Most of us, at some point tasted the pain of a sting of a jellyfish. Jellyfish are not only considered to be a nasty creatures that give you a painful sting but also a quite serious threat to today’s mariculture. It has recently been reported that jellyfish has been responsible for major fish kill in UK. Not only that high aggregation of jellyfish in fish farms can stop water flow leading to hypoxia but also the breakage of nematocysts during aggregation have been associated with fish kills due to toxic effects from broken toxic nematocyst- containing pieces which were able to get through the mesh. Nowadays, jellyfish are speculated to be a vector for well-known fish pathogen Tenacibaculum maritimum. Normally this pathogens would not do very well in the water column due to the competition from the other bacteria , however animals such as sea lice and jellyfish are thought to be a good carrier for those bacteria and provide a good substrate for survival of these organisms. A short study by Delannoy et al. (2011) have investigated the potential of jellyfish Pelagia noctiluca as a host for T. maritimum after P. noctiluca gained a special attention after major fish kills in one of the N. Ireland’s salmon farms in 2007.
The jellyfish were collected inshore and offshore during two great aggregation events in July and October near the salmon farm in N. Ireland. A mouth of 10 jellyfish were dissected out and part was used for Scanning electron microscope (SEM) analysis and part for DNA extraction and PCR analysis. A nested PCR was used with two universal primers 20F and 1500R . A bacteria culture of T. maritimum was used a positive control.
SEM analysis revealed the presence of filamentous bacteria from both locations. The PCR amplification had returned a 100% match with a positive control to the T. maritimum in 6 offshore samples. Further 3 samples produced a 99% match. As for the inshore samples PCR could not generate any amplicon which didn’t quite match the SEM analysis showing large numbers of similar bacteria. This was explained as an insufficient DNA concentration was available. The authors contributed that to the quality and quantity of fixation process which can affect DNA extracts. Therefore, neither the presence nor absence was confirmed.
Giving the fact that this study is of a particular importance especially now, that jellyfish are capable of destroying mariculture activities by means other than their toxins it seems like this study didn’t really “make an effort “. There was very small samples taken and also things like not able to get enough DNA should surely prompt them to perhaps repeat the study rather than publishing it with rather vague results. They did show that some samples have carried this pathogens but going as far as calling these organisms a disease carriers without more robust results seems a little bit over the top. Especially that was the first to report bacteria association with P. noctiluca, even though such as associations of bacteria and cnidarians has been known for good few decades. Due to the economic losses associated with fish kills studies like this are definitely useful and can perhaps be used in order to tackle the problem , however definitely more time and resources should be allocated toincrease the chance of getting more conclusive and strong results.
A review of Delannoy et al., (2011). Mauve Stingers (Pelagia noctiluca) as carriers of the bacterial fish pathogen Tenacibaculum maritimum. Aquaculture, 311:255-57
7 comments:
Good post EP
I was just wondering what you meant by cnidarians provide a good substrate for the survival of bacteria. Do they solely provide protection from the environment and competitors or do they have some kind of nutritional relationship with them?
Thanks
Dave
Hi Dave
Thanks for your comment. I didn’t mean that all of cnidarians are providing the substrate for this bacteria. Jellyfish and sea lice are speculated to be a good host for these bacteria and act as a vectors since bacteria can’t survive in water on their own and tend to do well on those two organisms. Nobody actually know this for sure, it is thought that jellyfish since they have very simple digestive system have some sort of association with the bacteria which are proteolytic and enzyme-producing so having those bacteria on their mouths could help in predigestion of prey. But as I said they are not quite sure about it yet. There is one paper by Barker et al. (2009 ) suggesting that they will be working on it so perhaps more clear results will be available soon.
You can have a look at two papers talking about this issue, one I’ve mention earlier :
Barker et al., 2009. Preliminary studies on the isolation of bacteria from sea lice, Lepeophtheirus salmonis, infecting farmed salmon in British Columbia, Canada. Parasitol Res. 105:1173–1177 and
Ferguson et al., 2010. Jellyfish as vectors of bacterial disease for farmed salmon (Salmo salar) J Vet Diagn Invest 22:376–382 – an earlier version of my paper.
Hey,
I enjoyed reading your post, I didn't realise that jellyfish were vectors for any kind of disease. I was just wondering if this is only a problem in fish farms, or whether there has been a recognised increase in fish disease in the sea. Also I was wondering whether this is a new phenomenon as jellyfish have obviously been around for a long time, and if its not what has been found to be the cause behind it if one has been recognised.
Hi Arainna
Thank you for your comment. I think the problem started to be recognised after those massive fish kills in fish farms which were coincided with jellyfish aggregation near the sites. I think studies focus now on fish farms mostly due to potential economic loses. Im not aware of any other papers that have investigated this as a general problem other than that concerning mariculture. As for your last question, most of studies are quite recent and have been carried out in the last few years. I guess it is quite fresh but in this same time it is quite likely that this has been going on for longer period but nobody recognised it. Moreover there is nothing for sure that these organisms are the vectors , most of it is still speculated.
Hey,
I guess it would make sense that fish in fish farms are more likely to be affected as the fish are trapped and have no way of escaping. I did some more research and found that the the jellyfish which caused the fish farm to be wiped out has not been recorded as present around the UK every year and the year of the disaster was classed as an exceptional event for the huge number of jellyfish seen in the area. However the paper I found also mentioned that there have been cases where these jellyfish have been reported in a number of salmon farm cages however few mortalities occurred. I have attached the link to the paper http://plankt.oxfordjournals.org/content/30/8/963.full, and I can't help wondering that with global warming and the migration of organisms such as the jellyfish that more 'diseases' and incidences such as this are likely to occur!
I think they are indeed. I just reviewed paper on tetrodotoxin which let’s be honest ,most people think they can get poisoned only if they travel to Asia, but they showed the migration of elongated puffer into the Med Sea and couple of people got poisoned. All to do with rising water temperatures and migration of species. Scary!
Comment from External Reader Anna Kintner, St Andrews University. "I wasn't involved in this study, but I am involved in its followup and I wanted to pull you up a little there. To answer your accusation of 'vague': The authors of this paper were given the Pelagia samples as part of a larger and separate study, and did not conduct conduct the (quite far out to sea) sampling themselves. Unfotunately, it isn't easy to just hop out and fetch more of this jellyfish species from offshore if your results are inconclusive. Furthermore, formalin-fixed samples of gelatinous zooplankton are notoriously difficult to obtain bacterial DNA from. (We are designing future studies to get around this problem, so hopefully this won't be inconclusive forever.) IMHO, I don't think that that any study which isn't completely bulletproof should be withheld from publication. Inconclusive results can be good to publish, if only to prompt further research and give other researchers an idea about what may or may not have worked. Otherwise, ineffective techniques may be used and re-used, and communication between working groups is limited to word of mouth. May I suggest, for future reviews such as this, that you try contacting some of the authors involved? You can get a lot of interpretation, speculation, and methodological explanation by contacting the researchers directly to have points clarified and ask questions, for example."
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