Caenorhabditis elegans
C. elegans is a nematode about 1 mm in length, and lives in the soil, especially rotting vegetation, in many parts of the world. Its average life span is about 2-3 weeks.
It has a nervous system with a ‘brain’ (the circumpharyngeal nerve ring). It exhibits behavior and is even capable of rudimentary learning. Neural structures include sensing organs in the head which responses to taste, smell, temperature and touch—and although C. elegans has no eyes, it can respond slightly to light. Caenorhabditis elegans is very well studied. Their whole genome was sequenced and it is the only creature to have had its neural system completely simulated. Open Worm Project
Here are some microscopy images and videos I took. (will be updated shortly)