Soft Dentin Results in Unique Flexible Teeth in Scraping Catfishes

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press ABSTRACTTeeth are generally used for actions in which they experience mainly compressive forces acting toward the base. The ordered tooth enamel(oid) and dentin structures contribute to the high compressive strength but also to the minor shear and tensile strengths. Some vertebrates, however, use their teeth for scraping, with teeth experiencing forces directed mostly normal to their long axis. Some scraping suckermouth catfishes (Loricariidae) even appear to have flexible teeth, which have not been found in any other vertebrate taxon. Considering the mineralized nature of tooth tissues, the notion of flexible teeth seems paradoxical. We studied teeth of five species, testing and measuring tooth flexibility, and investigating tooth (micro)structure using transmission electron microscopy, staining, computed tomography scanning, and scanning electron microscopy-energy-dispersive spectrometry. We quantified the extreme bending capacity of single teeth (up to 180Њ) and show that reorganizations of the tooth (micro)structure and extreme hypomineralization of the dentin are adaptations preventing breaking by allowing flexibility.Tooth shape and internal structure appear to be optimized for bending in one direction, which is expected to occur frequently when feeding (scraping) under natural conditions. Not all loricariid catfishes possess flexible teeth, with the trait potentially having evolved more than once. Flexible teeth surely rank among the most extreme evolutionary novelties in known mineralized biological materials and might yield a better understanding of the processes of dentin formation and (hypo)mineralization in vertebrates, including humans.

Evolution of long-toothed fishes and the changing nature of fish–benthos interactions on coral reefs

“…Scale bars represent 500 mm, 100 mm and 500 mm, respectively. NATURE COMMUNICATIONS | DOI: 10.1038/ncomms4144 ARTICLE flexible, elongate, closely spaced teeth [32][33][34][35][36] , similar to those seen in specialized detritivores on coral reefs. The similarity in morphology between marine and freshwater groups reflects a common challenge, selectively removing fine particulate material from algal turfs on a hard substratum (the epilithic algal matrix, EAM on reefs 37 and aufwuchs in the African rift lakes 33 ).…”

A functional evaluation of feeding in the surgeonfish Ctenochaetus striatus : the role of soft tissues

“…Specialized lip structures are also used by the suckermouth catfishes (Loricariidae) in freshwater systems. While many of these catfishes possess elongated teeth similar to those of Ctenochaetus [ 22 , 53 , 54 ], the catfishes feed quite differently, utilizing modified lip discs to adhere to the substratum while feeding [ 55 , 56 ]. The lips of suckermouth catfishes are covered in papillae and like the adhesive discs of Gobiesocidae [ 57 ] this morphology helps the fish ‘seal’ to uneven surfaces.…”

Functional and evolutionary anatomy of the African suckermouth catfishes (Siluriformes: Mochokidae): convergent evolution in Afrotropical and Neotropical faunas

“…Again, only in Loricariidae a high degree of interspecific variation in tooth shapes is seen, including bendable teeth in several genera (Geerinckx et al. ).…”

“…This is seen in both Neotropical families as well, that also obviously wear down their teeth while scraping them. Again, only in Loricariidae a high degree of interspecific variation in tooth shapes is seen, including bendable teeth in several genera (Geerinckx et al 2012).…”