31 December 2015

2015 was the best year ever for Marmorkrebs research

Back at the close of 2010, I made a prediction: that 2015 would see fourteen papers published on Marmorkrebs. How did I do? Here’s this blog’s traditional annual publication graph:

Coming into this last week of the year, I was worried, but a last minute publication helped me shame Nostradamus.

Being an academic, I must now add the caveats and qualifiers about my nailing it.

For this annual graph, I normally count peer reviewed journal articles and book chapters published during the year. But this year, there were a few new wrinkles. There were a bunch of book chapters in Freshwater Crayfish: A Global Overview that were published this year, but the book consistently gives its publication date as 2016 throughout. So I left those out, meaning we have a good head start on 2016 publications. I also left out a pre-print that came out later as a paper (no double dipping!) and some conference abstracts.

Not only were there more Marmorkrebs papers than ever, there was several notable ones.

We had two independent confirmations that Marmorkrebs were triploid organisms (one published, one in press), with one of the highest chromosome counts in the animal kingdom.

There was the first Marmorkrebs paper from a Japanese lab, with some interesting research on masculinizing Marmorkrebs.

There were several papers on the spread and risk assessment of Marmorkrebs and their prospects as disease vectors.

And there was the proposal that Marmorkrebs be given a new species name, Procambarus virginalis. I’ll be watching this one with interest to see if the community adopts the suggested new name. This is why I like “Marmorkrebs” as an informal name for these crayfish: it stays intact when formal taxonomic names change!

I’m feeling emboldened by this year’s successful prediction. But back in 2010, I also predicted there will be twenty papers in 2020. One should always revise predictions in the light of new data, however. Now that there are five more data points, the prediction machine (also known as a simple linear fit to the data) estimates that there will be sixteen Marmorkrebs papers published in 2020.

Place your bets, and I’ll meet you here in five years to find out.

Related posts

2008 was the best year ever for Marmorkrebs research
2009 was tied for the best year ever in Marmorkrebs research
2010 was the best year ever for Marmorkrebs research
2011 was not the best year ever for Marmorkrebs research
2012 was an average year for Marmorkrebs research
2013 was the second best year ever for Marmorkrebs research
2014 was a good year for Marmorkrebs research

29 December 2015

Vogt, 2015b

Vogt G. 2015. Bimodal annual reproduction pattern in laboratory-reared marbled crayfish. Invertebrate Reproduction & Development 59(4): 218-223. http://dx.doi.org/10.1080/07924259.2015.1089329


The marbled crayfish, Procambarus fallax f. virginalis, is a new research model and potent invader of aquatic ecosystems that reproduces by obligatory parthenogenesis. My data show that in captivity, it can reproduce throughout the year. However, when kept at constant 20 °C and natural photoperiod there were two prominent spawning maxima, one before the spring equinox and another one before the fall equinox. If temperature fluctuated between ~15 °C in winter and ~25 °C in summer, the first maximum was shifted beyond the spring equinox and the second maximum was shifted closer towards the fall equinox. These results indicate a bimodal annual rhythm for the reproduction in marbled crayfish that can be modulated by temperature. Comparison with P. fallax suggests that this rhythmicity was inherited from its sexually reproducing mother species. Potential consequences of my laboratory findings for wild populations of marbled crayfish in temperate and tropical regions are discussed. Since marbled crayfish can be kept in captivity for up to four years under a broad range of conditions, they offer the possibility to investigate endogenous circannual rhythms and their entrainment by environmental zeitgebers in decapod crustaceans.

Keywords: Marmorkrebs • Procambarus fallax • Decapoda • reproduction • circannual rhythm • zeitgeber

22 December 2015

The gamete record holder?

In a fun new review paper on the extremes of crustacean reproduction, Vogt writes (lightly edited):

The record in chromosome number in animals is hold by the freshwater crayfish Pacifastacus leniusculus trowbridgii with a diploid set of 376 chromosomes, corresponding to a chromosome number of 188 in the gametes (Niiyama, 1962). The second highest chromosome number was recently found in the triploid crayfish Procambarus virginalis (3n=276) (Martin et al., 2015). ... It reproduces by apomictic parthenogenesis, i. e. without meiosis, and therefore, the eggs should include 276 chromosomes as well, making Procambarus virginalis the new animal world record holder with respect to chromosome number of gametes.

I am not sure whether I would call the new egg of a Marmorkrebs a “gamete” or not. A quick look through a few (admittedly non-technical) dictionaries usually define gametes as cells that must join with other cells to create a viable embryo. A Marmorkrebs egg doesn’t meet that definition. A first-stage Marmorkrebs egg is probably better compared to a zygote in most diploid organisms than a gamete.

Still, common parlance calls the Marmorkrebs egg... well... an egg. And eggs are gametes.

As so often happens, life overflows the dikes erected by the schools. – Mario Bunge, Intuition and Science

Still, the high chromosome numbers of these crayfish species are fascinating, quibbles over categories notwithstanding.


Vogt G. 2015. Structural specialities, curiosities and record-breaking features of crustacean reproduction. bioRxiv.

14 December 2015

Pic of the moment: 14 December 2015

Exactly five years ago, I posted some word clouds made up of abstracts of Marmorkrebs papers. It’s long past time for an update!

This word cloud was made of the abstracts of Marmorkrebs papers from 2011 to 2015. Perhaps the biggest change from the earlier word clouds is that the genus name Procambarus is now reasonably large, with the specific name virginalis also appearing, albeit a bit smaller than the genus.

And just for fun, here’s an alternate version:

Related posts

Pic of the moment: 14 December 2010

01 December 2015

#Marmorkrebs #NoFilter

Here’s a collection of Marmorkrebs pics on popular social media site Instagram. I like scrolling through these pics, because it’s interesting to see the variation in colours or people’s crayfish. But as I’ve written before, make no mistake: if these are Marmorkrebs, their colour is diet and condition dependent. Their offspring won’t necessarily have that colour unless their conditions are similar.

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The curious case of crustacean colours