Role of the juvenile hormone on the differentiation of specialized integumental areas, “fenestrae”, in Schistocerca gregaria (Acrididae: Orthoptera)

Abstract

“Fenestrae” or “Slifer's patches” are highly permeable integumentary areas of locusts, segmentally arranged in the adult abdominal terga of males and females. In S. gregaria they arise, after being newly programmed, from epidermal cells, and the developmental pattern proceeds during the last two larval instars. In order to study the mechanism by which the cells that form these areas respond to the hormonal stimulus to change commitment, 4th- and 5th-instar larvae were surgically allatectomized or treated with precocene. When performed within the first 24 h of the 4th-instar, allatectomy, whether surgical or chemical, leads to the appearance of precocious adults, with the integumentary areas on all terga. If removal of the corpora allata is done after that period, the precocious adults have smaller integumentary areas, and if the removal is delayed for 48 h, differentiation of the areas does not occur at all in the last terga. Topical application of juvenile hormone to the sites of the presumptive areas of the 4th-instar larvae, allatectomized during the first 12 h, reduces the specialized differentiation. The presence or absence of juvenile hormone commits the integumentary-area-forming cells to the deposition of larval or specialized cuticle, respectively. The hormonal events during the larval instars and an asynchronism of the integumentary cellular cycle may explain the distribution of these integumentary areas.