C. elegans is a nematode worm that considers as one of the simplest multicellular model organism. It is a free-living soil animal that feeds on microbes in decaying plant environments while in vitro, it mainly feeds on bacterial lawn (40). Sydney Brenner has proposed C. elegans as an experimental model organism and it has been used in biological fields, it played a huge role in the understanding and development in the knowledge about multicellular organisms since 1960s (8). Genetics and organ development, programmed cell death studies, and describing the mechanism of RNA interference (RNAi) led to award Noble prizes in physiology for Sydney Brenner, John Sulston and Robert Horvitz, Craig Mello, and Andrew Fire respectively. …show more content…
elegans life is very short, begins with the embryo stage, followed by an unhatched egg, then the hatched worm develops through four larval stages (L1 to L4) that can be completed in 3 days before it become a 1 mm long adult (11, 41). C. elegans is considered a gonochorist organism, that means it exists in two sexes, hermaphrodite (XX) is the predominant sex and has approximately 959 somatic cells, while the less common sex is the male (X0) that has only 1031 cells (10, 42). The hermaphrodite can self-fertilize, that allows them to lay down about 300 – 350 eggs that would develop to genetic identical progenies (11). The pattern of cell divisions from the fertilized egg to the adult has been completely determined (6). C. elegans lives around 3 weeks and it remains transparent during its whole life cycle, making cell-level examination possible via microscopes. C. elegans goes under survival stage called dauer when there is no sufficient food and it can last up to nearly 4 months without food (46).
The nervous system of C. elegans is well studied, the adult worm has only 302 neuron cells and about 5000 synapse and the complete nervous system of the adult hermaphrodite has been reconstructed from electron micrographs of serial thin sections (7,48,49,50,51). The neurons have simple branching structures, and both the dispositions of cell processes, and the connections they make, appear to be largely invariant between animals. They can be assigned to 118 different 16 neuronal classes on the basis of morphology and synaptic