Rhachotropis, who? While this question may seem alien to most of us, it is commonplace to others. And to anticipate it: Rhachotropis is a genus of amphipod crustaceans (known as beach hoppers) that is widespread in the deep sea and one of the key players we encounter on this expedition. We, that is, the deep-sea taxonomists here on board, who, roughly speaking, deal with the identification and naming of species. And that can be damned difficult at times. Partly because specimens that we sample from the deep sea are too damaged to reliably name them. Partly because species can simply not be distinguished, since from the outside one species just looks like the other – although their DNA would tell you they are different (something that we call cryptic diversity). And above all, despite all the advances made after 150 years of deep-sea research, sampling the deep ocean floor remains a major challenge. And the forces of nature that we experienced during this trip made this more than clear to us: deep-sea research involves great effort and commitment, is logistically complex and only possible if everyone on board, crew and scientists, pull together.
Hence, naturally, deep-sea taxonomic work is a lengthy one, starting with sample collection, sieving, sorting (i.e. hand-picking individuals from the mud), photographing and initial rough identification, which, including genetic analysis, can already be achieved on board. However, the mammoth task follows in the home laboratory. Here species are further identified and, if recognized as new, named and described. How long this process may take cannot be quantified across the board, but several months to years are not uncommon. To speak figuratively, as a taxonomist you need a lot of stamina, i.e. being more of a long-distance runner than a sprinter. At the same time, however, taxonomy research is more sustainable than any other: species names are still valid after hundreds of years, and specimens from these historical descriptions are available in natural history collections.
But still, can’t the whole thing be shortened and why is it even important to name species? Living in a time of considerable environmental change, which also extends into the depths of the oceans, we want to know what are consequences for the resident biota? And these can be very different, depending on which species we are dealing with. Coming back to the Rhachotropis example, it makes a huge difference if we find Rhachotropis aculeata, a species common to the North Atlantic, or Rhachotropis boreopacifica usually found in the North Pacific, and thus likely to be an invasive species. Time is of the essence to identify all the different threats to the deep-sea fauna. Therefore, new methods in taxonomy are constantly being developed to accelerate taxonomic work, including modern imaging tools or molecular methods – just to mention metabarcoding or e-DNA, which are also being used here on board. Molecular methods can provide independent evidence of species identification and thus be a valuable addition to traditional morphology-based taxonomy.
According to current estimates, there are thousands upon thousands of species to be discovered in the deep sea, and it is clear that we can only preserve what we know. So, whatever species the next samples will bring to light, we name it!
