Structure of cephalic ganglia and their changes in the post-embryonic development of <Emphasis Type="Italic">Calliphora vomitoria</Emphasis> (L.) (Diptera,Calliphoridae)

The central nervous system of Calliphora vomitoria larvae is situated in the metathoracic and the first abdominal segments and is characterized by a high degree of oligomerization. It consists of only two ganglia: the supraoesophageal ganglion, or brain, and one large synganglion, a product of fusion of the suboesophageal ganglion, three thoracic, and all the abdominal ganglia. Weak development of the neuropil of the larval optic and olfactory lobes in the supraoesophageal ganglion is the result of a significant reduction of the head capsule and sensory organs in the larvae. The formation of the imaginal optic lobes begins at the III larval instar. The commissure of the future central body is present in the I instar larva, but formation of the imaginal structure of the central complex proceeds in the 3-day pupae and ends at the late pupal stage. The mushroom bodies are represented in the I instar larvae only by the pedunculi; the calyces can be distinguished in the II instar larvae but the final formation of their structure and the lobes of the imaginal type occurs at the pupal stage. The glomeruli in the deutocerebrum are also formed at a late stage of pupal development. Based on the degree of development of ganglia of the central nervous system, we can conclude that individual development of higher Diptera is characterized by deep de-embryonization.     

棉铃虫幼虫脑和咽下神经节的三维结构构建

【目的】解剖棉铃虫Helicoverpa armigera (Hübner) 5龄幼虫脑和咽下神经节及其内部神经髓形态结构,并分析和构建幼虫脑和咽下神经节以及各神经髓的三维结构模型。【方法】采用免疫组织化学方法解剖脑和咽下神经节的内部神经髓结构,利用激光共聚焦显微镜获取脑和咽下神经节扫描图像,然后利用AMIRA 三维图像分析软件进行图像分析,从而构建脑和咽下神经节的三维结构模型,并测量脑和咽下神经节以及内部各神经髓的体积,并分析了相对比例。【结果】 棉铃虫5龄幼虫脑和咽下神经节由围咽神经索连接在一起。脑主要由前脑、中脑和后脑3部分组成。前脑内包括视叶、蕈形体和中央体等形态结构较明显的神经髓。此外,前脑还包括其他位于脑的左右两侧以及背侧和腹侧大量神经髓区域,约占脑总神经髓的59.65%。这些神经髓区域边界不明显。中脑主要包括1对触角叶;后脑位于脑的腹侧和触角叶的下方,体积较小。咽下神经节由3个神经节融合构成,从前到后分别为上颚神经节、下颚神经节和下唇神经节,由于融合的紧密程度高,3个神经节间的边界不明显。【结论】阐明了棉铃虫5龄幼虫脑和咽下神经节的神经髓形态结构,构建了脑和咽下神经节以及内部神经髓的三维结构模型。三维模型可以任意旋转,能从任何角度观察脑、咽下神经节和内部不同神经髓的结构及其它们之间的空间关系。本研究结果对研究棉铃虫脑和咽下神经节信息接收、处理及调控行为的机制奠定了解剖学基础。     

Morphology of the larval and adult brains of the monarch butterfly, Danaus plexippus plexippus, L

Cell population and neuropile morphology of larval and adult brains of the monarch butterfly, Danaus plexippus plexippus, L., are compared. The larval brain is in continuous transition, the processes of adult brain development being underway from the earliest larval stages. It is characterized by a less diverse population of cells and more homogenous fiber areas than those of the adult. Neuroblasts, which divide to form the neurones of the adult brain, occur either in discrete proliferation centers or scattered among the larval ganglion cells. The larval brain contains, in addition to small homogeneous antennal centers and a distinct larval optic center, rapidly developing adult optic centers, corpora pedunculata, and protocerebral bridge. The larval brain lacks a central body. Major differences between larval and adult brains are clearly related to the increased dependence of the adult upon sensory input from the eyes and antennae.     

