The evolution of Strepsiptera (Hexapoda)

An evolutionary scenario for the enigmatic group Strepsiptera is provided, based on the results of a comprehensive cladistic analysis of characters of all life stages. A recently described fossil--+Protoxenos janzeni--the most archaic strepsipteran, sheds new light on the early evolution of the group and reduces the "morphological gap" between Strepsiptera and other insects. It weakens both current hypotheses--Coleoptera+Strepsiptera and Diptera+Strepsiptera (="Halteria"). The splitting into +Protoxenos (Protoxenidae) and the remaining Strepsiptera was linked with a distinct size reduction and many morphological changes. Unlike males of extant strepsipteran species, +Protoxenos was still able to process food. Mengeidae (+Mengea), with two small species, is the sister group of extant Strepsiptera. A unique characteristic of extant males (Strepsiptera s. str.) is the mouthfield sclerite. It is part of an air uptake apparatus which belongs to an extremely modified air-filled "balloon gut". Besides this, male strepsipterans possess specialised antennae and compound eyes, a strongly developed flight apparatus, large testes, and a sperm pump, whereas other organ systems are strongly reduced (e.g., fat body, malpighian tubules). Males are designed to find females within a few hours and to copulate. A dramatic change is linked with the split into Mengenillidae and Stylopidia. The change to pterygote hosts and the permanent endoparasitism of the females are evolutionary novelties acquired by the latter clade, and linked with far-reaching morphological transformations, e.g. the presence of unique brood organs. Hairy tarsal adhesive devices are present in males and guarantee efficient attachment to the host during copulation. A well-founded clade within Stylopidia is Stylopiformia, which are characterised by a unique fissure-shaped birth opening. The evolutionary development towards the most specialised and successful forms (parasites of aculeate Hymenoptera [e.g., Xenidae+Stylopidae], ca. 46% of the species) is a stepwise process. The presented evolutionary scenario comprises a complex network of functionally correlated morphological changes in primary larvae, secondary larvae, females and males.     

Cytoplasmic incompatibility and multiple symbiont infection in the ash whitefly parasitoid, Encarsia inaron

Terrestrial arthropods are commonly infected with maternally inherited symbionts that cause reproductive incompatibilities between hosts with differing infection status. Such symbionts can have major effects on the efficacy of a biological control program if releases are comprised of mixtures of differentially infected individuals. In this study, the ash whitefly parasitoid, Encarsia inaron (Hymenoptera: Aphelinidae) from Arizona was surveyed for the presence of heritable bacterial symbionts; experiments were also performed to test for two phenotypes known to be caused by Encarsia symbionts—cytoplasmic incompatibility and changes in oviposition behavior and host use. E. inaron has successfully reduced ash whitefly to non-pest status in all three locations it has been released (California, Arizona, and North Carolina) and is also notable as one of the only Encarsia species that is not autoparasitic, with both male and female wasps developing as primary parasitoids of whiteflies. We show that E. inaron is infected with both Wolbachia and Cardinium. While there was no effect of the symbionts on oviposition behavior or host use, crosses between doubly infected male wasps and uninfected females resulted in a severe reduction in the number of female offspring; male offspring production was unaffected. This study thus serves as a further warning that ascribing a phenotype to a symbiont with confidence depends on eliminating the possibility of a mixed infection, and establishes E. inaron as a useful model for dissecting Wolbachia–Cardinium interactions.     

Comparative histology of the testes of the spined loach Cobitis taenia L. and natural allotetraploids of Cobitis (Pisces, Cobitidae)

