We are accustomed to seeing the deep-sea portrayed as the home to scary-looking fish, but in reality, many different kinds of organisms live there. Most of these lack backbones, and many of them are “gelatinous”: transparent, fragile, and taking on a myriad of forms. There are two ways that we are discovering new layers of this diversity: First, using remotely operated submersibles (ROVs) we can collect fragile life forms which have not been studied before. Second, within the species that we think are familiar, we find new genetic diversity. As we look closer, we find that two similar-looking animals from different parts of the ocean are actually two different species. These results are important because we need to be able to census marine populations in order to understand ocean ecosystems, how they are linked, and how they might be changing. New genetic tools which allow you to easily assess who lives in the ocean require a lot of hard work before they can be accurately applied. We need to identify genetic sequences corresponding to each species, and see how variable those sequences are across different geographic spaces.

Another unexpected way that deep-sea diversity can inform us about life on earth pertains to the very origin of animals themselves. Comb jellies and sponges, both of which are abundant and diverse in the deep ocean, represent two evolutionary events in the transition from single-celled organisms to multicellular animals. By studying their genetics and relationships, we not only learn about where those species came from, but how we ourselves came to be.



Christianson, L.M., S.B. Johnson, D.T. Schultz, and S.H.D. Haddock. 2021. Hidden diversity of Ctenophora revealed by new mitochondrial COI primers and sequences. Molecular Ecology Resources, 22: 283–294. https://doi.org/10.1111/1755-0998.13459


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