Enrichment of metals in the jaws of fossil and extant polychaetes - distribution and function

Jawed polychaete annelids are successful in modern oceans, lust as they wer e in early Palaeozoic oceans: the fossil evidence bears witness to abundant and taxonomically diverse faunas. The jaws are composed of sclerotized pro teins and were used for grasping in sediment or capturing prey and therefor e needed to be resistant to wear. A nuclear microprobe, Particle-Induced X- ray Emission (PIXE) and Scanning Transmission ion Microscopy (STIM) techniq ues revealed all enrichment of metals, commonly Zn, Fe and Cu, concentrated mainly at the tips or delicate parts of the jaws. This suggests that accum ulation was regulated by the animal and that these elements had functional significance. Similar enrichment was detected in the jaws of Recent Polycha eta and has also been reported in stress-related, 'tool-like' exoskeletal s tructures of other animal groups, including arthropods, chaetognaths and mo lluscs. square Annelida, polychaete jaws, scolecodonts, fossil, extant, PIX E, STIM, metals, function.