hydractiniid Hydractinia symbiolongicarpus displays a division of labor among its polyps that comprise the colony: the gastrozooid (feeding and digestion), dactylozooid (defense and predation), and gonozooid (reproduction). Podocoryna carnea, a related hydractiniid hydrozoan, displays a complex life history that includes a benthic colonial stage and a pelagic medusa. Using publicly available RNA-seq data of the functionally specific polyp types of H. symbiolongicarpus and life cycle stages of P. carnea, we characterized the putative venom components and venom expression between these tissues. Based on this analysis, we can determine how the venom arsenal varies for specific tasks and between life cycle stages. Future work will include lineage-based transcriptomics on the stinging cells of H. symbiolongicarpus as well as functional characterization of specific venom components using CRISPR. Understanding how venom composition is influenced by various developmental and ecological factors will lead to a better understanding of venom diversity and function in cnidarians.