蟋蟀脑的解剖结构与生理机能

蟋蟀脑由前脑、中脑和后脑三部分组成。前脑由1对蕈形体、中央复合体和视叶构成;每个蕈形体由2个冠、柄及与柄相连的α叶和β叶组成,是信息联络整合部位;中央复合体由中央体和脑桥组成,主要参与感觉信息的加工过程;视叶由神经节层、外髓和内髓组成,是视觉系统的中心。中脑由主要组成成分为嗅觉纤维球的嗅叶组成,是嗅觉系统的中心。后脑向后与食道下神经节相连。     

Distribution of tachykinin-related neuropeptide in the developing central nervous system of the moth Spodoptera litura

Neuropeptides with similarities to vertebrate tachykinins, designated tachykinin-related peptides (TRPs), have been identified in several insect species. In this investigation we have utilized an antiserum raised to one of the locust TRPs, locustatachykinin-I (LomTK-I), to determine the distribution pattern of LomTK-like immunoreactive (LTKLI) neurons in the developing nervous system of the moth Spodoptera litura. A number of LTKLI neurons could be followed from the larval to the adult nervous system: a set of median neurosecretory cells (MNCs) in the brain, a pair of brain descending neurons and a few sets on neurons in the ventral nerve cord. The distribution of LTKLI neurons in the adult brain is very similar to that seen in other insect species with prominent arborizations in the central body, antennal lobes, mushroom body calyces, optic lobe neuropils and other distinct neuropil areas in the protocerebrum and tritocerebrum. A new finding is the presence of LTKLI neurosecretory cells with axon terminals in the anterior aorta and corpora cardiaca, suggesting for the first time a neurohormonal role of tachykinin-related peptide(s) in insects. During postembryonic development the number of LTKLI neurons in the ventral nerve cord decreases somewhat, whereas the number increases in the brain. Thus the functional roles of TRPs may change to some extent during development.     

Changes in brain amine levels associated with the morphological and behavioural development of the worker honeybee

Summary Changes in biogenic amine levels associated with the morphological and behavioural development of the worker honeybee are examined.A significant increase in amine levels in the head of the honeybee is associated with transition from the larval to pupal stage. Adult emergence is also accompanied by a significant increase in 5-HT levels in the brain, but no significant change in brain dopamine (DA) levels. NADA (N-acetyldopamine) levels increase during larval and pupal development, but in contrast to both DA and 5-HT, drop significantly during the transition from pupa to adult.Levels of DA in the brain of nectar and pollen forager bees, presumed to be among the oldest adults sampled, were found to be significantly higher than in nurses, undertakers or food storers. These results suggest that an age-dependent change in amine levels occurs in the brain of the worker bee. In the optic lobes, levels of DA and 5-HT were found to be significantly higher in pollen forager bees than in all other behavioural groups. Significant differences in amine levels in the optic lobes of nectar foragers and pollen foragers indicate that some differences in amine levels occur independent of worker age. The functional significance of differences in brain amine levels and whether or not biogenic amines play a direct role in the control of honeybee behaviour has yet to be established.Abbreviations DA dopamine - 5-HT 5-hydroxytryptamine or serotonin - NADA N-acetyldopamine     

L(1)trol and L(1)devl, Loci Affecting the Development of the Adult Central Nervous System in Drosophila Melanogaster

Adult optic lobes of Drosophila melanogaster are composed of neurons specific to the adult which develop postembryonically. The structure of the optic lobes and aspects of its development have been described, and a number of mutants that affect its development have been identified. The focus of every screen to date has been on disruption of adult structure or function. Although these loci were originally identified on the basis of viable mutants, some have proven capable of giving rise to lethal alleles. It seems reasonable to assume that mutants which strongly affect development of the imaginal-specific central nervous system may evidence abnormalities during the late larval or pupal stages when the adult central nervous system is undergoing final assembly and might show a lethal phase prior to eclosion (as is true for mutations at the previously defined l(1)ogre locus). We have carried out the first screen of autosomal and sex-linked late larval and pupal lethals to identify mutations that affect the development of the optic lobes. Our screen yielded nine mutants that could tentatively be grouped into three classes, depending on the neuroblast population affected and imaginal disc phenotypes. Two of these, including one that is allelic to l(1)zw1, were chosen for further analysis.     

Postembryonic development of Arg-Phe-amide-like and cholecystokinin-like immunoreactive neurons in the blowfly optic lobe

