Juvenile hormone agonists cause abnormal midgut closure and other defects in the moth, Plodia interpunctella (Lepidoptera: Pyralidae)

Abstract

Summary The midgut fails to close dorsally about 35 h (at 30°C) after newly laid eggs of Plodia interpunctella Hübner are treated by juvenile hormone (JH) agonists. Larvae hatch with malformed guts, but they die within the next 36 h. Midgut closure begins during dorsal closure, a stage during which the ectoderm covers the embryo's dorsal opening. During dorsal closure a normal embryo undergoes blastokinesis, so that the tip of the abdomen bends ventrally and touches the legs of the embryo's first thoracic segment. In embryos treated with JH agonists, the abdomen bends dorsally and the tip of the abdomen almost touches the back of the head. Other defects emerge after treatment with JH agonists. The tracheal system and the Malphigian tubules show abnormalities. The embryonic molt of treated embryos appears to be incomplete and subsequently such an embryo is stuck to its semi-molted cuticle as it endeavors to break out of the egg and fails. A few embryos are severely deformed and lack dorsal closure. They have a reduced tracheal system, few setae, malformed eye spots, and reduced tanning; however, even grossly deformed larvae show muscular contractions and attempt to hatch.