Nematodes Up Close and Personal

This week I started the process of nematode identifications to assess the differences in nematode communities at areas of wastewater treatment outflow and at sites without wastewater treatment plants. Because there are about 10,000 identified marine nematode species, with plenty of unidentified species, and differences between species can be exceptionally subtle, I have chosen to identify nematodes to the Genus level. This is one taxonomic level up from Species, and still provides high-quality information about the health of the ambient environment. There are a few indicators that scientists use to determine what type of nematode is under the microscope. A few notable ones are the amphid (the primary olfactosensory organ, which has different shapes in different nematodes), the buccal (mouth) cavity structure (whether or not there are teeth present and the overall shape), the cuticle texture, the orientation of reproductive parts, and the tail shape.

To identify a nematode, I look at all of these factors and use a dichotomous key (a step-by-step yes/no questionnaire) to identify the Family (the step above Genus), and then I go through a number of resources with pictures and more detailed descriptions of the different genera. So far I have learned the importance of drawing really detailed pictures and taking good notes because flipping through these resources is very time consuming. At some point, I will start recognizing the nematodes as ones I have already encountered, so I can go back to my notes and pictures rather than the other resources.

The picture I've included this week is of some of the nematodes I have drawn so far. In the first one at the top, I've indicated the shape of its amphid (which is the spiral), that it has a cup-shaped mouth, a series of dots that go across its body in rows, and that it has a claveate (club-shaped) tail. You can see other information from some of the other nematodes, as well as some empty spaces. Specifically in this set, number two is empty because the nematode was not of good quality on the slide so I decided to not identify it. It is better to not identify an animal than to guess in this field of work.

Over the next two-and-a-half months I will continue drawing, notating, and identifying these small animals to determine how the nematode communities differ at polluted and unpolluted sites. If you are interested in learning more about meiofauna, the smallest animals in the ocean, I was given the opportunity to co-author a post for NOAA and they just published it on their website. I have included the link here: https://oceanexplorer.noaa.gov/facts/marine-meiofauna.html. The relevant research expedition included in the web page is not one that I was on, but it is work that my advisor, Dr. Ingels, did, so feel free to read more about what we can learn from research expeditions in the deep sea, as well. 

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