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FAQs about Identifying Giant Clams, family Tridacnidae

Related Articles: Got Tridacna? A beginner's guide to keeping Tridacnid clams by Laurie Smith, Example Chapter from NMA Reef Invertebrates book, on Giant Clams, Tridacnids, A Brief Guide to the Selection and Placement of Tridacnid Clams by Barry Neigut, Tridacnid Health: Pinched Mantle Syndrome in Giant Clams by Dr. David Basti, Deborah Bouchard & Barry Neigut, Bivalves, Mollusks, Lighting Marine Invertebrates,

Related FAQs: Tridacnids 1, Tridacnids 2, Tridacnids 3, Tridacnids 4, Tridacnid Clam Business, Tridacnid Identification, Tridacnid Behavior, Tridacnid Selection, Tridacnid Compatibility, Tridacnid Systems, Tridacnid Lighting, Tridacnid Placement, Tridacnid Feeding, Tridacnid Disease, Tridacnid Reproduction, Bivalves, Bivalves 2, Lighting Marine Invertebrates,

Kitty in a Clam

Clam ID 9/26/10
Hello WWM Crew,
<Hello Jason>
I recently acquired a clam which was outgrowing its' previous home and I'm needing a bit of help identifying it. It is rather large at fourteen inches from end to end and approx seven or eight inches across when fully extended.
It has tentacles around the in-current siphon which ruled out gigas. It has some fairly prominent scutes but rather few, and those that are there are quite widely spaced. The Maximas that I've seen tend to have very closely spaced scutes and Squamosa tend to have many large scutes. Any help in Identifying this big guy would be greatly appreciated.
<Take a look at Tridacna derasa, I'm quite sure that is what you have.>
Thanks in advance
<You're welcome. James (Salty Dog)>
Jason Rupinski

Re Clam ID 9/26/10 - 9/27/10
Thanks for the quick reply. I had considered Derasa but the one thing that threw me off was that this clam only has four or five folds and they're fairly prominent. I have a small Derasa and it has seven or eight folds and the are not nearly as large as prominent as the folds on this clam. I've attached another pic of the clam. I took this pic when I was drip acclimating it and it hadn't opened up yet.
<Based on my limited experience with clams, I felt your clam was a derasa.
Since I do not have the time to do a study on Tridacna identification for you, I suggest you do so by reading James Fatherree's article on clam identification found here.
There are too many instances where querior's would like us to do the footwork for them rather than Google for themselves and find information that is readily available on the web. Please read here re "Asking The Web Web Media Crew a Question".
<You're welcome. James (Salty Dog)>

ARKive - your image of Tridacna tevoroa 5-7-09
Dear Robert,
I hope you do not mind me contacting you but in searching the internet for images of tevoro clam (Tridacna tevoroa) I found a fantastic image of yours on http://www.arrecifevivo.com/v2/index.php?option=com_content&task=view&id=93&Itemid=49 which I would be interested in using for ARKive, if you would like to become involved.
ARKive - www.arkive.org - is a unique conservation initiative.
<Ah, yes. A worthy effort. You are welcome (as are all non-commercial concerns) to free use of any of my content; per here: http://wetwebmedia.com/WWMUsePolicyStmt.htm
Thank you for your efforts. Bob Fenner>
Films, photographs and audio recordings of the world's animals, plants and fungi are being gathered into one centralised digital library. To date we have created digital multi-media profiles for nearly 4,000 species, digitising and storing more than 25,000 still images and over 60 hours of moving footage. These important audio-visual records are being preserved and maintained for the benefit of future generations and are being made available via the ARKive website.
I have attached some documentation that will tell you a lot more about the ARKive project. However, in summary:
· It is ARKive's current aim to compile audio-visual records for the 17,000-plus species currently threatened with extinction, according to the World Conservation Union's (IUCN) Red List of Threatened Species.
· We are looking for media (moving footage, still images, audio) to depict each species' life history as comprehensively as possible. In order for us to achieve this aim we need help from as wide a variety of donors as possible and would like to be able to add you to our list of contributors.
· The ARKive website acts as a showcase for image providers, displaying copyright and contact details with every image and links to each media donor's own web activities.
See examples of species which have been ARKived at www.arkive.org.
Please let me know if you would like to contribute to ARKive or if you have any queries.
I look forward to seeing your images.
Best wishes,
Eleanor Sans
"ARKive is a noble project, one of the most valuable in all of biology and conservation practice. It has whatever support I am able to give it."
Professor E. O. Wilson, Harvard University
"Over the past few decades a vast treasury of wildlife images has been steadily accumulating, yet no one has known its full extent - or its gaps - and no one has had a comprehensive way of gaining access to it. ARKive will put that right. It will become an invaluable tool for all concerned with the well-being of the natural world.'
Sir David Attenborough
Eleanor Sans
ARKive Media Research Assistant

