Glycerol-3-phosphate dehydrogenase isozyme variation in insects

Glycerol-3-phosphate dehydrogenase (GPD) serves a central function in the metabolism of carbohydrate for insect flight. This paper reports that the function is supported in a wide range of species by thorax-specific GPD isozymes. These have been discovered in nine of 14 orders in which winged forms have been tested, including all of the major orders except Lepidoptera and Odonata. Examples have been found in each of the Polyneoptera, Paraneoptera and Holometabola, occurring predominantly in larger, stronger fliers which use carbohydrate as a fuel. Thorax-specific GPD isozymes have been found only once (in a tiphiid female) in a flightless insect and in the Palaeoptera not at all.     

Allozyme variation in bumble bees (Hymenoptera: Apidae)

Allozyme variation at an average of 37.3 loci was assessed in queens of 16 Bombus and 2 Psithyrus bumble bee species from North America. The mean expected heterozygosity (H) for the Bombus species was 0.008 +/- 0.006 (95% confidence limits) and that for the Psithyrus was 0.007 +/- 0.007. These levels are significantly lower than found in other Hymenoptera but are comparable to those found in previous studies of bumble bees based on far fewer loci. Neutral mutation and random genetic drift can account for the observed variation, but this implies a very small effective population size for species of bumble bees.     

Glycerol-3-phosphate dehydrogenase (G-3-PDH; EC 1.1.1.8) variation in Brazilian stingless bees and in wasp species

In only 1 bee species(Tetragona clavipes) of 24 sampled in 145 colonies (0.69%) did we detect the presence of more than one allele for glycerol-3-phosphate dehydrogenase (EC 1.1.1.8), an enzyme that is involved in flight. In 34 colonies containing 9 wasp species, 5 colonies of only 2 species(Polybia paulista andP. sericea) showed variation in larval G-3-PDH (14.7%). The small amount of variation observed for theG-3-PDH-1 locus in the bee and wasp species analyzed in the present study agrees with that reported for the G-3-PDH system in other insects.Research supported by FAPESP and CNPq-PIG IV.     

Small-scale elevational variation in the abundance of Eufriesea violacea (Blanchard) (Hymenoptera: Apidae)

Eufriesea violacea (Blanchard) males were sampled in a small-scale elevational gradient in Southeastern Brazil and showed sequential peaks of abundance from lowest (700 m) to highest (1,100 m) altitudes during the sampling period. The influence of the temperature on the length of the egg-to-adult period and flowering dates of plants producing food (nectar) suggests that it may be one of the factors determining the distribution of male abundance along the altitudinal gradient. The results emphasize the importance of obtaining altitudinal stratified samples when studying Euglossini populations, especially when the studies are done at sites with marked topographical variation.     

Geographical patterns of mitochondrial DNA variation in Apis mellifera iberiensis (Hymenoptera: Apidae)

An extensive survey of mitochondrial haplotypes in honeybee colonies from the Iberian Peninsula has corroborated previous hypotheses about the existence of a joint clinal variation of African (A) and west European (M) evolutionary lineages. It has been found that the Iberian Peninsula is the European region with the highest haplotype diversity (12 haplotypes detected of the M lineage and 10 of the A lineage). The frequency of A haplotypes decreases in a SW-NE trend, while that of M haplotypes increases. These results are discussed in relation to hypotheses about the African origin of Apis mellifera and an early colonization of west Europe during intermediate Pleistocene glaciation events, followed by a regional differentiation. The extant pattern of haplotype frequency and distribution seems to be influenced at a regional scale by adaptation to local climatic conditions and the mobile beekeeping that has become a large-scale practice during the last decades. Other previous anthropogenic influences (Greek, Roman and Arab colonizations) are thought to be of minor importance in present day populations.     

Lipid distribution in salivary glands of larvae and adult bees (Hymenoptera: Apidae)

Cytochemical studies were carried out to establish lipid distribution in the salivary glands of larvae and adult bees, using the imidazole buffer technique. In the duct cells of the larval salivary gland, the reaction was positive in the epicuticle and negative in the glandular lumen. The absence of smooth endoplasmic reticulum and the presence of lipids in the intercellular space suggest that lipids absorbed from the haemolymph could be used in the constitution of the epicuticle, after having been conveyed through the epithelium. In adult workers (new-emerged, nurse and forager workers), the head salivary glands presented a positive reaction in the secretion in glandular lumen, identifying its lipidic nature.     

