How many neuroblasts build mushroom bodies in <Emphasis Type="Italic">Lucilia caesar</Emphasis> L. and <Emphasis Type="Italic">Musca domestica</Emphasis> L. (Diptera,Brachycera Cyclorrhapha)?

The green-bottle fly Lucilia caesar and the housefly Musca domestica differ greatly in the number of neuroblasts producing mushroom bodies. Four neuroblasts were found in each mushroom body of Lucilia pupae, and its calyx has a quadruple structure. In the housefly, the number of mushroom body neuroblasts rises up 20 in each brain hemisphere. This leads to a more complicated calyx structure. The neuroblast number observed in Lucilia and Musca is compared with that found in other Diptera.     

A subpopulation of mushroom body intrinsic neurons is generated by protocerebral neuroblasts in the tobacco hornworm moth, Manduca sexta (Sphingidae, Lepidoptera)

Subpopulations of Kenyon cells, the intrinsic neurons of the insect mushroom bodies, are typically sequentially generated by dedicated neuroblasts that begin proliferating during embryogenesis. When present, Class III Kenyon cells are thought to be the first born population of neurons by virtue of the location of their cell somata, farthest from the position of the mushroom body neuroblasts. In the adult tobacco hornworm moth Manduca sexta, the axons of Class III Kenyon cells form a separate Y tract and dorsal and ventral lobelet; surprisingly, these distinctive structures are absent from the larval Manduca mushroom bodies. BrdU labeling and immunohistochemical staining reveal that Class III Kenyon cells are in fact born in the mid-larval through adult stages. The peripheral position of their cell bodies is due to their genesis from two previously undescribed protocerebral neuroblasts distinct from the mushroom body neuroblasts that generate the other Kenyon cell types. These findings challenge the notion that all Kenyon cells are produced solely by the mushroom body neuroblasts, and may explain why Class III Kenyon cells are found sporadically across the insects, suggesting that when present, they may arise through de novo recruitment of neuroblasts outside of the mushroom bodies. In addition, lifelong neurogenesis by both the Class III neuroblasts and the mushroom body neuroblasts was observed, raising the possibility that adult neurogenesis may play a role in mushroom body function in Manduca.     

Not all dytiscidae have poorly developed mushroom bodies: The enigma of Cybister lateralimarginalis

The majority of diving beetles studied has completely differentiated but poorly developed mushroom bodies. The Kenyon cells are not numerous, the calyces are small, and the pedunculi and lobes have a simple structure. New Kenyon cells are produced by few solitary neuroblasts. Cybister lateralimarginalis makes an amazing exception. Its mushroom bodies are strongly developed and comprise numerous Kenyon cells, large calyces, and a peduncular apparatus of a complicated structure. The Kenyon cells are produced in polyneuroblast proliferative centers. The grounds of such strong development of the mushroom body in Cybister remain unknown.     

Mushroom Body Neuroblasts of the Lepidopteran Brain (Insecta: Lepidoptera)

A study of the brain of 47 species from 15 lepidopteran families has revealed that only one neuroblast corresponds to each calyx cup of the mushroom body and that mushroom body neuroblasts have been found in the imagoes of 13 out of 25 species caught in the field. It is considered that the proliferative centers consisting of several neuroblasts are not characteristic of lepidopteran mushroom bodies, whereras Kenyon cell neurogenesis in the imago appears to be a widespread phenomenon.     

