The Life and Times of Caenorhabditis elegans

 Behold the mighty Caenorhabditis elegans, a free-living transparent nematode about 1 mm in length that lives in the soil and thrives on eating decaying organic matter. C. elegens has exactly the 959 somatic cells for which the function of each and every one is fully known. (By comparison the human body has about 30 trillion cells, some 30 million times more than C. elegans.)

But what can nature do with only 959 cells? Well, C. elegens has acuticle (a tough outer covering, as an exoskeleton), skin cells, and a fluid-filled body cavity. The basic anatomy includes a mouth, pharynx, intestine, gonad collageneous cuticle and anus. It's reproductive system takes up most of the volume of the animal.  The 10 to 15 day lifespan of C. elegens is taken up with maturation from a fertilized egg (2 days), eating and pooping to sustain life (8 to 13 days) laying fertilized eggs for reproduction and (6 days) (d) hanging out until its 131 preprogrammed death cells cause its death to occur (2 to 7 days).

Some 320 of the C. elegens 959 cells form its neural network. It does not have a brain brain like that in our head but does have a brain like that in our stomach which the neurons are fixed in network to do its "thinking" with sensory signals and initiate subsequent "actions" as a result of its "thinking" process. (And, yes, it also has muscles with enables it to navigate by moving its tail.) That is, it behaves just as humans do but without consciousness or conscious awareness of its environment. 

The DNA of C.elegens is composed of 18,452 protein sequences (genes) of  which 11% are nematode specific and 89% are shared with us  H. sapiens humans.  (By comparison, humans have 20,000 to 25,000 genes of which about 75% are shares with C. elegens). Yes, C.elegens are are close biological cousins.

C. elegens has 302 C. neural cells of which 60 ciliated sensory neurons. some function in chemosensation, like gustation (taste) or olfaction (smell), while others function in thermosensation (temperature), mechanosensation (touch) or proprioception (sense of self-movement, force, and body position). They have no eyes but do have sensors to detect light.

The C. elegans nervous system has around 6393 chemical synapses, 890 gap junctions, and 1410 neuromuscular junctions , through which different signals can be exchanged between neurons and their targets. Like other animals, the worm signals through (a) small molecule neurotransmitters, such as acetylcholine, dopamine, serotonin and γ-aminobutyric acid, which can be released through synaptic vesicles (SVs), and (b) peptide neurotransmitters, such as insulin-like peptides.And, yes, C. elegens can even become addicted to nicotine.

So what does that make us Homo sapiens? That make us to be big nematodes with arms and legs rather than a tail and a big clump of highly organized neural cells in our skull we call a brain with group of cells that perform the same functions as in nematodes but with additional groups of cells which produce sensations and ultimately consciousness.

And what is the purpose of both species? Exactly the same purpose, ie. (a) to live and (b) to reproduce the species. And, indeed, that is the purpose of all living things.