Strukturierungsmechanismen der Crematogaster-Macaranga Ameisen-Pflanzen Assoziationen : ein kombinierter ökologischer und phylogenetischer Ansatz

One of the most species-rich ant-plant mutualisms worldwide is the palaeotropical Crematogaster-Macaranga system. The pioneer-tree genus Macaranga (Euphorbiaceae) is mainly inhabited by at least nine specific species of Crematogaster (Myrmicinae), of which eight belong to the subgenus Decacrema, as well as several species of Camponotus (Formicinae). Ant species are not randomly distributed among the Macaranga host plants but distinct patterns of associations have been found (Fiala et al., 1999 and references cited therein). The specificity of the associations is maintained in spite of common sympatric distribution of several host-plant species. Associations are, however, usually not species-specific and especially the Decacrema ants, that are the focus of this study, usually colonize several host plant species each. In this study I used a combined approach of ecological data as well as phylogenetic data based on mitochondrial DNA sequences in order to elucidate the factors determining the patterns found in the associations and the evolution of this mutualistic system between the specific Decacrema ant partners and their Macaranga host plants. Life history traits of seven different morphospecies found on the most common Macaranga host plants were compared and colony development was followed from colony founding on saplings to adult trees. Temporal variability of the associations between Decacrema ants and their respective host plants was also examined. Associations between Crematogaster ants of the subgenus Decacrema and their Macaranga host plants were found to be stable over periods of time, long enough to enable reproduction of the ant colony and (in most cases) the host plants, too. Life-expectancy of the ant colony seems to be shorter than that of the host plant in general. All adult trees still provide nesting space as well as food for the ants. Colonies from different morphospecies differed in longevity, the onset of alate production, queen number and mode of colony founding. The examined Decacrema species could be placed into two groups according to their life-history traits as well as on morphological grounds: The decamera-group and the captiosa-group, each named after one species that could be synonymized with one morphospecies included in the group. Members of the captiosa-group have larger colonies, presumably with a longer life-span, and a later onset of reproduction compared to the decamera-group. Additionally, queens of the captiosa-group found colonies on saplings as well as in the crown region of bigger trees, whereas queens of the decamera-group found colonies on saplings and small treelets only. Queens belonging to the captiosa-group are brown with relatively large eyes (= 1/3 of the head length), whereas queens from the decamera-group are smaller in size, are dark brown to black in colour and have smaller eyes (< 1/3 of the head length). On some of the host plants examined in this study lifespan of the host plant and their specific ant partners seemed to be well matched whereas on others an ontogenetic succession of specific Decacrema partner ants was found, when host plants were abandoned due to the death of comparatively short-lived ant colonies, usually from species belonging to the decamera-group. Ant-partners of saplings or young plants often differed from specific partner ants found on bigger trees. Only species belonging to the captiosa-group were found to re-colonize the crown region of adult trees, thus facilitating a change of ant species, when longlived host plant species were colonized by relatively short-lived species from the decamera-group first. When long -lived host plants were colonized by long-lived species from the captiosa-group associations were stabler: I did not find any temporal variation in ant-inhabitants then. Life-span of the ant colony as well colony founding behaviour of the different partner ant species therefore play an important role for these ontogenetic changes and the specificity of the associations over time. For the host plant the ontogenetic changes have a strong impact as uninhabited host plants that are not patrolled by workers of specific ant partners suffer higher herbivore damage. Uninhabited host plants may also be colonized by unspecific arboreal ants that only make use of the nesting space and/ or food offered by the plant but do not confer protection against herbivores. Stable associations with a specific ant partner are therefore most beneficial for the host plants. Usually ant colonies are monogynous, but changes in the colony structure were found locally in two Decacrema species. I found colonies that turned secondarily