Reproductive potential and nesting effects of Osmia rufa (syn. bicornis) female (Hymenoptera: Megachilidae)

The red mason bee Osmia rufa is a solitary bee belonging to the family Megachilidae, and is prone to nest in aggregations. Each female builds a nest separately in pre-existing cavities such as holes in wood and walls or empty plant stems. This is done by successively setting the cells in a linear series. In this study, we elucidate the nesting behavior and the reproductive potential of a single O. rufa female. The reproductive potential of nesting females was evaluated after the offspring finished development. We observed that an individual female may colonize up to five nest tubes and build 5-34 cells in them (16 on an average). During the nesting time the number of cells decreased with the sequence of nest tubes colonized by one female, which built a maximum of 11 cells in the first occupied nest and 5 cells in the last (fifth nest). Our observations indicated that 40% of nesting females colonized one nest tube as compared to 7% colonizing five nest tubes. Furthermore, in subsequent nest tubes the number of cells with freshly emerged females gradually decreased which was the reverse with males. Thus, the sex ratio (proportion of male and female offspring) may change during the nesting period. The female offspring predominated in the first two nesting tubes, while in the subsequent three tubes male offspring dominated. We also cataloged different causes of reduction in abundance of offspring in O. rufa females such as parasitization or problem associated with moulting

Hormonal Regulation of Response to Oxidative Stress in Insects—An Update

Insects, like other organisms, must deal with a wide variety of potentially challenging environmental factors during the course of their life. An important example of such a challenge is the phenomenon of oxidative stress. This review summarizes the current knowledge on the role of adipokinetic hormones (AKH) as principal stress responsive hormones in insects involved in activation of anti-oxidative stress response pathways. Emphasis is placed on an analysis of oxidative stress experimentally induced by various stressors and monitored by suitable biomarkers, and on detailed characterization of AKH’s role in the anti-stress reactions. These reactions are characterized by a significant increase of AKH levels in the insect body, and by effective reversal of the markers—disturbed by the stressors—after co-application of the stressor with AKH. A plausible mechanism of AKH action in the anti-oxidative stress response is discussed as well: this probably involves simultaneous employment of both protein kinase C and cyclic adenosine 3′,5′-monophosphate pathways in the presence of extra and intra-cellular Ca2+ stores, with the possible involvement of the FoxO transcription factors. The role of other insect hormones in the anti-oxidative defense reactions is also discussed

Effects of aging on the molecular circadian oscillations in Drosophila

Circadian clocks maintain temporal homeostasis by generating daily output rhythms in molecular, cellular, and physiological functions. Output rhythms, such as sleep/wake cycles and hormonal fluctuations, tend to deteriorate during aging in humans, rodents, and fruit flies. However, it is not clear whether this decay is caused by defects in the core transcriptional clock, or weakening of the clock-output pathways, or both. The authors monitored age-related changes in behavioral and molecular rhythms in Drosophila melanogaster. Aging was associated with disrupted rest/activity patterns and lengthening of the free-running period of the circadian locomotor activity rhythm. The expression of core clock genes was measured in heads and bodies of young, middle-aged, and old flies. Transcriptional oscillations of four clock genes, period, timeless, Par domain protein 1ε, and vrille, were significantly reduced in heads, but not in bodies, of aging flies. It was determined that reduced transcription of these genes was not caused by the deficient expression of their activators, encoded by Clock and cycle genes. Interestingly, transcriptional activation by CLOCK-CYCLE complexes was impaired despite reduced levels of the PERIOD repressor protein in old flies. These data suggest that aging alters the properties of the core transcriptional clock in flies such that both the positive and the negative limbs of the clock are attenuated

Table_1_Disruption of Adipokinetic Hormone Mediated Energy Homeostasis Has Subtle Effects on Physiology, Behavior and Lipid Status During Aging in Drosophila.PDF

<p>The impact of disruption of adipokinetic hormone (AKH) signaling was studied during aging in Drosophila in a sexually dimorphic manner. A mutant (Akh¹) producing a non-functional AKH peptide was compared with isogenized wild-type controls (w¹¹¹⁸), and Akh-rescue line where AKH was ectopically expressed in the mutant background (EE-Akh). Longevity, fecundity, and locomotor activity rhythms remained unaffected by lack of AKH signaling. While the strength of rhythms declined in general with age across all fly lines tested this was more so in case of Akh¹ flies. Negative geotaxis was significantly impaired in Akh¹ flies. Only young Akh¹ flies of both sexes and old Akh¹ females showed significantly higher body weight compared to age-matched iso-control flies (except in case of EE-Akh). Expression of genes involved in energy homeostasis and aging indicated that dTOR and Akt expression were elevated in Akh¹ flies compared to other genotypes, whereas AMPK and dFoxO expression levels were significantly reduced. Multivariate analysis of the distribution of lipid species revealed a significant accumulation of specific diglyceride (DG) and triglyceride (TG) lipid species, irrespective of sex, attributable in part due to lack of AKH. Moreover, irrespective of lack of AKH, older flies of all genotypes accumulated TGs. Taken together, the results strongly suggest that disruption of AKH has very subtle effects on physiology, behavior and lipid status during aging.</p