26 March 2022

Retained European Union law says you can’t retain Marmorkrebs in the United Kingdom

Dalek with Union Jack livery
I ran across this article of “pets you can’t have in the United Kingdom” and was a little surprised to see Marmorkrebs on the list. It is banned, along with four other crayfish species (Louisiana red swamp crayfish, signal crayfish, spiny-cheek crayfish, and virile crayfish).

It turns out the regulatory situation in England and Wales (but not Scotland or Northern Ireland?) is a little complicated.


Marmorkrebs were banned in 2016 as part of a European Union intiative. When the United Kingdom left the European Union, the regulations against Marmorkebs stayed as part of “retained EU law.” 

While the government website lists exemptions that people “may” be able to invoke to keep existing pets, it seems none of them would apply to Marmorkrebs. In particular, the “grandfather clause” allowing people to keep existing pets should not apply since Marmrokrebs don’t live as long as the regulations have been in effect.

I also have to snicker a bit about the rule that says if you have one of these animals, you must not let it reproduce. I’m not sure how you are supposed to prevent that in a parthenogenetic animal.

External links


The animals banned as pets in the UK - complete list


Invasive non-native (alien) animal species: rules in England and Wales


Form CRAY2: Application for a licence to keep non-native crayfish

18 March 2022

Katayama and colleagues 2022

COver to journal bioorganic Chemistry

Katayama H, Toyota K, Tanaka H, Ohira T. 2022. Chemical synthesis and functional evaluation of the crayfish insulin-like androgenic gland factor. Bioorganic Chemistry 122: 105738. https://doi.org/10.1016/j.bioorg.2022.105738




Insulin-like androgenic gland factor (IAG) from the marbled crayfish Procambarus virginalis is an insulin-like heterodimeric peptide composed of A and B chains and has an Asn-linked glycan at the B chain. IAG is considered to be a male sex hormone inducing the sex differentiation to male in decapod crustacean, although there is no report on the function of IAG peptide in vivo. In order to characterize P. virginalis IAG, we chemically synthesized it and evaluated its biological function in vivo. A and B chains were prepared by the ordinary solid-phase peptide synthesis, and three disulfide bonds were formed regioselectively by dimethyl sulfoxide oxidation, pyridylsulfenyl-directed thiolysis and iodine oxidation reactions. An IAG disulfide isomer was also prepared by the same manner. Circular dichroism spectral analysis revealed that the disulfide bond arrangement affected the peptide conformation, which was similar to the other insulin-family peptides analyzed so far. On the other hand, the glycan moiety attached at the B chain had no effect on the peptide secondary structure. Injection of the synthetic IAG and its disulfide isomer to female crayfish did not induce male characteristics on the external morphology, but both peptides suppressed the oocyte maturation in vivo. These results suggest that IAG has a pivotal role on the suppression of female secondary sex characteristics.


Keywords: Insulin-like androgenic gland factor •  Procambarus virginalis • peptide synthesis • masculinization

Synthetic insulin-like androgenic gland factor suppressed oocyte formation in marbled crayfish