BBC E-mail: New giant clam species discovered 8/30/08 <Thank you Neale. BobF>> Neale Monks saw this story on the BBC News website and thought you should see it. "The coral reefs in particular... may still harbour very large surprises," said Dr Richter. ** New giant clam species discovered ** Scientists have discovered the first new living species of giant clam in the Red Sea in over two decades. http://news.bbc.co.uk/go/em/fr/-/1/hi/sci/tech/7588857.stm

Tridacnid care & placement 4/1/07 <Hi Glen, Mich here.> I have recently purchased two Tridacnid clams which I am very pleased with. So pleased that I forgot their names and could use some help with the ID. Both are young clams, slightly larger than 4" long. In the attached picture I have tentatively identified T. derasa in the foreground and T. Crocea in the background (thanks to the descriptions in The Reef Aquarium, Vol 1). I am fairly sure about the ID of T. derasa due to the white, plate-like, symmetric shell which lacks scutes, displays very little ribbing and has a narrow byssus gland. The other, I believe, is T. Crocea due to the overflowing blue mantle, wavy edges and scutes prominent only on the upper shell margin. The rest of the shell has well-defined ribbing. Additionally, the shell edges are asymmetrical, with the hinge side being shorter than the byssus gland side. The byssus gland is also very large, rounded, and extends almost to the shell edge. A few of the eyespots also appear to extend above the mantle surface as if they were little, short tubes. I am less sure of this ID since it also comes very close to that of T. maxima and most pictures of clams are of beautiful mantles, not shell features. Line drawings are of very little help to me. <These ID's are correct.> Right now the clams are placed directly on a 6" DSB, the top 2" being comprised of CaribSea Reef Base substrate, which my sleeper goby loves to sift through in this little lagoon. I am concerned that as he does his work, the Reef Base falls onto the open mantle of the clam and may aggravate the clam. I have even seen the clam quickly close it's shell in order to eject a few particles which have fallen into its incurrent siphon. I'm sure that these animals are designed to contend with this situation, but should this be a concern? <I would move these clams.> Since my light source is two 65W PC 10,000K daylights and two 65W dual actinics (260W total), I am planning to move them up onto the rockwork to get closer to the light. <I think this is wise.> Currently they are 18" from the light source and 14" under the surface of the water, which is mediocre lighting. Moving them up on the rockwork would put them 5" - 7" closer, which should be much better for their health, but worse for our viewing pleasure. <May want to consider moving them even higher.> My only concern with placing them on the rocks is how to move them when they grow bigger. Do I rock them a bit and cut the byssus strands close to the rock? <I would avoid doing this if at all possible.> Can I damage the clam if I do this? <Absolutely. Hopefully the clams have not attached to the bottom of your tank. What I would do is lift these clams up off the sandbed and place them either on a flat rock, a large reef plug or in a clamshell and allow the byssal apparatus to attach. This will make the clam portable and allow you to move the clam if the need arises. Basically it provides options and I think options are good. More here and links in blue at the bottom: http://www.wetwebmedia.com/ca/cav1i3/Clam_care/Clam_care.htm -Glen

Giant Clam Species Identification - 02/24/06 I think I sent to wrong email address yesterday.... Nice website! I am trying to identity a couple giant clam specimens so I can read about their individual needs. Attached are photos of these specimens. Any help you can provide in identifying them would be very helpful. You will also notice that the brown clam's mantle is a bit washed out (white) in the middle. At night the incurrent siphon is more round than oval which is also concerning. I have been feeding it a combination of DT's marine live phytoplankton and marine snow typically daily. Lighting is 280 Watts T5 bulbs for 46G tank, both clams are within the top 10" of the tank. Thanks Greg <<Greg, the pictures won't open/are corrupted...do try sending again. Regards, EricR>>

Clam I.D. and care. 1/31/06 hey guys how is everything going. <Great, thanks for asking.> Well i recently purchased a small clam at my LFS and I know its super healthy it reacts to the slightest shadow or movement. I have had it for a week now. The problem is I don't know what type of clam it is. the guy at the store told me he thought it was either a maxima or Crocea. <Looks to be T. Crocea.> I have provided some pics so you can help me out. He is currently sitting about 14" under a custom sea life 130 watt fixture 65 of 10,000k and 65 of actinic. <Move him as close to the top of the tank as possible with this lighting. And remember to change your bulbs at least every 9 months.> I also have moon lights and am feeding him DT's Phytoplankton 3 days a week. any suggestion. <Keep calcium high and water quality stable.> please let me know thanks again. Ohh i almost forgot its a 30 gallon tank. <Adam J.>

