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At least 19 recordsLinked to original sources
PubMed2000

In vitro metabolism of aflatoxin B1 by larvae of navel orangeworm, Amyelois transitella (Walker) (Insecta, Lepidoptera, Pyralidae) and codling moth, Cydia pomonella (L.) (Insecta, Lepidoptera, Tortricidae).

Larvae of the navel orangeworm (NOW), Amyelois transitella (Walker), a major pest of almonds and pistachios, and the codling moth (CM), Cydia pomonella (L.), the principal pest of walnuts and pome fruits, are commonly found in tree nut kernels that can be contaminated with aflatoxin, a potent carcinogen. The ability of larvae of these insects to metabolize aflatoxin B1 (AFB1) was examined. A field strain of NOW produced three AFB1 biotransformation products, chiefly aflatoxicol (AFL), and minor amounts of aflatoxin B2a (AFB2a) and aflatoxin M1 (AFM1). With AFL as a substrate, NOW larvae produced AFB1 and aflatoxicol M1 (AFLM1). A lab strain of CM larvae produced no detectable levels of AFB1 biotransformation products in comparison to a field strain which produced trace amounts of only AFL. Neither NOW nor CM produced AFB1-8,9-epoxide (AFBO), the principal carcinogenic metabolite of AFB1. In comparison, metabolism of AFB1 by chicken liver yielded mainly AFL, whereas mouse liver produced mostly AFM1 at a rate eightfold greater than AFL. Mouse liver also produced AFBO. The relatively high production of AFL by NOW compared to CM may reflect an adaptation to detoxify AFB1. NOW larvae frequently inhabit environments highly contaminated with fungi and, hence, aflatoxin. Only low amounts, if any, of this mycotoxin occur in the chief CM hosts, walnuts, and pome fruits. Characterizations of enzymes and co-factors involved in biotransformation of AFB1 are discussed.

Aflatoxin B1↗
PubMed2004

Molecular phylogeny of Cotesia Cameron, 1891 (Insecta: Hymenoptera: Braconidae: Microgastrinae) parasitoids associated with Melitaeini butterflies (Insecta: Lepidoptera: Nymphalidae: Melitaeini).

Phylogenetic relationships among Cotesia Cameron (Braconidae) species parasitising Melitaeini butterflies were examined using DNA sequence data (mitochondrial cytochrome oxidase subunit I and NADH1 dehydrogenase genes, nuclear ribosomal DNA internal transcribed spacer region) as well as 12 microsatellite loci. Molecular data were available from ostensibly six species of Cotesia from 16 host butterfly species in Europe, Asia, and North America. Analysis of the combined sequence data using both maximum parsimony and maximum likelihood revealed two distinct Cotesia clades. In one clade (C. acuminata (Reinhard); C. bignellii (Marshall)) host ranges are apparently narrow and, although Euphydryas (s. lato) is well-utilised, permeation of Melitaea (s. lato) has been slight. In the other clade (C. melitaearum (Wilkinson); C. lycophron (Nixon); C. cynthiae (Nixon)) host utilization across the Melitaeini as a whole is more extensive and the data are consistent with more recent, or active, speciation processes. Neighbour-joining trees calculated separately for the two main clades based on chord distance (DCE) of microsatellite allele frequencies were consistent with phylogenetic trees obtained from the sequence data. Our analysis strongly suggests the presence of several additional, previously unrecognised, Cotesia species parasitising this group of butterflies.

Animals↗
PubMed2001

Neurogenesis in the developing visual system of the branchiopod crustacean Triops longicaudatus (LeConte, 1846): corresponding patterns of compound-eye formation in Crustacea and Insecta?

In the discussion on arthropod phylogeny, the structural evolution of compound eyes and optic ganglia in Crustacea and Insecta is an important topic. On the one hand, many morphological features as well as developmental aspects of the visual system in Insecta and Crustacea correspond in so much detail that eye design in these two groups is likely to have a common euarthropodan ancestor. On the other hand, however, some authors advocate a convergent evolution of the crustacean and insect visual system founding their arguments on differences in the arrangement of the visual neuropils and the fibre connections between Malacostraca and Entomostraca (the "entomostracan enigma"). Therefore, information about cellular aspects of visual system formation in entomostracan Crustacea is likely to enliven this debate, but is not yet available. To fill this gap, we examined the proliferation of neuronal stem cells in the developing visual system of the tadpole shrimp Triops longicaudatus (LeConte, 1846) (Entomostraca, Branchiopoda, Phyllopoda, Calmanostraca, Notostraca) by in vivo incorporation of the proliferation marker bromodeoxyuridine and subsequent immunohistochemical detection. Our results indicate that in the developing visual system of T. longicaudatus, three band-shaped zones containing neuronal stem cells are present corresponding to the proliferation zones found in Malacostraca. We therefore conclude that the ontogenetic mechanisms of visual-system formation are evolutionarily conserved (homologous) in Branchiopoda, Malacostraca, and Insecta.

