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Mispatterning in the ommatidia of Apis mellifera pupae treated with a juvenile hormone analogue.

To further understand the function of morphogenetic hormones in honeybee eye differentiation, the alterations in ommatidial patterning induced by pyriproxyfen, a juvenile hormone (JH) analogue, were studied by scanning and transmission electron microscopy. Prepupae of prospective honeybee workers were treated with pyriproxyfen and the effects on ommatidial differentiation were described at the end of the pupal development. The results show that the entire ommatidia, i.e., the dioptric as well as the receptor systems, were affected by the JH analogue. The wave of ommatidial differentiation, which progresses from the posterior to the anterior region of the pupal eyes, was arrested. In treated pupae, the rhabdomeres only differentiated at the apical axis of the retinula, the secondary and tertiary pigment cells did not develop their cytoplasm protrusions, and the cone cell quartet did not pattern correctly. Simultaneously, an intense vacuolization was observed in cells forming ommatidia. In a previous study we showed that pyriproxyfen exerts an inhibition on pupal ecdysteroid secretion. In this sense, the arrested ommatidial differentiation in pyriproxyfen-treated pupae could be due to a secondary effect resulting from an alteration in pupal ecdysteroid titers.

Animals↗

Hydroxyurea-induced partial mushroom body ablation in the honeybee Apis mellifera: volumetric analysis and quantitative protein determination.

Hydroxyurea (HU) treatment of first instar honeybee larvae was previously shown to cause mushroom body (MB) ablations. Predominantly, either one or both median MB subunits were ablated. This prompted us to analyze the effects of asymmetrical or symmetrical HU-induced MB ablation on both the morphology of the brain and on the level of three proteins (synapsin, PKA RII, and PKC), which are considered to play a role in synaptic plasticity, learning, and memory. In brains with one median MB subunit missing the volume of the overall MB calyx neuropil in the lesioned side was diminished by 35%. This strong reduction occurred although the remaining lateral MB calyx of the lesioned brain side was found to be significantly larger than that of the intact side. Accordingly, in brains with both median MB subunits missing the size of the remaining lateral calyces increased. The various types of MB ablation differentially affected the amounts of synapsin, PKA RII, and PKC expressed in the central brain. In animals with bilateral and thus symmetrical MB ablation (both median calyces ablated) the protein amount was found to be similar to that in control animals. However, unilateral MB ablation causes an increase in the amounts of the tested proteins in the intact brain side, while the levels in the ablated side were the same as in control animals. These findings not only show that HU-induced ablation of MB subunits is accompanied by volume changes and by changes in protein expression, but also suggest that these processes are highly regulated between the brain sides. The latter is of general importance in understanding the potential contribution of the MB subunits to learning and memory and their interaction between the brain sides.

Animals↗

Qualitative and quantitative determination of yohimbine in authentic yohimbe bark and in commercial aphrodisiacs by HPLC-UV-API/ MS methods.

The development and validation of a rapid qualitative and quantitative method based on an HPLC-UV-MS technique with atmospheric pressure chemical ionisation and electrospray ionisation for the analysis of yohimbine in a number of commercial aphrodisiac products is reported. HPLC with multiple-stage mass spectrometry experiments allowed the identification of the target compound and increased the selectivity of complex analyses such as those involved with multi-botanical preparations. The precision and the robustness of the method were improved by the use of two internal standards: codeine for UV detection and deuterium-labelled yohimbine for MS detection. Twenty commercial aphrodisiac preparations were analysed and the amount of yohimbine measured and expressed as the maximal dose per day suggested on product labels ranged from 1.32 to 23.16 mg.

Aphrodisiacs↗

Trophallaxis in the honeybee, Apis mellifera : the interaction between viscosity and sucrose concentration of the transferred solution.

Trophallaxis by honeybee foragers was studied under the experimental conditions of an arena. The behaviour of pairs of bees, one (donor) fed with 50-&mgr;l sucrose solutions and another unfed recipient, was analysed as a function of the sucrose concentration, the concentration at constant viscosity (kept constant by adding tylose, an inert polysaccharide), and of the viscosity of a 30% sucrose solution. By increasing the concentration of solutions, the rate at which the solution was transferred to recipient bees (transfer rate of solution, in &mgr;l/s) increased up to a maximum value for 30% sucrose solution, and decreased beyond this concentration (concentration experiment). At constant viscosity, no modulation was observed for the lower sugar concentration range (10-30%), while the transfer rate of solution clearly increased beyond 30% (concentration experiment at constant viscosity). For the 30% sucrose solution, the transfer rate decreased with increasing viscosity (viscosity experiment). If only the sucrose compound is comparatively analysed, the transfer rate of sucrose (in mg/s) increased similarly in the first two experiments. These results give behavioural evidence suggesting that donor bees are capable of modulating the trophallactic food transfer as related to the sucrose concentrations carried into their crops within a considerable wide range, but viscosity prevents it. It also suggests that trophallactic transfer rate does not depend on abdominal volume, for even when all donor bees attained similar loads (50 &mgr;l), transfer rate of solution increased along with the offered sucrose concentration. Results are discussed in relation to the information exchange performed in the foraging context displayed by foragers. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

Trophallaxis in the honeybee Apis mellifera (L.): the interaction between flow of solution and sucrose concentration of the exploited food sources.

