Photo Reactivity in clams bad?

[diveinheadfirst]

I have seen Clam Mania saying that healthy clams DO NOT react to light. That is contrary to everything else I have read, but the guy definitely knows how to farm a clam. So the great debate has begun, should a clam if healthy react to light? Is there any evidence that points towards either? Curious, very curious indeed.

happy reefing

 

[Christian0505]

What do you mean by react to light? Yes mine reacts if I cover the light. No it does not react if I add extra light. Got my little maxima for almost 2.5 years now, so I would say it’s healthy..

 

[diveinheadfirst]

What do you mean by react to light? Yes mine reacts if I cover the light. No it does not react if I add extra light. Got my little maxima for almost 2.5 years now, so I would say it’s healthy..

I mean, if you run your hand over the top of the clam, does it quickly retract its mantle. And is that quick photo reaction a good, or a bad sign?

 

[Christian0505]

I mean, if you run your hand over the top of the clam, does it quickly retract its mantle. And is that quick photo reaction a good, or a bad sign?

if I just run my hand over at the waterline level, no it does not react or just a tiny bit. If I block the radions above it completely (so it’s more or less in the dark) yes it reacts and retracts for about 50% but not fully closed. Just making a few shadows does not make it full retract.
Does this answer your question?

 

[diveinheadfirst]

if I just run my hand over at the waterline level, no it does not react or just a tiny bit. If I block the radions above it completely (so it’s more or less in the dark) yes it reacts and retracts for about 50% but not fully closed. Just making a few shadows does not make it full retract.
Does this answer your question?

Yes, perfectly actually!

 

[Christian0505]

Yes, perfectly actually!

Good, in my experience, clams will always react heavily once placed in a new tank. I therefore prefer to place the clam in a corner first, where less fish pass. Let it adjust there, before placing towards the middle of the tank for more light exposure.
Especially when you buy a small clam, place it in a corner, and add some phytoplankton to your tank. Small clams use both light and phytoplankton to survive. I’ve had a massive succes with mine and I just add phytoplankton from Colombo (which is just bottle phyto from the lfs) daily.
The maxima clam actually survived more **** than most of my corals… PO4 of 0,7 ppm, clam didn’t care… Heavy metals, lost 70% of the tank, clam didn’t care

 

[exnisstech]

My two react to light changes. I have read that its possible for them to get so used to the interruption of light by fish swimming by that they eventually stop reacting but so far mine still react but I have only had the derasa for 3 months and the maxima for 1 month.

 

[Christian0505]

My two react to light changes. I have read that its possible for them to get so used to the interruption of light by fish swimming by that they eventually stop reacting but so far mine still react but I have only had the derasa for 3 months and the maxima for 1 month.

in the end it’s a natural response of the clam to close; as being overshadowed means danger. However closing/retracting cost a lot of energy for the clam. Therefore if the clam constantly retracts in your tank it will die as no energy goes to growth anymore. Fish population in our tanks is alot more dense than in the wild were clams are found. Therefore you want a clam in your tank that does not constantly reacts. If it retracts a bit it is fine, just not fully closing everytime something passes by.

 

[Dburr1014]

Mine reacts if I wave my hand across. I think also that is a natural reaction. If it was on a wild Reef and a fish passing over it, possibly wanting to eat it, it would close up.

 

[SlugSnorter]

I mean, if you run your hand over the top of the clam, does it quickly retract its mantle. And is that quick photo reaction a good, or a bad sign?

They should retract if they sense danger, their exposed tissue is very weak, so they protect themselves with their shells. They have "eyes" that can sense changes in light.

 

[minus9]

A healthy clam should react in some way in regards to certain movement or shadows passing near them, it's a completely natural response. If a clam doesn't react at all to any movement/shadows/fish, etc...then I would be concerned about the clam's overall health. An unresponsive clam usually means it's too weak to respond and is just trying to survive, which isn't good.
I won't go into my diatribe about phyto, clam size and their need for it or not, as that has been covered so many times, but that myth continues to this day. I've never worried about fish swimming by my clams at all, but fish picking at clams is another story. Just put the clam in its intended place and crank the lights.

