Dr.Roy, does this sound like anything?

[crafty_50mitchell]

Hey all/Dr.Roy,
Well I have a 4 inch (give or take a .2) G.Chiragra who is acting strangely. Basically I had not seem him (usually very active) for four days, which is strange by itself since he comes out and does the cabbage patch for me every time he see's me at feeding time. Due to his size and the fact that he molted 1.5 months ago I do not feel it's shyness due to a molt. Ok back to the current situation, yesterday Im convinced he's gone the way of the dodo and decide to do a water change/mantis hunt and find him appearing to be pinned between a peice of liverock and the glass, not really curled up in a defensive position just kinda laying in there upside down. So I pull the rock back a little, and he stays in the same position (no he didnt fall to the sand bottom yet) and eventually curles up into a defensive posture, so I leave him alone for ten minutes or so, come back and find him directly below the place where I "think" he was stuck, on the substrate in the exact same position, not particularily defensive towards anything just postured in the same stance/angle that he was above. So I observe him for awhile and he appears to have a hard time getting around and james himself into rock crevices, around his burough, upside down with his telson just hanging out. Flash forward two hours from this time and it's time to target feed some corals in the tank and what do you know he's coming out to get food! So today I see him in his usual spot spying on me, waiting on food, and thoroughly enjoying the look of utter confusion on my face (and hunger Im sure as I was putting a couple monkey shrimp into the ten gallon right next to his ten gallon). So anyway Im sure I used this post just to tell somwhat of an off the wall mantis experience but I'd seriously like to know if anyone has observed behavior like that that isent associated with a molt or poor water conditions.
Cheers, Brian

 

[Gonodactylus]

Gonodactylids often rest by squeezing into a crevice and treating it like a cavity. Nine tiems out of ten when an animal is sick, it will die out of its cavity more or less in the open (although I had an animal die in its tube last night). Anyway, if it ate later, I wouldn't be too concerned.

Stomatopods have no known gravity detector and often lie on their sides or backs when the light is not coming from straight over head. If you watch them in their light-tight cavities, they often are on their backs or sides.

Roy

 

[crafty_50mitchell]

Thanks Dr.Roy, it's good to know that when stomatopods pass it's usually out in the open, most definetely good when water conditions for other inhabitants are considered.
Im suprised to hear that stomatopods have no natural gravity detection, mostly becuase I dont think Ive ever considered this topic regarding marine life (more specifically mantis shrimps). Have you run many studies researching how well they orient thmeselves in zero light conditions? Granted this must be somewhat difficult considering the wide spectrum of light they can pick up, but Im very curious about this topic now.
Thanks,
Brian

 

[Gonodactylus]

I've watched a lot of them in IR and out in the open they move properly oriented to the substrate. In cavities, they assume any orientation. If you provide light from below, this is a powerful stimulus and generally causes them to flip over on their back.

Roy

 

[crafty_50mitchell]

When you mention that they "generally causes them to flip over on their back" I'm wondering what keeps them from always flipping over, is their tactile sense of the substrate or maybe a hearing system (for lack of a better term right now) which senses shifts in balance (like our inner ear structures). Any information would be greatly appreciated as always Dr.Roy.
Brian

 

[crafty_50mitchell]

Sorry for that last post, I just re-read most of it and you did state that stomatopods have no known gravity detection. But while Ive got the reply thread going here do you have any theories on gravity detection? Again, curious as always.
-Brian

 

[Gonodactylus]

There is probably some proprioceptive informatio from the legs and antennules, but nothing like a statolith that crayfish and lobsters possess. When the light cues are strong, they seem to take priority.

Roy