Control of larval-pupal-adult molt in the moth Sesamia nonagrioides by juvenile hormone and ecdysteroids.

Sesamia nonagrioides (Lepidoptera: Noctuidae) larvae reared under long day (LD; 16L:8D) conditions pupate after 5 or 6 larval instars, whereas under short day (SD; 12L:12D) conditions they undergo up to 12 additional molts before pupating. This extended period of repeated molting is maintained by high levels of juvenile hormone (JH). Previous work demonstrated that both LD and SD larvae decapitated in the 6th instar pupate but further development is halted.

Gene encoding the prothoracicotropic hormone of a moth is expressed in the brain and gut.

The molts of lepidopteran insects are typically controlled by the brain-derived prothoracicotropic hormone (PTTH) that stimulates ecdysteroidogenesis in the prothoracic glands (PGs). We report here that the larvae and pupae of the moth Sesamia nonagrioides can molt without brain (PGs must be present), suggesting that there might be a secondary source of PTTH. We addressed this issue by characterizing spatial and temporal expression patterns of the PTTH gene.

Brain-independent development in the moth Sesamia nonagrioides.

The caterpillars of Sesamia nonagrioides developing under long-day (LD) photoperiod pupate in the 5th or 6th instar whereas under short day (SD) conditions they enter diapause and undergo several extra larval molts. The diapause is terminated within 1-3 instars upon transfer of SD larvae to the LD conditions. Brain removal from the 6th instar larvae promotes pupation followed by imaginal development; however, one third of the SD larvae and 12% of the LD larvae debrained at the start of the instar first undergo 1-2 larval molts.

Effects of ecdysteroid agonist RH-2485 reveal interactions between ecdysteroids and juvenile hormones in the development of Sesamia nonagrioides.

Larvae of Sesamia nonagrioides developing under long day (LD) conditions pupate in the 5th or 6th instar, whereas under the short day (SD) conditions, they undergo several supernumerary larval molts and are regarded as diapausing. The development in early larval instars occurs in the LD larvae at a moderate and in the SD larvae at a high juvenile hormone (JH) titer; ecdysteroid titer cycles similarly under both conditions. The transformation to pupa is initiated by a burst of ecdysteroids at undetectable JH levels, whereas extra larval molts in the diapausing larvae are associated with moderate JH titer and irregular rises of ecdysteroids.

Relationship between an increase of juvenile hormone titer in early instars and the induction of diapause in fully grown larvae of Sesamia nonagrioides.

The larvae of Sesamia nonagrioides (Lepidoptera: Noctuidae) grown at 25 degrees C and long photoperiod (16:8h light:dark) pupate in the 5th or 6th (mostly) larval instar, while the larvae reared under a short photoperiod (12:12h) enter diapause during which they consume some food and undergo up to 12 (usually 3-4) stationary larval molts. Diapause programming includes an increase of juvenile hormone (JH) titer in the hemolymph from about 20 to 50 nM in the 4th and 5th instar larvae (titer in earlier instars was not measured). JH I, II, and III are present in approximate ratio 1-2:10:1.

Juvenile hormone and diapause in the Mediterranean corn borer, Sesamia nonagrioides.

Juvenile hormone content of Sesamia nonagrioides larvae reared under different environmental conditions that induce diapause was studied using a bioassay on newly-emerged Tribolium confusum pupae. Two analytical methods were also used to measure JHIII content. Extracts from larvae that developed under different conditions of photoperiod and temperature caused different effects in T.

Fate of fumonisins B1 and B2 in steeped corn kernels.

Corn kernels naturally contaminated with fumonisins B1 and B2 were steeped by dipping the whole kernels in either water or a 0.3% solution of sodium bisulphite (pH = 5.7) for 6, 12, 24, 36 and 48 h.