Yaacov Lensky

The effect of sugars and Juvenile Hormone on the differentiation of the female honeybee larvae (Apismellifera L.) to queens

Abstract The effect of the addition of sugars to diet and topical application of Juvenile Hormone on the di-ferentiation of undetermined female larvae to queens was examined. The basic diet was Worker Jelly (WJ) with 4% glucose (G) and 4% fructose (F) added. Larvae reared on this diet emerged as workers only. Larvae reared on WJ with 8% G and 8% F differentiated to adult intermediates or workers. High amounts of G and F (16 to 20%) caused the larvae to develop to adult queens, intermediates and workers. When 2- to 3-day-old larvae were reared on WJ (with 4% of G and F, each) and topically treated with 10 μg Juvenile Hormone (JH) per larva, they differentiated and emerged only as queens. Lower amounts of JH (1 μq per larva) caused differentiation of larvae to 50% queens and 50% workers. The possible mode of action of sugars and Juvenile Hormone is discussed.

Ontogeny of the fine structure of the mandibular glands of the honeybee (Apis mellifera L.) workers and the pheromonal activity of 2-heptanone

Abstract In the present study we have tried to: (1) correlate, according to the age and polyethism of worker bees, the ontogeny of their mandibular glands and the age-dependent changes of 2-heptanone levels and (2) evaluate the role of 2-heptanone in some social behavioural interactions of the honeybee. 1. (1) Each mandibular gland of the worker honeybee, Apis mellifera (Hymenoptera: Apidae), consists of an axial cavity lined with a thin cuticular intima elaborated by a flat epithelium, and of numerous glandular units (type 3), each with a duct cell and a large polyploid glandular cell. Mitochondria and endoplasmic reticulum are preponderant organelles. The Golgi apparatus is reduced; its activity is lysosomal. With increasing age, the size of the gland and the amount of 2-heptanone per headspace sample progressively increased. The increasing quantity of 2-heptanone from 0.1 μl at emergence to 7 μl in foraging bees, is strictly correlated with hypertrophy of the mitochondria, which are engaged in the production of heterogeneous bodies. 2. (2) Similar age-dependent changes of 2-heptanone levels were found in mandibular glands of workers from docile and aggressive colonies and the amount of 2-heptanone in foraging bees of the two groups was alike. Neither crushed glands nor 2-heptanone showed any direct effect as an alarm pheromone on guardian bees at hive entrances. 2-heptanone had either an attractive or a repulsive effect on guards, according to the season; it showed a repulsive effect when added to sucrose solution which was visited by foragers. 2-heptanone had a temporary, repulsive effect on the visitation of flowers by foraging bees, hence it seems to act as a “forage-marking” pheromone. 2-heptanone does not inhibit the germination of pollen grains.

Flower and Nectar Characteristics of Nine Species of Labiatae and their influence on Honeybee Visits

SummaryThe anatomy of the nectary, the relative amount of nectar secreted, the composition of the nectar and its sugar concentration, were studied in 9 species of the family, Labiatae (Coridothymus capitatus, Melissa officinalis, Phlomis viscosa, Rosmarinus officinalis, Salvia fruticosa, S. hierosolymitana, S. judaica, Satureja thymbra, Stachys aegyptiaca). The visitng rate of the honeybees to the various species was investigated. The nectar is secreted from the asymmetrically thick, disc-like nectary, through modified stomata. These occur on the thicker side of the nectary only. There is a correlation between the volume of the nectary and the amount of nectar secreted. The larger the nectary, the more nectar it secretes. No correlation was found between the type of vascular tissue (phloem, xylem) and the sugar concentration in the nectar, Rosmarinus officinalis and Coridothymus capitatus were the species most frequently visited by honeybees. The quantitative relationship between sucrose, glucose and fruc...

Pheromonal activity and fine structure of the mandibular glands of honeybee drones (Apis mellifera L.) (Insecta, Hymenoptera, Apidae)

Abstract Experiments were conducted to determine the role of drone mandibular gland secretions in attracting flying drones and the effect of age on the secretory activity. Extracts of mandibular glands and of cephalic tissues were applied to cotton lures which were attached below balloons tethered at 8–12 m above the ground. Most flying drones were attracted to extracts of mandibular glands but a few were drawn to other cephalic tissues or to solvent controls. Histological and electron microscope studies showed that the structure of the tiny (0.12 mm long) mandibular gland varied according to age. Its secretory activity in 0–3-day old drones was evident from the abundant rough endoplasmic reticulum. At 7-days the glands were fully developed. After 9 days the glands were no longer active and showed an autolytic process; the product was stored in the gland lumen for further emission during drone mating flights.

