The invertebrate host of salmonid fish parasites Ceratonova shasta and Parvicapsula minibicornis (Cnidaria: Myxozoa), is a novel fabriciid annelid, Manayunkia occidentalis sp. nov. (Sabellida: Fabriciidae)

Abstract

The invertebrate host of salmonid fish parasites Ceratonova shasta and Parvicapsula minibicornis (Cnidaria: Myxozoa), is a novel fabriciid annelid, Manayunkia occidentalis sp. nov. (Sabellida: Fabriciidae) Abstract Myxosporea (Cnidaria: Myxozoa) are common fish parasites with complex life cycles that involve annelid hosts. Two economically important salmonid-infecting myxosporeans from rivers of the northwestern United States, Ceratonova shasta (Noble, 1950) and Parvicapsula minibicornis Kent et al., 1997, have life cycles that require a freshwater annelid host, identified previously as Manayunkia speciosa Leidy, 1859. This species was described originally from Pennsylvania, with subsequent records from New Jersey, the Great Lakes and west coast river basins. Despite apparent widespread distributions of both suitable fish hosts and the nominal annelid host, both parasites are restricted to river basins in the northwestern US and have never been recorded from the Great Lakes or the eastern US. In this study, we sampled 94 infected and uninfected annelids from two northwestern US rivers to confirm the identity of the host. We found these new specimens had mitochondrial COI sequences with no more than 4.5% distance from each other, but with at least 11% divergence from M. speciosa sampled from near the type locality (New Jersey) and Lake Superior. We did not recover any M. speciosa from either west coast river. The annelid from the Klamath and Willamette rivers showed marked sexual dimorphism that has not been reported in any Manayunkia described to date, though it is apparent that this had been missed in M. speciosa. Accordingly, we describe a new taxon, Manayunkia occidentalis sp. nov., and show that it can host both C. shasta and P. minibicornis. We suspect that previous records of Manayunkia from Pacific Northwest watersheds are likely to be M. occidentalis sp. nov. and not M. speciosa. Sampling of Manayunkia from additional localities is underway to test if the novel Manayunkia species is the only freshwater fabriciid annelid present across the Pacific Northwest.

Parvicapsula pseudobranchicola in the northeast Pacific Ocean is rare in farmed Atlantic salmon Salmo salar despite widespread occurrence and pathology in wild Pacific salmon Oncorhynchus spp.

“…Alternatively, infections with P. minibicornis are acquired by juvenile and adult Pacific salmon and increase in prevalence and/or severity following salmon migration to the ocean or into the river to spawn [ 7 , 8 , 44 ]. These patterns are consistent with a transmission scenario (TS-2) in which actinospores are restricted to the estuary and/or lower reaches of some salmon natal rivers [ 13 ]. Pink salmon and chum salmon juveniles migrate to the ocean between late February and late April and may be exposed to P. pseudobranchicola under either TS-1 or TS-2 scenarios.…”

“…[ 12 ]. With the exception of P. minibicornis whose invertebrate host is the freshwater polychaete Manayunkia occidentalis [ 13 ], the life cycles of Parvicapsula spp. are unknown.…”

Disease in Central Valley Salmon: Status and Lessons from Other Systems

“…For infectious agents with indirect life cycles that involve an additional host, this non-salmonid can be assessed for prevalence of infection. This additional host infection prevalence and density can provide information on infectious hot spots (e.g., annelid host (Manayunkia occidentalis; [Atkinson et al 2020]) for Ceratonova shasta; [Alexander et al 2014]).…”

Imperative role of electron microscopy in toxicity assessment: A review

“…The recent advances in EM technology have allowed discovery of new traits for distinguishing individual species from one another and even distinguishing between species (Hübner, Wagner, Lehmann, & Melzer, 2017). Moreover, it assisted in understanding of the function of distinct body sections (Atkinson, Bartholomew, & Rouse, 2020; Caira & Jensen, 2021).…”