Forager bees arriving at the hive after visiting a nectar source, unload the collected liquid food to recipient hivemates through mouth-to-mouth contact (trophallaxis). We analysed whether the main characteristics that define nectar in energetic terms, that is, rate of production (flow of solution), sucrose concentration and rate of sucrose production (sucrose flow) influence trophallactic behaviour. Individual bees trained to feed at a regulated-flow feeder offering sucrose solution were captured once the foraging visit was complete and placed in an acrylic arena with a recipient bee that had not been fed. The rate at which liquid was transferred during the subsequent trophallactic contact (transfer rate) was analysed as a function of the different solution flows and sucrose concentrations offered at the feeder. A relationship was found between transfer rate during trophallaxis and the flow of solution previously presented at the feeder. This relationship was independent of sucrose concentration when above a certain threshold value (ca. 22% weight on weight). We also analysed whether the rate of sucrose deliverance of the food source (sucrose flow) influenced the rate at which the solution was transferred. No clear relationship was found between the rate of sucrose deliverance during trophallactic events (sucrose transfer rate) and the sucrose flow presented at the feeder. The possibility that trophallaxis could be a communication channel through which quantitative information on food source profitability is transmitted among hivemates is discussed. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗

Programmed cell death in the honey-bee (Apis mellifera L.) larvae midgut.

The histochemical and cytochemical localization of acid phosphatase has been used in an attempt to map the sites of cellular lysis and death. Reaction product was found both in the brush border of the midgut epithelium and in the basal membrane. Vacuolar acid phosphatase activity was found in the regenerative epithelial cells. Extra-cisternal reaction product was associated with the endoplasmic reticulum which was dilated in lysed areas of the cytoplasm. Free acid and alkaline phosphatase activity was found in the basal area of the midgut epithelial cells and the former also occurred in the haemocoel. In the tracheoblastic cells only vacuolar acid phosphatase activity was seen. Chromatin aggregates were distributed throughout the nucleus and the nuclear envelope showed some infolding. Certain mature epithelial cells proved positive for anti-histone associated DNA fragmentation indicative of programmed cell death.

Acid Phosphatase↗

Histopathological and histochemical changes in honeybee larvae (Apis mellifera L.) after infection with Bacillus larvae, the causative agent of American foulbrood disease.

Morphological, histochemical and cytochemical changes were examined in honeybee larvae after infection with the bacterium Bacillus larvae. The results indicate cell necrosis in the midgut epithelium accompanied by increasing cell vacuolization and nuclear pyknosis following per os inoculation with B. larvae. Many autolysosomes were positive for acid phosphatase. Non-vacuolar acid phosphatase activity was also found in lysed cell compartments. No such activity was found in regenerative epithelial cells. Degradation of haemocytes, salivary glands and other tissues was also observed. Histochemical analyses after per cutaneous inoculation with B. larvae of three- and five-day-old honeybee larvae show intense non-vacuolar acid phosphatase activity followed by disintegration of infected salivary glands, epithelial cell cytoplasm and haemocytes.

Acid Phosphatase↗

Modes of cell death in the hypopharyngeal gland of the honey bee (Apis mellifera l).

Different modes of cell death have been revealed in the regressing hypopharyngeal glands of worker honey bees. The hypopharyngeal gland, which is well developed in young nursing bees to produce protein for larval food, was seen to regress naturally in foraging adult worker bees. A range of techniques including histology, cytochemistry, in situ TUNEL, Annexin V and Comet assays indicated that cells within the gland demonstrate progressive symptoms of apoptosis, necrosis and a vacuolar form of programmed cell death. The latter mode of cell death did not display chromatin margination, but was accompanied by an enhanced level of autophagic and hydrolytic activity in which a cytosolic source of acid phosphatase became manifest in the extra-cisternal spaces. Normal and annexin-positive cells were found to occur in the younger nursing bees, whilst necrosis and an aberrant vacuolar type of apoptosis predominated in the older foraging bees. The relevance of these results to the classification of programmed cell death is discussed.

Acid Phosphatase↗

Toxicity of cypermethrin and fenitrothion on the hemolymph carbohydrates, head acetylcholinesterase, and thoracic muscle Na+, K+-ATPase of emerging honeybees (Apis mellifera mellifera. L).

