Introduction to research and acanthocephalans


Introduction to research and acanthocephalans


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Acanthocephalans, known colloquially as “thorny-headed” worms, are parasites that possess a spiny eversible proboscis which is utilized to secure the worm in the gut of its host (see attached figure). They are found in invertebrates and in vertebrates, including fish where they are common (Goater et al. 2014. Parasitism: The diversity and ecology of animal parasites. Cambridge, England: Cambridge University Press.).

A study of parasites of creek chub, Semotilus atromaculatus from Baird Creek, Green Bay, yielded specimens from 3 genera of the phylum Acanthocephala (Pomphorhynchus, Acanthocephalus, and Neoechinorhynchus). This study focuses on the Acanthocephalus species found, using molecular (DNA sequence) data and morphological analyses. DNA sequence data from the 28S and 18S regions of the rRNA gene array indicates similarity with several Acanthocephalus species but no identical match.

Thus far, we have generated DNA sequence data of the 28S rRNA gene from 6 individuals of Acanthocephalus species collected from creek chub, by PCR amplification. Comparison of these sequences with sequences of other Acanthocephalus species available in GenBank ( has uncovered genetic differences with these other species, including the most probable match—Acanthocephalus dirus, an anatomically similar North American species with a wide distribution that includes Wisconsin. Preliminary morphological analysis through measurements of specimens on prepared slides suggests similarity to a species of Acanthocephalus that currently lacks genetic sequence data, A. parksidei that was described from the Pike River in southeastern Wisconsin (Amin, 1975. Journal of Parasitology, 61(2), 318-29.). However, Amin (1984, Proceedings of The Helminthological Society of Washington, 51(2):225-237) later synonymized A. parksidei with A. dirus. The molecular data generated so far in this study contradicts this synonymy and rather suggests that there are, in fact, two separate species.

In order to characterize Acanthocephalus sp. and discover its relation to A. parksidei and A. dirus, we will prepare stained whole mounts from preserved specimens that originate from a variety of fish host types, complete PCR amplifications of additional isolates, and use Scanning Electron Microscopy (SEM) for the first time on these Acanthocephalus specimens to generate additional data. We will then link genetic data to the morphology, and evaluate if Acanthocephalus sp. is a new species.

Minimal genetic data has been generated to characterize species of the genus Acanthocephalus and link those data to the morphology of the worms; therefore, data generated by this study will lead to additional research in the future and a significant expansion of knowledge regarding this understudied parasite. If the Acanthocephalus sp. being studied here is found to be a new species, this research would provide both a molecular and morphological description of the worm and eventually document it in the published literature. If Acanthocephalus sp. is found to be A. parksidei, then this research will rectify the incorrect synonymy of this species with A. dirus, establish it as a valid independent species, and provide the first sequence data from the species in GenBank.


Dr. Anindo Choudhury, Biology

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undergraduate, research, collaboration, biology, biomedical, parasites

Introduction to research and acanthocephalans