Animals↗
PubMed1990

Phyletic aspects of the distribution of 3-hydroxyretinal in the class Insecta.

The distribution of 3-hydroxyretinal (R3), a recently discovered retinoid used as the visual pigment chromophore in some insects, was investigated in the class Insecta using HPLC technology. We studied 138 species in 24 orders, sampling from a wide range of taxonomic groups as well as varied habitats. In addition to groups already known to have R3, we find this retinoid in Hemiptera (suborder Heteroptera), Plecoptera, Megaloptera, and Hymenoptera. We also find retinal (R1) in Hemiptera (suborder Homoptera), Mecoptera, and Trichoptera, groups previously thought to have only R3. The pattern of R3 occurrence indicates that this retinoid cannot be considered a phylogenetic marker, having a scattered distribution in the class Insecta as well as within some orders of insects. Several environmental factors that might influence the selection of chromophore have been considered, but none correlates with its distribution. The evolutionary reasons for the pattern of occurrence of R3 therefore remain unknown.

Animals↗
PubMed2001

Phylogenetic relationships inferred from ribosomal its sequences and biogeographic patterns in representatives of the genus Calopteryx (Insecta: Odonata) of the West Mediterranean and adjacent West European zone.

Western Europe is a reinvasion zone for the riverine dragonfly genus Calopteryx (Insecta: Odonata). Reinvasion may have been from central West Asia or from the West Mediterranean refugium. Phylogenetic relationships of West Mediterranean and West European taxa of the genus Calopteryx from different localities were inferred from sequences of the internal transcribed spacers (ITS1 and ITS2) of the nuclear ribosomal RNA genes. Twenty-six taxa belonging to the species groups C. splendens, C. meridionalis, C. haemorrhoidalis, C. virgo, C. xanthostoma, and C. exul were analyzed, with two North American species, C. amata and C. aequabilis, as outgroup. Sequence data and phylogenetic analyses were used to infer biogeographical patterns. The ribosomal spacers (ITS1 and ITS2) and the intervening 5.8S rDNA gene were amplified by PCR and sequenced. The ITS2 sequences of the West Mediterranean and West European calopterygids show no length variation but the ITS1 region was slightly variable in length. The sequence variation for ITS1 and ITS2 regions between different West Mediterranean and West European calopterygids was 14.5 and 6.1%, respectively. Phylogenetic relationships inferred from ITS sequences only partly confirm morphological data. A monophyletic origin of all West Mediterranean and West European species emerged. They are separated into two main clades; the splendens-like forms and the virgo/meridionalis/haemorrhoidalis group. Intraspecific variability, indicating different stages of speciation, was detected only in West Mediterranean representatives (e.g., C. xanthostoma) but not in invasive representatives in West Europe. The North African endemic C. exul is more closely related to the Italian C. s. caprai than to C. splendens sensu strictu. Based on the present information, Cretan populations are the only splendens-like taxa in addition to C. s. caprai that deserve subspecies status.

Animals↗
PubMed1979

The midgut of Tomocerus minor Lubbock (insecta, collembola): ultrastructure, cytochemistry, ageing and renewal during a moulting cycle.

The midgut cells of Tomocerus minor (Insecta, Collembola) were examined with the electron microscope and cytochemically. The midgut epithelium consists of a series of cells characterised by numerous mineral concretions scattered throughout the cytoplasm. Mitochondria are abundant; microvilli are well developed at the apical surface of the cell. A zonula continua (continuous junction) characterises the apical contact region of these cells. Polysaccharides, glycoproteins and carbohydrate components have been demonstrated on the surface of microvilli. Peritrophic membranes surround the food bolus and preserve midgut cells from mechanical abrasion. Lysosomes are present during the alimentary period and show strong acid phosphatase activity. During an intermoulting cycle, two stages can be observed: (1) the postexuvial feeding period during which cytoplasmic extrusions appear at the apical part of the cell: lysosomes increase in number and autophagic vacuoles appear. (2) The preexuvial fasting period; a new epithelium grows beneath the old one and pushes it into the lumen. Degeneration processes can be observed in the old epithelium. This excretory reactivity of the midgut epithelium has been compared to the cycle of the cuticle.