polygynous, possibly after the death of the original founding queen. Secondary polygyny therefore can prolong the life-span of the antcolony on its host plant, leading to a parallel life-history and stable association as it was the case in Macaranga bancana-Crematogaster captiosa. However, in the other association (Macaranga hypoleuca-Crematogaster cf. decamera) life-expectancy of the ant-colony is still much shorter than that of its host plant species, leading to a change in the specific ant partner at a later stage. Pleometrotic foundress associations that directly led to polygynous colonies in one species were also found locally, a phenomenon hardly ever reported from ants in general. Foundress associations were found to be more successful in establishing colonies than single queens. I found indications that this change in colony founding behaviour might be due to interspecific competition for the same host plant species with another Decacrema species specific to Macaranga. For the phylogenetic analysis partial mitochondrial cytochrome oxidase I and II were sequenced and Neighbor-Joining, Maximum Parsimony, Maximum Likelihood as well as Bayesian analyses were performed. The four different analyses yielded phenetic as well as phylogenetic trees that all had a similar topology. Ants of the subgenus Decacrema formed a monophyletic clade, indicating a single colonization event at the beginning of the Macaranga-Decacrema symbiotic system. In the phylogenetic analysis the decamera-group as well as the captiosa-group were confirmed and clearly separated from each other. However, two species that would have been placed into the decamera-group, due to morphological as well as life-history traits, formed a third separate clade within the Decacrema. These two species (msp. 7- group) as well as the decamera-group came out as the basal groups in the phylogenetic analysis. Thus, life -history traits of these two groups (relatively small colonies, early onset of alate production, colony founding in ground region only) would be the ancestral state for Macarangaassociated ants of the subgenus Decacrema. Changes in colony structure, like secondary polygyny, were found in the captiosa- as well as the decamera-group and are therefore independent of the affiliation within the phylogeny. I did not find evidence for strict cocladogenesis between the subgenus Decacrema and their Macaranga host-plants, although ecological interactions between the two partner groups are close and associations can be rather specific. The phylogenies presented here, along with the known association patterns indicate that host-shifting of the ants is common in some of the species, opening the possibility of sympatric speciation as a result of increased host usage. Additionally, the considerable geographic substructuring found in the phylogenetic trees suggests that allopatric speciation has played a major role in diversification of the Decacrema ants.Das paläotropische Crematogaster-Macaranga System bildet eines der weltweit artenreichsten mutualistischen Ameisen-Pflanzen Interaktionssysteme. Es gibt knapp dreißig myrmekophytischen Arten innerhalb der Pionierpflanzengattung Macaranga (Euphorbiaceae), welche hauptsächlich von mindestens neun, für diese Pflanzen spezifischen, Ameisen der Gattung Crematogaster (Myrmicinae) besiedelt werden. Die Taxonomie der Ameisen ist jedoch nur teilweise geklärt, weshalb ein Großteil der Arten bisher nur in Morphospezies untergliedert wurde. Acht dieser neun Morphospezies gehören der Untergattung Decacrema an. Zusätzlich sind einige Macaranga-Arten mit Ameisen der Gattung Camponotus (Formicinae) assoziiert, die ebenfalls spezifisch für diese Wirtspflanzengattung sind. Die Ameisenarten zeigen keine stochastische Verteilung bei der Besiedlung der Macaranga-Wirtspflanzen. Stattdessen finden sich distinkte Verteilungsmuster und spezifische Assoziationen zwischen bestimmten Ameisen- und Pflanzenarten (Fiala et al., 1999 und die darin zitierte Literatur). Diese Verteilungsmuster der Ameisen auf ihren Wirtspflanzen bleiben trotz des häufig sympatrischen Vorkommens mehrerer Macaranga-Arten bestehen. Die Assoziationen sind jedoch größtenteils nicht im engeren Sinn artspezifisch, daß eine Ameisenart ausschließlich eine einzige Wirtspflanzenart besiedelt, bzw. jede Pflanzenart ausschließlich mit einer einzigen Ameisenart assoziiert ist. Gerade die Arten der Untergattung Decacrema, mit denen sich diese Studie hauptsächlich beschäftigt, besiedeln meist mehrere Wirtspflanzenarten. Bisher ist sehr wenig darüber bekannt, welche Faktoren für die - vor allem auf Keimlingen und Jungpflanzen nachgewiesenen -Besiedlungsmuster verantwortlich sind und ob und wie lange diese auf größeren Wirtspflanzen erhalten bleiben. In der vorliegenden Arbeit habe ich deshalb die Strukturierungsmechanismen