24 June 2008

Crayfish eating monkeys!

Sea MonkeysAs I've mentioned previously, I've been finding a limiting factor in rearing Marmorkrebs to be getting them from early juvenile to the late juvenile stage. Now, I read in a new paper by González and colleagues that this is a fairly typical problem for aquacultured crayfish. They write:

The main constrains to intensified astacid culture are the unpredictable and usually poor survival and growth rates of juveniles during the first months of independent life, when feeding is a decisive factor(.)

Part of their solution to this problem is not one I probably would have thought of: Artemia.

Artemia, also known as brine shrimp, are tough little crustaceans. Aquarium owners have used them as live food for various tropical fish for decades. Some people have them in aquaria just on their own -- they were sold for years, and are still sold, as "Sea monkeys." The picture shown is one that any comic reader of a particular age will recognize. (And yes, I'm of that particular age).

I hadn't considered Artemia as crayfish food for a couple of reasons. First, I associate them more with salt water, as they usually live in inland salty lakes, rather than fresh. More to the point, Artemia tend to swim around in the water column, whereas crayfish -- even juveniles -- are more confined to the bottom. I would have thought it tricky for crayfish to catch the little Artemia.

Still, I am not one to argue with success. The González and colleagues paper reports that supplementing crayfish foodstuffs with Artemia nauplii significantly improved survival and growth. Now, growing Artemia is not that big of a deal, but it does require a bit of effort. So this paper looks at whether using a mix of live Artemia plus artificial diets based on Artemia can accomplish the same thing as using live Artemia alone.

The short answer is, "Yes."

The two feeds testing in the paper were ArteMac-3 and Proton #2. Crayfish fed on these and some live Artemia did just as well as those that fed on the live Artemia. I plan on looking into both of these soon, but in the meantime, I'm going to rear up some Artemia for the next batch of juvenile Marmorkrebs.


González A, Celada JD, González R, García V, Carral JM, Sáez-Royuela M. 2008. Artemia nauplii and two commercial replacements as dietary supplement for juvenile signal crayfish, Pacifastacus leniusculus (Astacidae), from the onset of exogenous feeding under controlled conditions. Aquaculture: In press. http://dx.doi.org/10.1016/j.aquaculture.2008.06.015

19 June 2008


As I mentioned, my new animal housing arrived recently. Putting it together took a while, but was reasonably straightforward. The biggest task was just sorting all the many boxes and keep them organized.

The main rack is taller than I am, and I'm not short. I'm probably going to have to get another footstool for my students.

All the boxes concerned with the mechanical and electronic parts of the system: sump, pumps, sterilizers, and so on.

Boxes containing the actual tanks the animals will live in, some lids, and a bit of overflow drainpipes.

Two years worth of supplies. Hopefully, there will be more money in two years...

"And if you order now, we'll even throw in this handy toolkit with everything you need to assemble your new animal care system and keep it running! Now how much would you pay?"

My REU student Stephanie surveying the nearly complete critter condo. Starting in July, Stephanie will be taking up Marmorkrebs research for about a year. This picture is "nearly complete" because the company neglected to send one needed component: screens to keep the animals from getting out of the tanks through the outflow of each tank. They're apparently in the process of getting a new manufacturer to make that particular part, but it should be here soon.

18 June 2008

Pic of the Moment: 18 June 2008

This image summarizes the scientific literature about Marmorkrebs in a graphic format.

This image was built by taking the text of all the abstracts from this blog and posting them into a fascinating new web program called Wordle. It generates the image with more frequently appearing words in the text appearing larger.

If I was really ambitious, I would have removed some of the Blogger text (which is why things like my name and "Posted" pop up relatively large). But I'm not that ambitious right now.

13 June 2008

Some assembly required

A guy goes away for a couple of days to a meeting, and comes back his lab to find...

That's right, there's no boxes better than NSF-funded boxes.

Of course, the boxes are not the important bit. The important bit is the new animal care system contained within, which will house a significantly expanded Marmorkrebs breeding and research colony. I had been expecting this for some time. It was actually on campus in Central Receiving many weeks ago, but it was delivered until yesterday (when I was gone) due to an initial error in ordering.*

Just for the heck of it, I'll be posting pictures as this goes in.

Now, where did I put that screwdriver...?

* Note to up and comers starting research labs: Ordering systems at universities are needlessly complex. You will make mistakes. Try to be nice to people in purchasing so they will be inclined to forgive you when you make mistakes.)

Vogt, 2008

Vogt G. 2008. Investigation of hatching and early post-embryonic life of freshwater crayfish by in vitro culture, behavioral analysis, and light and electron microscopy. Journal of Morphology 269(7): 790-811. http://dx.doi.org/10.1002/jmor.10622


The late embryonic and early post-embryonic life period of freshwater crayfish, which is the main time period of organogenesis, is poorly investigated because of the protective brooding behavior of crayfish mothers. A combination of in vitro culture, behavioral observations, and microscopic investigations of organs involved in hatching, attachment, exploration of the environment, and searching and processing of food yielded deeper insights in this important period of life. Experiments were performed with the robust parthenogenetic marbled crayfish. The following results were obtained: (1) Marbled crayfish can be raised in simple in vitro systems from 80% embryonic development to juvenile Stage 4 with up to 100% survival; (2) Hatching is prepared by chemical weakening of the egg shell and completed by levering actions of the hatchling’s appendages; (3) The telson thread, a safety line that keeps the hatchling secured to the mother, is formed by secretions from the telson and the detaching inner layer of the egg case; (4) Molting Stage-1 juveniles are secured by an anal thread that results from delayed molting of the hindgut; (5) Active attachment of the hatchlings to the maternal pleopods with their 1st pereiopods is achieved by an innate fixed action pattern; (6) In vitro, juveniles are motile from Stage 2 despite incomplete development of their balance controlling statocysts. Movement pattern and social behavior vary greatly among individuals; and (7) Feeding starts in Stage 3, when the mouthparts and the gastric mill are fully developed. Onset of feeding is innate and does not require maternal contributions. In vitro culture of the isogenic marbled crayfish is recommended for broader use in research because it enables not only time and stage-specific sampling but also precisely timed experimental manipulations.

Keywords: marbled crayfish • in vitro culture • hatching • development • digestion • sense organs

12 June 2008

TCS 2008 review

Poster session view
This picture sort of sums up the Summer 2006 meeting of The Crustacean Society for me: all a bit of a blur. But I also put this up to show that you could see the ocean from the poster session.

My student Sakshi and I made the seven hour drive to Galveston, gave our poster, saw a couple of talks this morning (notably on cave biology -- cool stuff!), turned around and came back today. Whew!

The good news was that this quick trip up was definitely worth it. We got some feedback on the poster that may explain some puzzles we've had from one of the few people who had concrete information. And I met someone who specifically wanted to talk to me about some writing.

It only takes one thing to make a trip worthwhile, and I got two.

I had a bit of a bad moment when I walked into the room where the poster session was being held, and saw every space available was occupied by another poster. Decided to cover up an announcement temporarily to display the poster, as shown below.

TCS poster
Poster title redacted for security reasons.

Although I didn't have an opportunity to talk to anyone about Marmorkrebs during my brief cameo appearance, I did get a few ideas ideas for opportunities to do so.

03 June 2008

Crayfish in German

Perhaps one of our German readers can provide the translation of the interspersed titles in the comments section...?