Research

Research on Biodiversity

Background

The phylum Nematomorpha is one of approximately 35 animal phyla. Nematomorphs are obligate parasites of arthropod hosts but are free-living in aquatic environments as adults. Gordiids, or freshwater nematomorphs, can be up to 3m long and suddenly seem to appear in domestic sources of water (swimming pools, toilets, pet bowls). Human encounters interactions with these worms are quite common, often leading to numerous unnecessary trips to the doctors or veterinarians. About 300 species of nematomorphs have been described worldwide, but we estimate that there may be as many as 1,900 species globally. At the current rate of taxonomy, it would take over 500 years to describe the remaining species within this relatively small group.

Our current project will reinvestigate the members of the Gordiida, with specific focus on the fauna in Central and South America. New World gordiids have been well documented from North America and Argentina, but outside of these immediate areas, few records are known from this species rich area. Recent reviews of the gordiid fauna from South and Central America suggest that many species are only known from isolated records but that the species diversity is extremely rich. Study of gordiids in the Americas will allow us to investigate a gradient on a continuous landmass, from moderate regions in the United States, to tropical areas in South America, and to investigate the impact of continental separation and subsequent faunal exchange through Central America. This project will use both traditional and a revolutionary sample collection, site and species identification technique, allowing us to overcome obstacles hampering previous large-scale investigations.

Collections

We are currently involved in collecting specimens from around the world. Over the last year, we have collected several new species from Africa. Two of these species have been successfully reared in the laboratory and are being used as model systems to study host-parasite interactions.

Over the past years, we have also collected new species from the United States, Costa Rica, Kenya, Canada, Mexico, and Cameroon. In addition, scientists from around the world are sending us new specimens; several of these are likely to represent new species. We have received specimens from places such as Taiwan, New Zealand, Nicaragua, and Malaysia.

To learn more, visit our website at: www.nematomorpha.net

Research on Host-parasite coevolution

Background

Who is infected with whom and why? In the field of parasitology, the answer to this question should seem straightforward. However, the paradigm of host-parasite specificity is not as simple as it first appears. As one of the unifying principle concepts in parasitology, host specificity, in a broad sense, defines the parasite’s niche; each parasite species inhabits a specific and unique variety of host species. This niche can range from narrow, a parasite species able to infect only one host species, to broad, a parasite species capable of infecting dozens of different host species. However, the ultimate and proximate determinants leading to the success or failure of host-parasite combinations are not well understood.

To understand the drivers of host specificity, we must first gain an understanding of how these symbionts interact at ecological and genetic levels. To that end, my current research is investigating how the host-parasite unit interacts with tertiary pathogens (bacteria), with a special emphasis on understanding how the immune systems of the two symbionts interact and have coevolved.

Our research has focused on two main areas:

1. Study of the hairworm immune system. Research into the immune system of parasites is largely lacking. My lab seeks to quantify the complexity of the hairworm immune response and to compare the immune system of this parasite to other metazoans, to elucidate what immune components the parasite has at its disposal. Preliminary next generation sequencing (NGS) data from bacteria-injected parasites show that their immune system is highly complex and includes several central components missing in their sister phylum, the nematodes.

2. What is the immunological role of the parasite symbionts within the unit? First, we need to know how juvenile hairworms interact with bacteria within their hosts. Since they do not feed by mouth, exposure to, and interaction with, bacteria will not occur in the gut as in most animals. We will study whether whole or parts of bacteria enter the hairworm’s body by absorption through the cuticle. Once this has been determined, we will address the question of whether hairworms change their immune gene expression rates during a host-challenge. This aim will lay a foundation to address the question of whether defense of the host-parasite unit becomes a shared responsibility of both symbionts. Preliminary data from NGS reads indicate that many immune factors are upregulated in response to host injection with bacterial LPS.

Collecting with student in the Manzano Mountains, NM