The latest Paper of the Month for Parasitology is ‘Large-scale genetic investigation of nematode diversity and their phylogenetic patterns in New Zealand’s marine animals’ and is available open access.

Do you spend much time around the marine environment? Whether it be going for a swim at your local beach, taking the kids or dogs for a stroll at your local estuary or seabird colony – you have undoubtedly been in very close proximity to these parasitic worms!

Nematodes are one of the most speciose groups of animals, and a significant proportion of them are parasitic. In the marine environment, due to difficulty of identification, and the fact that they live inside other animals, parasitic nematodes are seldom studied. In New Zealand particularly, we know little about what nematodes occur in marine animals, what impact they have on their hosts, and how their diversity and distribution might change in the future. If we want to predict how the world’s marine ecosystems will respond to natural and human induced pressures, first we need to know what animals (including parasites!) live in any given environment, and how they interact with each other and their environments.

Our study aimed to characterize genetically the biodiversity of parasitic nematodes that infect a range of New Zealand marine animals. The results come from an extensive parasite biodiversity survey carried out between 2019 and 2021 where we took a broad, collaborative and opportunistic approach. We wanted to make the most of already deceased organisms, and minimise unnecessary need for euthanizing New Zealand’s wildlife. Some agencies that were crucial in obtaining specimens included the Wildlife Hospital Dunedin (https://www.wildlifehospitaldunedin.org.nz), Wildlife Management International (https://www.wmil.co.nz), the Department of Conservation (https://www.doc.govt.nz), and the National Institute of Water and Atmospheric Research (https://niwa.co.nz). Such collaborations provided unique sampling opportunities and made available many marine animals that have never before been investigated for their parasitic nematodes (including these nematodes from a deep-sea shark)

We dissected 611 host individuals of 94 animal species including 39 seabird, 40 teleost fish, 10 chondrichthyan, one marine mammal and four cephalopod species. It shows a time-lapse of Jerusha dissecting a Snares crested penguin. We used genetic data to identify nematodes to the lowest taxonomic level possible and presented phylogenetic trees of the dominant groups to illustrate their genetic diversity. We revealed a high diversity of parasitic nematodes (23 taxa) infecting New Zealand’s marine animals. Many of the host-parasite associations are new records, and 7 species are reported in New Zealand waters for the first time.

Our study represents the first large-scale, genetically based biodiversity survey of parasitic nematodes from a range of host taxa in New Zealand’s marine environment. Why should you care? Well, some species recovered have the potential to kill their hosts, or cause concern for their conservation. Some are potentially zoonotic too, which means humans can be infected (almost 40% of fish dissected hosted zoonotic Anisakis spp.). The main take away from our study is that it provides a baseline dataset that can act as a starting point for future comparisons to assess how parasite diversity and distributions change over time at a large scale. We mentioned above that nematodes constitute a significant proportion of the world’s biodiversity. We think that they deserve a proportionate effort to document their occurrence!

The paper “Large-scale genetic investigation of nematode diversity and their phylogenetic patterns in New Zealand’s marine animals“ by Jerusha Bennett, Robert Poulin and Bronwen Presswell, published in Parasitology, is available open access.