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Morphological, gene sequence, host tissue tropism, and life cycle characteristics were utilized to describe the myxozoan, Myxobolus rasmusseni n. sp. from fathead minnow, Pimephales promelas, collected from reservoirs in southern Alberta. Results from serial histological sections of whole heads showed that myxospores were contained within irregular-shaped and sized coelozoic capsules (=plasmodia). Clusters of membrane-bound, myxospore-filled plasmodia filled the head cavities of juvenile fathead minnows, leading to the development of large, white, disfiguring lesions in mid to late summer. Bilateral exopthalmia (pop-eye disease) was a common outcome of M. rasmusseni n. sp. development. BLASTn search of a 1974 bp sequence of the 18S rDNA gene isolated from myxospores indicated that M. rasmusseni n. sp. was distinct from other coelozoic and histozoic Myxobolus spp. cataloged in GenBank. 18S rDNA gene sequences from triactinomyxon spores released from the oligochaete Tubifex were 100% identical to sequences from myxospores collected from syntopic fathead minnows. Results from a longitudinal survey of the 2020 cohort of fathead minnows showed that young-of-the-year are exposed at 1–5 mo and that 60–90% of these had developed myxospore-filled lesions approximately one year later. Data regarding potential sources and timing of M. rasmusseni n. sp. emergence in fathead minnow populations are needed.

Parasites have been neglected from most biodiversity surveys even though they are an essential component of ecosystems and intimately associated with the free-living communities within them. Parasites with complex life cycles, such as digenean trematode flatworms, utilize at least two host species within an ecosystem for their development and transmission, taking advantage of species networks to complete their life cycles. Despite this knowledge, our understanding of the processes that contribute to parasite community assembly, and which limit their geographic distributions, are rudimentary, including the importance of host diversity. Utilizing recent advancements in the identification of cryptic trematode species through molecular barcoding, we examined patterns of community assembly involving 79 species in six Alberta lakes over three years. Specifically, we focused on spatiotemporal variation in trematode diversity within their snail first intermediate hosts (component communities), how this might relate to host diversity through the specificity of host-parasite relationships, and the role of certain environmental factors in structuring these communities. We found substantial natural fluctuations of trematode communities through space and time within these lakes. Trematode communities were diverse, showing an overall positive relationship with snail diversity, but were often dominated by a few common species. We found that ecoregion and lake trophic status were key predictors for the presence of these trematode species. Such information is key for understanding how biodiversity alterations may affect parasite community composition, as well as our ability to formulate predictive models, by considering how this could influence both species richness and evenness.

Swimmer's itch is an allergic condition that occurs when the motile and infectious stage of avian schistosomes penetrate the skin of an individual. Flatworm parasites that cause swimmer's itch belong to the family Schistosomatidae. They utilize a variety of different species of bird and mammal as definitive hosts, and rely on different species of snail, in which they complete their larval development to culminate in a motile, aquatic, infectious stage called a cercaria. Recently, qPCR-based assays have been developed to monitor for swimmer's itch-causing trematodes in recreational water. This environmental DNA approach has been useful for quantifying the abundance of the free-living cercaria, the causative agent of swimmer's itch. However, the existing qPCR test amplifies from all known schistosome species, making it excellent for assessing a site for swimmer's itch potential, but not useful in determining the specific species contributing to swimmer's itch or the likely hosts (snail and bird) of the swimmer's itch-causing parasites. Thus, species-specific resolution built into a qPCR test would be useful in answering ecological questions about swimmer's itch cause, and efficacy of control efforts. This paper details bird, snail, and cercaria surveys conducted in the summer of 2018, that culminated in the development and deployment of four species-specific qPCR assays, capable of detecting Trichobilharzia stagnicolae, Trichobilharzia szidati, Trichobilharzia physellae, and Anserobilharzia brantae in recreational water. These assays were used to assess the relative abundance of each parasite in water samples collected from lakes in Northern Michigan. Keywords: qPCR, Trematodes, Swimmer's itch, Environmental transmission, Recreational water, Trichobilharzia, Schistosoma, eDNA