30 August 2011

Crayfish kryptonite

When I talked on Dr. Kiki’s Science Hour last week about Marmorkrebs, Kirsten asked me at one point, “What’s their kryptonite?”

On the show, thinking on my feet, I said that Marmorkrebs might have some competitive disadvantages because they are a small species, and size is a very important factor in crayfish competition when animals are in one-on-one interactions. (When you match individuals for size, Marmorkrebs hold their own, however).

This is a similar question to the one I fielded at the Ecological Society of America meeting a few weeks ago. One crayfish get loose in a watershed, there is not much that you can do.

In a bit of l’esprit d’escalier, I might have added in my reply to Kiki that the kryptonite of marbled crayfish might be their reliance on humans. In general, crayfish are not all that mobile. Yes, some species are comfortable with leaving the water and making a portage to a new home, but in general, they will spread from one watershed to another only fairly slowly. They are horrible once they get established, but they have a hard time getting that first toehold without humans moving them around.

Left to their own devices, Marmorkrebs never would have made it to Madagascar, or Japan, or anywhere else. In North America, Marmorkrebs are human captives. Let’s keep it that way.

26 August 2011

Dr. Kiki’s Science Hour

This week, I had a lovely live chat with Dr. Kirsten Sanford, a.k.a. Dr. Kiki on Dr. Kiki’s Science Hour! She titled Episode 110, “Invasion of the Marmorkrebs!”

You can listen to the audio, as well as subscribe to the show’s audio and video feeds, here.

Additional: And the video is now up on iTunes, YouTube, and elsewhere!

16 August 2011

Celebrate diversity: Stingrays

This news story is a good example of the surprises animal keeping throws up:

Sea Life London Aquarium staff were shocked to discover two female stingrays were pregnant, despite that they have had no male contact for two years. ...

It is not unknown for rays to store sperm and wait until “they decide the timing is right” before they give birth, head curator at the central London attraction Paul Hale said.

Could it be parthenogenesis? A quick peek in Google Scholar reveals no records of parthenogenesis in the group. Stingrays’ cousins, sharks, can reproduce without sex, however (previously covered here). That means it is at least plausible to be parthenogenesis rather than sperm storage.

Somebody better be collecting DNA from all those baby stingrays to test this!

At any rate, this story does give me an excuse to watch this:

Hat tip to David Shiffman. Photo by by TGIGreeny on Flickr, used under a Creative Commons license.

An Achilles’ heel?

ResearchBlogging.orgLast week, at my Ecological Society of America talk, one of the questions asked afterwards was, “Could the fact that Marmorkrebs are genetically identical be exploited to control introduced, unwanted populations?”

I said, “No.”

One of the things I admire about crayfish is that they are tough little survivors. Unfortunately, this means that they are hard to get a handle on once they’re loose.

I think it’s fair to say that the weapons used to control crayfish populations are blunt instruments. There have been culls to lower the numbers. Dams to try to stop the spread (Dana et al., 2011). And an approach that might be best summarized by this famous quote by Sigourney Weaver:

Peay and colleagues (2006) have conducted a number of trials with broad applications of biocides. These are the freshwater equivalent of nuking everything from orbit. Their results have been variable at best in eliminating crayfish from water bodies.

We are so far from any kind of control that targets crayfish in general that something that targets Marmorkrebs in particular is a pipe dream.


Dana ED, García-de-Lomas J, González R, Ortega F. 2011. Effectiveness of dam construction to contain the invasive crayfish Procambarus clarkii in a Mediterranean mountain stream. Ecological Engineering 37:1607-1613. http://dx.doi.org/10.1016/j.ecoleng.2011.06.014

Peay S, Hiley PD, Collen P, Martin I. 2006. Biocide treatment of ponds in Scotland to eradicate signal crayfish. Knowledge and Management of Aquatic Ecosystems 380-381: 1363-1379. http://dx.doi.org/10.1051/kmae:2006041

09 August 2011

Got recipes?

Marmorkrebs probably don't make very good eating compared to other crayfish species, as they are a rather small crayfish. But many that shouldn't stop you from checking out Invasivore.org, a site devoted to the notion that one of the best features about invasive species is the sense of retribution we can get for the harm they do to ecosystems when we eat them.