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At least 523 records · Page 29Linked to original sources
PubMed1999

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↗
PubMed2001

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↗
PubMed1996

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↗
PubMed1999

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↗
PubMed2001

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↗
PubMed1975

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↗
PubMed1976

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↗
PubMed1975

Structural specialization in the dorsal retina of the bee, Apis mellifera.

Electron microscopic investigations on the eye of the worker bee showed that the ommatidia located in the uppermost part of the dorsal half of the eye are characterized by a distinct structural specialization: Nine visual cells contribute microvilli to the rhabdom over its full length. Within these rhabdoms the microvilli are arranged in at least three different directions. This specialization affects an area of at least 60 ommatidia. The most dorsal eye region differs, therefore, structurally from all other regions which have been investigated to date. Because the ommatidia in question are oriented skyward, their peculiar structure is discussed with respect to several concepts of polarized light detection by the bee.

Animals↗
PubMed1991

Genetic differences in learning behavior in honeybees (Apis mellifera capensis).

Workers from colonies of Cape honeybees show marked phenotypic differences in performance in proboscis extension reflex (PER) conditioning. Analysis of these differences using parthenogenetic offspring groups permitted the estimation of genotypic values and revealed a high degree of genetic variability that is evident among related as well as unrelated bees. The results obtained from related groups are of particular importance, since they demonstrated the existence of strong genetic variability among individuals of the same colony. Quantitative analysis yielded high estimates of additive genetic effects and low estimates of dominance effects. Selection of individual workers resulted in an explicit increase in genetic variance of the next generation (G1). However, selection of bees from the parthenogenetic G1 generation, which was done to obtain parthenogenetic G2 offspring, did not lead to further improvement in selection. This observation suggests that recombination of linked genes underlying proboscis extension reflex was negligible during selection in parthenogenetic groups. Taken together with further behavioral analysis (Brandes and Menzel, 1990; Brandes et al., 1988), results from these quantitative genetic experiments suggest that additive genetic factors contribute significantly to variability among individuals for associative learning.

Animals↗