Summary The adult optic lobes of the blowfly Calliphora erythrocephala were found to be innervated by more than 2000 neurons immunoreactive to antisera raised against the neuropeptides FMRFamide, its fragment RFamide, and gastrin/cholecystokinin (CCK). All of the CCK-like immunoreactive (CCK-IR) neurons also reacted with antisera to RFamide, FMRFamide and pancreatic polypeptide. A few RFamide/FMRFamide-like immunoreactive (RF-IR) neurons did not react with CCK antisera; they reacted instead with antisera to Leu-enkephalin and Met-enkephalin-Arg⁶-Phe⁷. The RF-IR neurons are, thus, heterogeneous with respect to their contents of immunoreactive peptides. Two of the RF-IR neuron types innervating the adult optic lobes could be traced in their entirety only after following their postembryonic development, because of the complexity of the trajectories of the immunoreactive neuronal process in the adult insect. The majority of the cell bodies of the RF-IR and CCK-IR neurons lie within the optic lobes and are derived from imaginal neuroblasts of the inner and outer optic anlagen. Six of the peptidergic neurons are, however, metamorphosing larval neurons with their cell bodies in the central part of the protocerebrum. The full extent of immunoreactivitiy is not attained in some of the neurons until the late pupal or early adult stage. The larval optic center was also found to be innervated by neurons immuno-reactive with both RFamide and CCK antisera. The cell bodies of these RF-IR/CCK-IR neurons are located near the developing lamina (one on each side). In the 24 h pupa, the cell bodies of these neurons are still immunoreactive, but thereafter they cannot be immunolabeled apparently due to cell death or a change in transmitter phenotype.     

Pre-existing neuronal pathways in the developing optic lobes of Drosophila

We have identified a set of larval neurones in the developing adult optic lobes of Drosophila by selectively labelling cells that have undergone only a few mitoses. A cluster of three cells is located in each of the optic lobes near the insertion site of the optic stalk. Their axons fasciculate with fibres of the larval optic nerve, the Bolwig's nerve, and then form part of the posterior optic tract. These cells are likely to be first order interneurones of the larval visual system. Unlike the Bolwig's nerve, they persist into the adult stage. The possibility of a pioneering function of the larval visual system during formation of the adult optic lobe neuropil is discussed.     

昆虫嗅觉系统结构与功能研究进展

昆虫的脑由前脑、中脑和后脑组成,其中前脑含有高级感觉中枢,如蘑菇体和中央复合体,控制昆虫的学习、记忆和运动等高级神经活动;中脑包含触角叶,是嗅觉神经中心;而后脑则通常不发达,主要包括内分泌神经元和控制进食与消化的运动神经元。不同于其他物种,昆虫由于其特殊的生活习性,听觉和视觉系统相对退化,主要依赖嗅觉来捕食、交流和求偶,因此嗅觉系统尤其发达。本文综述了目前对昆虫的脑部主要神经结构和功能(中央复合体、蕈形体和触角叶结构)以及昆虫脑部结构遗传变异(性别异构,不同发育时期、不同昆虫以及昆虫与其他动物的脑部结构差异)的研究进展,并总结了目前昆虫脑对信号的加工处理和识别机制的研究结果。     

Evidence for brain-derived neurotrophic factor-like neuropeptide in brain of the silk moth Bombyx mori during postembryonic periods

Brain-derived neurotrophic factor-like neuropeptide is produced in the brain of the silk moth, Bombyx mori. Immunocytochemical studies of brain and retrocerebral complex of larvae, prepupae, pupae and adults showed that four pairs of median neurosecretory cells and six pairs of lateral neurosecretory cells which had different immunoreactivities to BDNF peptide. Day-1 adult brains showed no evidence of neurons stained by anti-BDNF antibodies. Those reactivities, which were much stronger in median cells than in lateral cells, were the weakest in an earliest larval stage and a latest pupal stage but the strongest in late larval stage. Median neurosecretory cells projected their axons into the contralateral corpora allata by decussation in the median region, nerve corpora cardiaca (NCC) I, and nerve corpora allata (NCA) I, whereas lateral neurosecretory cells extended their axons to the ipsilateral corpora allata via NCC II and NCA I.     

Postembryonic development of serotonin-immunoreactive neurons in the central nervous system of the blowfly,Calliphora erythrocephala

Summary The postembryonic development of serotonin-immunoreactive (5-HTi) neurons was studied in the optic lobe of the blowfly. In the adult fly there are 24 5-HTi neurons invading each optic lobe. The perikarya of two of these neurons are situated in the dorso-caudal part of the protocerebrum (LBO-5HT neurons; large bilateral optic lobe 5-HTi neurons). The cell bodies of the remaining 22 neurons are located anteriorly at the medial base of the medulla (2 innervating the lobula, LO-5HT neurons; and 20 neurons innervating the medulla, ME-5HT neurons). The two central neurons (LBO-5HT neurons) are derived from metamorphosing larval neurons, while the ME- and LO-5HT neurons are imaginai optic lobe neurons differentiating during pupal development.The 5-HTi neurons of the optic lobe seem to have different ancestors. The LBO-5HT neurons are probably derived from segmental protocerebral neuroblasts, whereas the ME-and LO-5HT neurons are most likely derived from the inner optic anlage. The first 5-HTi fibers to reach the imaginal optic lobes are seen in the late third instar larva and are derived from the LBO-5HT neurons. The first ME- and LO-5HT neurons become immunoreactive at 24 h (10%) pupal development. At about 96 h (40%) of pupal development all the 5-HTi neurons of the optic lobes have differentiated and attained their basic adult morphology. The further development mainly entails increase in volume of arborizations and number of finer processes. The differentiation and outgrowth of 5-HTi processes follows that of, e.g., columnar neurons in the optic lobe neuropils. Hence, 5-HTi processes invade neuropil relatively late in the differentiation of the optic lobe.     

