Viral Heroes

When people mention viruses, the first thing that springs to mind is often disease and mortality, however relatively little is known about viruses existing within the marine environment or their effects on, and interactions with other marine organisms. The majority of the work is currently based on commercially important species which have suffered mass mortalities at the hands of viruses which we don’t yet seem to fully understand, for example White Spot Syndrome Virus of Penaeid shrimp. However, with recent technological advances in sampling techniques and identification methods, more studies on viruses seem to be possible.

There are thousands of species, and even whole phyla which do not yet have any related viruses described for them, one of these phyla being Echinodermata. This study by Gudenkauf et al. (2014) works to find and identify and viruses associated with 3 different species of sea urchin off the coast of Hawaii. The team used a viral metagenomics approach to sample viruses in the urchin tissues, nearby sediments and the surrounding seawater. Over 80% of the viral DNA was attributed to phages, while the remaining DNA came from megaviruses, phycodnaviruses and densoviruses, with the densoviruses receiving the most attention. Of the relatively little work done on viruses in the marine environment, densoviruses have received notable attention, having mixed effects on various species of shrimp. In some species, the presence of densoviruses has been associated with delaying the mortality of its host when infected with WSSV, alternatively, in a different species of the same genus, densoviruses are known to cause stunted growth and lesions. In the case of the 3 echinoderms studied, all seemed very healthy and none were displaying any symptoms of diseases, therefore until further work is carried out in this field, I think it could be assumed that the viruses present here are of no threat to their hosts (though it must be said the sample size was very small).

I believe this work highlights the importance of further work on viral associations with marine organisms. I am sure that most, if not all marine organisms will have some sort of interaction with viruses throughout their lifetime. I think it would be interesting to consider the possibility that many organisms may play host to resident viral communities, as they do bacterial communities, which may also aid in a small part of their normal functioning. There are few previous studies discussing the effects of densoviruses on various Penaeid shrimp, but from what I have read, at least in these few cases, viral activity/behavior seems to have many different effects and can be influenced by the presence of other viruses. So while viruses tend to be overlooked if they are not causing problems or being actively searched for, I think they could actually be more significant than previously thought.

B. Gudenkauf, J. E. (2014). Discovery of urchin-associated densoviruses (family Parvoviridae) in coastal waters of the Big Island, Hawaii. Journal of General Virology, 652-658.

Available at: http://jgv.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.0607800#tab2