Biology a question

rossb · #1 01-27-2003, 01:41 PM

To begin with I am not having any tank problems and no fish are exhibiting any problems, this is just a question. I know this is a bit morbid, but I was wondering what type of a post mortem you do on your dead things. Do you try to figure the cause of death?

Also I think I have an evil critter in my tank that is attacking my shrimp and crabs. I suspect something like a Mantis. This morning my SLF crab, that was ½ through a molt, was the latest victim. I have been placing Bob’s mantis trap out without any luck. Where do these things like to hide? Any tips that could help me narrow down the search area?

Thanks…ross

Delphinus · #2 01-27-2003, 03:43 PM

Usually, there isn't much left to do any kind of analysis on, in a matured tank ... things are recycled within hours. ...

From what I've heard, if you have a mantis, sometimes you can hear an unexplained clicking sound coming from the tank. Of course the reverse isn't necessarily true, if you hear an unexplained clicking sound it could be a pistol shrimp which are supposedly harmless.

You could be onto something. Your tank has been up and running for a while, for this many crustaceans to go missing or maimed/injured unexpectedly ... there might well be a predator of sorts.

Hopefully, one of our more experienced mantis catchers can jump in here and offer something useful .... Dez you out there???

good luck

PS. hope you don't mind but I'm going to move this into the main reefing forum in the hopes it will get more hits...

Dez · #3 01-27-2003, 04:25 PM

I didn't dismantle my tank until I saw the critter. I had clicking noises come from the tank... I was in denial, I thought it was a pistol shrimp because no fish were missing...maybe a chromis or two...my hermit crabs and snails slowly dissappeared ( I thought that was normal...).. My sallylightfoot crab dissappeared, couldn't figure it out. Well, I lived like that for about 6 months, then I finally saw the bugger...a mantis shrimp.

I took an afternoon and removed every piece of rock and still didn't find it... then I squirted hot water in the rocks with holes and heard a sound in one of the holes..

Cracked the rock open and found it..

Des

#4 01-27-2003, 06:32 PM

there are a million ways to remove mantis shrimp but the one i use is a luxury method, as i have alot of tanks at all times I will remove all cared for livestock from the suspect tank, and I will then starve the tank untill the bugger comes out looking for food, then i usually put in a mantis trap of sorts baited with some fresh fish, works like a charm for me, but mabey not practical without many extra tanks.
As for post mortem, I have been wholesaleing for a few years and have seen many dead fish, most of the time I can tell by looking at the dead fish what it died from but sometimes I do open the fish up and find out what killed them. I usually move larger fish which makes this easier. If you suspect a fish is cynide caught open it up and look for signs, usually the organs will be jellied. If you do find a cynide induced death, take the dismantled fish back to the LFS you got it from and let them know that the fish died cuz it was captured with the use of cynide, hopefully they will look into it and change suppliers(ask what there doing about it) if they do nothing let them know that you and all your buddies will no longer purchase fish from their store, if you dont do this you yourself are encourgaging the use of cynide fishing. There are many sites that explain symptoms of a cynide caught fish, check a good search engine...

rossb · #5 01-27-2003, 10:57 PM

Well I had a look at the crab and it is pretty ripped up. I originally thought it was molting but on closer inspection it had its shell split open. It was alive and fine yesterday. I removed all of the rocks from that side of the tank, and put all of the ones with holes in them in my sink (they are almost all the ones I bought rather than made). The rest are in salt water in my mixing tank. So any ideas how to flush this guy out with out hurting the rocks?

BTW I have had 3 bits of advice and 3 offers to take it if I can keep it alive.

Bob I · #6 01-27-2003, 11:10 PM

Quote:

BTW I have had 3 bits of advice and 3 offers to take it if I can keep it alive.

I DIBS'd first, but that is of no consequence, it MUST be found. DEZ said he squirted hot water into the holes one at a time until he heard something. The he split the rock. That is just repeating what he said. If there is no concern about keeping the rock alive, I would put them in HOT water one at a time. Just my idea, as I have never had that problem.

Aquattro · #7 01-27-2003, 11:25 PM

CLub soda works really well, as does fresh water. Mantis shrimp don't like fresh water.

Delphinus · #8 01-27-2003, 11:32 PM

What is the texture of the exoskeleton of a mantis? Is it hard, like a lobster, crayfish or crab; or is it softish like a cleaner shrimp (or other shrimp)?

Van down by the river · #9 01-28-2003, 11:34 AM

Mantis shrimps Stomatopoda, have a thin carapace similiar to Lysmata grabhami- Cleaner shrimp. Logic would state that some of the larger species due to their size would have a thicker and harder Carapice.
Some species are quite large, up to 38cm ( I couldn't find anything bigger).

Rather than hot water, destroying other organisms (sponges,etc) which may have a negative effect on water quality. Maybe try the pointy end of a zip tie, sewing needle,nail or other hard/flexible object to "spear" the holes in the rock.
I have heard of success with the starving method as well. Their lair can often be found by debris. broken shells,
sediment ejected while cleaning their den, or previous victim remnants.
I have also witnessed them use small stones or shells to cover/hide the entrance. If you can catch them alive they make interesting animals for a small species tank.