Brain development in the yellow fever mosquito Aedes aegypti: a comparative immunocytochemical analysis using cross-reacting antibodies from Drosophila melanogaster

Considerable effort has been directed towards understanding the organization and function of peripheral and central nervous system of disease vector mosquitoes such as Aedes aegypti. To date, all of these investigations have been carried out on adults but none of the studies addressed the development of the nervous system during the larval and pupal stages in mosquitoes. Here, we first screen a set of 30 antibodies, which have been used to study brain development in Drosophila, and identify 13 of them cross-reacting and labeling epitopes in the developing brain of Aedes. We then use the identified antibodies in immunolabeling studies to characterize general neuroanatomical features of the developing brain and compare them with the well-studied model system, Drosophila melanogaster, in larval, pupal, and adult stages. Furthermore, we use immunolabeling to document the development of specific components of the Aedes brain, namely the optic lobes, the subesophageal neuropil, and serotonergic system of the subesophageal neuropil in more detail. Our study reveals prominent differences in the developing brain in the larval stage as compared to the pupal (and adult) stage of Aedes. The results also uncover interesting similarities and marked differences in brain development of Aedes as compared to Drosophila. Taken together, this investigation forms the basis for future cellular and molecular investigations of brain development in this important disease vector.     

Structural organization of the brain and subesophageal ganglion of male Aedes aegypti (L.) (Diptera : Culicidae)

The brain and subesophageal ganglion of male Aedes aegypti (L.) (Diptera : Culicidae) are described from cryofractures and silver-stained, semithin (0.5 μm) serial sections of whole heads observed in the scanning and light microscopes. The brain and subesophageal ganglion of male A. aegypti are fused. The major structures of the brain include the protocerebral lobes and bridge, the mushroom bodies, central complex of the protocerebrum, the mechanosensory regions and olfactory loves of the deutocerebrum, and the tritocerebrum. Major commissures of the brain are the anterior optic tract, central commissure, posterior dorsal commissure, and subesophageal commissure. The structural associations of brain components with each other and the subesophageal ganglion, as well as the paths of the major nerve tracts in male A. aegypti are described and compared with those in other Diptera.     

Central brain postembryonic development in Drosophila: implication of genes expressed at the interhemispheric junction

Postembryonic brain development of Drosophila has become recently a subject of intense investigations. In particular, the linotte (lio) mutants display strong structural defects in the mushroom bodies and the central complex. The Lio kinase is expressed in a glial structure at the interhemispheric junction of late larval and young pupal brain. With the aim of identifying new genes involved in the formation of adult central brain structures, 821 enhancer-trap Gal4 lines were generated and screened for late larval expression. We identified 167 lines showing expression at or near the interhemispheric junction of third-instar larval brain, an area from which the central complex differentiates. Adult brains from 104 of these 167 lines were analyzed through paraffin sections. This secondary screen allowed the recovery of five central brain mutants. Of 89 control lines showing various patterns of expression excluding the interhemispheric junction, only one anatomical mutant was isolated. These six mutations, which have been thoroughly characterized, affect the midline area of the adult brain with phenotypes of split central complex structures and/or fused mushroom body lobes. This work opens the way for further analysis of the molecular and cellular events involved in central brain reorganization during metamorphosis.     

Proliferation pattern and early differentiation of the optic lobes in Drosophila melanogaster

Summary The larval and early pupal development of the optic lobes in Drosophila is described qualitatively and quantitatively using [³H]thymidine autoradiography on 2-m plastic sections. The optic lobes develop from 30–40 precursor cells present in each hemisphere of the freshly hatched larva. During the first and second larval instars, these cells develop to neuroblasts arranged in two epithelial optic anlagen. In the third larval instar and in the early pupa these neuroblasts generate the cells of the imaginal optic lobes at discrete proliferation zones, which can be correlated with individual visual neuropils.The different neuropils as well as the repetitive elements of each neuropil are generated in a defined temporal sequence. Cells of the medulla are the first to become postmitotic with the onset of the third larval instar, followed by cells of the lobula complex and finally of the lamina at about the middle of the third instar. The elements of each neuropil connected to the most posterior part of the retina are generated first, elements corresponding to the most anterior retina are generated last.The proliferation pattern of neuroblasts into ganglion mother cells and ganglion cells is likely to include equal as well as unequal divisions of neuroblasts, followed by one or two generations of ganglion mother cells. For the lamina the proliferation pattern and its temporal coordination with the differentiation of the retina are shown.     