der Crematogaster-Macaranga Assoziationen auf zwei verschiedenen Ebenen untersucht: sowohl die Stabilität und Aufrechterhaltung der rezenten Beziehungsmuster als auch mögliche historische Gründe für deren Entstehen. Hierfür habe ich zunächst vergleichend die Dynamik dieser Assoziationen von Jungpflanzen bis hin zu adulten Bäumen untersucht, als auch Aspekte der Evolution des Systems. Für die Untersuchung der Evolution dieses Systems wurde eine Verwandschaftsanalyse der Ameisen der Untergattung Decacrema auf molekularer Ebene mit mitochondrialer DNA von Cytochrom-Oxidase I und II durchgeführt. Um mögliche historische Faktoren aufzudecken, die zu diesen Besiedlungsmustern geführt haben könnten, wurden die Ergebnisse der dieser Verwandtschaftsanalyse dann mit dem vorhandenen Stammbaum der Wirtspflanzenarten verglichen und speziell vor dem Hintergrund der ökologischen Daten diskutiert. Zudem wurden life-history traits (Charakteristika der Lebensgeschichte) von sieben verschiedenen Morphospezies, die auf den häufigsten Macaranga-Arten vorkommen vergleichend untersucht, und deren Kolonieentwicklung von der Koloniegründung auf Keimlingen bis hin zu adulten Bäumen erfasst. Assoziationen zwischen Ameisen der Untergattung Decacrema und ihren Macaranga-Wirtspflanzen waren zumindest so lange stabil, daß sowohl die Ameisen als auch in den meisten Fällen die Wirtspflanzen ihre reproduktive Phase erreichen konnten. Generell scheint die Lebensdauer der Ameisenkolonien kürzer zu sein, als die ihrer Wirtspflanzen. Alle Wirtspflanzen behielten ihre Attraktivität für Ameisen bei, indem sie auch im Adultstadium Nahrung und Nistraum zur Verfügung stellten. Kolonien der sieben untersuchten Morphospezies unterschieden sich in Lebensdauer, Beginn der Reproduktionsphase, Gynie und der Art der Koloniegründung. Die untersuchten Decacrema-Arten können mit Hilfe der Unterschiede in ihren life-history traits, als auch nach ihrer Morphologie in zwei Gruppen unterteilt werden: die decamera-Gruppe und die captiosa- Gruppe, jeweils benannt nach einer beschriebenen Art innerhalb dieser Gruppe, die mit einer in vorherigen Arbeiten verwendeten Morphospezies synonymisiert werden konnte. Arten innerhalb der captiosa-Gruppe haben, im Vergleich zu Arten der decamera-Gruppe, größere Kolonien, wahrscheinlich eine längere Lebensdauer und erreichen ihre reproduktive Phase später. Königinnen der captiosa-Gruppe können sowohl in Keimlingen als auch in der Kronenregion größerer Bäume Kolonien gründen, wohingegen gründende Königinnen der decamera-Gruppe ausschließlich bodennah auf Keimlingen und kleineren Bäumen gefunden wurden. Zudem unterscheiden sich die Königinnen von Arten der beiden Gruppen in ihrer Morphologie: Königinnen der captiosa-Gruppe sind bräunlich gefärbt und haben relativ große Komplexaugen (= 1/3 der Kopflänge), während Königinnen der decamera-Gruppe relativ klein und dunkelbraun bis schwarz gefärbt sind. Zudem haben sie relativ kleinere Komplexaugen (< 1/3 der Kopflänge). Bei einigen der untersuchten Assoziationen scheinen die Lebensdauer der Wirtspflanzen und ihrer spezifischen Ameisenkolonien gut aufeinander abgestimmt zu sein, wohingegen bei anderen eine ontogenetische Sukzession von verschiedenen spezifischen Decacrema-Arten gefunden wurde. Dies war vor allem dann der Fall, wenn Wirtspflanzen zunächst von Arten der decamera-Gruppe besiedelt waren, deren relativ kurzlebige Kolonien früh abstarben. Da nur Königinnen von Arten der captiosa- Gruppe auch in der Kronenregion größerer Bäume Kolonien gründen können, kommt es in diesen Fällen zu einem Wechsel in der Ameisenbesiedlung. Die Assoziationen zwischen langlebigen Wirtspflanzenarten und den langlebigeren Kolonien von Arten der captiosa-Gruppe waren stabiler. Bei diesen Assoziationen wurde kein Wechsel der spezifischen Ameisenart über die Zeit festgestellt. Die Lebensdauer der Ameisenkolonien sowie das Gründungsverhalten von Königinnen spielen deshalb eine wichtige Rolle bei der ontogenetischen Sukzession der Ameisenbesiedler auf den Wirtspflanzen. Die ontogenetischen Wechsel in der Besiedlung sind für die Wirtspflanzen von großer Bedeutung, denn in Zeiten, in denen sie nicht von einer intakten und der Größe der Pflanze entsprechenden Kolonie bewohnt sind, fehlt ihnen der Schutzeffekt der Ameisen gegen Herbivorie. Unbewohnte Bäume können sowohl von spezifischen Decacrema-Arten der captiosa-Gruppe wiederbesiedelt werden als auch von unspezifischen arborealen Ameisenarten, die zwar den angebotenen Nistraum und/ oder Nahrung nutzen, jedoch keinen Herbivorieschutz gewähren. Aus diesem Grund sind möglichst stabile Assoziationen mit einer spezifischen Decacrema-Art für die Wirtspflanze von Vorteil. Kolonien der Decacrema-Arten sind normalerweise monogyn. Lokal wurden jedoch Kolonien von zwei Arten entdeckt, di

