Pattern formation in the egg of the leafhopper Euscelis plebejus Fall. (Homoptera): Developmental capacities of fragments isolated from the polar egg regions

Abstract

The egg of the leafhopper Euscelis plebejus has been separated into three fragments [for nomenclature, see Sander, K. (1976). Advan. Insect Physiol. 12, 125–238] by two constrictions in order to exclude the middle egg part from possible terminal influences on pattern specification. Middle fragments of freshly laid eggs (two pronuclei or one nucleus) differentiate middle segments of the embryonic pattern. The segment composition of those partial patterns varies with the position of the two constrictions. Eggs subdivided at later stages of development produce similar partial patterns in the middle fragment, but with more segments. The mode of segment expression in single and double fragmented eggs is compatible with the assumption that the metameric pattern is differentiated by a sequence of short-range inductions rather than by an extensive gradient field.