Hypomorphic mutation of the <Emphasis Type="Italic">dilp6</Emphasis> gene increases DILP3 expression in insulin-producing cells of <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The effect of strong hypomorphic mutation of the insulin-like protein DILP6 (dilp6), synthesized in the fat body, on the expression intensity of insulin-like protein DILP3 synthesized in median neurosecretory cells (MNCs) of D. melanogaster brain was examined. The intensity of DILP3 expression in the MNCs of the larvae was evaluated immunohistochemically using antibodies against DILP3 and confocal microscopy. For the first time, it was demonstrated that, in dilp6 ⁴¹ mutants, there was a sharp increase in DILP3 expression level. The data obtained indicate the existence of negative feedback coordinating the expression of insulin-like proteins synthesized in MNCs and peripheral tissues of Drosophila.     

Role of arylalkylamine <Emphasis Type="Italic">N</Emphasis>-acetyltransferase in regulation of biogenic amines levels by gonadotropins in <Emphasis Type="Italic">Drosophila</Emphasis>

The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the arylalkylamine N-acetyltransferase (AANAT) was studied in young females of wild-type D. virilis and D. melanogaster. 20E feeding of the flies led to a decrease in AANAT activity in both species when dopamine (DA) was used as substrate, but did not affect the enzyme activity when octopamine (OA) was used as substrate. JH application increased AANAT activity with DA as substrate in both species, but did not change it with OA as substrate. AANAT activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous ^56f . A decrease in the enzyme activity was observed in the mutant females as compared to wild-type. Mechanisms of regulation of DA level by gonadotropins in Drosophila are discussed.     

Volatile chemical release by bethylid wasps: identity, phylogeny, anatomy and behaviour

The structures of volatile chemicals released by parasitic wasps in the family Bethylidae are shown to correspond to the subfamily to which the species belong. Species in the Epyrinae release skatole (3-methylindole) and species in the Bethylinae release a spiroacetal (2-methyl-1,7-dioxaspiro [5.5]undecane): these compounds are chemically very different. The enantiomeric composition of the spiroacetal differs between congeneric species. Chemical release is a discrete event under the active control of both male and female wasps. Structural differences between the mandibular glands and intramandibular glands suggest the mandibular glands to be the source of released volatiles. Real-time mass spectrometry shows that the spiroacetal is released by Goniozus nephantidis females during dyadic resource contests, with release more common during more aggressive interactions. Chemical tagging with deuterium further shows that the volatile is released by the loser of an agonistic interaction and not the winner. The function of spiroacetal and skatole release by bethylids is discussed.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 837–852.     

Physical forces constrain the depth distribution of the abundant native mussel Elliptio complanata in lakes

1. Unionid mussels often account for a large portion of benthic biomass and contribute to nutrient cycling and sediment processes, but are thought to be limited to shallow areas (<2–3 m). 2. The depth distribution and body size of Elliptio complanata were compared in seven Canadian Shield lake basins of different sizes to test what factors determine the upper and lower limit of their depth range. Specifically, I tested whether (i) the upper range of their distribution is limited by exposure to winds and wave action and (ii) the lower range of their distribution is limited by the depth of the thermocline or by the boundary of mud deposition. 3. The average depth distribution of E. complanata shifted to greater depths in larger lake basins. When comparing individual transects, maximum mussel density was found deeper at more exposed sites. Mussel size decreased with increasing depth and was larger, on average, in larger lake basins. These results suggest that physical forces limit the upper range of mussel distribution in lakes. 4. The maximum depth at which mussels were found in different lakes was closely related to thermocline depth. However, mussels were commonly observed below the predicted depth of the mud deposition boundary. The thermocline limits the lower range of mussel distribution in lakes, probably by limiting food availability and by determining water temperature. Substratum type does not limit the lower distribution of mussels. 5. These results suggest that unionid mussels are present in the deeper parts of the littoral zone, especially in large lakes. Therefore, comparisons of mussel populations between sites and between lakes would be biased unless the full depth distribution of these mussels is considered. These results also suggest that long‐term changes in the thermal structure of lakes could affect the range of unionid mussel populations and their functional role in littoral ecosystems.     