The spined loach Cobitis taenia L. creates exclusively diploid and mixed diploid–polyploid populations. Allotriploid females, which co-exist with C. taenia or C. elongatoides and a few tetraploid males and females dominate in most Cobitis mixed populations. They reproduce gynogenetically and produce triploid eggs that are stimulated to development by sperm from Cobitis males. Some of these eggs are fertilized, which leads to the production of bisexual tetraploids. Males of C. taenia (2n = 48) from a diploid population in Lake Klawój, Northern Poland (46 individuals) and from a mixed Cobitis population in the Bug River, Eastern Poland (7 individuals), and three tetraploid males (4n = 98) from the same mixed population were examined. All the fish were analyzed karyologically and histologically. Tubules with cysts of the testes of C. taenia from both populations were filled with germ cells at various developmental stages. Among fishes from Lake Klawój sperm maturation in batches simultaneous with the batch spawning of C. taenia females was found. The testes of the loach C. taenia, from a mixed population in the Bug River, were filled with spermatozoa over the entire reproductive season. Sperm maturation in batches was not observed. Sperm maturation in batches seems to be only connected with a few diploid males in this population. So, a continuous process of spermatogenesis in their testes is required. Only in the testes of all tetraploid Cobitis males were cells characteristic of the early stages of spermatogenesis observed, i.e. without spermatids and spermatozoa. Furthermore, the histological sections of the testis of a male captured in August, revealed fragments with connective tissue between the germ cells. However the participation of tetraploid, infertile Cobitis males in the process of reproduction in the investigated mixed population remains controversial. The results obtained so far, reveal that even the infertile sperm of tetraploid males may induce gynogenesis in Cobitis triploid females.     

Armillaria jezoensis,a new symbiont ofGaleola septentrionalis (Orchidaceae) in Hokkaido

NineArmillaria isolates obtained from the roots ofGaleola septentrionalis in Hokkaido were identified asA. jezoensis by means of mating tests. Cultures of these isolates were similar in colony morphology, mycelial growth and rhizomorph formation on each of malt extract-dextrose agar (MDA), potato-dextrose agar (PDA), andG. septentrionalis root extractdextrose agar (GDA) media, showing better mycelial growth and rhizomorph formation on GDA medium.     

Oogenesis in Acerentomon gallicum Jonescu (Protura)

Summary At the onset of previtellogenesis, the oocytes of Acerentomon gallicum begin to grow and increase their content of organelles. The nuage material in the oocytes at first increases in amount, then declines gradually to disappear completely from oocytes that have attained 50 m in diameter. During the growth period, new dictyosomes, mitochondria and ribosomes appear. Numerous vesicles become detached from the cell membrane and subsequently fuse into cisternae, thus forming extensive complexes of the rough endoplasmic reticulum. In oocytes with diameters between 50 and 100 m the Golgi complexes show a considerable increase in activity, and many lamellar bodies arise from mitochondria that have undergone specific transformation.This work was supported by Government Problem Grant II-1.3.13     

Structural organization and distribution of the symbiotic bacteria <Emphasis Type="Italic">Wolbachia</Emphasis> during spermatogenesis of <Emphasis Type="Italic">Drosophila simulans</Emphasis>

Electron microscopy and morphometric analysis have shown that the symbiotic bacteria Wolbachia occur the testis cells D. simulans during spermatogenesis and are absent in mature spermatids. Bacteria did not affect the structural organization of testis cells, which have a typical morphology during morphogenesis. Bacteria were distributed along the meiotic spindle microtubules near the mitochondria. They increased in number in spermatids at the stage of elongation. Endosymbionts aggregated at the spermatid distal end and contained many vacuoles but were absent at the spermatid proximal end near the nuclei. It was shown for the first time that the diameter of spermatids in a strongly infected line was two of three times that in a noninfected line. We hypothesize that the increase in the number of endosymbionts during spermatid elongation can affect the chromatin condensation in the spermatozoon.Translated from Ontogenez, Vol. 36, No. 1, 2005, pp. 41–50.Original Russian Text Copyright © 2005 by Dudkina, Kiseleva.     

