Do Clams Have Eyes?

[GuyWalker1219]

Do Clams Have Eyes?
By Guy Walker on Jan 03, 2013

​

Recently I was asked by a fellow reefer "Do clams have eyes? If not how do they know something is close to retract there mantles so quickly?" It was refreshing to be asked a question I had not heard before in my 20+ years in the hobby nor did I know the answer. The question kept returning to my thoughts throughout that day so I began researching the topic and not only do tridacnid clams have eyes, their eyes even contain zooxznthellae. Tridacna clams have hundreds of eyes along the edges of their siphonal tissue (mantle). T. crocea and T. maxima can also have eyes on top of raised tubercles scattered over the mantle surface. These eyes are used mostly to detect shadows, which warn the clam of potential predators. The eyes are also sensitive to green, blue, and ultraviolet light. This helps the clam to position itself toward the light to expose as much zooxanthellae as possible. The eyes may also function to detect excessive amounts of potentially harmful UV wavelengths. So next time your gazing upon that awesome clam at the local fish store remember it may very well be looking right back at you. ​

 

[sutton6989]

One of my friends asked me this about my clam and I had no idea.. thanks for the awesome info

Sent from my SAMSUNG-SGH-I777 using Tapatalk 2

 

[deuce]

I have two clams in my tank and I never knew that they are looking back at me, changes how I look at them

 

[alberthiel]

Believe it or not, but I am sure you do, most hobbyists who keep clams in their tanks IMO know far too little about them and as a result run into problems with them. One question I get asked a lot is what are the threads on the bottom of the Clam ... and you may have been asked the same thing quite a few times. For those who do not know they are called the Byssal theads or gland and it is important when buying a clam that they are not damaged when the clam is removed from whatever tank they are in, or when moving a clam in one's own aquarium. You may want to write an article about the Byssal threads as well ... just a thought FWIW

 

[GuyWalker1219]

Believe it or not, but I am sure you do, most hobbyists who keep clams in their tanks IMO know far too little about them and as a result run into problems with them. One question I get asked a lot is what are the threads on the bottom of the Clam ... and you may have been asked the same thing quite a few times. For those who do not know they are called the Byssal theads or gland and it is important when buying a clam that they are not damaged when the clam is removed from whatever tank they are in, or when moving a clam in one's own aquarium. You may want to write an article about the Byssal threads as well ... just a thought FWIW

Thank you very much Albert I'm honored to receive feedback from someone with so much experience and expertise in this hobby. I think I will take you up on that suggestion and write that article I have also been thinking of writing something about predatory flatworms. I am by no means an expert on clams but have been keeping them for several years now and agree with you most people who own them know far to little about them. At one time I had a total of 26 clams calcium demand was insane another thing people do not think about when purchasing clams. Again thanks for the feedback and would love to hear any suggestions you may have.

 

[Zack]

26 clams? How much calcium were you having to dose to keep a stable calcium level?

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[Socoreefer]

Funny thing is , I asked myself the other nite if they had eyes ! Lol

 

[BigJohnWoody]

This is really interesting. I have 2 clams and when I read this I chuckled to myself while clicking on it. I was sure that I knew the answer and that it was no. Been doing this for close to three years now and still feel like a total noob. This is definitely one of those hobbies where you are always a noob. Really makes me stop and think how I answer questions of people just starting because we were all there at one time. Great write up and thank you!

 

[jedimasterben]

Mind = Blown

 

[skinz78]

Mind = Blown

Hahaha good one!

 

[alberthiel]

Thank you very much Albert I'm honored to receive feedback from someone with so much experience and expertise in this hobby. I think I will take you up on that suggestion and write that article I have also been thinking of writing something about predatory flatworms. I am by no means an expert on clams but have been keeping them for several years now and agree with you most people who own them know far to little about them. At one time I had a total of 26 clams calcium demand was insane another thing people do not think about when purchasing clams. Again thanks for the feedback and would love to hear any suggestions you may have.

Ys indeed, more info on Clams would help a lot of people IMO, and if you have kept that many I suspect that you could write a whole series of articles on them indeed, covering such topics as the mantle, eyes for sensing movement an light, siphons, pests such as boring snails and pyramid ones (Pyramidellidae), pinched mantle disease and more.

On flatworms though that is IMO such a vast topic that it may not be that easy to cover as you would have to cover more than just the plan aria but also pest red bugs, black bugs, parasitic and non parasitic ones, then there is AEFW, and even the large clam flatworm, and more if you go into parasitic copepods such as Tegastes and Parategastes, and even sea spiders that attack corals such as Acropora ... in essence such a wide topic that it would take a lot of articles to cover all of them. In my new book Nano Reef Aquariums I think the section on them is well over 25 pages, and I have not even covered all of them. It is another one of those areas that a lot of hobbyists are not really familiar with IMO .. I believe it is a good topic but would require a lot of research and a large number of articles ... but yes it is certainly a good topic even if you do not cover them all. If I can be of any help let me know.

 

[alberthiel]

Funny thing is , I asked myself the other nite if they had eyes ! Lol

And as you found out they do indeed !

 

[alberthiel]

Mind = Blown

Good to see you here Mr Ben ...

