Influence of temperature and carbon dioxide concentration on juvenile hormone titre and dependent parameters of adult worker honey bees (Apis mellifera L.)

It is known that juvenile hormone plays an important role in the regulation of labour division and of the different life spans, and that the microclimate of the bee hive is characterized by its high CO₂ concentration and its varying temperature depending on the presence of brood.We have investigated the influence of microclimates characteristic of breeding and broodless areas on the juvenile hormone titre in the haemolymph and whole body extracts, on the corpora allata in vitro activity, on the degradation of juvenile hormone and on the dry weight of the hypopharyngeal glands using bees of known ages. A microclimate of 35°C and 1.5% CO₂, as observed in the breeding area, induces a rapid and pronounced increase in the juvenile hormone titre. On the other hand, this titre remains low in bees kept at 27°C and 1.5% CO₂, a microclimate associated with broodless combs. Rates of juvenile hormone synthesis by corpora allata in vitro were found to be extremely low, even in the presence of farnesenic acid, and not related to the juvenile hormone titre. In vitro incubation of juvenile hormone in haemolymph revealed no degradation while injected juvenile hormone was found to be degraded and taken up by the gut at rates only weakly correlated with the juvenile hormone titre.We propose a hypothetical model for the regulation of the juvenile hormone titre as well as the course of labour division by the varying microclimates observed in the bee hive.     

Female odours promote the activation of sheltered kissing bug Rhodnius prolixus males and modulate their orientation

The existence of a pheromone emitted during copulation has been reported for Rhodnius prolixus (Hemiptera: Reduviidae) Stål. Adults possess one pair of metasternal glands (MGs) from which female R. prolixus release volatiles mainly at night. We investigated whether these volatiles emitted by adult R. prolixus can modulate sexual‐related behaviours of opposite and/or same sex individuals. We first used a shelter bioassay to test if adult activity patterns can be affected by chemical signals emitted by opposite sex conspecifics. We observed that males left the shelter more frequently in the presence of females, showing higher activity and an increase of intrasexual copulation attempts. Females showed no shelter‐related activation in the presence of male odours. Second, we used a locomotion compensator device to investigate whether females or males show oriented responses to odours emitted by adults. We found that males oriented towards air currents carrying female odours but females did not orient towards odours emitted by adults. Finally, we observed that males oriented towards the female MG compounds. Thus, a volatile chemical signal emitted by females from their MGs promoted the activation of sheltered males and modulated orientation to air currents.     

Juvenile hormone involvement in Drosophila melanogaster male reproduction as suggested by the Methoprene-tolerant mutant phenotype

Juvenile hormone (JH) involvement in male reproduction is poorly understood. In Drosophila melanogaster adults, JH deficiency has been shown to result in lowered protein synthesis in male accessory glands. To probe additional roles, we have examined males homozygous for a null allele of Methoprene-tolerant (Met). This gene is involved in the action of JH, possibly at the JH receptor level, and Met²⁷ null mutants reflect a diminution of JH action. Met²⁷ males were found to have reduced protein accumulation in male accessory glands and to court and mate wild-type females much less avidly than do either Met⁺ or Met²⁷; Met⁺ transgenic males. Exposure of Met²⁷ males to methoprene partially rescued the courtship deficiency. However, sperm transfer as reflected by fertility of Met²⁷ fathers was found to be similar to that of Met⁺. Taken together with previous work examining the JH-deficient mutant apterous, these results corroborate JH involvement in protein synthesis in the male accessory glands and suggest a role for JH in promoting male mating behavior in these flies.     

Dose-dependent influence of Campoletis sonorensis polydnavirus on the development and ecdysteroid titers of last-instar Heliothis virescens larvae

Campoletis sonorensis calyx fluid arrests the development of last-instar Heliothis virescens larvae and is associated with the gross degeneration of the host's prothoracic glands. Through manipulations of ovary supernatant, Campoletis sonorensis polydnavirus (CsV) was found to be the only component of calyx fluid responsible for causing host developmental arrest. Venom from C. sonorensis had no effect on host development. Suspensions of CsV were quantified, and various doses were injected into last-instar hosts. The percentage of larvae developmentally arrested was dose dependent. In addition, larvae not arrested by injection with CsV suspensions were developmentally delayed in a dose-dependent manner. Hosts were delayed in the stage in which they were injected and, after recovery, developed at normal rates. Measurements by radioimmunoassay indicated that developmental delay was due to a suppression of ecdysteroid titers. After a dose-dependent period of suppression, hemolymph ecdysteroid titers recovered and reached titers comparable to those observed in saline-injected controls. Examination of prothoracic glands from developmentally delayed larvae revealed that partial degeneration occurred. Comparisons of the number and mean size of surviving gland cells and the length of developmental delay suggested that surviving gland cells may compensate for degenerated cells by increasing their ecdysone production.     