Regulation of Reproductive Function in DrosophilaFemales Due to Hormonal Interaction Under Stress Is Genetically Determined

The effect of heat stress (38°C) on the content of octopamine (OA) and 20-hydroxyecdysone (20HE) was studied under normal and stressful conditions in adult flies of Drosophila virilislines contrasting in the level of the juvenile hormone (JH). The wild-type flies (line 101) exhibited a pronounced sex dimorphism for the content of both OA and 20HE, which was substantially lower in this line than in flies of the mutant line 147. The level of both hormones increased in flies of line 101 exposed to heat stress, whereas it remained unchanged in flies of line 147 under the same conditions. The effect of heat stress on the level of JH metabolism and fertility was also studied in D. melanogasterwild-type lines and lines carrying mutations in genes responsible for OA and DA syntheses. In octopamineless females of the Th ^nM18line and in females of the Steline characterized by a doubled content of DA, JH degradation differed from normal: it was increased in both young and mature Th ^nM18females, while decreased in young and increased in mature Steflies. Fertility was substantially lower in the Stethan in the wild-type line. Flies of all of the D. melanogasterlines produced a stress response; however, in mutant lines, both fertility and stress reactivity of the systems controlling JH metabolism differed significantly from that of the wild-type lines. The role of JH, 20HE, OA, and DA interaction in regulation of Drosophilareproduction under stressful conditions is discussed.     

The effect of mutations altering biogenic amine metabolism in Drosophila on viability and the response to environmental stresses

Dopamine (DA) content, tyrosine decarboxylase (TDC) activity and survival were studied under normal and environmental stress conditions in the ste and e strains carrying ebony mutation increasing DA level and the octopamineless strain Tbetah(nM18) of Drosophila melanogaster. Wild-type strains Canton S and Oregon R, and strain p845 from which Tbetah(nM18) strain was derived were used as controls. Sexual dimorphism of TDC activity, DA content, and survival in flies of all D. melanogaster strains under study was found. Tbetah(nM18) mutation sharply reduced TDC activity in females, while ebony had no such effect. DA content and survival under heat stress in Tbetah(nM18) flies did not differ from those in the wild type. ste and e flies had drastically increased DA content under normal conditions, dramatically decreased survival under heat stress, but increased survival under starvation. DA content and survival under heat stress were also studied in the reciprocal hybrids (males) F(1) of the cross D. virilis strains 101 (wild type) and 147 with X-linked mutation, which significantly increases DA content. 147x101 males had a considerably higher DA content and lower survival than 101x147 ones. Individuals of all D. melanogaster strains under study developed the stress reaction, as judged by changes in TDC activity and DA levels. The role of biogenic amines in the stress reaction development and adaptation to environmental stresses in Drosophila is discussed. Arch. Insect Biochem. Physiol. 55:55-67, 2004.     

Effects of juvenile hormone and 20-hydroxyecdysone on alkaline phosphatase activity in Drosophila under normal and heat stress conditions

The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the alkaline phosphatase (ALP) has been studied in young females of wild-type Drosophila virilis and Drosophila melanogaster under normal conditions and under heat stress (38 degrees C). Both 20E feeding of the flies and JH application led to a substantial rise in ALP activity. ALP activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous(56f). A decrease in the enzyme activity was observed in the mutant females as compared to wild type. A rise in JH and 20E levels was found not to prevent the response of ALP to heat stress, but to change its stress-reactivity. Mechanisms of regulation of dopamine (DA) level by gonadotropins in Drosophila are discussed.     

Biogenic amines regulate the reproductive function in Drosophila as neurohormones

We studied the influence of experimental increase in the octopamine and dopamine content on the level of juvenile hormone degradation, oogenesis, and fertility in wild type D. virilis flies. Feeding of flies on octopamine led to a significantly decreased level of juvenile hormone degradation (increased titer) in young and sexually mature females, rather than in males, markedly decreased the number of vitellogenic (stages 8-10) and mature (stage 14) oocytes), and sharply reduced fertility. Feeding of flies on dopamine decreased the juvenile hormone degradation (increased titer) in young wild type females and increased it (lowered the juvenile hormone titer) in sexually mature females, as well as decreased the fertility of wild type females to a level characteristic for D. virilis line with a mutation doubling the endogenous dopamine level. A possible mechanism of the influence of these amines on the reproductive function in Drosophila as neurohormones is discussed and a conclusion is drawn that the reduced fertility of females at an increased level of amines appears to be related to an increased level of ecdysteroids, which is caused by an increased, as a result of decreased degradation, juvenile hormone titer.