Mitogenic effects of 20‐hydroxyecdysone on neurogenesis in adult mushroom bodies of the cockroach,Diploptera punctata

The purpose of this study was to examine the mitogenic effects of 20‐hydroxyecdysone on neurogenesis in mushroom bodies of the adult cockroach, Diploptera punctata. The occurrence of neurogenesis was studied immunocytochemically after in vivo labeling with 5‐bromo‐2′‐deoxyuridine (BrdU). The number of BrdU‐labeled cells in the mushroom bodies was high shortly after adult ecdysis, then gradually decreased, and proliferation ceased on day 8. 20‐Hydroxyecdysone injection during the early adult stages significantly delayed the decrease in mitotic activity. Moreover, 20‐hydroxyecdysone injection during the late stage stimulated quiescent mushroom body neuroblasts to initiate their mitotic activity in a dose‐dependent manner. These results indicated that the mushroom body neuroblasts of this insect become quiescent in the maturing central nervous system, but retain the capacity for proliferation if exposed to appropriate environmental signals. We conclude that 20‐hydroxyecdysone has a mitogenic effect on neurogenesis in mushroom bodies of this insect. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 264–274, 1999     

中华蜜蜂蕈形体的发育

中华蜜蜂(Apis cerana cerana)的脑由前脑、中脑和后脑三部分构成,蕈形体位于前脑的背侧,是其重要的学习及其他复杂行为的整合中心。通过对中华蜜蜂工蜂的幼虫、蛹及成虫的蕈形体形态发育的观察研究,发现中华蜜蜂的蕈形体包含约1000个成神经细胞,它们最终形成了蕈形体的所有Kenyon细胞。这些成神经细胞来自于在新孵化的幼虫脑中已存在的四丛成神经细胞,每一丛细胞的数量不多于45个。蕈形体柄区的出现约在3龄幼虫,而α叶和β叶在5龄幼虫已可明显辨认。冠区出现较晚,大约在蛹期的第二天以后。由于社会性昆虫复杂的学习、记忆和认知需求,其蕈形体的体积和复杂程度都优于其他昆虫。     

Early development of the Drosophila mushroom bodies, brain centres for associative learning and memory

We have studied the formation of Drosophila mushroom bodies using enhancer detector techniques to visualize specific components of these complex intrinsic brain structures. During embryogenesis, neuronal proliferation begins in four mushroom body neuroblasts and the major axonal pathways of the mushroom bodies are pioneered. During larval development, neuronal proliferation continues and further axonal projections in the pedunculus and lobes are formed in a highly structured manner characterized by spatial heterogeneity of reporter gene expression. Enhancer detector analysis identifies many genomic locations that are specifically activated in mushroom body intrinsic neurons (Kenyon cells) during the transition from embryonic to postembryonic development and during metamorphosis.     

Longicorn beetles (Coleoptera: Cerambycidae) differ considerably in the degree of their mushroom body development

A duality in the general structure of the mushroom body in longicorn beetles is confirmed. This duality is associated with the fact that they are formed by two solitary neuroblasts or two neuroblast clusters on each side of the brain and are manifested as a bipartite structure of both the calyx, which is the main sensory input, and the peduncular apparatus. Within the studied longicorn beetles, modifications in the general structure of mushroom bodies have been found; these modifications are caused by two oppositely directed morphogenetic processes, namely, the concentration of structures and their compartmentalization. The concentration leads to disappearance of the bipartite structure of the peduncular apparatus, whereas compartmentalization leads to a secondary subdivision of these structures into anatomically distinct subsections. This process is most pronounced in the peduncle and lobes. The mushroom bodies are best developed and differentiated in the members of the subfamily Lamiinae.     

Mcm3 replicative helicase mutation impairs neuroblast proliferation and memory in Drosophila

In the developing Drosophila brain, a small number of neural progenitor cells (neuroblasts) generate in a co‐ordinated manner a high variety of neuronal cells by integration of temporal, spatial and cell‐intrinsic information. In this study, we performed the molecular and phenotypic characterization of a structural brain mutant called small mushroom bodies (smu), which was isolated in a screen for mutants with altered brain structure. Focusing on the mushroom body neuroblast lineages we show that failure of neuroblasts to generate the normal number of mushroom body neurons (Kenyon cells) is the major cause of the smu phenotype. In particular, the premature loss of mushroom body neuroblasts caused a pronounced effect on the number of late‐born Kenyon cells. Neuroblasts showed no obvious defects in processes controlling asymmetric cell division, but generated less ganglion mother cells. Cloning of smu uncovered a single amino acid substitution in an evolutionarily conserved protein interaction domain of the Minichromosome maintenance 3 (Mcm3) protein. Mcm3 is part of the multimeric Cdc45/Mcm/GINS (CMG) complex, which functions as a helicase during DNA replication. We propose that at least in the case of mushroom body neuroblasts, timely replication is not only required for continuous proliferation but also for their survival. The absence of Kenyon cells in smu reduced learning and early phases of conditioned olfactory memory. Corresponding to the absence of late‐born Kenyon cells projecting to α′/β′ and α/β lobes, smu is profoundly defective in later phases of persistent memory.     