“Male factors” in ticks: their role in feeding and egg development

Summary

Female ticks of the family Ixodidae utilize their salivary glands as the major organs for fluid balance, secreting back into the host a dilute saliva. Feeding is composed of three phases: a preparatory phase (1–2 days) during which the tick establishes the feeding lesion, a slow phase (~7 days) during which body weight increases 10-fold, and a rapid phase (~1 day) in which body weight increases a further 10-fold. Following engorgement, the salivary glands are resorbed by an autolytic process triggered by an ecdysteroid hormone. If a female is removed from the host prior to repletion, her subsequent behaviour depends mostly on two factors: the degree of engorgement achieved and whether or not she has mated. If removed during the preparatory or slow phase of engorgement, the salivary glands are not resorbed, the tick will lay virtually no eggs and she will reattach to a host if given the opportunity, all of this irrespective of whether she is virgin or mated. If removed during the rapid phase of engorgement, however, mated females will not reattach to a host even if given the opportunity. Instead, they will resorb the salivary glands within 4 days post-removal and lay a batch of eggs. Virgin females removed after exceeding 10-fold the unfed weight likewise refuse to resume feeding if given the opportunity, but salivary gland reabsorption is delayed (to 8 days post-removal); if any eggs are laid, they are infertile. A number of chemical “factors” entering the female during copulation influence her feeding behaviour and egg development. Here we discuss the complexities of these interactions and suggest how they might be adaptive to ticks in nature.     

A comparative ultrastructural study on ultimobranchial glands of some Israeli anurans (Bufo viridis,Rana ridibunda and Hyla arborea)

Summary The comparative fine structure of ultimobranchial (UB) glands of adult Israeli anurans (Bufo viridis, Rana ridibunda, Hyla arborea) taken in the wild during the breeding season is presented. Common aspects of the UB secretory cells are considered with especial reference to secretory granules, lipid droplets and tonofilaments. In B. viridis a second cell type with large electron-dense cytoplasmic granules is found in UB follicles. R. ridibunda and H. arborea UB follicles have a second cell type similar to goblet cells in appearance and these appear to be discharging their mucoid contents into the lumina of the follicles. The possible significance of these various cell types is considered.I am indebted to the Central Research Fund of London University for an award for apparatus and travel enabling a short research visit to the Dept. of Zoology, The Hebrew University, Jerusalem and am particularly indebted to Dr. Dvorah Boschwitz and her colleagues for their enormous help during my visit. I would also like to thank Alan D. Phillips for his assistance in the analysis of the material made possible by an award from the Science Research Council. My thanks are also due to Raynor L. Jones for his excellent technical assistance.     

Chemotaxonomy of water beetles based on their pygidial gland constituents

The mainly aromatic pygidial gland constituents of 45 water beetle species (Hydradephaga; Dytiscidae, Haliplidae) have been investigated. Chemical data were obtained by mass spectrometry, thin layer and gas chromatography and UV-spectrometry. Investigations on Agabus melanarius showed these gland substances were species specific and constant. Seasonal quantitative variations are probably due to variations in population structure and overwintering bionomics. The phylogenetic tree based on the distribution of pygidial gland constituents shows that taxa fall into three chemical groups (sesquiterpenes, aromatic compounds, hydroxycarboxylic acids). This grouping is generally in accordance with other taxonomic conceptions. Other chemical differences correspond to the morphology of the larva and pupa (Copelatus, Hydroporus melanarius). The position of several chemically diverging taxa (Haliplidae, Laccophilinae, Hydaticus) should be clarified by using further techniques such as morphology or considering the biogenesis of the water beetle compounds.