<font size="2" face="Verdana, Helvetica, sans-serif">IMO. Heat. Plain and simple. Two degree temp swings can be fatal to a clam. I am pretty sure none here who lost a clam has a chiller on their system. Right? How many online had a chiller? Take a look at the time frame of this happeneing. Record heat waves all across North America. Before I buy another clam I am placing a chiller on my system. Easy as that.
Here is my thoughts on causes.
Vibrio, It is found on EVERY tridacnid in nature. I have three other bivalves(a small clam, mussel and oyster) in my tank. None died. So no virus IMO. Has anyone involved in this approached an actual Marine Bio who specializes in tridacnids? None have as far as I can see. All I see is guys like us trying to make sense of something that is so far above our heads it isn't funny. Distributors are in the same boat. Has any distributor had a huge scale wipe out like is going on in our tanks? Maybe one store and even then it wasn't the stock that big distributors carry. It was numbered at aroudn ten. Maybe. Have the harvesters/suppliers had large scale wipe outs? no. If it is only affecting the end purchaser that means you have to look for commonalities in all tanks. The one I see is heat. In summertime temps go up. Temps go up we have more losses.
Unless something drastic happens reefs don't change two degrees in the time frames we see in our tanks. We can see a swing of two degrees in less than an hour in some cases. Can you imagine the energy it would take to raise the temp of a reef by two degrees in a couple of hours?? It takes one kilojoule to heat one pound of water one degree fahrenheit or one calorie to heat one gram of H2O by one degree celsius. Now to heat millions of gallons of moving/turbulent H2O on a reef by two degrees you would need (say 1,000,000 gallons) 16,000,000 Kjoules
one lb of water is ~ one pint. With there being 8 pints in a gallon that means 1,000,000 gallons weighs 8,000,000 lbs. 8,000,000 times 1kjoule per degree times two for two degrees gives us
16,000,000 KILOjoules of energy. And that is assuming a constant heating of all the water in question. No cooling due to wind or evaporation or cooler water coming in with the current. But with the reef water being changed so rapidly, it would take much more to get the reef to shift by two derees.
That is my .02 on this whole thing.. lol
Personally we need to stop blaming the stores, shippers, suppliers etc. The cause is right in our own homes. IMO
Deb,
Gaping doesn't necessarily mean your Derasa is on it's way out. I have seen my purple max one gape and was fine for the longest time. In a thread on RC a distributor even says gaping isn't always a sign of impending death. So there is hope yet. :D