The Larval Development of Imaginal Disks

Larval regulation of adult longevity in a genetically-selected long-lived strain of Drosophila

“…3 coincides with the third larval instar. It has also long been known that the major portion of imaginal disc growth takes place during this period of time (Church & Robertson, 1969;Nothiger, 1972;Bryant, 1987). The body weight data shown in Table 4 support the view that there is some relationship between body weight and the expression of the ELP.…”

On the Inheritance of Differentiated Traits

“…This notion could be tested by removal (for example, by somatic crossing over) of a Y-chromosome that is suppressing the lethal effects of a rearrangement involving both heterochromatin and a sex-linked recessive locus in an X Y male (see Lindsley et al, 1960). The inactivation of genes by position effects occurs very early in development (Baker, 1971 ;Nothiger, 1972;Garcia-Bellido, 1972) so that these parental differentiators can probably act directly at the creation of the differential. Only superstructural differentials can be maintained and replicated in the absence of the differentiators; differentials of other types cannot.…”

“…The imaginal disk cells of the larvae of Drosophila are predestined to give rise to particular adult tissuesfor example, antennae or thorax (Nothiger, 1972;Garcia-Bellido, 1972). The establishment of this predestined or 'determined' state occurs quite early in the development of the larvae and it is inherited for many cell generations before metamorphosis leads to the overt expression of the consequences of a 'determined' state.…”

“…Differentiator molecules in the egg, if not themselves replicated, must become diluted by cell division and so they must also act on small numbers of cells. The 'determination' of imaginal disk cells in Drosophilu does seem to involve small numbers of cells (Nothiger, 1972; Garcia-Bellido, 1972). If the differentials created in these few cells can be replicated and inherited, then' cell division will amplify the numbers of such 'determined' cells.…”

Neoplasia in Poikilotherms

“…The discs arise at definite sites during embryogenesis and consist of groups of epithelial cells which appear strikingly similar morphologically. With the onset of metamorphosis, cell division in the discs ceases and differentiation begins which ultimately leads to formation of their corresponding imaginal structures in the adult (Nothiger, 1972). Hadorn (1966) found that the events of metamorphosis in imaginal discs of Drosophila can be prevented by transplanting them directly into the abdomens of adult flies.…”