Genome degeneration affects both extracellular and intracellular bacterial endosymbionts

The obligate intracellular bacterial endosymbionts of insects are a paradigm for reductive genome evolution. A study published recently in BMC Biology demonstrates that similar evolutionary forces shaping genome structure may also apply to extracellular endosymbionts

Micro-habitat and season dependent impact of the invasive Impatiens glandulifera on native vegetation

The impact of invasive species is often difficult to assess due to species × ecosystem interactions. Impatiens glandulifera heavily invaded several habitat types in Central Europe but its impact on native plant communities is rated ambiguously. One reason could be that the impact differs between habitat types or even between environmentally heterogeneous patches (micro-habitats) within one habitat type. In the present study a vegetation survey was performed within heterogeneous riverside habitats in Germany investigating the impact of I. glandulifera on native vegetation in dependence of environmental conditions. The vegetation was recorded in summer and spring because of seasonal species turnover and thus potentially different impact of the invasive plant. We found that the cover of I. glandulifera depended on environmental conditions resulting in a patchy occurrence. I. glandulifera did not have any impact on plant alpha-diversity but reduced the cover of the native vegetation, especially of the dominant species. This effect depended on micro-habitat and season. The native vegetation was most affected in bright micro-habitats, especially those with a high soil moisture. Not distinguishing between micro-habitats, plant species composition was not affected in summer but in spring. However, environmental conditions had a higher impact on the native vegetation than I. glandulifera. We conclude that within riparian habitats the threat of I. glandulifera to the native vegetation can be rated low since native species were reduced in cover but not excluded from the communities. This might be due to patchy occurrence and year-to-year changes in cover of I. glandulifera. The context-dependency in terms of micro-habitat and season requires specific risk assessments which is also an opportunity for nature conservation to develop management plans specific to the different habitats. Particular attention should be given to habitats that are bright and very wet since the effect of I. glandulifera was strongest in these habitats

Taxonomic Revision of the Obligate Plant-Ants of the Genus Crematogaster Lund (Hymenoptera, Formicidae, Myrmicinae), Associated with Macaranga Thouars (Euphorbiaceae) on Borneo and the Malay Peninsula

The taxonomy and natural history of ants of the genus Crematogaster Lund, 1831 (Crematogaster borneensis-group of the former subgenus Decacrema) obligately associated with myrmecophytic host-plants of the euphorb genus Macaranga are reviewed. Within this group of ants Crematogaster borneensis André, 1896 (with five subspecies and four varieties), Crematogaster captiosa Forel, 1910 as well as Crematogaster decamera Forel, 1910 have previously been described from SE Asia. Here we synonymise C. borneensis subsp. capax Forel, 1911, C. borneensis subsp. hosei Forel, 1911, C. borneensis subsp. sembilana Forel, 1911, and C. borneensis var. macarangae Viehmeyer, 1916 with C. borneensis André, 1896. Crematogaster borneensis var. harpyia Forel, 1911, C. borneensis var. insulsa Forel, 1911, C. borneensis subsp. symbia Forel, 1911, and C. borneensis subsp. novem Forel, 1911 are synonymised with C. captiosa Forel, 1910. In addition we describe five new species: C. claudiae sp. nov., C. hullettii sp. nov., C. linsenmairi sp. nov., C. maryatii sp. nov., and C. roslihashimi sp. nov.. Seven of these eight species are placed into two informal species subgroups based on queen morphology, life-history characters and a formerly published molecular phylogeny. Keys are provided for the identification of queens and workers, as well as natural history information on the eight ant species. The morphology of these Macaranga-associated Crematogaster (formerly Decacrema) species is compared to the only other three species described for this former subgenus in SE Asia, i.e. C. angulosa André, 1896, C. biformis André, 1892 and C. cephalotes Smith, 1857

