The Science of It All


Lake Ölfusá, along Road 1 in southern Iceland west of Eyrarbakki.

Now that the days have slowly grown from three hours of daylight to more than nine hours, I am happy to get out to conduct my field research once again. This is an excellent opportunity to explore and experience Iceland in all its beautiful ruggedness. Although winter is not over, there are still opportunities to get out and drive through coastal Iceland to do my snail collections. I can tell you it is very beautiful to be on a rocky shoreline with heavy snowfall despite freezing fingers and 20-50 mph winds. I have been experiencing this for the last couple of months, but my most recent trip was a week of activity away from my home at Hólar University College. The week included meeting the President of Iceland, receiving a prestigious grant, presenting my research as an invited speaker at the University of Iceland, exploring a lava tunnel, slippery roads, desolate landscape, and of course, snow, snow, and more snow.

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My Fulbright/National Science Foundation Arctic Research project in Iceland is a survey that examines the parasite fauna inside marine and freshwater snails. Many parasites use snails as intermediate hosts, on their way to their definitive (final) host where the parasite will become sexually mature and reproduce. Trematodes are the best example of this; of the 25,000-trematode species, nearly all of them use a snail as the intermediate host. Snails can also be a dead-end host for other parasites. In this case, a particular  stage of the parasite may penetrate the snail or be ingested but can never be transmitted or reach its adult stage. Researchers can therefore use snails to identify if a particular parasite lives in an area; this is what we call an indicator species. This is exactly what I do to study hairworms (Phylum: Nematomorpha), the subject of my Ph.D. dissertation.

To get to Iceland on a Fulbright Fellowship, I proposed to look through marine and freshwater snails to examine the current diversity of parasites in snails. The purpose of this study is to provide baseline data so that in the future I can come back and see if any new parasites have moved into the area. This is particularly important because as global change is occurring, new migratory birds are moving into Iceland. When this happens, it is possible to bring new parasites to an area that may or may not establish themselves. Of course, not all the parasites in Iceland, including the residents and transients, will be found in snails, because not all parasites use a snail or live in the water for that matter. But at least I will be able to find a percentage of the total parasites in snails and thus I hope to use this method in the future to examine parasites in other regions of the world. Needless to say, these host-parasite relationships are much more complex but for the purposes of this write-up and my study in Iceland, I have tried to keep it simple.

So far, I have focused on marine snails because since late October, the Icelandic winter has made it difficult to access freshwater sites (they are inaccessible due to road closures or frozen). For now, I visit the coastal sites and collect in freezing rain or snow. The best part of field work is getting outside and in Iceland, I can see various parts of the country and visit quaint, seaside towns. After collecting, the snails are returned to the lab where I place them on slides and scan their tissue for parasites. Each parasite found is identified to the order, class, family, genus, or species (some groups are easy than others to identify). I also count how many of each parasite is present and take pictures.

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Although all parasites are fascinating, I hold a special love for one in particular–the hairworm. Studying diversity of parasites in Iceland was one way I could also investigate hairworms in snails in Iceland. To date, no species of hairworms have been identified from Iceland. I have only found evidence of their existence here in a 1905 publication in the Journal of the Asiatic Society of Bengal: Volume 71, Part 3. A section is written by renowned zoologist Nelson Annandale who was the Deputy Superintendent of the Natural History Section of the Indian Museum.  He wrote a section titled “Note on the Hair-Worms in Oriental and European Folklore”. This was interesting to me, but of particular interest is the statement that “…the hair-worms are said to come down with the rain”. Annandale goes on to explain that the British museum has specimens of Gordiids (freshwater hairworms) that were collected by Wallace (assumed to be Alfred Wallace) who noted on the label that they are “sky-snakes”. I remember reading these sentences two years ago and they were pivotal in my decision to apply to Fulbright because this is like the species I study in Oklahoma which emerges from the ground after heavy bouts of rain.

The hairworm life cycle is fascinating, and I am using this venue to share them with you. One reason they are so fascinating is their complex life cycle and what they do to their hosts. Below is an excerpt from my dissertation:

In freshwater habitats, hairworms do not feed but instead find mates and reproduce during their short two to eight-week, free-living phase of the life cycle. After mating, female hairworms lay millions of eggs freely in the water, on submerged rocks or twigs, or buried in submerged gravel depending on the species. After hatching, a small, nonmobile larva is released and falls to the bottom of the water column where a variety of aquatic invertebrates can ingest it. Larvae that find themselves in an appropriate paratenic host (transport host to terrestrial system) are most likely to complete their life cycle. Larvae can also be ingested by aquatic snails that can serve as dead-end hosts. In the paratenic host, hairworm larvae encyst (dormant), awaiting ingestion by a final arthropod host. This occurs when the paratenic host (ex: chironomid larvae) molts to an adult and leaves the aquatic system with the hairworm cyst still inside. In the terrestrial system, the adult chironomids may be ingested by an omnivorous beetle. As the hairworm cyst passes through the digestive system of the beetle host, it excysts, burrows into the hemocoel and begins feeding on the fat body of the beetle. During development, the microscopic (~40-60 micrometer) larvae grow to 70 centimeters in length for some North American species and up to 2 meters for some species in tropical regions. As the developing, parasitic juvenile hairworm reaches adulthood, the hairworm begins to manipulate the behavior of their arthropod host to seek water, where worms emerge as free-living adults.

Since arriving in Iceland, I have observed some hairworms in parasitology collections at Keldur, the Institute for Experimental Pathology, University of Iceland and at the Icelandic Institute of Natural History. Additionally, a local student in the lab at Hólar University, gave me specimens she found while conducting her own research on fish diet. These specimens will be the first described for Iceland and are currently on their way to the U.S. for DNA analysis for species identification (if any).

Since starting this article, I have learned that I will be receiving the Leifur Eiriksson Foundation Fellowship. This is a huge honor that will allow me to extend my stay in Iceland through the summer, beyond the Fulbright time of September 2017-May 2018. This will allow me to conduct more robust research and pay for research expenses. For graduate students, research expenses are always a challenge if one is not funded. So far, I have managed to receive money from small grants and amazing donors who believe in the process of science and my work. So, for now, I am off to explore more parasites in Iceland! Thank you for reading!

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