28 Nov 2002

Cherax Trouble

Dear Blue Lobster:

I recently acquired a cherax speciman, air-mailed from Australia last week. Since then I've had the cray in a 50-gallon freshwater aquarium. The water was seasoned from known-safe tap-water, since I didn't feel using creek water containing local microorgasms would be safe for the cherax. Feeding him bloodworms, earthworms, and lettuce the cherax seemed fine until this Thanksgiving evening.

Returning home with several tubs of leftovers from a Thanksgiving dinner, I proceded to feed my cherax some chilled, roasted turkey (in 2mm strips), mashed potatoes (by means of a cotton swab) and gravy (through an eyedropper). Sirs, after feeding him this meal I left my aquarium room for several hours — and returned to find my cherax in his current state!

My cherax is now lying on his side, twitching, with a string of dark fecal matter trailing from its anus and several strange, white beads of mucus oozing from its mouth-parts. I immediately checked the water for pH levels and nitrids and found the results to be not only well within acceptable limits for the cherax but also identical to my last such test made 16 hours prior to this one. Increasing the intensity of the flow to and from the filter and increasing oxygen levels in the tank seemed to ease the twitching but the cherax is still mostly inert. At this moment its only activity is gill-fanning and the occasional eye-cleaning movement.

I've seen molts begin like this (aside from the feces and mucus), but at this stage in the process the carapace should have split by now, and there is no indication of such with my cherax. There are also no signs of acute parasitic infestation. What could be causing this strange behaviour in my cherax? I fear it will die soon if I can not identify the problem and treat it. Do any of these symptoms seem familiar to anyone reading this forum?

Please contact me if you have any information regarding this!

Thank you.

P.S. His name is Bob.

Dear Gentle Sir:

It sounds like your aquarium environment is sound and it's safe to assume that Bob is not molting as the fecal matter should not be trailing from his anus at this point. We shall instead focus on Bob's last meal, an ironic "thanksgiving" if ever there were one.

The holiday menu appears to have been quite healthy: a meat (turkey), a starch (mashed potatoes), and a fat (gravy) in small, well-balanced portions equal to his size and dietary needs. Most crays would be lucky to get even shrimp tails after New Year's Eve, let alone a down-home thanksgiving meal. One might surmise that Bob, a lowly invertebrate held in the same esteem as a mosquito or a late-night snack, is simply dying of happiness.

Barring such a comfortable death, which is sadly unlikely, a few other possible causes may exist, each more insidious than the last.

Copper, known as Cu in the periodic table, is a soft metal used to kill invertebrates. In some cultures the family meal during holidays is cooked with copper. Immigrants used pennies to stuff their turkey, chicken, or game hen to symbolize the wealth and good fortune they wished for their family. After taking the copper out of the bird, the flesh was still saturated with high levels of the metal.

If your family cooked the turkey in this manner, you may have unknowingly introduced copper into your tank which then killed your cray. if this is true, then God help you.

Another possible explanation is Crayfish Plague. This disease eats at the cray's shell and soft innards, eventually resulting in the cray's death. Potatoes grown in Ireland often live in flooded fields where crays take up residence in the late Spring. During this time the potato crop would have absorbed the plague, harmless to the plant and humans but deadly to your cray when fed the mashed tuber. Check for spots on your cray's shell.

One last thing to consider is food poisoning. Did you or anyone else at your family dinner feel ill after the meal? Do you know for a fact that all of the food was cooked properly and handled by clean hands? Salmonella poisoning is responsible for more food-related illness than all other causes combined, and your crayfish is vulnerable to it too. E. coli could also be the culprit if someone didn't wash properly after defecating and may explain the "diarrhea" your cray is exhibiting.

Sadly for you, sir, I would guess Bob is dead by this point. It will be a very lonely holiday season. My condolences go out to you and your family during this dark time.

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