Glycerol-3-phosphate dehydrogenase (EC 1.1.1.8) from Dunaliella tertiolecta. I. Purification and kinetic properties

A rapid purification procedure for glycerol-3-phosphate dehydrogenase from Dunaliella tertiolecta (strain 19-6 of the algal collection of the Univ. of Göttingen), the initial enzyme in the glycerol cycle, has been developed on the basis of affinity chromatography on Blue Sepharose and subsequent desalting by Sephadex G-50. The achieved purification was 126-fold. The pH optimum of dihydroxyacetone phosphate reduction is 7, that of glycerol-3-phosphate oxidation is about 9. The in vitro enzymatic activity obtained from cell extracts is higher than the required activity for the observed glycerol production rates under osmotic stress in vivo.     

Mitochondrial DNA sequence variation of the bumblebee,Bombus ardens (Hymenoptera: Apidae)

The bumblebee, Bombus ardens, is a valuable natural resource, and is most notably utilized for greenhouse pollination. In order to gain a greater understanding of the population genetic structure and the genetic diversity of this species, we sequenced a portion of the mitochondrial COI gene corresponding to the “DNA Barcode” region (658 bp) from 160 individuals collected over 15 Korean localities. Uncorrected pairwise distances among the eight haplotypes suggested low intraspecific genetic diversity, with a maximum sequence divergence of 0.3%. Such a low level of intraspecific genetic diversity was further reflected in local populations, particularly to islet populations, such as those of Youngheungdo, Jakyakdo, and Ulleugdo, which had zero genetic diversity. Geographically, one haplotype (BARBA01) was widespread and dominant, with a frequency of 90.6% (145 among 160 individuals). Other haplotypes were restricted to one to three localities and had low frequency. Overall, a very high rate of per generation female migration ratio (Nm = 4.6 to infinite) and a very low level of genetic fixation (F_ST = 0 to 0.099) were detected between pairs of localities, suggesting that the B. ardens populations on the Korean peninsula are panmictic, which is consistent with our understanding of their dispersal capability.     

Bombus impatiens (Hymenoptera: Apidae): an alternative to Apis mellifera (Hymenoptera: Apidae) for lowbush blueberry pollination.

The pollination effectiveness of the commercially reared bumble bee Bombus impatiens Cresson, was compared in field studies to the honey bee, Apis mellifera L., for lowbush blueberry, Vaccinium angustifolium Ait. A preliminary study indicated that B. impatiens had potential as an alternative pollinator. In a 3-yr study, percentage fruit set, percentage harvested berries, berry weight, and seeds per berry were compared in blueberry fields stocked at 7.5 A. mellifera hives per hectare to 5, 7.5, or 10 B. impatiens colonies per hectare. Percentage of harvested berries (yield) was significantly higher in fields stocked with B. impatiens at 10 colonies per hectare. No other parameters measuring pollinator effectiveness were significantly different at 5, 7.5, or 10 colonies per hectare. Flower handling time was significantly faster for B. impatiens and it more frequently collected blueberry pollen. All parameters of pollinator effectiveness were similar for B. impatiens, A. mellifera, and native wild bees in a follow-up study. Overall, B. impatiens was a suitable alternative to A. mellifera.     

Inbreeding depression and family variation in a social insect, Bombus terrestris (Hymenoptera: Apidae)

Arid and semi-arid ecosystems often exhibit diverse plant growth forms in water-limited environments, but it is unclear whether resource competition (interference) is actually important in structuring communities. We chose a diverse Chihuahuan desert shrubland to examine the response of the plant community to experimental removals of selected perennial plant species or groups of species. Four treatments involved the removal of all individuals of all species of a single functional group (functional group removals: shrub removal, succulent removal, subshrub removal, perennial grass removal). Three other treatments involved removing species within functional groups. These seven treatments plus a control (no plants removed) were replicated six times each in 25×25 m experimental plots, in summer 1995. Permanent belt transects were surveyed for number and sizes of all vascular plants in spring and fall in 1997, 1999, 2000, and 2001. Those plots from which the dominant shrub, Larrea tridentata , was removed had not recovered in total plant cover or volume by 2001, but cover and volume in all other treatments were similar to those in control plots. Relatively few species demonstrated a positive response to the removal of other species or functional groups. The perennial grass group and forbs were the most responsive; perennial grass cover increased in the shrub removal treatment relative to the control but treatment differences diminished after dry growing seasons in 2000 and 2001. Results over the first five years suggest that either environmental conditions or intrinsic biological characteristics limit the ability of most plant species to respond to the removal of substantial fractions of community biomass and composition in the short term. Such slow response by both dominant and less abundant components of the community has implications for the recovery of semi-arid systems after human disturbance or other events leading to the reduction of biological diversity.     

