The free-living nematode Caenorhabditis elegans, 1 mm long, grows on an agar plate, feeding on a lawn of Escherichia coli bacteria. (a) An experimenter selects an individual worm with a platinum wire. (b) A developing population with adults, juveniles and eggs. (c) Two adult worms mating, along with larval worms and eggs. The two sexes are a male and a self-fertile hermaphrodite, which is a female that makes 300 of its own sperm. The male, the smaller adult worm, has the copulatory organ at its tail anchored at the hermaphrodite mid-body vulva. Its sperm will also fertilize the hermaphrodite's eggs. Images provided by the author.
The C. elegans nervous system. Top: diagrams from ‘The mind of a worm’ [1, figs 6 and 7]. Bottom: a worm expressing the fluorescent protein GFP in its entire nervous system. The hermaphrodite nervous system contains precisely 302 neurons, the male, 383 (46% of its somatic nuclei). The nerve ring surrounding the pharynx contains complex circuitry governing most aspects of behaviour. This is the closest thing the worm has to a ‘brain’. The ventral nerve cord contains motorneurons that govern undulatory locomotion. Many sensory neurons have endings arrayed around the mouth. The extra male neurons are mostly situated in the tail where they form the circuits for mating. (Picture from Hang Ung, Jean-Louis Bessereau laboratory, France, with permission.)
Large paper prints were marked with Rotring Rapidograph coloured pens to trace neurons through the stack of images. Movie film reel of serial EM images shown in the background. (MRC archives, Hall laboratory, Albert Einstein College of Medicine.)