Reproduction, development, and symbiosis are deeply rooted and this is particularly evident in marine invertebrates. The eggs, embryos, and larvae of annelids, bivalves, bryozoans, cnidarians, crustaceans, echinoderms, gastropods, and poriferans tend to form partnerships with microbial symbionts and these are interconnected with host function. The theme of this research topic—that is led by Dr. Tyler Carrier—focuses on the functional role of these interactions during reproduction and embryonic development, how these interactions change in response to environmental variants, and over evolutionary time. This work primary uses echinoderms and sponges as comparative and experimental systems, and pairs experimental field and laboratory work with molecular ecology, next-generation sequencing, and microscopy.

Two main takeaways from this research topic, thus far, are:

• Environment-induced morphological change in the larva (phenotypic plasticity) correlates with predictable, bidirectional shifts in microbiome composition that precedes and then correlate with the phenotype to form phenotype-specific microbial communities.
• Transitioning from feeding (planktotrophy) to non-feeding (lecithotrophy) corresponds with a reduction in microbiome diversity and cell abundance, loss in associating with a diet-specific microbiome, and the acquisition of a nutritional and reproductive endosymbiont. This endosymbiont is suspected to be the agent of this transition in developmental life-history.