white spotted mantle

Real Reefs

New member
I got in 4 crocea's about 3 weeks ago. I have slowly moved them up to be about 8-10 inches below my 400W bulbs. Over the last week they have developed white spots in their mantles about the size of a pen point. The clam furthest from the light seems to have some kind of bleeching which looks like a light/ whiteish band running the entire length of the mantle. All mantles are fully extended and the clams react to shadows rapidly. Any suggestions?
Do a search for my previous post on white spot disease (WSD) or clam disease. I have written about this condition briefly.
I recently (5 weeks ago) purchased a 4" crocea that i found out later was a wild caught Vietnamese clam. Anyhow, I hadn't looked too closely at the mantle upon purchase, but realised when I got it home that I could make out 6 tiny white pin-point spots on the mantle. I grew extremely concerned and wound up emailing Daniel Knop wondering what it was and if perhaps it could be the dreaded white spot clam disease. He thought not as the white pin point spots were not raised. Well, I put the clam in a Q tank for 3 weeks for observation and I noticed the spots slowly changing> They went from a distinct pin-point white spot to a blurred blotch maybe 3* the original size, and appeared more of a faded grey. Was it some sort of mild bleaching due to stress? I don't know....but, those faded spots gradually disappeared as well and now the mantle is completely free of any irregularities. I also saw another larger area of bleaching beginning on the outer edge of the mantle in one spot, this has completely disappeared as well. The clam seemed to improve once I moved it out of the Q tank (96 watt PC's only) and just left it alone in my main tank (400w MH) which is a pretty stable environment. I don't know what caused this, but I would guess stress from shipping (at least in my case).
Have you noticed any changes in the spots with respect to size or number?
cromax: Did these clams that you noticed the "embedded" form of the WSD die or did they recover? Did it spread to other healthy clams?

Also: I FW dip all my clams before they enter the display due to losing a large amount of clams to the clam disease last summer...
3 of the clams are around 5" and 1 is 3". Af riend also got some 3" clams in the same shipment. His also developed the spots but they have started to fade in his clams. I hope the same happens to mine. I was worried because I have several other clams, maxima's, squamosa's and a derasa ranging from 4-10" and I would hate to loose them. My quarentine system will only be ready in about 4 weeks but the clams were at a great price (an addict has to rationalize a purchase:D). I did a search but only came up with white spot disease in small clams.
OK, this is interesting as I know of others who have bought some croceas out of the same shipment as I did. The one other crocea I saw in my friends tank had these spots as well...hmmmm, I still thought it was either mantle patterning or bleaching due to stress...now I am beginning to wonder....but the spots are just about gone so who knows.
A crocea i bought about 2 months ago had a few spots and i assumed it was some bizarre form of bleaching. It still has about 5 spots on it's mantle and has shown growth and reacts well and has good colour. After reading this thread i'm getting a little worried. I've got 6 other clams and would be VERY upset if this was WSD. The other clams all check out ok and have all shown recent growth.

Do the number of spots increase as the disease progresses? Are there any tell-tale signs of decline from WSD other than alive one day and dead the next??

Good discussion. Basically with white spot disease there are raised tiny dots, and as time progresses the number of dots increases. The disease is highly contagious and clams that are affected do not show any signs of discomfort until they are overwhelmed with the parasite. This could take months. High temps (86 degrees and above) do seem to potentiate growth of the cysts.

I have also observed what mia1974 has observed. These "nodes" appear slightly larger than the beginning stage of white spot disease, and they sometimes increase in number. You must look very carefully, but these nodes are raised "bumps" on the mantle. Clams that I have owned with this condition seem to have these little white nodes dissappear after a few weeks and where the node disappears there is an equally minute bleaching where the node used to be. I have only observed this on croceas. The croceas with this survived.

It is possible that our clams get WSD, but are able to fight them off if conditions are favorable. Or, perhaps the little white nodes are a different condition altogether. I don't know.

There is one thing for certain: Any nodes or "white spots" on clams is NOT NORMAL at any developmental stage, and affected individuals should be quarantined, particularly if you have a sizable investment in clam stock.
Cromax: Thank-you for answering this post tonight...now I will at least be able to sleep knowing I won't lose my entire clam collection again! I noticed that the nodes only went away when I placed the clam back in the main display which is very stable, so perhaps it is a stress-related thing and if a parasite, a less destructive one...
I wonder...is this a crocea specific disease? Does WSD occur with other tridacnids as well?

From what cromax states the outbreak that I am going through seems to be crocea specific, but, the WSD that Knop details in his book affects all clams (I saw pics in his book of infected maximas, croceas and squamosas).
At what point does the clam become overwhelmed? Would it be covered with spots or just show a few??

The WSD in Knops book shows pics of clams that literally have THOUSANDS of tiny tiny white spots that appear almost like a dusting on the clam. Think of the worst case of ick you have ever seen on a fish and thats what it looked like. When I emailed him he said that hardly any research had been done on incubation periods with this disease so it was difficult to ascertain how quickly it would spred to other clams. He did say in the book that healthy large maximas could hold out for months, while smaller clams perished within weeks.
Makes me wonder...My crocea has been in my tank for about 2 months now and the number hasn't changed tho the positions of white spots have. I hate having to decide whether to pull him or leave him...