Fast spread of a fungal parasite in an invasive supercolony

Dissertação de mestrado em Evolução e Biologia Humanas, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra.O diagnóstico paleopatológico continua a lidar com o dilema que conecta, paradoxalmente, um alto número de casos de mortalidade infantil e a reduzida variedade de doenças referenciadas como “possíveis” causas da morte: infeções, doenças metabólicas e traumatismos. A presença de porosidade óssea, como única evidência macroscópica frequente em muitos casos arqueológicos infantis, é extremamente alta nas porções cranianas e pós-cranianas e pode atribuir-se à patologia, ao desenvolvimento biológico, e/ou à diagénese. No entanto, a distinção macroscópica da sua origem não é fácil, e a junção intrínseca entre este tipo de doenças, fornece evidências conflituosas que dificultam o diagnóstico diferencial. Com o propósito de desenvolver outras metodologías mais precisas do que a simples observação a olho nu, o objectivo deste estudo é realizar um exame topográfico (cortical) da superfície óssea, para testar a fiabilidade do Microscópio Electrónico de Varrimento (MEV) como ferramenta diagnóstica não destrutiva. A base desta investigação radica na determinação de diferenças entre as manifestações ósseas mencionadas anteriormente, e as possíveis diferenças entre indivíduos de idades diferentes. A amostra compõe-se por 9 esqueletos articulados e um conjunto de fragmentos ósseos, que podem atribuir-se à existência de um total de 29 indivíduos segundo o NMI obtido a partir dos ossos temporais. Estes restos, não adultos, foram exumados da Praça de Armas do castelo da vila Alentejana de Amieira do Tejo (Portugal), e datam dos séculos XIX e XX. Depois da realização da estimativa macroscópica da idade à morte, 70 amostras foram estudadas e fotografadas com um microscópio binocular Leica MD6, e observadas num Microscópio Electrónico de Varimento JEOL JSM-5400 a 20KV no modo de electrões secundários. Para este fim, os restos foram cobertos com uma camada de Carbono num Evaporador de Vácuo JEOL JEE-4X. Apesar de que a idade a morte estimada oscilara entre os 0-6 anos de idade - através das características dentais macroscópicas - foi observado um desfasamento entre o grau de desenvolvimento ósseo, com idades muito mais precoces, e o dentário, com idades mais avançadas. Isto pode estar associado com eventos stressantes durante a vida (p.ex. Malnutrição, condições do meio ambiente, doenças...), sobretudo, naquelas estruturas porosas encontradas para além dos 5-10mm. do extremo do osso. A bibliografía sobre o contexto socioeconómico da região mostra precariedade, insalubridade e uma alta taxa de mortalidade infantil. Este estudo exploratório mostra que é essencial desenvolver novas metodologias que esclareçam a etiologia multifatorial que envolve este tipo de alterações, dado que permite combinar um excelente detalhe, uma boa resolução, simplicidade no emprego, e o pré-requisito de ser não destrutiva. Até a data o controverso estudo que envolve os sinais porosos só tem tido sucesso com evidências patognomónicas. São precisos mais estudos que potenciem a funcionalidade da microscopia de varrimento, sobretudo, se tencionamos encontrar características microscópicas patológicas que permitam depurar o diagnóstico macroscópico. Ao mesmo tempo esta dissertação salienta as consequências do estudo da infância, já que esta fração demográfica supõe o reflexo mais próximo dos parâmetros do meio ambiente e da economia, e permite também inferir sobre restrições culturais, práticas de aleitamento e certos tabus alimentares, características extremamente importantes para a pesquisa populacional antropológica.Paleopathological diagnosis continues to struggle with the quandary that connect, paradoxically, a high number of infancy mortality cases, and the reduced variety of disease referenced as “possible” causes of death: infections, metabolic diseases and trauma. Bone porosity presence, as a single common macroscopic evidence found in many archaeological infant cases, is extremely high in their cranial and post cranial skeleton and may be attributed to pathology, biological development, and/or diagenesis. However, to distinguish those origins macroscopically is not easy, and the intrinsic junction between this kinds of sickness, provide conflicting evidences that makes difficult the differential diagnosis. With the purpose of developing other more precise methodologies than the simple observation with the naked eye, the aim of this study is to perform a topographic (cortical) surface exam, to test the reliability of the Scanning Electronic Microscopy (SEM) as a non-invasive diagnostic tool. The base of this investigation lie in determining differences between the bone manifestations mentioned above and possible differences between different age individuals. The sample consists of 9 single non-adult skeletons and an ossuary settlement of non-adult bone fragments (compound by a total of 29 individuals according to the MNI obtained by temporal bones), recovered inside the castle of Amieira do Tejo villa (Alentejo, Portugal), and dating from the 19th and 20th centuries. After performing the macroscopic age at death estimation, 70 samples were studied and photographed with a Leica MD6 binocular microscope, and selected porous areas were further observed in a JEOL JSM-5400 Scanning Electron Microscopy (SEM) at 20KV in secondary electron mode. For this end, the remains were carbon coated in a JEOL JEE-4X Vacumm Evaporator. Despite the age at death was between 0-6 years old as estimated by the macroscopic study of dental characteristics, a mismatch between bone and teeth development degree was observed, being the first younger thant the second. This, is possibly associate to stressful events during life (e.g. malnutrition, environmental conditions, diseases…), above all, that porosity structure found beyond 5-10mm from the bone end. The bibliography about the socioeconomic context of the region shows precariousness, unhealthiness, and a high infant mortality rate. This exploratory study shows it is essential to develop news methodologies to shed light on the multifactorial aetiology this type of alterations entailed, as they allows to combine an excellent detail, a good resolution, simplicity of operation, and the prerequisite of being nondestructive. At the present moment, the controversial study involving porous signals only have had success with pathognomonic evidences. Further studies that enhance the functionality of the scanning electron microscope are needed, especially if we intend to find pathological microscope features that enable to polish macroscopical diagnosis. At the same time, this dissertation points out the consequences of childhood studies, as this demographic fraction supposes the most closely reflection of environmental and economic parameters, as well as allow to infer about cultural restrictions, breastfeeding practices and certain food taboos, a very remarkable characteristics for anthropological populational research