从弹尾纲和原尾纲的亲缘关系质疑缺尾纲（=近昆虫纲）的有效性

鉴于弹尾目（跳虫）和原尾目的尾部都没有尾须（cerci）,Brner于1910年就把这两类归并为一个类群缺尾纲（Ellipura）,这一分类阶元长期被许多昆虫学家沿用至今。Kukalová-Peck(1987 )在讨论化石双尾虫（?）附肢的总体结构（ground plan）时,认为跳虫和原尾虫的腹部侧板更原始,附肢无转节,将二者归纳成近昆虫纲（Parainsecta）。但是从形态特征、内部结构、比较精子学、变态类型和胚后发育等的特点以及线粒体DNA和核糖体DNA的测序分析结果,显示弹尾纲与原尾纲之间存在诸多重要差异,不具备较为密切的亲缘关系,我们不支持（弹尾纲+原尾纲）组成缺尾纲或近昆虫纲。据此建议取消缺尾纲（=近昆虫纲）这一分类阶元。     

A preference assay for quantifying symbiont choice in fungus-growing ants (Attini, Formicidae)

We describe a bioassay for the quantification of cultivar preference (symbiont choice) of fungus-growing ants. The bioassay simultaneously presents mycelium of multiple pure cultivar genotypes to worker ants in a cafeteria-style test arena, and preferred versus non-preferred cultivar genotypes can then be identified based on the ants’ quantifiable behavioral tendencies to convert any of the offered mycelium into a fungus garden. Under natural conditions, fungus-growing ants are likely to express such cultivar preferences when mutant cultivars arise in a garden, or when colonies acquire a novel cultivar from a neighboring colony to replace their resident cultivar. We show that workers from different nests of the fungus-growing ant Cyphomyrmex costatus exhibit repeatable preferences vis-à-vis specific cultivar genotypes. The identified preferred and rejected cultivars can then be used in a performance assay to test whether the ants prefer cultivar genotypes that are superior in enhancing colony fitness (measured, for example, as garden productivity or colony growth), as predicted by symbiont-choice theory. Received 24 February 2006; revised 23 June 2006; accepted 26 June 2006.     

Antibiotic production by the cyanobacteriumNostoc muscorum

A broad spectrum antimicrobial antibiotic is produced byNostoc muscorum (Lancashire Polytechnic Culture Collection 23) during the post-exponential phase of growth. The antibiotic inhibits the growth of bacteria, notably multiple-resistantStaphylococcus aureus, and a biocide resistantPseudomonas aeruginosa: fungi such as the biodeteriogens,Cladosporium herbarum andHormoconis resinae and yeasts such asCandida albicans andC. pseudotropicalis. The antibiotic has an apparent molecular weight of 2000–3000 Daltons. Production appears to be dependent upon the limitation of one or more nutrients in the medium. author for correspondence     

Rickettsiaceae, rickettsia-like endosymbionts, and the origin of mitochondria

Accumulating evolutionary data point to a monophyletic origin of mitochondria from the order Rickettsiales. This large group of obligate intracellular -Proteobacteria includes the family Rickettsiaceae and several rickettsia-like endosymbionts (RLEs). Detailed phylogenetic analysis of small subunit (SSU) rRNA and chaperonin 60 (Cpn60) sequences testify to polyphyly of the Rickettsiales, and consistently indicate a sisterhood of Rickettsiaceae and mitochondria that excludes RLEs. Thus RLEs are considered as the nearest extant relatives of an extinct last common ancestor of mitochondria and rickettsiae. Phylogenetic inferences prompt the following assumptions. (1) Mitochondrial origin has been predisposed by the long-term endosymbiotic relationship between rickettsia-like bacteria and proto-eukaryotes, in which many endosymbiont genes have been lost while some indispensable genes have been transferred to the host genome. (2) The obligate dependence of rickettsiae upon a eukaryotic host rests on the import of proteins encoded by these transferred genes.The nature of a proto-eukaryotic cell still remains elusive. The divergence of Rickettsiaceae and mitochondria based on Cpn60, and the evolutionary history of two aminoacyl-tRNA synthetases favor the hypothesis that it was a chimera created by fusion of an archaebacterium and a eubacterium not long before an endosymbiotic event. These and other, mostly biochemical data suggest that all the mitochondrion-related organelles, i.e., both aerobically and anaerobically respiring mitochondria and hydrogenosomes, have originated from the same RLE, while hydrogenosomal energy metabolism may have a separate origin resulting from a eubacterial fusion partner.     

