22 July 2010

Drugs in the water affecting crustaceans’ precious bodily fluids?

ResearchBlogging.orgYou shouldn’t be able to call a species anything you want.

Yes, biologists switched to using Latin names for species because we recognized that common names were too variable and imprecise. Still, that doesn’t mean that common names are infinitely flexible.

A crustacean story has been making the rounds in the news, and alas, the news stories are often botching the basics. I wish I could be surprised. News stories based on journal articles seem to be a never ending well of things to correct.

The first time I saw the article was at New Scientist. Then I spotted it on the front of The Age here. Then I saw it again time here, which was what finally set me off. But before this post went up, it also got featured on National Geographic and Improbable Research.

I had looked at the article abstract, and I thought, “Wait. The headline said this was a shrimp. The abstract says nothing about a shrimp.”

The sometimes interesting but often irritating Science Daily has a picture of the senior author, Alex Ford (right), holding something I would not call a shrimp. It’s an amphipod. I can only find one other picture of this species on the web, on Ford’s home page here. In fact, the title of the Science Daily blurb was exactly that of the journal article – except that the word “amphipod” had been replaced by “shrimp.”

The Age referred to this beast as a “prawn”, and showed a picture of something normally called a prawn, Penaeus monodon, which is an entirely different beast. And it gave it the lurid title referring to crustaceans “getting high.”

The third article showed a picture of another species (Crangon crangon) that is not even close to the one studied in the paper. And this time, the article referred to the animals becoming “suicidal”!

Does calling an amphipod a “shrimp” or a “prawn” matter? Yes! People eat shrimp and prawns, but not amphipods. Bu changing the common name, you introduce a whole new set of worries and fears about the safety of people’s food. It’s made worse considering that the third article is at a website called “Fish2Fork,” which strongly suggests they think it’s a seafood story.

The paper is actually quite interesting, but it shows neither animals “seeing the light” (title and article 1), “getting high” (article 2) or “becoming suicidal” (article 3).

The behaviours that the authors are testing are the tendency of amphipods to swim towards a light (phototaxis) or tendency to swim up or down (geotaxis). I am guessing the former is where “seeing the light” comes from, but “seeing the light” doesn’t capture the actual behaviour well at all. I would expect “seeing the light” to mean that the amphipods gained some ability to see something they couldn’t before.

The authors didn’t just test the effect of Prozac, but two other drugs, and the neuroactive chemical serotonin (which Prozac interacts with and which is often important to crustaceans), and a natural parasitic infection (acanthocephalans).

Amphipods that were infected with parasites, given serotonin, or given Prozac all tended to be more likely to be attracted to light, and more likely to be swimming upwards. Thus, amphipods are more likely to be out in the water in bright light, where they would be more susceptible to being eaten by predators. This, of course, is what parasites “wants” so that they can infect the next host in their life cycle. Still, this is hardly “getting high” or “suicidal” in the way people think of those phrases.

Further reading of the paper reveals a less straightforward interpretation than the headlines say. Guler and Ford didn’t measure the drug concentrations in the water where they collected their animals. They argue that their values are within the ballpark that other researchers have recorded in “STP effluent”. (I don’t know what “STP” means, because the authors don’t define it. A little help here? You know, for those of us who don’t speak acronym.)

Complicating matters further is that the authors tested five concentrations for the drugs they tested, ranging from 0 to 10 µg per liter, but it seems only one concentration of Prozac (0.1 µg per litre) caused a significant difference in the amphipods’ behaviour. So if we’re taking enough anti-depressants, there may not be a problem?

Finally, they only used males in this experiment, and there is no explanation why.

This paper is interesting, but it’s yet another case of the researchers and press release writers working too hard.

For more fun with headlines, see the stuff I’ve written with Carin Bondar!

Additional: Deep Sea News also got to this one.


Guler Y., & Ford A. (2010). Anti-depressants make amphipods see the light Aquatic Toxicology. DOI: 10.1016/j.aquatox.2010.05.019


Unknown said...

STP = Sewage Treatment Plant

The study used males only to standardize the protocol. Many studies in toxicology have demonstrated different effects between males and females which would create noise in the results. For example, serotonin controls many functions in crustacean biology including gonadal development i.e. oogenesis vs spermatogenesis, growth and colour changes. Hence, scientists generally choose males as females maybe in different stages of reproduction/moulting creating confounding factors

The authors found results mainly around 100ng/l (but also 10ng/l). In fact, phototaxis scores were elevated for all exposures but did not meet the conservative Bonferonni requirements which were p < 0.0125 but in many cases were P < 0.05. Google Bonferonni for the relative merits of this statistic.

Why only based around a certain concentration?, well the authors suggested that this maybe due to a finite amount of serotonin. The author of the blog may not be aware that fluoxetine doesn't increase serotonin but increases the re-uptake of serotonin in the synapse. The authors of the article suggest that the non-monotonic concentration response maybe due to finite amounts of serotonin produced by the amphipods over the exposure period. Other scientists have suggested in maybe due to regulation within the shrimp (sorry amphipod!; sorry E.marinus).

There is no such thing as a shrimp or a prawn. In fact, throughout the English speaking world the term shrimp has been attributed to crustaceans across many families and orders. In fact, the generic term of amphipods such as Gammarus minus in US springs or freshwater shrimp or scuds. I don't think the media can be too much to blame trying to generalise to their audience when they might not know what Echinogammarus marinus is or indeed an amphipod, especially when the specific species is not the issue (it’s just a laboratory model) to test effects in the environment. More importantly, are the effects which "maybe" occurring in the environment?

What the blog author is correct about is the suggestions by the media of "anxiety" or "suicide" which is incorrect and over sensationalism. What the author of the blog must also understand is that the reporters who write the articles don't always write the headlines which are done by specialist headline writers.

Bjørn Østman said...

Do you really think it's too much of a stretch to go from phototaxis to "seeing the light"? I don't have a problem with authors trying to be a little poetic, as long as it doesn't misinform.

Zen Faulkes said...

Bjørn: You're right. "See the light" is about the least of the worries here.