 

[alberthiel]

Hahaha good one!

Yes the JediMaster always finds good ones indeed, and if you need to find anything out about Lighting and LED's he is the definite source to go to !

 

[skinz78]

Ys indeed, more info on Clams would help a lot of people IMO, and if you have kept that many I suspect that you could write a whole series of articles on them indeed, covering such topics as the mantle, eyes for sensing movement an light, siphons, pests such as boring snails and pyramid ones (Pyramidellidae), pinched mantle disease and more.

On flatworms though that is IMO such a vast topic that it may not be that easy to cover as you would have to cover more than just the plan aria but also pest red bugs, black bugs, parasitic and non parasitic ones, then there is AEFW, and even the large clam flatworm, and more if you go into parasitic copepods such as Tegastes and Parategastes, and even sea spiders that attack corals such as Acropora ... in essence such a wide topic that it would take a lot of articles to cover all of them. In my new book Nano Reef Aquariums I think the section on them is well over 25 pages, and I have not even covered all of them. It is another one of those areas that a lot of hobbyists are not really familiar with IMO .. I believe it is a good topic but would require a lot of research and a large number of articles ... but yes it is certainly a good topic even if you do not cover them all. If I can be of any help let me know.

There are lots of sticky's in the clam forum that cover these topic's, although there isn't one on flatworms.

 

[alberthiel]

There are lots of sticky's in the clam forum that cover these topic's, although there isn't one on flatworms.

I will have to take a look at them. Thanks for pointing it out ... and on Flatworms .. there is one real large one that is a pest and will kill a Clam but the smaller ones e.g. Planaria are not that frequently a problem for Clams. What can be a problem is fireworms that crawl on and sometimes in the Clam through one of the siphons or chew away at the byssal filaments and try to get inside the clam through the bottom. Pyramid snails are a bigger problem and so are boring sponges but out of all pests of Clams flatworms are not the major problem unless you are thinking of a specific, the same as the large one I am referring to.

Here is a picture of it :

(from my new book from the section on Clam pests)

 

[GuyWalker1219]

Ys indeed, more info on Clams would help a lot of people IMO, and if you have kept that many I suspect that you could write a whole series of articles on them indeed, covering such topics as the mantle, eyes for sensing movement an light, siphons, pests such as boring snails and pyramid ones (Pyramidellidae), pinched mantle disease and more.

On flatworms though that is IMO such a vast topic that it may not be that easy to cover as you would have to cover more than just the plan aria but also pest red bugs, black bugs, parasitic and non parasitic ones, then there is AEFW, and even the large clam flatworm, and more if you go into parasitic copepods such as Tegastes and Parategastes, and even sea spiders that attack corals such as Acropora ... in essence such a wide topic that it would take a lot of articles to cover all of them. In my new book Nano Reef Aquariums I think the section on them is well over 25 pages, and I have not even covered all of them. It is another one of those areas that a lot of hobbyists are not really familiar with IMO .. I believe it is a good topic but would require a lot of research and a large number of articles ... but yes it is certainly a good topic even if you do not cover them all. If I can be of any help let me know.

The Polyclad flatworm (phrikoceros mopsus) would be my subject. I have had a few experiences with this flatworm over the years and have to admit although deadly to clams I find them to be fascinating creatures. I remember the first time I had seen one years ago gliding over a large rock and then disappearing and thinking how it reminded me of a science fiction movie creature. This is the sign of a true reef nerd I guess even though these guys have caused me some misery in the past I can see the beauty and be fascinated by such a creature. Thank you for the offer of help I am sure you will receive a few PM's from me asking advice and I truly appreciate it.

 

[alberthiel]

The Polyclad flatworm (phrikoceros mopsus) would be my subject. I have had a few experiences with this flatworm over the years and have to admit although deadly to clams I find them to be fascinating creatures. I remember the first time I had seen one years ago gliding over a large rock and then disappearing and thinking how it reminded me of a science fiction movie creature. This is the sign of a true reef nerd I guess even though these guys have caused me some misery in the past I can see the beauty and be fascinated by such a creature. Thank you for the offer of help I am sure you will receive a few PM's from me asking advice and I truly appreciate it.

I agree with you that there are at least two aspects to everything of that nature:

- its deleterious effects and nature and what it can cause to happen
- its beauty as a life form, abstracting what it causes to happen

And I feel like you that one can be fascinated by the beauty of even the worst of animals or life forms, and their mode of living, feeding, behaving etc. even if OTOH when writing about it in the context that you are going to, its predatory nature is what will be highlighted the most of course.

Phrikoceros has several species as you probably know but I am not sure whether they are all predatory on Clams large and small, but P. mopsus has definitely been identified as such.
P. baibaiye
P.diadaleos
P. fritillus
P. galacticus
P. katoi
P. mopsus

Look forward to seeing the article and as I said if you need any help or have questions feel free to ask ... Kindly
Albert

 

[Reef Breeders]

Yes, clams have primitive light sensing "eyes" called eye spots on the edge of their mantles. That is why they react suddenly when a shadow passes over, or a fish swims by.

 

[Jgomez324]

Good write Up!!