Post on 30-Dec-2015
description
transcript
SIU SOM Logo
Microtome for cutting ultrathin tissue sections
Panulirus interruptus, the California spiny lobster
Stomatogastric ganglion
Synaptic contacts within a small region of nervous tissue
Shape of one nerve cell
(in lobster stomatogastric ganglion)
Reconstructing cell shape from sections
Drosophila melanogaster, the laboratory fruit fly
Head
Thorax
Abdomen
the cardia in the fly digestive tract
Elaboration of cardia structure, along the main line of fly evolution
in cross section of fly nerve cord“Giant” nerve fibers ( * )
Giant fibers conduct signals from antennae to flight muscles.
Drosophila melanogaster
Muscina pascuorum
Minettia magna
Fly species differ in their distributions of nerve-fiber diameter.
Tipulidae, Tipula bicornis Forbes Lauxaniidae, Minettia magna (Coquillett)
Tabanidae, Tabanus calens Linnaeus Syrphidae, Helophilus fasciatus Walker
Bombyliidae, Sparnopolius sp. Bombyliidae, Poecilanthrax sp.
How can evolution adjust the properties of individual nerve cells?
Charles Darwin Letter to T.H. Huxley 1859
One point which has greatly troubled me; . . . what the devil determines each particular variation? What makes a tuft of feathers come on a cocks head, or moss on a moss rose?