Light and electron microscopical study of two types of endocrines cell in the midgut of the adult worker honeybee (apis mellifera)

The occurrence, development and ultrastructure of two types of gut endocrine cell have been studied in the midgut of adult honeybees. These cells, one of a basal granular type and one of a vesicular type, are evenly distributed throughout the posterior three-quarters of the midgut. Each crypt complex contains one of each cell type, both of which may be derived from the same stem cells as the enterocytes. They already contain their respective secretory product while still in the nidus. Both reach the midgut lumen by a narrow apex and are therefore of the open type. The granular cells release their secretory granules at the cell base in a typical endocrine way. In young vesicular cells the secretory vesicles are released at the cell base and in the intercellular spaces. Old cells are still filled with vesicles when they are shed in the midgut lumen. This seems to indicate that these cells have both an endocrine (or paracrine) and an exocrine function, the latter apparently by holocrinc release.     

Feinstrukturen im komplexauge der blattschneiderbiene Megachile rotundata (F.) (hymenoptera,apidae)

Zusammenlassung Es wurden Ommatidien der dorsalen Augenhälfte von Megachile-, einer solitären Bienenart, elektronenmikroskopisch untersucht. Die Kristallkegelmasse der Semperschen Zellen (euconer Typ) stößt in breiter Front an die Cornealinse und bildet dadurch gegenüber anderen euconen Augen vermutlich ein verbessertes optisches System. Die 4 Fortsätze der Semperschen Zellen ziehen bis zur Basalmembran, wo she anschwellen und dicht mit Schirmpigment gefüllt sind.Die Hauptpigmentzellen enden distal in einem schmalen Bereich an der Cornea, proximal kurz unterhalb vom Kristallkegel. Die Nebenpigmentzellen rind in ihrem gesamten Verlauf von der Cornea bis zur Basalmembran mit Pigmentgrana angefüllt. Die bei Apis beschriebene basale Pigmentzelle jedes Ommatidiums gibt es bei Megachile nicht. An ihre Stelle treten die erwähnten basalen Anschwellungen der Fortsätze der Semperschen Zellen.Die Retinulae bestehen aus je 9 Sehzellen. Sie bilden ein Rhabdom vom geschlossenen Typ, das im distalen Teil des Ommatidiums aus den in der Mitte sich breitflächig berührenden und gleichartig ausgerichteten Mikrovilli der beiden Sehzellen Nr. 1 und 5 besteht. Diese beiden Rhabdomere werden auf der einen Seite von den Rhabdomeren der Zellen 2–4, auf der anderen von denen der Zellen 6–8 flankiert, die wiederum allesamt gleichartig, jedoch rechtwinklig zu ersteren angeordnet sind.Basalwärts folgt ein Bereich, in dem rich die Rhabdomere der Sehzellen 2–4 und 6–8 verlängern, wobei sich 3 und 7 breit berÜhren. Die Mikrovilli der Zellen 1 und 5 erscheinen an die Peripherie abgedrängt. Die 9. Retinulazelle ist im basalen Drittel am Rhabdom beteiligt.Die Pigment- und Semperschen Zellen besitzen außer den üblichen Organellen Centriolen, gewinkelt angeordnet oder in Tandem-Stellung. In den Retinulazellen entsprechen these den Basalkörpern von Cilien, die nach distal Tubuli (gelegentlich werden auch Fibrillen mit periodischen Strukturen gefunden) aussenden, nach basal dagegen Wurzelfibrillen, die sich zu einem Wurzelfaden vereinigen. — Die Ergebnisse werden diskutiert und vor allem mit denen, die an Apis erzielt werden, verglichen.

