24 February 2009

A problem of plurals

German language summaryAs most readers will probably know, Marmorkrebs is essentially a German word that more or less means “marbled crab.” I advocate using this word to refer to parthenogenetic marbled crayfish because it is distinctive and unlikely to be confused with other crayfish species that also happen to be marbled.

There are always some risks of importing words from one language to another, however. As more people have started to discuss parthenogenetic marbled crayfish in English language forums, I have started to see a single such individual referred to as “a Marmorkreb.” I do not speak German, so I'm going out on a bit of a limb here, but I don’t think that is correct.

In German, there are many different ways to pluralize a noun, including adding an -s at the end. But that probably doesn't even make the top five (!) way to pluralize. Thus, that Marmorkrebs ends in an -s doesn’t imply that it is a plural.

Of course, English has its own share of strange pluralization rules and exceptions. Perhaps most relevant here is the pluralization of fish. If you have many fish of the same type, then the plural is fish. If you have many fish of different types, then the plural is fishes. Then are some English words that end in -s that are not plural.

Several research papers use it as both the singular and plural (i.e., “one Marmorkrebs, many Marmorkrebs”). I suggest Marmorkrebs be used for one individual and for many, and that it be added to the list of words that look like plurals but aren’t, next to tweezers and pants and scissors.

17 February 2009

Marmorkrebs foraging

10 February 2009

Owning clones

I was in a pet store for something completely unrelated, and just happened to look, as one will do when browsing in a store, at things nearby... and spotted the headline, "CRAYFISH CLONES," on the cover of the new issue of Tropical Fish Hobbyist.

I knew what that was about, and knew I had to have a copy. Here's how TFH describes the article online:

Owning Clones
Author: Mark Robbins

Once the stuff of science fiction, cloning is not only happening in real-world laboratories, but also in home aquariums! One hobbyist relates his tale of keeping and multiplying the marbled crayfish, an all-female self-cloning species that one day just might help to feed the world.

Additional: The full text of this article is now available online.

04 February 2009

Big top inverts

Circus of the Spineless is a blog carnival celebrating invertebrates both crunchy and squishy. Check out the latest edition, #35, here, and the main blog for the carnival here. I'd be recommending it even if this edition didn't feature a recent post on Marmorkrebs, rhythms, and aggression.

And if I may direct your attention to our center ring, ladies and gentlemen, I am pleased to say that this blog will be hosting an upcoming edition of the Circus of the Spineless later this year! (Much later, as it happens. November, to be exact.)

03 February 2009

Laying down the law

I've spent some time working visiting a lot of websites and typing in "crayfish" in an attempt to find laws that might be relevant to people who are interested in keeping Marmorkrebs as research subjects or pets. Here's a short summary of what I've found so far.

States regulating import or sale of crayfish: Arizona, California, Minnesota, Utah

States prohibiting release of crayfish into local waters: Alabama, Arkansas, Florida. It goes without saying that pets should never, ever be released into the wild regardless of whether a local law prohibits it or not.

I'm not done searching websites yet, but I've put what I have so far here.

Update: Utah added to the list regulating import on 4 April 2009.

01 February 2009

Farca Luna and colleagues, 2009

Journal of Biological Rhythms coverFarca Luna AJ, Hurtado-Zavala JI, Reischig T & Heinrich R. 2009. Circadian regulation of agonistic behavior in groups of parthenogenetic marbled crayfish, Procambarus sp. Journal of Biological Rhythms 24(1): 64-72. http://dx.doi.org/10.1177/0748730408328933


Crustaceans have frequently been used to study the neuroethology of both agonistic behavior and circadian rhythms, but whether their highly stereotyped and quantifiable agonistic activity is controlled by circadian pacemakers has, so far, not been investigated. Isolated marbled crayfish (Procambarus spec.) displayed rhythmic locomotor activity under 12-h light:12-h darkness (LD12:12) and rhythmicity persisted after switching to constant darkness (DD) for 8 days, suggesting the presence of endogenous circadian pacemakers. Isogenetic females of parthenogenetic marbled crayfish displayed all behavioral elements known from agonistic interactions of previously studied decapod species including the formation of hierarchies. Groups of marbled crayfish displayed high frequencies of agonistic encounters during the 1st hour of their cohabitation, but with the formation of hierarchies agonistic activities were subsequently reduced to low levels. Group agonistic activity was entrained to periods of exactly 24 h under LD12:12, and peaks of agonistic activity coincided with light-to-dark and dark-to-light transitions. After switching to DD, enhanced agonistic activity was dispersed over periods of 8-to 10-h duration that were centered around the times corresponding with light-to-dark transitions during the preceding 3 days in LD12:12. During 4 days under DD agonistic activity remained rhythmic with an average circadian period of 24.83 ± 1.22 h in all crayfish groups tested. Only the most dominant crayfish that participated in more than half of all agonistic encounters within the group revealed clear endogenous rhythmicity in their agonistic behavior, whereas subordinate individuals, depending on their social rank, initiated only between 19.4% and 0.03% of all encounters in constant darkness and displayed no statistically significant rhythmicity. The results indicate that both locomotion and agonistic social interactions are rhythmic behaviors of marbled crayfish that are controlled by light-entrained endogenous pacemakers.

Keywords: circadian regulation • agonistic behavior • social hierarchy • locomotion • crustacea • marbled crayfish