Bacteriocyte dynamics during development of a holometabolous insect, the carpenter ant Camponotus floridanus

<p>Abstract</p> <p>Background</p> <p>The carpenter ant <it>Camponotus floridanus </it>harbors obligate intracellular mutualistic bacteria (<it>Blochmannia floridanus</it>) in specialized cells, the bacteriocytes, intercalated in their midgut tissue. The diffuse distribution of bacteriocytes over the midgut tissue is in contrast to many other insects carrying endosymbionts in specialized tissues which are often connected to the midgut but form a distinct organ, the bacteriome. <it>C. floridanus </it>is a holometabolous insect which undergoes a complete metamorphosis. During pupal stages a complete restructuring of the inner organs including the digestive tract takes place. So far, nothing was known about maintenance of endosymbionts during this life stage of a holometabolous insect. It was shown previously that the number of <it>Blochmannia </it>increases strongly during metamorphosis. This implicates an important function of <it>Blochmannia </it>in this developmental phase during which the animals are metabolically very active but do not have access to external food resources. Previous experiments have shown a nutritional contribution of the bacteria to host metabolism by production of essential amino acids and urease-mediated nitrogen recycling. In adult hosts the symbiosis appears to degenerate with increasing age of the animals.</p> <p>Results</p> <p>We investigated the distribution and dynamics of endosymbiotic bacteria and bacteriocytes at different stages during development of the animals from larva to imago by confocal laser scanning microscopy. The number of bacteriocytes in relation to symbiont-free midgut cells varied strongly over different developmental stages. Especially during metamorphosis the relative number of bacteria-filled bacteriocytes increased strongly when the larval midgut epithelium is shed. During this developmental stage the midgut itself became a huge symbiotic organ consisting almost exclusively of cells harboring bacteria. In fact, during this phase some bacteria were also found in midgut cells other than bacteriocytes indicating a cell-invasive capacity of <it>Blochmannia</it>. In adult animals the number of bacteriocytes generally decreased.</p> <p>Conclusions</p> <p>During the life cycle of the animals the distribution of bacteriocytes and of <it>Blochmannia </it>endosymbionts is remarkably dynamic. Our data show how the endosymbiont is retained within the midgut tissue during metamorphosis thereby ensuring the maintenance of the intracellular endosymbiosis despite a massive reorganization of the midgut tissue. The transformation of the entire midgut into a symbiotic organ during pupal stages underscores the important role of <it>Blochmannia </it>for its host in particular during metamorphosis.</p