Aesthetes are organs in

chiton Chitons () are marine molluscs of varying size in the class Polyplacophora ( ), formerly known as Amphineura. About 940 extant and 430 fossil species are recognized. They are also sometimes known as sea cradles or coat-of-mail shells or suck ...

s, derived from the mantle of the organism. They are generally believed to be tiny 'eyes', too small to be seen unaided, embedded in the organism's shell, acting in unison to function as a large, dispersed,

compound eye A compound eye is a Eye, visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidium, ommatidia, which are tiny independent photoreception units that consist of a cornea, lens (anatomy), lens, and p ...

. However, in 2013 studies suggested that aesthetes may serve the function of releasing material to repair the

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods an ...

, a

proteinaceous Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respon ...

material covering the shell and protecting it from abrasion. This turned out to be false, as it was conclusively demonstrated in November 2015, that aesthetes are image forming eyes. This layer is constantly worn away by waves and debris as a function of their rugged habitat, and must be continuously replaced to protect the shell. Some chitons also have larger lens-bearing eyes.

References

Chitons Mollusc anatomy {{Chiton-stub