---

Fine structure of the compound eye in the leaf-cutter bee Megachile rotundata (F.) (hymenoptera, apidae)

Summary Ommatidia in the dorsal part of the compound eye in female Megachile (a solitary bee) were studied with the electron microscope. The crystalline conesubstance of the Semper (type cells eucone) borders a wide area of the cornea, which probably implies an improved optical system compared with other eucone eyes. The four processes of the Scraper cells extend to the basement membrane, where they enlarge and are filled with screening pigment. The iris pigment cells end distally by impinging on a small area of the cornea and (unlike other ommatidia with an eucone form of crystalline cone) they do not overlap the corneal cells. The retinal pigment cells are entirely filled with pigment granules. A basal pigment cell as described in each ommatidium in Apis does not occur in Megachile. Instead, one finds the basal swellings of the Semper cell processes mentioned above.Usually the retinula consists of nine retinular cells arranged in a closed rhabdom. In the distal part of the ommatidium, this rhabdom is built by microvilli of the retinular cells number 1 and 5, aligned in one direction each perpendicular to the next. These two rhabdomeres are bordered on one side by the rhabdomeres of cell 2–4, and on the other side by those of cells 6–8. Again, these rhabdomeres are all aligned in one direction perpendicular to that of cell 1 and 5. Further down towards the base, there is an area in which the rhabdomeres of the retinular cells 2–4 and 6–8 face another as mentioned above, whereas those microvilli belonging to cell 1 and 5 seem to be forced away towards the periphery of the rhabdom.In addition to common organelles, both the pigment cells and Semper cells contain centrioles arranged at an angle or in tandem. In the retinular cells, they correspond to the basal bodies of cilia, and they give rise to tubules (sometimes striated fibrils are found). However, towards to base they give rise to striated fibrils which unite in a root fibre. — The results are discussed and compared with those known of Apis.

---

---

Fur ihre technische Hilfe danken wir besonders herzlich Frl. A. Hennig.     

Zonal distribution of bumblebee species (hymenoptera,apidae) in the North of European Russia

The bumblebee fauna of the North of European Russia includes 34 species. The trends in bumblebee diversity within the region are characterized. The species richness is the greatest in the middle taiga subzone and decreases from south to north, reaching its minimum in the Arctic tundra. Based on analysis of the zonal differentiation of bumblebee species, only four of them were found to be true arctic forms: Bombus (Alpinobombus) polaris, B. (Al.) balteatus, B. (Al.) hyperboreus, and B. (Pr.) lapponicus glacialis, whereas the rest belong to the temperate, boreal, and subboreal groups.     

Allozyme variation in the stingless bee Trigona fuscobalteata (hymenoptera,apidae) from Peninsular Malaysia

• 1.1. A population of Trigona fuscobalteata from Peninsular Malaysia was analysed for genetic variation at 9 gene-enzyme systems comprising 13 loci.
• 2.2. Two gene-enzyme systems (phosphoglucomutase and isocitrate dehydrogenase) were polymorphic in the 20 colonies studied.
• 3.3. Isocitrate dehydrogenase was represented by duplicate genes.
• 4.4. The number of loci for several enzyme systems appeared to be different from that reported for the Australian stingless bees.

     

Phylogenetic analysis of Starmerella apis in honey bees (Apis mellifera)

Honey bees are among the most effective pollinators that promote plant reproduction. Bees are highly active in the pollen collection season, which can lead to the transmission of selected pathogens between colonies. The clade Starmerella comprises yeasts that are isolated mainly from bees and their environment. When visiting plants, bees can come into contact with Starmerella spp. The aim of this study was to determine the prevalence and phylogenetic position of S. apis in bee colonies. Bee colonies were collected from nine apiaries in three regions. Ten colonies were sampled randomly from each apiary, and pooled samples were collected from the central part of the hive in each colony. A total of 90 (100%) bee colonies from nine apiaries were examined. Starmerella apis was detected in 31 (34.44%) samples, but related species were not identified. The 18S rRNA amplicon sequences of S. apis were compatible with the GenBank sequences of Starmerella spp. from India, Japan, Syria, Thailand, and the USA. The amplicon sequences of S. apis were also 99.06% homologous with the sequences deposited in GenBank under accession numbers JX515988 and NG067631 .This is the first study to perform a phylogenetic analysis of S. apis in Polish honey bees.     

