Nanostructures in diatom frustules: Functional morphology of valvocopulae in cocconeidacean monoraphid taxa

Nanopositioning is one of the most intriguing challenges in nanoelectronics and photonics. As the optoelectronic circuit components become more and more complex, the importance of nanopositioning becomes critical. For example, in single-mode fiber telecommunications it is easy to show that an alignment deviation as small as a few tens of nanometers can yield to 50 percent of loss performance. Diatoms are unicellular plants occurring in almost every aquatic environment. Their main morphological character is the frustule, a silica cell wall that consists of two valves, encasing the protoplasm, joined together by a girdle. The girdle is composed of a series of silica bands (copulae) linked together along their margins. In several diatom species, the first girdle bands (valvocopulae), which associate the valves with the rest of the girdle, appear different in shape and bring specific nanostructures devoted to facilitate this linkage. The species of the diatom family Cocconeiclaceae show elaborate linkage systems between the valves in which functionally complex valvocopulae are involved. Different levels of complexity and functional efficiency are recognizable in the valve-valvocopula and valvocopula-valvocopula linkages of different cocconeiclacean taxa. This work briefly reviews the morphological characteristics and the functional role of the nanostructures involved in the linkages; in fact, we firmly believe that they are stimulating models for design and manufacturing engineers working in the technological nanoworld.