Comparative effects of sublethal doses (0, 0.1, 0.2. 0.4, 0.8, and 1 nmol/bee) of cypermethrin and fenitrothion have been studied on emerging honeybees. The insecticides were injected intrathoracially between the third and the fourth segment. Biochemical effects were determined over a 3-h period. Both cypermethrin and fenitrothion led to a significant hypoglucosemia and hypotrehalosemia 15 min after injection, but cypermethrin seemed more active than fenitrothion at the same doses. A recovery phase appeared for glucosemia and trehalosemia, 60 min after injection. The higher toxicity of cypermethrin than fenitrothion also appeared in this period, where it took a longer time for honeybees to reestablish carbohydrate levels following cypermethrin than fenitrothion injections. The low values of the correlation coefficients (r) for glucose versus trehalose levels led to the supposition that no typical functional interaction between glucose and trehalose could be considered to be involved in this experience. Na+, K+-ATPases activity was significantly inhibited (P< 0.05) by cypermethrin and maximum percentage inhibition was reached (45%) at 1 nmol/bee. The kinetic analysis of honeybee's acetylcholinesterase inhibition by fenitrothion, indicated that this insecticide acts (P< 0.05) on acetylcholinesterase activity. The percentage inhibition exceeded 60% at 0.2 nmol/bee. This result revealed that in general cypermethrin and fenitrothion share common biochemical effects on carbohydrates, although their neurotoxic effects on honeybees might be different.

Acetylcholinesterase↗

Effect of juvenile hormone on short-term olfactory memory in young honeybees (Apis mellifera).

Reliable retention of olfactory learning following a 1-trial classical conditioning of the proboscis extension reflex (PER) is not achieved in honeybees until they are 6-7 days old. Here we show that treatment of newly emerged honeybees with juvenile hormone (JH) has a profound effect on the maturation of short-term olfactory memory. JH-treated individuals display excellent short-term (1 h) memory of associative learning at times as early as 3 days of age and perform consistently better than untreated bees for at least the first week of their lives. By contrast, the retention of long-term (24 h) memory following a 3-trial conditioning of the PER is not significantly improved in JH-treated bees. Our study also shows that experience and (or) chemosensory activation are not essential to improve learning performance in olfactory tasks. The lack of accelerated development of long-term retention of olfactory memories in JH-treated honeybees is discussed in the context of neural circuits suspected to mediate memory formation and retrieval in the honeybee brain.

Aging↗

Laboratory and field studies on the effects of the antibiotic tylosin on honey bee Apis mellifera L. (Hymenoptera: Apidae) development and prevention of American foulbrood disease.

Laboratory and field studies were conducted to determine the effectiveness of the antibiotic tylosin in preventing and controlling infections of American foulbrood disease (AFB) of honey bees. Studies conducted on immature worker bees maintained in the laboratory revealed that honey bee larvae could tolerate quite a range of doses of antibiotic in their diet. Intermediate doses of tylosin protected very young larvae from becoming infected by Bacillus larvae at a concentration of 1.5 x 10(8) spores/ml of diet. Antibiotic treatment had no measurable effects on larval or pupal developmental rates until the dose reached a lethal level. Bees in field colonies readily consumed tylosin in powered sugar, up to a level of 800 mg/7 g sugar. No negative colony effects were noted at any dosage rates. Protection against infection by American foulbrood was compared to results obtained with 200 mg Terramycin, the standard dose of the only substance currently registered for foulbrood control. Both 200 mg Terramycin and 100 mg tylosin protected the colonies for up to 3 weeks. A 200-mg dose of tylosin protected the colony for an additional week. Doses of 100 mg or more of tylosin were adequate to eliminate signs of AFB infection in overtly diseased colonies.

Animals↗

The transmission of deformed wing virus between honeybees (Apis mellifera L.) by the ectoparasitic mite varroa jacobsoni Oud

Under field conditions, Varroa jacobsoni were shown to be highly effective vectors of deformed wing virus (DWV) between bees. Adult female mites obtained from honeybee pupae naturally infected with DWV contained virus titers many times in excess of those found in their hosts and, beyond that, which might be expected from a concentration effect. It is therefore possible that DWV may be capable of replicating within V. jacobsoni. Bees which tested positive for DWV exhibited characteristic morphological deformity and/or they died during pupation. Asymptomatic bees had much lower virus titers than those which were deformed or had died during pupation. It is therefore suggested that for DWV to cause pathology it must be present in pupae above a certain concentration. The amount of DWV vectored by V. jacobsoni will depend on the mites' level of infection, which will in turn depend on whether they had fed previously on dead or deformed bees and also on the rate of replication of the virus within the mites. Consequently, developing bees infested with large numbers of mites could suffer a high incidence of deformity if the mites are heavily infected or harbor an especially virulent strain of virus. A positive relationship was found between increasing numbers of mites on individual bees and the incidence of morphological deformity and death. This probably reflected the large number of viral particles transmitted by the mites, which resulted in many multiply infested bees dying before emergence. These results demonstrate the importance of the role of viruses when considering the pathology of V. jacobsoni and that much of the pathology previously associated with the effects of mite feeding could be attributed directly to secondary pathogens vectored by V. jacobsoni. Copyright 1999 Academic Press.

