Discovery, Prevalence, and Persistence of Novel Circular Single-Stranded DNA Viruses in the Ctenophores Mnemiopsis leidyi and Beroe ovata

Abstract

Gelatinous zooplankton, such as ctenophores and jellyfish, are important components of marine and brackish ecosystems and play critical roles in aquatic biogeochemistry. As voracious predators of plankton, ctenophores have key positions in aquatic food webs and are often successful invaders when introduced to new areas. Gelatinous zooplankton have strong impacts on ecosystem services, particularly in coastal environments. However, little is known about the factors responsible for regulating population dynamics of gelatinous organisms, including biological interactions that may contribute to bloom demise. Ctenophores are known to contain specific bacterial communities and a variety of invertebrate parasites and symbionts; however, no previous studies have examined the presence of viruses in these organisms. Building upon recent studies demonstrating a diversity of single-stranded DNA viruses that encode a replication initiator protein (Rep) in aquatic invertebrates, this study explored the presence of circular, Rep-encoding single-stranded DNA (CRESS-DNA) viruses in the ctenophores Mnemiopsis leidyi and Beroe ovata collected from the Skidaway River Estuary and Savannah River in Georgia, USA. Using rolling circle amplification followed by restriction enzyme digestion, this study provides the first evidence of viruses in ctenophores. Investigation of four CRESS-DNA viruses over an 8-month period using PCR demonstrated temporal trends in viral prevalence and indicated that some of the viruses may persist in ctenophore populations throughout the year. Although future work needs to examine the ecological roles of these ctenophore-associated viruses, this study indicates that viral infection may play a role in population dynamics of gelatinous zooplankton.

An Unconventional Flavivirus and Other RNA Viruses in the Sea Cucumber (Holothuroidea; Echinodermata) Virome

“…Next generation DNA sequencing technology applied to viral metagenomics has enabled surveillance of viruses associated with invertebrate tissues. These studies, along with the mining of metazoan transcriptomes, have led to the discovery of novel viral lineages in aquatic invertebrates and broadened the host range of several viral families [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. While the majority of viral surveillance and discovery is focused on grossly normal individual specimens of aquatic metazoa, viral metagenomics has been used to examine the presence of potential pathogenic viruses through comparative asymptomatic/disease affected individuals [ 16 ].…”

An Unconventional Flavivirus and other RNA Viruses in the Sea Cucumber (Holothuroidea; Echinodermata) Virome

“…Next generation DNA sequencing technology applied to viral metagenomics has enabled surveillance of viruses associated with invertebrate tissues. These studies, along with mining metazoan transcriptomes, led to the discovery of novel viral lineages in aquatic invertebrates and broadened the host range of several viral families [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. While the majority of viral surveillance and discovery is focused on grossly normal individual specimens of aquatic metazoa, viral metagenomics has been used to examine the presence of potential pathogenic viruses through comparative asymptomatic/disease affected individuals (reviewed in [16]).…”

Partial Recovery of Macro-Epibenthic Assemblages on the North-West Shelf of the Black Sea

“…The Black Sea suffers from the combined effects of anthropogenic eutrophication, overfishing and climate forcing (Mee et al, 2005;Oguz and Gilbert, 2007). By the early 1990s, as a result of unrestrained nutrient inputs, coupled with overexploitation of fish stocks (Daskalov, 2002), habitat loss though intensive near-bottom trawling (Revkov et al, 2018) and the invasion of exotic species (Shiganova, 1998;Shiganova et al, 2003;Siokou-Frangou et al, 2004), this once highly productive habitat was considered a dead zone (Mee, 2006;Todorova et al, 2019). It was characterised by high levels of anthropogenic nutrients delivered by the Danube, Dniester and Dniepr rivers, periodic massive phytoplankton blooms, and anoxic bottom waters during the growing season with virtually no sign of macroscopic epibenthic life, as described elsewhere (Diaz and Rosenberg, 2008;Samyshev and Zolotarev, 2018).…”

“…M. leidyi was first noted in the Black Sea in the early 1980s (Shiganova, 1998) and reached peak densities in the late 1980s and early 1990s (Shiganova et al, 2001). The species represented a trophic "dead-end" and had well documented effects on planktonic and pelagic biodiversity until it rapidly declined subsequent to the introduction of the predatory ctenophore Beroe ovata in 1997 (Shiganova et al, 2003(Shiganova et al, , 2018Siokou-Frangou et al, 2004;Oguz and Velikova, 2010). Effects of these and other invasives on benthic ecosystems are, however, not well understood (Akoglu et al, 2014a;Minicheva, 2015).…”