Morphometric changes and the hormonal activity of the corpus allatum in the adult male of the desert locust

Time-course haemolymph juvenile hormone titres in solitarious and gregarious adults of Schistocerca gregaria, and their relation to pheromone emission, CA volumetric changes and oocyte growth

The haemolymph JH III titres in solitarious and gregarious adult desert locusts, Schistocerca gregaria, were examined in relation to corpus allatum (CA) volumes, aggregation-maturation pheromone production in males and oocyte growth in females. The JH titres of gregarious females were generally higher than those of solitarious females at all ages studied. The titre patterns, however, were similar: relatively high on day 10, dropping to low levels between days 20 and 25, before rising again by day 25. In the solitarious males, the JH titre was very low on day 10 after fledging, but increased gradually and reached a maximal amount on day 30. The JH titre in gregarious males was low on day 10, elevated on day 15 coinciding with the start of the production of the pheromone, and dropped to a relatively low level on day 20 around the time of maximal pheromone production, then rising again by day 25. These results suggest that biosynthesis of the pheromone is associated with a high JH titre peak in the haemolymph. Although a clear relationship was found during the first gonadotropic cycle between JH titres, on one hand, and CA volume and oocyte growth, on the other, in both phases, no such correlation could be discerned in the second cycle.

The embryonic diapause of Aulocara elliotti (Orthoptera, Acrididiae). Histological and morphometric changes during diapause development and following experimental termination with juvenile hormone analogue

Progressive hypertrophy of fat body, muscles, gonads and pleuropodial glands was observed with lengthening diapause incubation in embryos of Aulocara elliotti. Embryonic hemolymph stained more darkly and lipoid materials accumulated in the fat body and other tissues. Gradual increase in volumes was observed in the corpora cardiaca, corpora allata and ventral head glands (ecdysial glands). Termination of diapause was achieved in embryos treated with juvenile hormone analogue (JHA) (4 ethyl phenyl 6.7 epoxy geranyl ether--87%, Stauffer Chemical) applied directly to the egg undiluted or when eggs were immersed in a 10% solution in methanol. Treated embryos terminating diapause underwent rapid teratological morphogenesis, achieving pigmentation and sclerotization as in definitive embryos without engulfing their yolk. In treated embryos which remained in diapause, unusual paired masses of pigmented cells, resembling the melanotic pseudotumors of Drosophila, were observed ventral and lateral to the stomodeum and are thought to be subesophageal body cells (pericardial cell homologues). In some embryos these cells were enlarged, lysed or their nuclei rhexic and pycnotic. This response suggests these cells are target organs for JHA, or perhaps for ecdysone or its precursor released by JHA treatment. Endocrine glands in treated embryos had significantly larger volumes (.01) than those of controls or untreated embryos. The ventral head glands of treated embryos appeared to be cytoplasmically depleted. It is suggested that JHA triggered the release of stored ecdysone (or its precursor produced in the ventral head gland) at a rate too rapid for normal morphogenetic processes, such as dorsal closure, to accompany epidermal maturation. The response to JHA cannot be interpreted as juvenilization, but rather must be considered to be precocious maturation. These results indicate that: 1. diapause development involves a transfer of nutrient materials from the yolk into the fat body and other embryonic tissues where they are available to meet the demands of post-diapause morphogenesis; 2. that embryonic diapause in A. elliotti is a consequence of endocrine deficiency which probably results ultimately from the lack of neurosecretory stimulus from the brain-corpora cardiaca complex; and 3. that the subesophageal body cells, and perhaps the pericardial cells, play an essential role in the embryonic physiology, perhaps in the production of carrier protein and/or an essential growth regulator.