**9. References**


**11** 

**The Growth of Chalcedony** 

*Instituto de Investigaciones Bioquímicas (INIBIBB) CONICET, Universidad Nacional del Sur (UNS) Departamento de Biología, Bioquímica y Farmacia* 

María Prado Figueroa

 *Bahía Blanca, Argentina* 

**(Nanocrystalline Silica) in Electric** 

The Rajidae Family are weakly electric fish (Fessard, 1958). *Psammobatis extenta* (Rajidae Family) is a South American electric fish. Electric organs of the electric fish have constituted the choice system for studying the biochemistry, morphology, physiology and cell biology of the nervous cholinergic system (Barrantes *et al*., 1983; Changeux, 1981; 2010; Fox *et al*., 1990; Prado Figueroa *et al*., 1995; Wittaker, 1977). Electric organs derive embryologically

The electric organs (EO) of *Psammobatis extenta* produce weak electrical discharges to the surrounding environment. Electrocytes have evolved and differential independently, losing the contractile ability. In previous works we employed a microanalysis (EDS-SEM) and documented the presence of aluminium and silicon in significant concentrations. Zinc,

Silicon (Si) is an essential nutrient for animal biology (Carlisle 1982). It has been shown that silicon is required for bone, cartilage and connective tissue formation (Bissé *et al.* 2005). Silicon may function as a biological cross-linking agent and may contribute to the architecture and resilience of connective tissue (Schwarz 1973). Aluminium (Al) and Si accumulations have been detected in electric organs by a combination of scanning electron microscopy and X-ray spectrometry (EDS-SEM) (Prado Figueroa *et al*., 2008). Al and Si have been also detected in the human cerebral cortex from elderly people by using EDS/SEM (Perl and Brody 1980, Candy *et al*. 1985). These inorganic elements are related to

Biomineralization is the process by which living organisms produce minerals, often to harden or stiffen existing tissues. Chalcedony is a microcrystalline fibrous form of silica (SiO2) and it is the product of biomineralization by silica (Erhlich *et al*., 2010). We have identified chalcedony in living fish electric organs by using a standard polarized light microscope (Prado Figueroa *et al*., 2008). In plane-polarized light, chalcedony is rounded in

pathological changes in the human brain (Candy *et al.* 1985, Tokutake *et al*. 1995).

from myoblasts and are constituted by cells called electrocytes.

oxygen and cupper were also localized.

**1. Introduction** 

**Organs from Living Marine Fish** 