The effect of soluble sugars in stored royal jelly on the differentiation of female honeybee (Apis mellifera L.) larvae to queens

Abstract The composition of sugars and their level in fresh royal jelly (RJ), worker jelly (WJ) and stored royal jelly (SRJ) were established. The effect of SRJ soluble sugars on the differentiation of female larvae was studied. The sugar level of RJ removed from cells with 1- to 3-day-old larvae (RJ 1–3) was about 4 times higher than that of WJ of corresponding age (WJ 1–3) (12.4 vs 3.1%), when calculated on the basis of fresh matter. The ratio fructose: glucose (F:G) in RJ 1–3 (1.43) and in WJ 1–3 (1.37) was almost equal. The crystals formed in SRJ and analyzed by GLC, as well as by optical, polarizing and scanning microscope, were composed of fructose (F), glucose (G) and sucrose (S). The level of F was 83.7% of the total sugar content of crystals. Female honeybee larvae reared on SRJ supplemented with 198 mg F + 38 mg G/g food, an amount similar to that of SRJ crystals, resulted in the emergence of adults as queens: (40%), intercastes (23%) and workers (37%). The importance of availability of soluble sugars vs solid crystals in the larval food on the induction of “queenlines” is discussed.

Separate protein body compartments of the worker honeybee (Apis mellifera L.)

Abstract 1. 1. Protein of adult worker bees are secreted from their exocrine glands in royal jelly and in venom or in eggs laid by laying workers in queenless colonies. 2. 2. The present report examines the protein composition of head and thoracic glands, venom glands, fat body and ovaries, the relation of these proteins to haemolymph proteins and the possible exchange of macromolecules between glandular compartments, the haemocoele and the organs located in the haemocoele. 3. 3. The identity of proteins from various compartments was established by double-diffusion, immunoelectrophoresis, gradient acrylamide slab gel electrophoresis and isoelectric focusing. 4. 4. Royal jelly is composed of proteins secreted from hypopharyngeal, mandibular and postcerebral, but not from thoracic glands. 5. 5. No immunological identity was found between the proteins of royal jelly, venom and haemolymph. The glands producing the two secretions seem to be separate compartments from the haemocoele with regards to macromolecular traffic. 6. 6. In contrast to the exocrine glands many of haemolymph proteins were shared by the fat body and the ovaries. 7. 7. Some aspects of macromolecular traffic between the body compartments in insects are discussed.

The sting sheaths of honey bee workers (Apis mellifera L.): Structure and alarm pheromone secretion

Abstract To evaluate the contribution of the sting sheaths of the worker to the defensive behaviour of a bee colony, we studied their fine structure and the effect of their secretions on the reaction of guards. (1) The structure of the proximal part of the sting sheath integument has all the characteristics of a primitive exocrine gland: porous cuticle with enlarged pore canals and epicuticular pores, and hypertrophied epithelial cells secreting an electron dense material. The non-volatile part of the secretory product embedded the setae of the sheaths. (2) Individual recipient guards in the laboratory and as a group at hive entrances in a beeyard displayed defence behaviour only when stimulated with either sting sheaths or with setaceous membrane, but not with any other gland or organ. Enhanced defensive reaction of guards has been observed when a venom gland or Koschewnikows glands, are added to either sting sheaths or to setaceous membrane. (3) We demonstrate for the first time that the sting sheaths have the structure of an exocrine gland and that their secretions induce defensive behaviour in guards.

Ultrastructure of the Spermatozoon of the Mature Drone Honeybee

SummaryMature spermatozoa of drone honeybees (Apis mellifera), obtained from seminal vesicles, were examined with an electron microscope by negative staining and by serial sectioning. The structure is described, and illustrated in photomicrographs.

Proteins of the honeybee (Apis mellifera L.) body surface and exocrine gland secretions

Abstract In this paper, soluble proteins are demonstrated on the surface of the honeybee cuticle. Polyacrylamide gel electrophoresis revealed an 80 kDa doublet on workers, queens, and drones showed a single band at a slightly higher molecular weight. Several additional queen- or drone-specific proteins were observed. The presence of soluble cuticular surface proteins may be a general phenomenon because they were also present on insects of two other orders, Orthoptera and Hemiptera. Exocrine gland secretions from the Nasanov glands of workers and the tarsal glands of both female castes and drones also contained soluble proteins. Proteins of tarsal gland secretions may contribute to the milieu of surface proteins because the electrophoretic profiles of cuticular proteins and tarsal secretions were similar. In contrast, the electrophoretic profile of proteins from Nasanov gland secretions was distinct from the profile of the tarsal gland secretion. Proteins on the cuticular surface or in exocrine gland secretions could also affect social interactions. Surface cuticular proteins and those associated with exocrine glands may function in pheromone degradation, as slow release substances, or as caste- or sex-specific modulators of pheromone activity.

Juvenile hormone induction of ‘queenliness’ on female honey bee (Apis mellifera L.) larvae reared on worker jelly and on stored royal jelly

Abstract 1. 1. The effect of topical treatment with juvenile hormone—1 (JH-1) on the induction of ‘queenliness’ on undifferentiated female honeybee larvae reared in the laboratory on basic or modified diets of worker jelly (WJ) or of stored royal jelly (SRJ) was examined. 2. 2. Morphological criteria of ‘queenliness’ were established. 3. 3. A dose-response effect of JH-1 (from 0.01 μg to 100 μg/larva) on the differentiation of larvae reared on WJ-40 to queens was established. 4. 4. JH-1 treatment of larvae reared on SRJ has restored their capabilities to differentiate as queens. 5. 5. The weight of larvae that differentiated to queens was higher (213–255 mg) than that of intercastes (182–233 mg) or of workers (179–214). 6. 6. The possible mode of action of juvenile hormone and sugars in the induction of ‘queenliness’ is discussed.