Three-dimensional reconstruction of mushroom body neuropils in the polychaete species <Emphasis Type="Italic">Nereis diversicolor</Emphasis> and <Emphasis Type="Italic">Harmothoe areolata</Emphasis> (Phyllodocida,Annelida)

Mushroom bodies are prominent brain neuropils present in most arthropod representatives. Similar structures in the brain of certain polychaete species are possibly homologous to these structures. Using three-dimensional reconstruction techniques, we investigated the structural composition of the mushroom body neuropils in the polychaete species Nereis diversicolor and Harmothoe areolata. Comparative analysis revealed a common organization of neuropil substructures in both species that closely matches the basic assembly of arthropod mushroom bodies. Concurring with earlier homology assessments, these neuroarchitectural similarities provide support for a common origin of mushroom body neuropils in polychaetes and arthropods. Beyond that, differences in the morphological differentiation of neuropil substructures indicate polychaete mushroom bodies to show a high degree of morphological variability, thus impeding the quest for a common ground pattern of these brain centers.     

Proliferation pattern of postembryonic neuroblasts in the brain of Drosophila melanogaster.

The spatio-temporal proliferation pattern of postembryonic neuroblasts in the central brain region of the supra-esophageal ganglion of Drosophila melanogaster was studied by labeling DNA replicating cells with 5-bromo-2'-deoxyuridine (BrdU). There are five proliferating neuroblasts per hemisphere in larvae just after hatching: one in the ventro-lateral, and the other four in the postero-dorsal region of the brain. Dividing neuroblasts increase during the late first-late second instar larval stages, reaching a plateau of about 85 neuroblasts per hemisphere. Most neuroblasts cease dividing 20-30 hr after puparium formation (APF), while only four in the postero-dorsal region continue making progenies until 85-90 hr APF. The four distinct neuroblasts proliferating in the early larval and late pupal stages are identical; they lie in the cortex above the calyces of the mushroom bodies (corpora pedunculata), proliferating over a period twice as long as that for the other neuroblasts. Their daughter neurons project into the mushroom body neuropile, and hence are likely to be the Kenyon cells. The cell-cycle period of the four neuroblasts (named mushroom body neuroblasts: MBNbs) is rather constant (1.1-1.5 hr) during the mid larval-early pupal stages and is longer before and after that. The total number of the MBNb progenies made throughout the embryonic and postembryonic development was estimated to be 800-1200 per hemisphere.     

Mitogenic effects of 20-hydroxyecdysone on neurogenesis in adult mushroom bodies of the cockroach, Diploptera punctata

The purpose of this study was to examine the mitogenic effects of 20-hydroxyecdysone on neurogenesis in mushroom bodies of the adult cockroach, Diploptera punctata. The occurrence of neurogenesis was studied immunocytochemically after in vivo labeling with 5-bromo-2'-deoxyuridine (BrdU). The number of BrdU-labeled cells in the mushroom bodies was high shortly after adult ecdysis, then gradually decreased, and proliferation ceased on day 8. 20-Hydroxyecdysone injection during the early adult stages significantly delayed the decrease in mitotic activity. Moreover, 20-hydroxyecdysone injection during the late stage stimulated quiescent mushroom body neuroblasts to initiate their mitotic activity in a dose-dependent manner. These results indicated that the mushroom body neuroblasts of this insect become quiescent in the maturing central nervous system, but retain the capacity for proliferation if exposed to appropriate environmental signals. We conclude that 20-hydroxyecdysone has a mitogenic effect on neurogenesis in mushroom bodies of this insect.     

