A gradient of morphogenetic information involved in muscle patterning.

The results of grafts performed in the larva of the beetle Tenebrio molitor reveal that the position at which certain adult muscle attachments form is specified by a regulative, rather than a mosaic, mechanism. The results of grafts involving the rotation of squares of integument through 180 degrees or 90 degrees, or the antero-posterior transposition of two adjacent rectangles of integument, show that the site of muscle attachments in the antero-posterior axis of an abdominal sternite is specified by an epidermal segmental gradient of positional information. This gradient is presumed to be identical to the gradient which specifies cuticular patterns in this insect. There is a good correlation between the effect of grafts on adult muscle morphology and cuticular patterns.