to which identified common and diverse structural features of the vp1 protein surface between different virus species under marnaviridae. 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 it's unique receptor-binding mechanism. in the structural analysis of the capsid's cryo-em maps and atomic models, pymol 1.4 was used to obtain a root-mean-square-deviated (rmsd) per residue, which provided a value for structural diversity. analysis for the structural proteins vp1, vp2, and vp3, suggested that vp1 was responsible for the host-specificity of the virus, and was based off of the diversity in the vp1 protein. when looking at a structural phylogeny of marnaviridae based on vp1s, local structural diversity that is reflected can be used to better predict the targeted algal hosts of different marnaviridae viruses. ecology distribution while harnav was initially isolated from british columbian waters, it has been found that harnav is also capable of infecting h. akashiwo strains originating from japan, thus suggesting that members of marnaviridae may have a wide distribution throughout the pacific ocean. as viruses within the marnaviridae family have been identified from shrimp and prawn aquaculture species in chinese waters, this further supports marnaviridae being widespread across the pacific ocean from north america to asia. 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. heterosigma akashiwo rna virus (harnav) the complex relationship between harnav and other viruses capable of infecting h. akashiwo is important in terms of understanding how viruses play a role in h. akashiwo bloom dynamics. when compared to heterosigma akashiwo nuclear inclusion virus (haniv), it is demonstrated that although both viruses infect host strains from the northeast pacific (with harnav also able to infect host strains from japan), they each targeted different subsets of host strains. the difference in host range between the two viruses suggests that they likely coexisted within the local environment, each infecting their specific hosts, therefore it is possible to infer the strain composition of h. akashiwo population over its blooming period. studies have shown that h. akashiwo's susceptibility to viruses tends to shift over the course of the bloom, with the cells being much more resistant to viral infection after the bloom has collapsed. this suggests that viruses may have played an important role in regulating the h. akashiwo bloom. similarly, a study done on the viral assemblage composition of harnav has shown that the diversity of harnav is correlated with the composition of its host, therefore also suggesting that harnav influences the composition of h. akashiwo. bacillarnavirus 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. viruses under bacillarnavirus have been shown to target chaetoceros in natural environments, with different species targeting specific strains of the diatom. 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. guinardia delicatula rna virus gdelrnav is a bacillarnavirus species that infects the bloom-forming diatom guinardia delicatula present in temperate coastal waters. strains of this virus have only been successfully isolated shortly after the summer bloom of g. delicatula. 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. aurantiochytrium rna virus (aurnav) thraustochytrids are considered to be important decomposers in ecosystems. aurantiochytrium rna virus (aurnav) has been shown to infect thraustochytrids together with another virus, sicyoidochytrium minutum dna virus (smdnav). studies have revealed that these two viruses maintain different fluctuation patterns from each other, with aurnav showing a significant increase in abundance following an increase of aurantiochytrium sp. thraustochytrids (which decompose organic matter during the decline of h. akashiwo bloom), while smdnav did not demonstrate this pattern. 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. prevalence in aquaculture glass post-larvae disease penaeus vannamei is an important shrimp aquaculture species that is cultured globally, and most notably in china. however, due to the glass post-larvae disease (gpd), a highly pathogenic disease that spreads quickly within aquaculture sites, the industry has suffered significant losses in recent years, resulting in economic instabilities. shrimp infected with gpd show signs of slower movements and responses, along with color change in liver pancreatic tissues (full brown to light brown). 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. growth retardation disease prevalence of growth retardation disease (grd), which causes decreased growth rates and precocious puberty in the freshwater prawn macrobrachium rosenbergii, has led to significant financial losses within the chinese aquaculture industry of this prawn. generally, mature male and female prawns are 10 cm and 8 cm in body length respectively, however when impacted by grd, the prawns exhibit early maturity, wherein males demonstrate mating behaviours at 6 cm and females possess eggs at 5 cm. the impacts of grd have led to decreases in prawn production of more than 50% in some cases. through metatranscriptomic sequencing of the viromes of healthy prawns and prawns with grd, and phylogenetic analysis of the resulting rna sequences, four marna-like viruses were placed in the marnaviridae family. these viruses, referred to as macrobrachium rosenbergii viruses (mrv) mrv3, mrv4, mrv5, and mrv6, have sequences which are 9242, 8887, 8548, and 9153 base pairs in length respectively. mrv3, mrv5, and mrv6 were found to be novel viruses, with mrv3 being placed in the genus labyrnavirus, and mrv5 and mrv6 belonging to the genus sogarnavirus. in contrast, mrv4 was characterized as being a previously identified beihai picorna-like virus in the genus kusarnavirus.