Hybrid carrot seed crop pollination by the fly Calliphora vicina (Diptera: Calliphoridae)

Many insect species can contribute to crop pollination; however, most growers remain highly dependent on the managed honey bee (Apis mellifera L.) for this service. The European Blue Blow Fly Calliphora vicina Robineau‐Desvoidy, 1830 is one species with potential use as a pollinator. It occurs worldwide and is easy to rear. Caged trials conducted within a hybrid carrot (Daucus carota L.) seed crop found C. vicina to be an effective pollinator. Seed yield (number and weight) from field‐grown carrot plants caged with C. vicina, but excluding all other large flower visitors (body width > 3 mm), was similar to seed yield from uncaged plants in the presence of honey bees (Apis mellifera L.) and other insects. In contrast, caged plants without C. vicina produced 10‐fold less seed. Under open field conditions, C. vicina spent an average of 71.0 s per umbel compared to 54.4 s for honey bees; however, under caged conditions, C. vicina spent more time on average per umbel (128.9 s). Counts of C. vicina and honey bees on umbels outside of cages and C. vicina inside cages found that honey bees were most abundant on days with maximum temperature > 25°C, while C. vicina was more abundant on cooler days around 20°C. C. vicina may therefore be a useful pollinator of crops grown in isolation cages for plant breeding purposes as well as in open fields when climatic conditions are less favourable for optimal honey bee activity.     

Histological structure of tripartite mushroom bodies in ground beetles (Insecta, Coleoptera: Carabidae)

Contrary to members of the suborder Polyphaga, ground beetles have been found to possess tripartite mushroom bodies, which are poorly developed in members of basal taxa and maximally elaborated in evolutionarily advanced groups. Nevertheless, they do not reach the developmental stage, which has been previously found in particular families of beetles. It has been pointed out that a new formation of the Kenyon cells occurs during at least the first months of adult life, and inactive neuroblasts are found even in one-year-old beetles. It has been suggested that there is a relation between the Kenyon cell number and development of the centers of Kenyon cell new-formation.     

General structure of the mushroom body calyx in brachycera orthorrhapha flies (Diptera)

The mushroom body calyx in Brachycera Orthorrhapha flies is extremely diverse in the degree of development. In general, the calyx has the anterior, posterior, and dorsal lobes, as well as “sleeves” of glomerular neuropil surrounding Kenyon cell fibers. The anterior lobe of the calyx is found in all species studied. The most complex structure of the calyx is characteristic of the families Empididae and especially Bombyliidae, in which it has all the parts listed above. Brachycera Orthorrhapha flies have three fiber bundles of Kenyon cells, in contrast to four bundles in Drosophila. It is assumed that each mushroom body in Brachycera Orthorrhapha flies is formed by descendants of three single neuroblasts.     

Cloning and expression analysis of a muscarinic cholinergic receptor from the brain of ant,Polyrhachis vicina

Muscarinic acetylcholine receptors (mAchRs) are the predominant cholinergic receptors in the central and peripheral nervous systems of animals. They also have been found in various insect nervous systems. In this article, a full‐length cDNA of a pupative mAchR (PmAchR) was obtained from the brains of ant Polyrhachis vicina by homology cloning in combination with rapid amplification of cDNA ends. PmAchR encodes a 599‐amino acid protein that exhibits a high degree of homology with other mAchRs. Real‐time quantitative RT‐PCR analysis showed that PmAchR is differentially expressed in the brains of workers, males, and females. By in situ hybridization, it is revealed that PmAchR is widely expressed in different soma clusters of the brain, including the mushroom bodies, the antennal lobes, as well as the optic lobes (OL), and the most intensely staining is found in Kenyon cells. Nonetheless, there are more positive nerve fibers in the OL of males' brains than in females' and workers' brains. © 2011 Wiley Periodicals, Inc.     

