Structure and development of neuronal connections in isogenic organisms: variations and similarities in the optic system of Daphnia magna.

It is readily apparent upon examination and comparison of organisms of the same and related species that to a large extent genes control morphological features. One means to ascertain the role and degree of genetic control is to study in detail the anatomy and development of a particular structure, say an identifiable neuron, in a population with a fixed genome, and at different stages of morphogenesis. The small crustacean, Daphnia, is well suited for this type of study, since it reproduces parthenogenically, its development is easily staged, and its nervous system is reasonably simple. In this paper comparisons of detailed morphology of neurons in the visual system of adult Daphnia magna are considered. Results indicate that gross features of the system are reproduced within the clone, but some of the finer details are not reproduced.