16 Dec 2003

Craw-Mamma Questions

Dear Blue Lobster:

we have a 36 gallon tank with 1 blue crayfish and 1 red crayfish and some other misc fish. red (her) and blue (him) have mated many times lately and weve noticed eggs on her underside. she has made her nest in a cave area and she hasent been out in almost 2 weeks. she is also now turning green. she doesnt look fussy so we dont think its moss... but im concerned it will kill her. is this normal ? should we force her out and remove this structure so she nests in an open area with better water circulation ? your help is greatly needed...

Dear Gentle Sir:

Firstly, let us discuss identification of your crays. It seems that the red female cray is a procambarus clarkii, commonly known as the Red Swamp Crayfish, while the blue male is a procambarus alleni, commonly referred to as the Blue Lobster. These species are found in the American Deep South swamps and ponds and are easy to breed and maintain, hence their commercial distribution as pets around the world.

Your Red Swamp Cray is what we call in berry, reffering to the berry-like mass of eggs under her tail. She is indeed pregnant and in just a few short days your tank will be crawling with hundreds of tiny baby crayfish (called craybies by professionals) of the hybrid type procambarus alleni × clarkii. Since this is a coupling of a Blue Lobster and a Red Swamp Cray, we can expect the craybies to be purple, which is a rarity in the crustacean world.

Your concern for the craybies very valid. During berry, the female cray secretes a hormone into the water that will keep the male at bay. After hatching, the mother will care for her offspring, letting them ride under her tail; however, after this period the mother and any other crays will consider the hatchlings as food. It is time to remove all other creatures from the tank lest you risk them being eaten. The world of the crayfish is a savage one filled with hunger, violence, and death.

As for the green coloration of the Red Swamp Cray, the most likely explanation is that the cray is simply changing colors. The exoskeleton itself is semi-transparent and a cray's coloration actually comes from its muscles and blood. Cray coloration changes for every occasion, including pregnancy, mating, and dying. A crayfish's color may change over life too, and water chemistry factors in as well. Assuming she doesn't seem agitated and the eggs aren't shriveling, she will be fine.

Good luck and enjoy your thousands-strong brood of hungry craybies!

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