Tridacnid ID - 01/28/06 Hello Wet Web Media Friends, <<Hello Darryl>> Like many before I love (like very much) your website... Thank you. <<Good to hear.>> I have the opportunity to purchase a clam, I've been wanting one for a couple years but have felt my tank wasn't ready, it is now a thriving two years old. <<Cool!>> The clam in question is the one in the attached pictures. I am told it is a Tridacna Squamosa but from the research I have done I believe it is a Tridacna Crocea clam, can you confirm my suspicion for me as this will obviously have an effect as to the placement of the clam in my tank (among other things). <<Hmm...the pics are a bit fuzzy, but the absence of 'prominent' scutes (the scalloped projections on the shell), and the color/pattern, lead me to think you are correct.>> I am also concerned about the opening as it seems quite large. It has great coloring and it responds well to the fish swimming by, very responsive opening and closing. <<It does look to be "gaping" a bit...but this may simply be dir to handling/shipping stress. The responsiveness is a good sign.>> I have a 180 gallon tank with 2x250watt 10,000k metal halides, 2 96 watt 10,000k power compact fluorescents and a 96 watt actinic. The clam would be about 8" from the top of the water and directly under a halide that is another 6-8" from the top of the water. It would be sitting on the center of a rock 'plate' that is about 12" in diameter. Would this be a good place for him/her? <<Should be fine, though this is really more light than it "requires" to survive. I have two T. crocea sitting on the bottom of a 30" tank (6" DSB/24" water column) under 250w 10K MH lighting. They have been thriving and growing for more than 18 months now.>> I have already used Wet Web Media and other sources to answer the rest of my questions (assuming I'm correct in the identification:) <<Excellent!>> Thank you for your time, Darryl K. Edmonton, Alberta
<<Welcome, EricR...Columbia, SC>>

Coral question and clam identification? Water quality in 55 gallon tank. PH 8.4 Ammonia 0 Nitrite 0 Nitrate 0 Calcium 340ppm Alkalinity 9.8 dKH Salinity 1.025 Temp 78 - 80 Lighting 1-Actinic 95w VHO 1- Aquasun 95w VHO 1-Actinic 30w Coralife 1- 10,000k 30w Coralife <Okey-dokey> This piece of coral is about 6 inches from the top of the tank and has looked like this for a few days now. <lighting is somewhat weak for this Neptheid (AKA "Kenyan Tree Coral"), but unlikely to elicit this response> It was about 12 inches from the top a few weeks ago and looked good when I moved it but now it looks like this. <perhaps a just acclimating> Is this normal or is it to close to the top of the tank? <definitely not too close... in fact, this beautiful coral will turn turquoise under a bank of VHO blues (2-4 lights)> Also can you please identify this type of clam for me. It has a brownish look to it although it looks a little different in the picture. Thank You. <I would need a better picture to be sure but you may have a very interesting clam here! Tridacnids are rather easy to identify but yours looks like it could be a hybrid of two species known to hybridize. The mantle is conspicuously like a T. squamosa... but the shell does not have the characteristic worn scutes of a T. squamosa, and instead looks worn and ribbed like a T. derasa. Still the picture is not clear enough. A close up of the shell and mantle separately would help if clear. Best regards, Anthony>

Tridacnid clam Hi Bob, <Anthony Calfo in your service> I have a really good relationship with my LFS. <excellent! a blessing that not all aquarists enjoy> Due to this I am able to order some unusual items, and can pick them up on delivery from the suppliers, before they even enter their tanks. For this reason I sometimes have to rely on them for quality, and it works out to be beneficial 99% of the time. However about 3 1/2 months ago I asked for them to get some Tridacnid clams, and gave my list of preference. When I arrived they had hand picked a blue Maxima or derasa (my guess I was too excited to ask) for me still in it's bag and difficult to visualize. <T. maxima it is> When I got home it unfortunately had some brown areas along both sides of the mantle (see picture enclosed). <not unfortunate... perfectly natural and rather common pigmentation> I thought it was just due to being under poor lights and it would recover. <will not change my friend> I have had it for over thee months in my 125g reef. It is within 2 feet of the lights which are 2-140 actinic VHO for 8 hrs/day and directly under one of three 175 cheapie 55K Venture MH for 4 hrs/day. I replaced the MH. about 6 weeks ago as it was slightly yellow, the new one is much whiter. Is this just some normal marking or am I in for trouble. <relax and enjoy this beauty... a nice specimen> The clam is always extended and closes very fast when a fish swims too close. <very good responses...healthy> Any ideas would be appreciated. <Tridacnids are graded by color on export and few of the "cover girl" blue seen in books and magazines make it to the USA. Some Germans and many more Japanese aquarists are willing to pay a much higher dollar for select ultra blue clams than American aquarists. So... we do get some very nice clams... but most/many have variable pigmentation. Your specimen is very nice overall and likely a better deal at under $100 compared to the $300-600 USD needed to get a hand picked (ultra grade) pure blue specimen> Thanks Larry
<best regards, Anthony>
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