Genome Sequence Analysis of CsRV1: A Pathogenic Reovirus that Infects the Blue Crab Callinectes sapidus Across Its Trans-Hemispheric Range

Abstract

The blue crab, Callinectes sapidus Rathbun, 1896, which is a commercially important trophic link in coastal ecosystems of the western Atlantic, is infected in both North and South America by C. sapidus Reovirus 1 (CsRV1), a double stranded RNA virus. The 12 genome segments of a North American strain of CsRV1 were sequenced using Ion Torrent technology. Putative functions could be assigned for 3 of the 13 proteins encoded in the genome, based on their similarity to proteins encoded in other reovirus genomes. Comparison of the CsRV1 RNA-dependent RNA polymerase (RdRP) sequence to genomes of other crab-infecting reoviruses shows that it is similar to the mud crab reovirus found in Scylla serrata and WX-2012 in Eriocheir sinensis, Chinese mitten crab, and supports the idea that there is a distinct “Crabreo” genus, different from Seadornavirus and Cardoreovirus, the two closest genera in the Reoviridae. A region of 98% nucleotide sequence identity between CsRV1 and the only available sequence of the P virus of Macropipus depurator suggests that these two viruses may be closely related. An 860 nucleotide region of the CsRV1 RdRP gene was amplified and sequenced from 15 infected crabs collected from across the geographic range of C. sapidus. Pairwise analysis of predicted protein sequences shows that CsRV1 strains in Brazil can be distinguished from those in North America based on conserved residues in this gene. The sequencing, annotation, and preliminary population metrics of the genome of CsRV1 should facilitate additional studies in diverse disciplines, including structure-function relationships of reovirus proteins, investigations into the evolution of the Reoviridae, and biogeographic research on the connectivity of C. sapidus populations across the Northern and Southern hemispheres.

Effects of Infectious Diseases on Population Dynamics of Marine Organisms in Chesapeake Bay

“…Bitter crab disease (Hematodinium perezi), Reovirus CsRV1, Vibrio sp., Paramoeba perniciosa, Lagenidium callinectes, Picorna-like virus Mortality, growth, recruitment Small et al 2019, Shields and Squyars 2000, Messick and Shields 2000, Messick 1994, Johnson 1977, Bowers et al 2010, Messick and Kennedy 1990, Flowers et al 2016a, Spitznagel 2019, Newman and Ward 1973, Sprague 1970, Morado 2011 Striped bass (Morone saxatilis)…”

“…It is associated with mortality of blue crabs in soft-shell production (Bowers et al 2010), and prevalence may be increased in wild crabs in close proximity to soft crab shedding facilities and in larger animals (Flowers et al 2018). Originally described in 1977 (Johnson 1977), CsRV1 was cryptic in wild crabs until molecular tools became available for its detection (Flowers et al 2016a). The average prevalence of CsRV1 was found to be 20% in the Chesapeake Bay (Flowers et al 2016b).…”

Climate and season are associated with prevalence and distribution of trans-hemispheric blue crab reovirus (Callinectes sapidus reovirus 1)

“…Environmental variation and host life history may combine to drive the evolution of CsRV1 virulence. Sequence analyses of the CsRV1 RNA-dependent RNA polymerase gene (Flowers et al 2016a) and whole genome sequences of CsRV1 (M. Zhao unpubl. data) indicate that there are different genotypes of CsRV1 at different latitudes.…”

“…The virus infects hemocytes, gills, nervous system, and connective tissue, which in turn invades the brain and thoracic globules and is associated with tremors and paralysis (Johnson 1977). CsRV1 has been previously identified in wild blue crabs from the US Atlantic and Gulf coasts and from southern Brazil (Bowers et al 2010, Flowers et al 2016a. The prevalence of CsRV1 has been found to be spatially and temporally variable along the northern Atlantic coast of the USA (Flowers et al 2016a,b).…”

Prevalence of the pathogenic crustacean virus Callinectes sapidus reovirus 1 near flow-through blue crab aquaculture in Chesapeake Bay, USA

“…Genome structure and sequence shows that CsRV1 is closely related to Scylla serrata reovirus (SsRV or mud crab reovirus, MCRV) (Tang et al 2011, Flowers et al 2016b, which has caused mass mortality of mud crabs S. serrata cultured in China (Weng et al 2007). CsRV1 has similarly been associated with blue crab mortalities in soft-shell crab production ('shedding') systems in which wild-captured pre-molt crabs ('peelers') are held for several days until ecdysis to increase their commercial value.…”