Pervasive associations between Cybaeus spiders and the bacterial symbiont Cardinium

Cardinium is a recently discovered maternally transmitted bacterial endosymbiont in the Bacteroidetes that has thus far been documented in five arthropod orders. While its effects on his hosts are largely unknown, a few strains have been shown to manipulate host reproduction in parasitic wasps and in mites, either by transforming males into females, or by causing mating incompatibilities between infected males and uninfected males. Cardinium has recently been reported to be widespread in spiders, and in this study, we document pervasive infections in Cybaeus spiders, which are some of the most abundant yet understudied spiders in the understory of moist Western North American forests. 12/20 species, as well as 96% of individuals in a local population of Cybaeus signifer were infected. Phylogenetic analysis revealed three closely related symbiont haplotypes within Cybaeus. Haplotypes clustered within geographically close species, suggesting that horizontal transmission might be quite high in this symbiont lineage.     

Progress on the genetics of the N2-fixing actinorhizal symbiont Frankia

The actinomycete Frankia is of fundamental and ecological interests for several reasons including its wide distribution, its ability to fix nitrogen, differentiate into sporangium and vesicle (specialized cell for nitrogen-fixation), and to nodulate plants from about 24 genera. Here, we present a review on the genetics performed so far on Frankia. At the end of July 2001, 293 kbp of Frankia DNA sequences were found in the databases. Thirty five percent of these sequences corresponded to full gene or gene cluster sequences. These genes could be divided according to their role into 6 key activities: gene translation (rrnA and tRNA ^pro gene), proteolysis (pcr genes), assimilation of ammonium (glnA and glnII), protection against superoxide ions (sodF), nitrogen fixation (nif cluster), and plasmid replication. We present a review of these genetic islands; their function, expression, localization and particular properties are discussed. A comparative analysis of Frankia nif genes from various strains and species is presented. An improved nomenclature for some of these genes is suggested to avoid conflicts. Frankia plasmids DNA sequences are also presented. The novel trends in Frankia genetics are described.     

Ultrastruktur des Pseudoculus vonEosentomon (Protura,Insecta)

Zusammenfassung In der Feinstruktur unterscheidet sich der Pseudoculus vonEosentomon nicht wesentlich von dem der Acerentomiden. Durch einen Endokutikulaporus treten die dendritischen Fortsätze zweier Sinneszellen, jeweils umgeben von einer Hüllzelle, in den Außenraum des Pseudoculus ein. Der Außenraum wird nach distal von einer äußeren Kutikulaschicht — vermutlich Epikutikula — abgeschlossen. Sie vermittelt durch regelmäßig angeordnete lange Spalten die Verbindung zur Außenwelt. Am Grunde der Spalten finden sich Porentubuli, die mit den Hüllzellen oder den distalen Fortsätzen der Dendriten Kontakt haben können. Aus der Feinstruktur kann geschlossen werden, daß der Pseudoculus als Chemo-, Hygro- und/oder Thermorezeptor fungiert.

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Ultrastructure of the pseudoculus ofEosentomon (Protura, Insecta)

Summary Concerning its fine structure the pseudoculus of Eosentomon is quite similar to that of Acerentomide Protura. There are two sensory cells innervating the organ. From each of them one dendritic process derives, surrounded by one enveloping cell. The processes of these four cells enter the distal cavity of the pseudoculus through a pore in the endocuticular layer. The cuticular layer of the cap seems to consist of epicuticle only. It is furrowed by long clefts connecting the distal cavity of the organ with the outside. Poretubules insert at the base of the clefts and may have contact with the cell membranes of both enveloping cells and dendritic processes. According to its structure the pseudoculus may function as chemo-, hygro- and/or thermoreceptor.

Für technische Mitarbeit danke ich Frau G. Raabe, für die Anfertigung der Zeichnung Frau C. St. Friedemann.     