Juvenile hormone III induced ultrastructural changes in the hypopharyngeal glands of honeybee Apis mellifera L. (Hymenoptera : Apidae) without and with infection by Nosema apis zander (Microsporidae : Nosematidae)

In the fully activated hypopharyngeal gland of the worker honeybee, Apis mellifera (Hymenoptera : Apidae), there were numerous electron-dense secretion granules, large secretion masses, free ribosomes, and arrays of endoplasmic reticulum. Injection of juvenile hormone into the honeybee caused crystallization of the secretion granules. After 1 and 7 days following the injection, both free and attached ribosomes were depleted from the cytoplasm. The depletion of ribosomes from the cytoplasm of the hypopharyngeal gland cells was observed only in honeybees infected by Nosema apis after injection of juvenile hormone. The appearance of an increasing number of lysosome-like bodies in the cytoplasm suggests that juvenile hormone activates the lysozymes, which leads to the degeneration of the hypopharyngeal glands.     

Sperm use economy of honeybee (Apis mellifera) queens

The queens of eusocial ants, bees, and wasps only mate during a very brief period early in life to acquire and store a lifetime supply of sperm. As sperm cannot be replenished, queens have to be highly economic when using stored sperm to fertilize eggs, especially in species with large and long‐lived colonies. However, queen fertility has not been studied in detail, so that we have little understanding of how economic sperm use is in different species, and whether queens are able to influence their sperm use. This is surprising given that sperm use is a key factor of eusocial life, as it determines the fecundity and longevity of queens and therefore colony fitness. We quantified the number of sperm that honeybee (Apis mellifera) queens use to fertilize eggs. We examined sperm use in naturally mated queens of different ages and in queens artificially inseminated with different volumes of semen. We found that queens are remarkably efficient and only use a median of 2 sperm per egg fertilization, with decreasing sperm use in older queens. The number of sperm in storage was always a significant predictor for the number of sperm used per fertilization, indicating that queens use a constant ratio of spermathecal fluid relative to total spermathecal volume of 2.364 × 10^?6 to fertilize eggs. This allowed us to calculate a lifetime fecundity for honeybee queens of around 1,500,000 fertilized eggs. Our data provide the first empirical evidence that honeybee queens do not manipulate sperm use, and fertilization failures in worker‐destined eggs are therefore honest signals that workers can use to time queen replacement, which is crucial for colony performance and fitness.     

Hygropreference and brood care in the honeybee (Apis mellifera)

Terrestrial organisms need to limit evaporation from their bodies in order to maintain a homeostatic water balance. Owing to a large surface to volume ratio, arthropods are particularly susceptible to desiccation and have evolved behavioural and physiological mechanisms to conserve water. In social insects, water balance is also affected by the interactions between nestmates and by the architecture of the nest. For honeybees, humidity is particularly important for the brood because it affects the hatching success of eggs and because, unlike ants, honeybees cannot relocate their brood to parts of the nest with more favourable humidity. To advance the understanding of the water economy in honeybee nests, we investigated whether workers exhibit a hygropreference when exposed to a gradient of 24-90% relative humidity (RH) and whether the expression of this preference and their behaviour is affected by the presence of brood. The results show that young honeybee workers in the absence of brood exhibit a weak hygropreference for approximately 75% RH. When brood is present the expression of this preference is further weakened, suggesting that workers tend to the brood by distributing evenly in the gradient. In addition, fanning behaviour is shown to be triggered by an increase in humidity above the preferred level but not by a decrease. Our results suggest that humidity in honeybee colonies is actively controlled by workers.     

High-performance liquid chromatography (HLPC) measurement of catecholamines in single honeybee brains reveals caste-specific differences between worker bees and queens in apis mellifera

1. Catecholamines were determined by HPLC in honeybee brains using automatized extraction and on-line detection with an electrochemical detector.2. This method has high sensitivity in the range of fmols. Thus, catechols can be measured in single brains as well as in parts of brains.3. The comparison of brains of worker bees and queens shows a caste-specific content of eatecholamine concentrations in worker bees and queens.4. The amount of norepinephrine and dopamine are higher in queens than in worker bees.5. The differences are not caused by the different size of the respective brains, but reflect a difference in the two female castes.     