Glycerol-3-phosphate dehydrogenase is induced by glucocorticoids in hepatocytes and hepatoma cells in vitro

Previous studies have shown that cytosolic glycerol-3-phosphate dehydrogenase (GPDH; EC 1.1.1.8) can be induced by glucocorticoids in mammalian brain, mammary gland, and thymus, but it was thought that no induction occurred in liver. We report here that GPDH is induced by glucocorticoids in several lines of hepatoma cells and in rat hepatocytes cultured in vitro. When rat hepatoma cells of clone FU5AH were exposed to 3 μM hydrocortisone (HC) for 3 days, GPDH specific activity increased greater than sixfold over control. The rate and extent of induction were similar in exponentially growing and stationary-phase cultures of cells. Four other hepatoma cell lines were inducible to a lesser extent, and three lines were not inducible. GPDH was also induced by glucocorticoids in cultures of hepatocytes isolated from livers of 6-day-old rats. The enzyme was induced threeto fourfold by the synthetic glucocorticoid, dexamethasone, in the presence of 1 nM insulin, but the induction was not observed in the absence of insulin.     

Isoenzymes related to flight activity inTetragonisca angustula (Hymenoptera:Apidae:Meliponinae): Evidence of postranslational modification of the hexokinase and detection of new glycerol-3-phosphate dehydrogenase variants

To detect genetic markers, electrophoretic analyses were carried out onTetragonisca angustula, a stingless bee well adapted to its wide area of occurrence, which is becoming economically important because of the quality of its honey. Polymorphism of the enzyme hexokinase was detected and it was demonstrated that, although it presents two bands in meliponines, this enzyme is under the control of a single locus whose product probably undergoes postranslational modification. The more common allele occurs in the twoTetragonisca subspecies studied here, but the other seems to be characteristic of only one subspecies. Four variants involving the two glycerol-3-phosphate dehydrogenase loci are also described. These two enzymes share the property of presenting two electrophoretic bands, one of which is characteristic of actively flying adult thoraces.     

Frugivory by a stingless bee (Hymenoptera: Apidae)

Frugivory is not frequent among bees. Although stingless bees visit aged fruits for pulp, the use of fresh fruits is recorded only for Trigona hypogea Silvestri, a species that does not visit flowers. Here we report the occurrence of frugivory in Trigona amazonensis (Ducke), a flower-visiting stingless bee.     

Microsatellite loci for euglossine bees (Hymenoptera: Apidae)

The Neotropical Euglossini (Hymenoptera: Apidae) are important pollinators of many flowering plants, particularly orchids. Lack of highly polymorphic genetic markers for euglossine species has limited the study of their social organization and inbreeding. We therefore developed microsatellite markers for two species, Eulaema nigrita (11 loci) and Euglossa cordata (nine loci), most of which were highly polymorphic in the source species and in a range of related euglossine bees.     

Generic relationships within the Euglossini (Hymenoptera: Apidae)

ABSTRACT. .The relationships among the euglossine genera are examined. These genera form two natural groups, Exaerete+Euglossa , and Eufriesea+(Eulaema+Aglae). Each genus is discussed separately giving generic synonymy, biological notes and a complete species list. In addition, a key to the genera is provided.     

Fungi associated with Bombinae (Apidae: Hymenoptera) in North America

Eleven genera of fungi were isolated from overwintered queens of six species of Bombinae, as well as Penicillium from their nests. Hirsutella and Metarrhizium are suggested for the first time to be pathogens of BombusThis survey of fungi was part of a more general study of the natural enemies and associates of these bees in Ontario (3).