Immunocytochemical distribution of pigment-dispersing hormone in the cephalic ganglia of polyneopteran insects

Material detectable with antisera to the pigment-dispersing hormone (PDH) is regarded as a component of the circadian clock residing in some insects in the optic lobe. This paper demonstrates that the position of the PDH-positive neurones and the course of their processes are similar in all representatives of the insect cohort Polyneoptera. A basic morphological pattern, which includes the proximal frontoventral (Pfv), distal posteriodorsal (Dpd) and posterioventral (Dpv) clusters of PDH-positive neurones, was found in the examined species of locusts, crickets, walking sticks, cockroaches, earwigs and termites. The Pfv cluster is located close to the accessory medulla and usually consists of a set of smaller and a set of larger perikarya. The Dpd and Dpv clusters occupy a dorsal and a ventral position, respectively, at the distal edge of the medulla. These clusters are lacking in stonefly and praying mantid species. The fan-like arrangement of PDH-positive fibres within the frontal medulla face (the locusts and the praying mantid have an additional, smaller fan on the posterior medulla face) is another characteristic feature of Polyneoptera. One (two in the locusts and the praying mantid) nerve bundle runs from the optic lobe to the lateral protocerebrum where it ramifies. One branch gives rise to a fibre network frontally encircling brain neuropile in the area of mushroom bodies. One thin fibre in the crickets and the earwig, and several thicker and anastomosing fibres in the other insects, connect the brain hemispheres. The arrangement of other PDH-positive structures specifies taxa within Polyneoptera. Specific features comprise the presence of PDH-positive perikarya in protocerebrum (walking stick and termite), deutocerebrum (cricket, walking stick, and one cockroach species), tritocerebrum (another cockroach species), and the suboesophageal ganglion (cricket, walking stick and termite). In the walking stick and the termite, PDH-positive fibres pass from the cephalic to the frontal ganglion and from there via the recurrent nerve to the corpora cardiaca where they make varicosities indicative of peptide release into the haemolymph.     

atonal regulates neurite arborization but does not act as a proneural gene in the Drosophila brain

Drosophila atonal (ato) is the proneural gene of the chordotonal organs (CHOs) in the peripheral nervous system (PNS) and the larval and adult photoreceptor organs. Here, we show that ato is expressed at multiple stages during the development of a lineage of central brain neurons that innervate the optic lobes and are required for eclosion. A novel fate mapping approach shows that ato is expressed in the embryonic precursors of these neurons and that its expression is reactivated in third instar larvae (L3). In contrast to its function in the PNS, ato does not act as a proneural gene in the embryonic brain. Instead, ato performs a novel function, regulating arborization during larval and pupal development by interacting with Notch.     

烟青虫成虫脑结构解剖和三维模型构建

【目的】解剖分析烟青虫 Helicoverpa assulta 成虫脑的结构,并构建脑三维结构数字化模型。【方法】利用神经突触蛋白抗体,对烟青虫成虫脑进行免疫组织化学染色标记,利用共聚焦激光扫描显微镜获得脑扫描数码图像,并结合三维图像分析软件对烟青虫脑结构进行识别分析,构建三维模型。【结果】突触蛋白抗体免疫染色将烟青虫脑和颚神经节的神经髓区域清晰标记出来。烟青虫成虫脑与颚神经节愈合而成为一体,中间具有一个孔洞,为食道穿过的通道。脑主要包括前脑、中脑和后脑3部分。依据染色标记结果识别和构建了至少16个脑神经髓结构。这些神经髓包括边界清晰的视叶、前视结节、蕈形体、中央复合体和触角叶及其亚结构。除此之外,还包括围绕这些神经髓的其他前脑神经髓区域,但这部分前脑神经髓内部边界模糊,不容易细分,而将其与颚神经节区域作为一个整体标记为中间脑,占脑总神经髓的55.05%。【结论】识别出烟青虫脑的主要功能结构区域,并成功构建了三维模型。该研究结果为进一步研究烟青虫脑接收、处理和整合感觉信息及调控行为的机制奠定了解剖学基础,并为研究烟青虫或其他昆虫脑结构发育、变异和重塑提供结构形态和体积大小依据。