Meeting Abstract
The bearded fireworm, Hermodice carunculata (Annelida: Amphinomidae), is a widespread mobile corallivore throughout the Atlantic Ocean. Due to its extensive geographic distribution, abundance, and survival under low oxygen conditions, it may serve as a model organism for hypoxia studies, which are increasingly important with the projected escalation of hypoxia zones in the future. Molecular, morphological, and physiological responses of H. carunculata to hypoxic conditions were investigated to estimate the dissolved oxygen (DO) level at which they are affected. Five bearded fireworms were exposed to one of three levels of DO in 40-liter tanks for seven days: 2.5 (± 0.25) mg/l, 4.5 (± 0.25) mg/1, and 7 (± 0.25) mg/1 (normal DO). No reference genome exists for the species, so a combined reference transcriptome was assembled from all sequences and utilized to align the RNAseq data from individuals for differential gene expression analysis. Additionally, we monitored oxygen uptake rates throughout the experiments and conducted morphometric analyses of branchial morphology. Pairwise comparisons of transcriptomes revealed up-regulation of key hypoxia and stress response genes and down-regulation of metabolic pathway genes in the worms under hypoxia. Differences in gene regulation were noted between the two experimental groups, indicating the DO levels chosen were distinct enough to invoke differing responses. The oxygen uptake rates and filament number were higher in the hypoxic treatments, indicating 7 days is enough time to induce morphological and physiological responses to hypoxia. The results allow us to infer the threshold DO level for hypoxic response in this abundant and environmentally tolerant coral predator, and to predict downstream responses.
