Marnaviridae is a family of positive-stranded RNA viruses in the order Picornavirales that infect various photosynthetic marine protists.

[5] Interactions between members of the Marnaviridae family and their hosts have notable significance in marine ecology, and are also relevant within the aquaculture industry.

[6][7] An unclassified sequence, Baishivirus, has been suggested to be the possible pathogen of glass post-larvae disease, which is prevalent in shrimp aquaculture.

[9] The name "marnaviridae" is based on its genome type (RNA virus - rnaviridae), together with the prefix "ma" being derived from the Latin word mare (sea).

[6] HaRNAV was isolated from water collected in the Strait of Georgia in British Columbia, Canada, from a concentrated virus assemblage using the host H. akashiwo (NEPCC 522).

[10] Further metagenomic studies have yielded 653 Marnavirus-like sequences,[12] prompting the proposal for a taxonomic reorganization to incorporate the new data into existing frameworks.

Additionally, there are 653 virus sequences that have been identified (via metagenomic analysis) as possibly belonging to the family Marnaviridae.

VP1 also contains a unique EF-loop connected to the extra β-strand in the jelly roll fold which protrudes from the surface of the virus particle.

A CD-loop is also present on VP1 which obscures the canyon structure that binds host receptors in the related Picornaviridae family.

[17] Marnaviridae genomes consist of linear, non-segmented, positive-sense single-stranded RNA 8.6-9.6 kb in length.

[5] One exception to the typical genome organization of Marnaviridae is Aurantiochytrium single-strand RNA virus 01 (AuRNAV01) which has a third ORF that encodes a protein with unknown function.

[4] When the virus infects H. akashiwo, a toxic bloom-forming alga, it replicates inside the cytoplasm of its host, and is distributed either singly or in groups as crystalline arrays.

Within those that are aligned in crystalline arrays, sectioned particles show that they are either packaged completely (electron dense), or incompletely (ring-shaped).

[17] In tests involving the species Chaetoceros socialis forma radians RNA virus (CsfrRNAV), full and empty capsids were analyzed by their atomic structure to which identified common and diverse structural features of the VP1 protein surface between different virus species under Marnaviridae.

[17] Unlike viruses under Picornaviridae, Marnaviridae have an extra EF-Loop, implying the usage of a unique receptor-binding mechanism.

A possible binding site for algal hosts were also found in E1E2 and/or CD loops, which could play a critical role in its unique receptor-binding mechanism.

[8][9] Furthermore, sequencing of RNA viromes originating from Limnopolar Lake in the Antarctic revealed four Antarctia picorna-like viruses (APLV), one of which, APLV-3, was found to cluster with the Marnaviridae family, thereby further expanding the family's potential distribution southwards to a cold, freshwater environment in Antarctica.

[30] In terms of ecological impact and species diversity in the ocean, the genus Chaetoceros is considered to be a major taxonomic group, playing an essential role as primary producers during bloom periods.

Studies have suggested that these viruses play important roles in controlling and regulating the population of Chaetoceros, thus influencing the spring bloom and subsequently affecting the local marine ecosystems as well.

[31] GdelRNAV is a Bacillarnavirus species that infects the bloom-forming diatom Guinardia delicatula present in temperate coastal waters.

This suggests that the virus may play a role in decreasing host populations at the end of the summer bloom, although other parasites of G. delicatula are also likely involved.

This suggests that AuRNAV likely targets hosts that can effectively utilize dead phytoplankton cells, therefore the virus is also a vital part of the bloom dynamic.

In the 24 to 48 hours after infection, shrimps also exhibit swollen gill filaments, as well as the entire body becoming more transparent and brittle (hence the name of the disease).

Discovered through metagenomic sequencing of a P. vannamei sample infected with GPD, Baishivirus has been suggested to be a member under the Marnaviridae family, and was found to contain three ORFs within its 9.895 kb long genome.

Baishivirus is theorized to be the primary pathogen of the disease, providing a possible entryway into finding preventive measures against GPD in the shrimp industry.