The feeding preference of mycophagous Collembola varies with the ectomycorrhizal symbiont

The interactions of the collembolan insect Proisotoma minuta with ectomycorrhizal and/or pathogenic fungi was examined in three experiments: (1) in vitro analysis of feeding patterns, (2) in vitro food preference test, and (3) in situ analysis of ectomycorrhizal colonization in relation to population density. The ectomycorrhizal fungi Laccaria laccata, Pisolithus tinctorius, Suillus luteus, Thelephora terrestris and the pathogenic fungi Rhizoctonia solani were employed in all experiments. In vitro and in situ experiments revealed that Pr. minuta consumed all the ectomycorrhizal fungi tested but the feeding pattern and consumption varied with each isolate. In a comparative in vitro feeding preference test, where Pr. minuta was given a choice, R. solani was grazed more heavily than the ectomycorrhizal fungi. Among the ectomycorrhizal fungi examined, Pi. tinctorius was consumed significantly less than L. laccata, S. luteus or T. terrestris in the presence of R. solani. A 10-week in situ analysis of loblolly pine (Pinus taeda L.) seedling root systems inoculated with Pr. minuta revealed that ectomycorrhizal colonization was significantly less than that of control plants (without Pr. minuta). Collectively, these data suggest that mycophagous Collembola may play a major role in the distribution and biomass of ectomycorrhizal fungi in the rhizosphere of tree seedlings.     

同源盒基因(Hox)与哺乳动物生殖

哺乳动物的同源盒基因（Hox）与果蝇的同源异形基因是同源基因,该基因编码的DNA片段含183碱基对,转录由61个氨基酸残基组成的蛋白质保守结构域,称同源异型域.Hox基因碱基顺序及在染色体中的位置都是高度保守的.Hox基因在体节结构分化等空间信息调控中起着重要作用,按特异的空间模式赋予每一体节其自身的特点.近年来的研究表明,Hox基因不但影响胚胎发育,而且与成体生殖系统分化有关,在着床期子宫接受态的建立及子宫蜕膜反应的发生等生殖过程中起着重要的调节作用.     

A divergent Cardinium found in daddy long-legs (Arachnida: Opiliones)

Recent studies indicate that a newly described bacterial endosymbiont, Cardinium, is widespread in arthropods and induces different reproductive manipulations in hosts. In this study, we used a portion of the 16S rRNA gene of the Cardinium to screen 16 Opilionid species from the suborder Palptores. We found the incidence of Cardinium in these Opiliones was significantly higher than in other pooled arthropods (31.2% versus 7.2%, P = 0.007). Phylogenetic analyses using maximum parsimony (MP) and Bayesian analysis revealed two distinct clades in Opiliones. One is a divergent monophyletic clade with strong support that has so far not been found in other arthropods, and a second one contains Cardinium both from Opiliones and other arthropods. There is not complete concordance of the Cardinium strains with host phylogeny, suggesting some horizontal movement of the bacteria among Opiliones. Although the divergence in the sequenced 16S rRNA region between the Cardinium infecting Opiliones and Cardinium from other arthropods is greater than among Cardinium found in other arthropods, all are monophyletic with respect to the outgroup bacteria (endosymbionts of Acanthamoeba). Based on high pairwise genetic distances, deep branch, and a distinct phylogenetic grouping, we conclude that some Opiliones harbor a newly discovered Cardinium clade.     

Natural co-infection of Babesia caballi and Encephalitozoon-like microsporidia in the tick Anocentor nitens (Acari: Ixodidae)

The present paper reports the occurrence of natural co-infection of Babesia caballi and Encephalitozoon-like microsporidia in the tick Anocentor nitens. Engorged females of ticks, collected from a naturally B. caballi-infected horse, were incubated at 27 degrees C and relative humidity over 83%. After a 6-day incubation period, Giemsa-stained smears prepared from hemolymph were examined microscopically under oil immersion. B. caballi infected ticks were dissected and samples of midgut tissue were examined by transmission electron microscopy, through which free sporokinetes were seen in the cytoplasm of gut epithelial cells. In addition, Encephalitozoon-like microsporidia were observed inside the parasitophorous vacuoles in the same cell in which sporokinetes of B. caballi were found and also in some neighbour cells. They presented different morphological stages, suggesting a sequential phases of development.