Reef Chemistry Question of the Day #35 Mollusk Teeth

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #35

The radular teeth of mollusks can contain substantial amounts of:


A. Silicon and iron
B. Potassium and cobalt
C. Boron and sulfate
D. Sodium and chloride
E. Zinc and bromide

Good luck!

























.

 

[WindeyD]

Guessing D

 

[ritter6788]

Since the teeth are used to scrape I'm guessing A.

 

[Sam8fish]

Definitely A.

 

[DFW]

E??

 

[Velodog2]

It is A.

 

[Randy Holmes-Farley]

And the answer is...A. Silicon and iron This was a tough question. Good answers!

It turns out that the teeth (called radula) of many mollusks contain substantial silicon. The teeth are used for scraping algae from rocks (or glass in reef tanks). Consequently, they rapidly wear down and are quickly replaced. These radula are quite chemically complex, containing lots of different ions. The exact chemical composition is dependent on the species and family. The radula of limpets, such as Patella vulgata, contain large amounts of Si (up to 35%) and Fe (up to 51%), and substantial amounts of Al, Ca, K, Mg, Na, and P. The radula of chitons seem to be more variable, with Zn in particular varying substantially between species.

It seems likely that these and other mollusks get the silicon necessary to form their radula from diatoms that they consume, rather than from the water column. However, if reef tanks are kept artificially low in silica, and do not have much in the way of diatoms for the mollusks to consume, it is a possibility that these organisms may become deficient in silicon. It has been claimed by some hobbyists that many mollusks do not live as long in reef aquaria as they do in the wild, although I’ve not seen any definitive data in this respect. Many hypotheses have been proposed, and it stands to reason that a deficiency in silicon might be considered as one of the possibilities, if, in fact, mollusks die prematurely in reef tanks.