Abstract
There is a need for more information on the relationship between diseases and fluctuations of wild populations of marine animals. In the case of Callinectes sapidus reovirus 1 (CsRV1, also known as RLV), there is a lack of baseline information on range, prevalence and outbreaks, from which to develop an understanding of population‐level impacts. An RT‐qPCR assay was developed that is capable of detecting 10 copies of the CsRV1 genome. In collaboration with state, federal and academic partners, blue crabs were collected from sites throughout the north‐eastern United States to assess the northern range of this pathogen. In addition, archived crab samples from the Chesapeake Bay were assessed for CsRV1 by RT‐qPCR and histology. PCR‐based assessments indicate that CsRV1 was present at all but one site. Prevalence of CsRV1 as assessed by RT‐qPCR was highly variable between locations, and CsRV1 prevalence varied between years at a given location. Mean CsRV1 prevalence as assessed by RT‐qPCR was >15% each year, and peak prevalence was 79%. The wide geographic range and highly variable prevalence of CsRV1 indicate that more study is needed to understand CsRV1 dynamics and the role the virus plays in blue crab natural mortality.
Highlights
Marine animals are affected by an array of infectious agents that may significantly change their abundance (Lafferty, Porter & Ford 2004)
To assess CsRV1 in wild blue crabs, we developed a highly sensitive real-time quantitative PCR assay (RT-qPCR)
The correspondence in sensitivity and efficiency between standard curves produced from double-stranded RNA (dsRNA) and DNA indicates that the reverse transcription step of the RT-qPCR process was very efficient
Summary
Marine animals are affected by an array of infectious agents that may significantly change their abundance (Lafferty, Porter & Ford 2004) In sessile organisms such as corals and oysters, the effects of disease on populations are well documented Populations of blue crabs (Callinectes sapidus) exhibit interannual fluctuations in abundance in their North American range, as exemplified by the well-studied population in the Chesapeake Bay (Colton et al 2013; MD DNR 2014). Much of this variation may reflect fluctuation in recruitment and predation (Orth, van Montfrans & Fishman 1999; Hines 2007; Facendola & Scharf 2012). Receiving recognition among resource managers, and proposed more than a decade ago, is the possibility that diseases play a significant role in blue crab natural mortality (Messick & Shields 2000; Shields 2003; CBSAC 2014)
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