Juvenile niches select between two distinct development trajectories and symbiosis modes in vent shrimps

Abstract

AbstractMost animal species have a singular developmental pathway and adult ecology, but developmental plasticity is well-known in some like honeybees where castes display profoundly different morphology and ecology. An intriguing case is the Atlantic deep-sea hydrothermal vent shrimpRimicaris hybisae/chaceithat share dominant COI haplotypes but develops into either the symbiont-relianthybisaewith a hypertrophied head chamber (in the Mid-Cayman Spreading Centre) or the mixotrophicchaceiwith a narrow head chamber (on the Mid-Atlantic Ridge). Here, we use X-ray micro-computed tomography and fluorescentin situhybridization to show that key anatomical shifts in both occur between the juvenile-subadult transition, when those developing intohybisaehave fully established symbiosis but notchacei. On the Mid-Atlantic Ridge the diet ofR. chaceihas been hypothetically linked to competition with the obligatorily symbiotic congenerR. exoculata, and we find anatomical evidences thatR. exoculatais indeed better adapted for symbiosis – suggesting thechaceimorph could be an adaptation to prevent competitive exclusion. Our results suggest that the two distinct development trajectories are likely selected according to the diet available to the juveniles, determined by whether energetically sufficient symbiont colonisation has occurred before reaching subadult stage.