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.

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