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Someone traded in a crayfish, no idea what species. About five-six inches. Brown, with blue legs. Claws have the, ah, rounder shape, rather like some of the Australian crayfish. (Guess I'd better take photos, huh?)
It was hiding behind a lift tube constantly, so I leaned a nice big slate against the front of the tank, making a shaded cave, crayfish moved right in and has dug itself in a bit more securely since then. Fairly timid, I've never seen it when the lights are on (however, I've never been in the store while tank lights are off, thanks to timers), reacts to presence of food slowly unless dropped within 3 inches in front of it. I haven't seen it tailflick even once so far, it'll just slowly back into a corner and then make all effort to claw whatever's bothering it, instead of bouncing all over the tank.

Was dropping some food on it last week, noticed worm-looking things attached to it.

Pale translucent white. They haven't seem to changed locations at all since I first noticed them. One end gloms onto the crayfish's shell, the other "head" end remains unattached. Seem to prefer the underside, joints, and overall softer parts of the crayfish. The largest ones (biggest one at least 1.5cm when extended) are all attached to the crayfish's head, essentially retracted and hiding in its... eye sockets, for lack of a better term. There are a few attached to just hard shell, but those that I've observed are tiny (at most 2mm when extended). The "head" end almost resembles a snail or flatworm, it appears to be flattened, and sort of pinches outward into a pair of short antenna-looking structures. There may be a second pair of similar structures right behind the first pair, but I need to take a look again. As far as I've seen, they spend most of their time retracted, but when I drop food in front of the crayfish, they're extended and waving around, reacting at about the same time as the crayfish itself.

So. Anyone have any idea what these things are?

EDIT: topic clarification

A picture would help but by your description these are likey a leech called Branchiobdellida. Rinse the crayfish under cold water and srub lightly with a soft toothbrush everyday untill gone, It may take up to two weeks.

I've seen similar worms on wild caught crayfish and tried to pick them off with tweezers, but once the crayfish was out of the water the worms seemed to retract into the crayfishes shell and I couldn't grab hold of them.

Anyone have an idea of how to treat this, meds or heat? Are you going to try the soft toothbrush technique?

Sounds like crayfish leaches. I don't know a safe way to get rid of them. I do know that at a molt there are a few minutes before they move off the old shell to the new. If you actually see it molt you can remove a clean cray. The leaches will move very quickly after the molt to re-locate the host, so if you don't witness the molt it will do you no good.

Thanks for the informaion badflash. Is this almost exclusively seen in wild caught crays only? Can a tank bred cray get worms if there are no wild caught crays kept with them?

They can ride in on plants (eggs too), or other inverts added to the tank. Proper isolation and decon of new things is the way to avoid this.

I got a cray just the other day and noticed on it's head was something like this. Whiteish in colour, one end stuck onto the cray, the other end with numerous little "arms". It was on the head for about 10 minutes and I haven't seen it since.

I assumed it was a hydra.

Sounds like a hydra to me. The worms that I saw actually drill a hole in the shell and retract into it when disturbed. Thats why I've never been able to catch one with tweezers.

Quoting this from a man who soon may actually turn into a crayfish someday.

"Those little fellas would be called [Annelid Branchiobdellida] sounds interesting? lol They are a family of leech believe it or not and most usually not harmful (commensal relationship) and most of the time beneficial to the crayfish, really depends on what species you have. Pretty difficult to get rid of them really unless you feel like taking a soft toothbrush to your crayfish mate? No joking!

Leaches have a low tolerance for salt, so therefor it makes sence to treat these little fellas with salt should you wish to control the infestation. If this is the case, I suggest the same treatment for Temnocephalans, simply submerge your crayfish in a bath of 50 % seawater for 2-3 hours.

Now you are going to ask, how do I do that?

Damn good question really! You will have to be pretty close on this measeure.

Grab a set of scales and measure out 35grams of salt
If you don't have micro scales a good teaspoon is around 4.7grams, so 5 nice teaspoons will do.
I don't mind what salt you use, personally I prefer pool salt.
Throw that in 250ml of boiling water and stir in until dissolved.
Then take 1.750ml of water from your crayfish mates tank put it in a 4litre ice cream container or something similar with high sides.
Add the dissolved salt solution to it and stir again.
Drop an airstone to keep the water nice an aerated.
Set up an alarm clock to 3 hours in the future.
Drop your crayfish in and make sure it can not escape.
Go clean out you little mates tank.
Come back and remove when the alarm goes off.
Repeat every 7 days if needed.


This may not get rid of them but it will have a small effect on the control of them. I would also suggest you clean out the tank and all the ornaments during the time while you are waiting for the alarm to go off. Important to do this when you have enough cycled water ready to refill your tank straight away after treatment.

I have seen several reports of very good results from this treatment.

Good luck.

Thanks BiffMalawi, this treatment sounds a lot easier than the toothbrush method. But now I'm curious, why does the man/women you quoted say that it may be benificial depending on species?

You know what I have no clue I never pursued it as I just figureed the leachy things would just gross me out so I wouldn't tolerate them anyway. I'll ask him and get back to you.