Local honeybee (Apis mellifera mellifera L.) populations in the Urals

The COI-COII intergenic region of mitochondrial DNA (mtDNA) was studied in local honeybee (Apis mellifera mellifera) L. populations from the Middle and Southern Urals. Analysis of bee colonies in these regions revealed apiaries enriched in families descending from A. m. mellifera in the maternal lineage. These results confirm the suggestion of preservation of A. m. mellifera refuges in the Urals and provide grounds for work on the preservation of the gene pool of this bee variety, valuable for all Russia.     

Visual discrimination of radial cues by the honeybee (Apis mellifera)

This is a systematic study of the discrimination of black radially symmetrical patterns presented on a white vertical background and subtending 45 degrees or 50 degrees at the point of choice in a Y-maze apparatus. Before discrimination can occur, the ability to fixate is promoted by any radial pattern irrespective of the number of symmetry axes. A ring of spots can also stabilize the eye before the positions of the spots are discriminated.Cues for discrimination are of two main types. First, with fixed patterns of sectors or spots, the cue is the location of an area of black relative to the fixation point, and the particular number of axes is less important than the size of the individual areas. Secondly, evidence is presented for a family of filters with large fields and coarse tuning that detect patterns of radially symmetrical edges. These filters become more evident when the patterns are made of thin black radial bars or when they are rotated at random during the training. An angular shift of one radial pattern relative to the other, or a difference between numbers of bars, is best discriminated when one of the patterns but not the other has angles of 30 degrees, 60 degrees, or 120 degrees between radial edges, and least when the angles are 90 degrees. Baffles in the apparatus make the bees pause and fixate so that discrimination is improved. When targets are rotated during the learning process, radial cues for discriminations must be presented as edges, not as spots or areas. Besides detecting and fixating flowers, this system could be useful to estimate the perfection of their symmetry.     

微孢子虫和狄斯瓦螨分别侵染后的意蜂血淋巴蛋白质含量变化

微孢子虫Nosema apis和狄斯瓦螨微孢子虫Nosema apis和狄斯瓦螨 Varroa destructor (Acari: Varroidae)均为危害意蜂Apis mellifera的重要寄生虫,该文对其危害后意蜂血淋巴蛋白质含量的变化进行了研究。用考马斯亮蓝法测定了意蜂受侵染后血淋巴的蛋白质总量,并用高压超薄层等电点聚焦法进行血淋巴蛋白质分类。结果显示,病蜂血淋巴蛋白质总量,在人工感染微孢子虫后1～10天呈微孢子虫Nosema apis和狄斯瓦螨 Varroa destructor (Acari: Varroidae)均为危害意蜂Apis mellifera的重要寄生虫,该文对其危害后意蜂血淋巴蛋白质含量的变化进行了研究。用考马斯亮蓝法测定了意蜂受侵染后血淋巴的蛋白质总量,并用高压超薄层等电点聚焦法进行血淋巴蛋白质分类。结果显示,病蜂血淋巴蛋白质总量,在人工感染微孢子虫后1～10天呈上升趋势,然后逐渐下降,感染后12～27天保持在感染前意蜂血淋巴总蛋白质含量水平以下。螨侵染后意蜂血淋巴蛋白质含量明显增高,与健康意蜂相比差异极显著。高压超薄层等电点聚焦分析表明：狄斯瓦螨自然侵染意蜂后,意蜂血淋巴蛋白质组分与健康对照组相比发生了明显改变。这些结果提示,意蜂对于微孢子虫或狄斯瓦螨的侵染产生了一定的免疫反应。     

Visual resolution of the orientation cue by the honeybee (Apis mellifera)

Bees were trained to discriminate between a pattern with two or more black bars and a similar pattern with the bars at right angles. Earlier measures of the resolution of oblique black and white regular gratings of different periods were confirmed. The positions of the training bars were shifted every 5 min to prevent the bees from using their locations as cues. To measure the length of the detectors of edge orientation, the trained bees were tested with targets filled with parallel short black/white edges of various lengths. The minimum individual length of edge required to discriminate the orientation cue was found to be near 3 degrees, and similar for vertical, horizontal and oblique edges. This is the first time that this kind of resolution has been measured in an invertebrate. The bees learn and recognize the edge orientation, not the lay-out of the pattern.