The crayfishes with blue, brown, reddish coloration were observed in one watercourse (Latvia). Blue ones I observed only few times. What factors are responsible for blue coloration?
I know that in terrestrial isopods the specimen becomes purple when it is infected with an iridovirus. Not sure if this is the case in crayfish too.
Crayfish carapace contains two proteins (large molecules, rich in variously colored pigments), closely related:
- Crustacyanine of blue color,
- Astaxanthin whose light absorption properties (and therefore color) vary depending on whether it is free (orange red) or attached to crustacyanine and then purple blue.
Dear Ton and Oum! Thank you for your answers! In this case more reliable seems protein version. One of my colleagues added the third version - coloration depends on temperature. This version was based on some observations, when blue crayfishes were observed in springs (temperature approximately +7-10 degrees). The specimen in picture was observed in autumn, in small river with low water temperature. Of course, several observations are not an argument, but is it possible, that water temperature can change protein balance?
+1. Not seldom in aquariums crayfish species Procambarus cubensis from North America should be really blue-coloured... I suppose, the colouration (variation of colours within several limits) in all cray-fishes should be genetically programmed. The dependence from environmental factors exists but is strongly limited by genes.
++2. The males of Rana arvalis (Anura:Ranidae) in springs are sometimes almost blue. The similarities can exist...
Ton, this is just a guess, but I have seen different colors in ampipods based on diet. Maybe stable isotope analysis would help.
Pete
Same species individuals from same metapopulation (e.g. same stream or basin) can vary in colour, e.g. Papuan Cherax pulcher (own observations). Temperature variation are minimal since specimens of different colour can be found at the very same location.
Of course, Cherax prefer limestone habitats and this could be different from Astacus habitat in the Baltics, but in Pskov Region of W Russia (less than 100 km from boundary with Latvia) in Osovik / Fenevo villages (large system of lakes connected by channels and streams) blue morphs are abundant (again, own observations from 1990).
Sorry, no answer to your question, just some more data.
This one could help:
https://www.anemoon.org/Portals/0/Plaatjes/Spuisluis/juli%202014/Coloration%20in%20crustaceans_GAA-Wade-Jan10.pdf
Thank you, Dmitry! If this question is interesting for others too, I can recommend one article more: Nicholas M. Wade, Mike Anderson, Melony J. Sellars, Ron K. Tume, Nigel P. Preston and Brett D. Glencross. 2012. Mechanisms of colour adaptation in the prawn Penaeus monodon. The Journal of Experimental Biology 215, 343-350 / doi:10.1242/jeb.064592
More about blue decapods: https://edition.cnn.com/2019/06/14/us/blue-lobster-arnolds-bar-massachussetts-trnd/index.html
I had a Pacifastacus leniusculus that was the normal brown color when I caught it, but changed to a uniform bright blue after several molts in captivity. In this case it could have been diet or temperature (or a combination of the two) as it was being held at a warmer temperature than in the wild.
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Preprint A Model of Color Vision for Remote Sensing 1
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