 

[Christian0505]

A healthy clam should react in some way in regards to certain movement or shadows passing near them, it's a completely natural response. If a clam doesn't react at all to any movement/shadows/fish, etc...then I would be concerned about the clam's overall health. An unresponsive clam usually means it's too weak to respond and is just trying to survive, which isn't good.
I won't go into my diatribe about phyto, clam size and their need for it or not, as that has been covered so many times, but that myth continues to this day. I've never worried about fish swimming by my clams at all, but fish picking at clams is another story. Just put the clam in its intended place and crank the lights.

Funny, could you please send me a chat with your findings about phyto?

 

[minus9]

Funny, could you please send me a chat with your findings about phyto?

Reference both James Fatherree's books and I'll find the study shortly.

 

[minus9]

Aquarium Invertebrates: Tridacnid Clams (Usually) Don’t Need to Be Fed in Aquaria

James discusses the myth that Tridacnid clams must be fed in order to prevent starvation.

reefs.com

 

[OrionN]

I think clams will reacts to changes in light intensity. In the wild and in our tanks, waves will cause change in intensity of light reach the mantle certain way. It takes energy to react, like closing the shell, and also will lose that benefit of getting light energy when the mantles retracted. The clams that always react to these benign changes will not do as well as the clams that adapted and do not react to these changes. However, when a predator swim by and may take bites, the clams will need to react to these changes, or else they will get chunks taken off of their mantles.

It stands to reason that healthy clams will adapt and react to changes in light intensity, but they will likely be able to decern between benign changes and the changes that can result in injury due to predator shadows.

 

[hart24601]

It has been my experience that mantle retraction caused from movement depends on quite a few things. Species plays a part, gigas and derasa tend not to retract much.

The biggest item that impacts retraction based off movement, not light intensity - that’s another discussion , is time spent in captivity and the motion around the tank. When I had long term clams even the “jumpy” ones eventually stopped retracting when light passed overhead. Some took months, others years. I donated all my clams to the local zoo so right now I don’t have any, but have had hippo, crocea, teardrop, maxima, gigas, squammy all in the same system before and they all eventually stopped the jerking when passing a hand over them.

So I couldn’t vote yes/no because it’s situationally dependent on quite a few variables.

 

[MoshJosh]

They have "eyes" right, I always figured they were hiding from a perceived threat when reacting to shadows/movement.

 

[hart24601]

They have "eyes" right, I always figured they were hiding from a perceived threat when reacting to shadows/movement.

Spot on, for my systems I suppose since nothing picks on them they eventually stopped retracting. Probably depends on the fish load over the light and room traffic if they “lean” to stop.

 

[OrionN]

It has been my experience that mantle retraction caused from movement depends on quite a few things. Species plays a part, gigas and derasa tend not to retract much.

The biggest item that impacts retraction based off movement, not light intensity - that’s another discussion , is time spent in captivity and the motion around the tank. When I had long term clams even the “jumpy” ones eventually stopped retracting when light passed overhead. Some took months, others years. I donated all my clams to the local zoo so right now I don’t have any, but have had hippo, crocea, teardrop, maxima, gigas, squammy all in the same system before and they all eventually stopped the jerking when passing a hand over them.

So I couldn’t vote yes/no because it’s situationally dependent on quite a few variables.

I agree that it not a simple yes no. Life and nature are more complex and smarter that just simple change due to this or that. Complicated and adapting of animals an are wonderful and complicated.
I did not vote either.

 

[diveinheadfirst]

Thanks for everyone’s input, it’s been super informative and this discussion was EXACTLY what I had hoped to spur when I posted initially.
I appreciate all of you and happy reefing!!