New England mussels reveal Evolution doesn’t always take thousands of years.

Scientists at the University of New Hampshire (UNH) have found that blue mussels that call a vast swath of the New England shoreline home seem to have evolved a defense response to an invading species of crab in the very short time scale of 15 years:

Freeman looked at the inducible defense – shell thickening – of blue mussels (Mytlius edulis) in the presence of two invasive crab species in New England, the Asian shore crab Hemigrapsus sanguineus and the green crab Carcinus maenas. While Carcinus was introduced to New England from Europe between 150 and 200 years ago, Hemigrapsus is a relative newcomer, arriving from Asia to New Jersey in 1988. While previous research had established that mussels recognize Carcinus, it had not be determined if they recognize Hemigrapsus. And, crucial to the design of Freeman’s study, Hemigrapsus is not present north of mid-coast Maine.

“This set up a chance to look at populations that had been exposed to the predators for varying lengths of time,” says Freeman. “We wanted to know, how is it that these mollusks can recognize a crab that is historically not present in North America?”

Freeman exposed mussels native to the northern – above mid-coast Maine – and southern New England to both Carcinus and the Hemigrapsus. Both populations thickened their shells when exposed to waterborne cues of Carcinus, but only the southern mussels – Freeman describes them as “more worldly” – expressed inducible shell thickening in the presence of Hemigrapsus.

“The mussel’s inducible response to H. sanguineus reflects natural selection favoring the recognition of this novel predator through rapid evolution of cue specifity or thresholds,” Freeman and Byers write.

Findings were consistent in two experiments over two years, one in a laboratory setting in Nahant, Mass., and one in the field at Woods Hole, Mass. “The consistency over two years and two sites really suggests an underlying robust mechanism,” says Byers, who is Freeman’s dissertation advisor.

Sure it’s a small step to go from not recognizing to recognizing a new crab species as dangerous, but Evolution works in small steps. It’s not at all surprising to scientists that this change came about—indeed Evolution would predict such a change—it’s the speed in which the change happened that’s amazing.

While this sort of rapid evolutionary response to predators has been exhibited in some other species, all have been vertebrates. The blue mussel, which Freeman describes as the lab rat of marine biologists, is an invertebrate “that people assume is not very bright,” he says. Yet his findings indicate that within the brief span of 15 years, it has evolved an inducible response to a new predator.

How do mussels evolve so quickly? In southern New England, the scientists say, mussels are prey to many crabs as well as other marine species. “When Hemigrapsus came along the mussels’ wheels were well-greased to respond,” says Byers. “That’s our best guess.”

Byers helps put the impact of the research in context. Because extensive data does not exist on invasive ecology, “there’s a tendency to extrapolate any data you get on an invasive species. But here we show that the response from the prey differs over just a couple hundred kilometers.”

Natural selection at work. In environments with the new crabs the mussels evolved to deal with that threat. Of course this will do nothing to appears the IDiots who will demand to know why the mussels didn’t evolve into a tree or Volkswagen and then chuckle smugly to themselves thinking they said something frighteningly clever.

Found via Skepchick.

12 thoughts on “New England mussels reveal Evolution doesn’t always take thousands of years.

  1. Our Lord designed the mussel to do this. This is only happening because the conditions are right to ‘switch on’ the feature that has been intelligently designed into the shell.  The chance that it could hit by random mutation on just the right set of DNA at the right time is vanishingly small. Darwinist have always said we can not see evolution because the time scales are too long, now they claim it happens in 15 years.  God must therefore exist.

  2. Les: Of course this will do nothing to appears the IDiots who will demand to know why the mussels didn’t evolve into a tree or Volkswagen and then chuckle smugly to themselves thinking they said something frighteningly clever.

    … and stupid. LOL LOL LOL LOL LOL

  3. That was sarcasm. I was trying to parody Kent Hovind. Rest assured Ill accept the earth as flat before I believe Creationism.

  4. Ah, sorry Max, but sometimes sarcasm is tough to detect in an all text medium like this. grin

    LH, your’s was so obviously a parody that I don’t think anyone’s gonna take the bait on it.

  5. I know Les. Trouble is I have seen similar across the net. I sit here sometimes and think “They can not be serious”.

    actually I think what gives it away is the fact that I didnt say

    OUR LORD DESINED THE MUSEL TO DO THIS. IT IS ONLY HAPENING BECOSE THE CONDISIONS WEER RITE.

    etc etc. BTW did you get my sub re UK creationists- it seemed to go through ok, but you know the troubles I’ve had with A-OH-Hell as an ISP.

  6. Isn’t it possible that these mussels just learned that they should harden when these new crabs come around because these new crabs ate their brothers? I mean, come on. Evolution isn’t the same as figuring something out.

    I think these scientists have been studying these crabs habitat for 15 years, and jumped at an imagined opportunity to prove something useful out of it.

    LH, if it makes you feel any better, I thought you were expressing your beliefs when I read your post. I wouldn’t have “bitten” or anything, but I believed you.

  7. Bob: Isn’t it possible that these mussels just learned that they should harden when these new crabs come around because these new crabs ate their brothers? I mean, come on. Evolution isn’t the same as figuring something out.

    Of course it’s not, Bob.  smile
    Although, it’s a bit different to training a god … woops … dog – can’t train a god, can ya?
    I’ve got some muscle brained mates who told me that they (the mussels) had a summit meeting of the best musseled brains in the mussel world (oysters were not invited and the clams didn’t clam up – they just abstained) … sent some faxes, did some internet searches and a unanimous agreement was reached … we gotta harden our shells guys … done! 
    I will survive. Too fucking easy.  LOL

  8. Bob asks…

    Isn’t it possible that these mussels just learned that they should harden when these new crabs come around because these new crabs ate their brothers? I mean, come on. Evolution isn’t the same as figuring something out.

    That assumes the mussels have enough of a thought process to figure anything out to begin with.

    Evolution can give the appearance of figuring things out simply because the creatures that don’t respond to the stimuli end up being eaten leaving only those that do respond behind. It’s not that the mussels figured out that the new crabs were dangerous, it’s that all the ones who didn’t respond to the threat perished leaving only the ones who did to continue producing new mussels.

    It’s similar to bacteria that become resistant to antibiotics. It’s not that they have enough intelligence to figure out how to keep from dieing when exposed to antibiotics, it’s that the ones that are resistant to it are left behind to continue making new bacteria with the same trait. Eventually you kill off most of the non-resistant bacteria and the antibiotic becomes ineffective.

    I think these scientists have been studying these crabs habitat for 15 years, and jumped at an imagined opportunity to prove something useful out of it.

    Yes, they’re such shallow and vain people those scientists.

    LH, if it makes you feel any better, I thought you were expressing your beliefs when I read your post. I wouldn’t have “bitten

  9. Bob – I believe it was one of Darwin’s contemporaries (but I am too lazy to look it up) that came up with a competing theory of speciation and variation that goes something like that. 

    The example I remember said that Giraffes basically used to have really short knecks.  They began stretching their knecks to reach the higher, tasier leaves, and over many generations, they eventually all had long knecks due to the stretching efforts of previous generations. 

    Of course, it doesn’t in anyway take into account that generally genetics cannot be altered in such a way, a species will change due to survival of the fittest.  In the case of the mussels, the whole species ended up with thicker shells, because only the ones WITH thicker shells survived the crabs and were able to then go on and make new mussels, which carried the thicker shell trait of their parents.  Thinner shells got eaten and taken out of the gene pool, until there were no more thinner shelled mussels.

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