Fate map of the eye-antennal imaginal disc in the stalk-eyed fly Cyrtodiopsis dalmanni.

Hypercephaly, in the form of lateral extensions of the head capsule, is observed in several families of Diptera. A particularly extreme form is found in diopsid stalk-eyed flies, in which both eyes and antennae are laterally displaced at the end of eyestalks. We have studied the developmental basis of this exaggerated morphology in Cyrtodiopsis dalmanni. Diopsid eye-antennal imaginal discs are divided into anterior and posterior portions, which are joined by a narrow "disc-stalk" of intervening tissue. We established a fate map for this disc by cutting it into fragments and culturing them in vivo by injecting them into host larvae. The adult eye and dorsal head capsule structures, including the eyestalk and the ocelli, are derived from the posterior portion of the disc, while ventral adult structures such as the antenna and the palpus are derived from the anterior portion of the disc. Thus both posterior and anterior disc portions give rise to structures that are widely separated in the adult head. Moreover, structures that are adjacent in the adult are derived from different regions of the disc. These results confirm and extend previous conclusions about regional identity in diopsid eye-antennal discs that were based on the analysis of molecular markers.