The Syngnathidae (seahorse and seadragon) is among evolution’s most “beautiful and wonderful” species. A remarkable example involves the pygmy seahorse (Hippocampus bargibanti). It lives obligatorily on gorgonian corals mimicking its polyps with pink coloration and skin protuberances. Unique for seahorses, pygmy seahorses retain juvenile paedomorphic stunted snouts, resembling the coral’s polyps. We analyzed the tiny seahorse’s genome discovering the genomic bases of several adaptations to their mutualistic life including massive losses of conserved noncoding elements affecting growth and metamorphosis-related pathways. Comparative RNA- and ATAC-Seq analyses during their ontogeny suggest that their stunted snout arises via craniofacial remodeling due to loss of hoxa2b, as further evidenced by in-situ hybridization and CRISPR experiments. Another sample of camouflage is the leafy seadragon, aptly named for its many leaf-shaped appendages covering its body - an extraordinary camouflage mimicking its coastal seaweed habitat. Global climate change-induced loss of seagrass beds now severely threatens the existence of this enigmatic species. Here, we present the de novo assembled leafy seadragon genome that revealed genomic signatures of rapid evolution and positive selection in core genes related to camouflage, and allowed us to predict historical and contemporary population dynamics. The leafy seadragon has historically a small population size likely due to its specific habitat requirements and minimal dispersal ability that further exacerbate its vulnerability to climate change. By modeling future habitat availability considering climate change viable conservation strategies are deduced.
 

seahorse,camouflage,climate change,conservation