Developmental organization of the mushroom bodies of Thermobia domestica (Zygentoma, Lepismatidae): insights into mushroom body evolution from a basal insect

The mushroom bodies of the insect brain are sensory integration centers best studied for their role in learning and memory. Studies of mushroom body structure and development in neopteran insects have revealed conserved morphogenetic mechanisms. The sequential production of morphologically distinct intrinsic neuron (Kenyon cell) subpopulations by mushroom body neuroblasts and the integration of newborn neurons via a discrete ingrowth tract results in an age-based organization of modular subunits in the primary output neuropil of the mushroom bodies, the lobes. To determine whether these may represent ancestral characteristics, the present account assesses mushroom body organization and development in the basal wingless insect Thermobia domestica. In this insect, a single calyx supplied by the progeny of two neuroblast clusters, and three perpendicularly oriented lobes are readily identifiable. The lobes are subdivided into 15 globular subdivisions (Trauben). Lifelong neurogenesis is observed, with axons of newborn Kenyon cells entering the lobes via an ingrowth core. The Trauben do not appear progressively during development, indicating that they do not represent the ramifications of sequentially produced subpopulations of Kenyon cells. Instead, a single Kenyon cell population produces highly branched axons that supply all lobe subdivisions. This suggests that although the ground plan for neopteran mushroom bodies existed in early insects, the organization of modular subunits composed of separate Kenyon cell subpopulations is a later innovation. Similarities between the calyx of Thermobia and the highly derived fruit fly Drosophila melanogaster also suggest a correlation between calyx morphology and Kenyon cell number.     

Comparative histology of mushroom bodies in carnivorous beetles of the suborder polyphaga (Insecta, Coleoptera)

Mushroom bodies in beetles of the families Histeridae, Staphylinidae, Cantharidae, Trogossitidae, Peltidae, Cleridae, Malachiidae, and Coccinellidae are shown to be rather poorly developed. The calyx region of the mushroom bodies in these beetles never forms two separate cups, and the peduncular apparatus includes a unified shaft almost over its entire length. Only the pedunculus contains two separate shafts in a few cases. Two proliferative centers consisting of one to three neuroblasts are often found in each Kenyon cell group. The shift from carnivorous to feeding on pollen or leaves, which has taken place in some taxa, does not visibly affect the degree of mushroom body development.     

Mining and utilization of mushroom ESTs for microsatellites

In the present study we report on the exploitation of expressed sequence tags (ESTs); (1) to investigate whether microsatellite densities are significantly differed among Pleurotus ostreatus, Lentinula edodes and Agaricus bisporus ESTs, (2) between development stages of mycelia and fruiting bodies and (3) to identify microsatellite primer pairs that could be used in mushroom genetic studies. Analyses of ESTs indicated that three mushroom species and tissues showed statistically significant microsatellite densities. A total of 23 EST-microsatellite primer pairs were developed and tested on two species of mushrooms. The use of these microsatellite primer pairs could be used in genetic studies of mushroom species.     

Localization of Glutamate in the Nervous System of the Fly Drosophila melanogaster: An Immunocytochemical Study

Localization of glutamate in the central nervous system of the fly Drosophila melanogaster was studied using highly specific polyclonal rabbit antibody to glutamate conjugated to the bovine serum albumin. Glutamate was revealed in the mushroom body Canyon cells, whose processes were traced in the stem of the mushroom bodies, then entered their - and -blades. A group of four glutamate-containing cells (vln) is located ventrally on the border of the lateral procerebrum and medulla. The main process of each cell formed glutamate-containing varicose branchings in the dorsal part of the mushroom body cup. It has been established that lateral neurons of the central body of the F1- and Fml-types were immunostained positively for glutamate. The obtained data on distribution of glutamate-containing cells in the brain centers studied in Drosophila indicate participation of glutamate in integration of the sensory information and locomotor coordination.