Journal Article↗

The effects of genotype, foraging role, and sucrose responsiveness on the tactile learning performance of honey bees (Apis mellifera L.).

We analyzed sucrose responsiveness and associative tactile learning in two genetic strains of honey bees under laboratory conditions. These strains differ in their foraging behavior. Bees of the "high" strain preferentially collect pollen. "Low"-strain bees mainly forage for nectar. Responsiveness to different sucrose concentrations and tactile learning were examined using the proboscis extension reflex. Acquisition, extinction of conditioned responses, and responses to an alternative tactile stimulus were tested. High-strain bees are more responsive to sucrose than low-strain bees. Regardless of genotype, pollen foragers are more responsive to sucrose than nectar foragers. In bees of both strains we find the same relationship between responsiveness to sucrose and acquisition. Bees responding to low sucrose concentrations show more often the conditioned response during acquisition than those responding only to higher sucrose concentrations. Extinction of conditioned responses depends on the response probability during acquisition. Discrimination between the two tactile stimuli is affected by genotype but not by responsiveness to sucrose. High-strain bees discriminate better than low-strain bees. Our experiments thus establish links between division of labor, responsiveness to sucrose, and associative learning in honey bees.

Animals↗

The retina-lamina projection in the visual system of the bee, Apis mellifera.

Single Golgi impregnated visual cells and their axons were treated from the retina to the first synaptic layer (lamina) in serial electron microscopic sections. This analysis of the retina-lamina projection was undertaken in the upper dorso-median eye region which is known to be involved in the perception of polarized light. For identification of individual visual cells and their fibres a numbering system was used which relates the number of each of the nine visual cells within one retinula to the transverse axis of the rhabdom (TRA) (Fig. 1). Because of the twist of the retinula along its course to the basement membrane (Fig. 6), individual visual cells change their position relative to any eye-constant co-ordinate system. Each axon bundle originating from one 9-celled retinula performs a 180 degrees-rotation before entering the lamina (Fig. 2). The direction of rotation (clockwise or counter-clockwise), which may differ even between adjacent bundles, is related to the two mirror-image types of rhabdoms in the corresponding retinulae and is opposite to the direction of rhabdom twist. Thus, even in small groups of the in total 5500 ommatidia in the eye of the bee, two types of retinulae exist which can be characterized by the geometry of the rhabdoms as well as by the direction of rotation of the retinulae and the axon bundles (Fig. 1). Visual cell numbers 1, 2, and 9, the microvilli of which are oriented in the direction of TRA, form three long visual fibres terminating in the second synaptic layer (medulla). In cross sections of laminar pseudocartridges they appear as the smallest fibre profiles arranged in a symmetrical line of the pseudocartridge bundle (=the transverse axis of the pseudocartridge; TPA) (Fig. 4). The remaining six fibres (cell numbers 3-8) only project to the lamina (short visual fibres; svf's). Two of them (cell numbers 5 and 6), which are the largest cells in the proximal retinula and have their microvilli perpendicularly arranged to TRA (Fig. 1), give rise to the two thickest axons of the underlaying pseudocartridge. In cross sections, t he connecting line of these two axons is orthogonally oriented to TPA (Fig. 5). A model was developed, in which all long visual fibres originate from ultraviolet receptors and in which the polarization sensitivity of the basal ninth cell is enhanced by the twist of the rhabdom. Finally, this model is discussed in light of behavioral experiments revealing the ultraviolet receptors as the only cells involved in the detection of polarized light.

Animals↗

Second-order ocellar neurons in the brain of the honeybee (Apis mellifera).

Electrophoretic injection of Procion Yellow M-R4 into the ocellar tract of the worker bee has revealed the following: Two types of giant axon run from the lateral ocellus to the circumesophageal neuropile, where one branches ipsilaterally and the other contralaterally. A third type comes from the median ocellus and can be traced into the cervical connectives. The largest dendritic complex is in the circumesophageal neuropile; in addition, fiber endings have been demonstrated in the following areas: in the subretinal region, along the optic commissure, in the medulla interna, in the subesophageal ganglion and between the neurosecretory cells of the pars intercerebralis. -- The giant fibers are enclosed in a glial sheath. Three types of cell body are described. One is associated with the glia; another, larger cell type comprises giant-axon somata. The third type of cell is small, and cannot yet be identified. Some of the histological results are discussed with respect to the possible function of the ocellus.

Animals↗