Acid Phosphatase↗
PubMed2006

The mitochondrial genome of the entomophagous endoparasite Xenos vesparum (Insecta: Strepsiptera).

In this study, the nearly complete sequence (14,519 bp) of the mitochondrial DNA (mtDNA) of the entomophagous endoparasite Xenos vesparum (Insecta: Strepsiptera) is described. All protein coding genes (PCGs) are in the arrangement known to be ancestral for insects, but three tRNA genes (trnA, trnS(gcu), and trnL(uag)) have transposed to derived positions and there are three tandem copies of trnH, each of which is potentially functional. All of these rearrangements except for that of trnL(uag) is within the short span between nad3 and nad4 and there are numerous blocks of unassignable sequence in this region, perhaps as remnants of larger scale predisposing rearrangements. X. vesparum mtDNA nucleotide composition is strongly biased toward A and T, as is typical for insect mtDNAs. There is also a significant strand skew in the distribution of these nucleotides, with the J-strand being richer in A than T and in C than G, and the N-strand showing an opposite skew for complementary pairs of nucleotides. The hypothetical secondary structure of the LSU rRNA has also been reconstructed, obtaining a structural model similar to that of other insects.

Animals↗
PubMed2006

Phylogeny and biogeography of ice crawlers (Insecta: Grylloblattodea) based on six molecular loci: designating conservation status for Grylloblattodea species.

Ice crawlers (Insecta: Grylloblattodea) are rarely encountered insects that consist of five genera representing 26 species from North America and Asia. Asian grylloblattids are the most diverse, but North American ice crawlers (genus Grylloblatta) are known for their adaptation to cold conditions. Phylogenetic relationships among grylloblattid species and genera are not known. Six genes were sampled in 35 individuals for 18S rRNA, 28S rRNA, histone 3, 12S rRNA, 16S rRNA, and cytochrome oxidase II from 21 populations of Grylloblatta, three populations from Japan (genus Galloisiana), and three populations from Russia (genus Grylloblattina). Phylogenetic analysis of these data with two mantophasmid outgroups in POY supported monophyletic genera, with Grylloblatta as sister to Grylloblattina. Grylloblatta was shown to contain two major lineages: a clade in Northern California and Oregon and a clade in Washington and Oregon. One new species and six candidate species are proposed. IUCN Red List Conservation Criteria were implemented to designate conservation status for each lineage.

Animals↗
PubMed2003

Polymerase chain reaction amplification of the Bag320 satellite family reveals the ancestral library and past gene conversion events in Bacillus rossius (Insecta Phasmatodea).

Polymerase chain reaction amplifications of genomic DNA in 17 individuals of bisexual and parthenogenetic populations of three subspecies of Bacillus rossius (Insecta Phasmatodea) revealed that the species still harbours the whole variability of the ancestral Bag320 satellite family, since monomers of all non-hybrid Bacillus taxa plus private sequences occur in it. Bag320 monomers had not been rescued as a major satellite component in B. rossius, but possibly represent the remnant of a set of diverging sequences present in the Bacillus ancestor. Following the library hypothesis, these monomer variants have been differently amplified along the evolutionary pathways leading to present taxa in agreement with the mitochondrial phylogeny of the genus. The putative converted tracts observed are explained as the results of past gene conversion events.

Analysis of Variance↗
PubMed2003

Masquerading as self? Endoparasitic Strepsiptera (Insecta) enclose themselves in host-derived epidermal bag.

We report here the case of a metazoan parasite, a strepsipteran, that manipulates host epidermal tissue and wraps itself within it; which probably camouflages the endoparasite and is recognized as "self" by the host. This mechanism is one of immune avoidance among parasitoid insects. The host-derived epidermal "bag" might have enabled Strepsiptera to radiate to disparate hosts compared with the relatively few taxa (596 species) described so far. They have been recorded as parasitizing 34 families belonging to seven orders of Insecta. We also report a mechanism of insect ecdysis between the first- and second-instar larva, while enclosed in the bag.

Animals↗
PubMed1996

A nuclear gene for higher level phylogenetics: phosphoenolpyruvate carboxykinase tracks mesozoic-age divergences within Lepidoptera (Insecta).

The sequence of phosphoenolpyruvate carboxykinase (PEPCK) has been previously identified as a promising candidate for reconstructing Mesozoic-age divergences (Friedlander, Regier, and Mitter 1992, 1994). To test this hypothesis more rigorously, 597 nucleotides of aligned PEPCK coding sequence (approximately 30% of the coding region) were generated from 18 species representing Mesozoic-age lineages of moths (Insecta: Lepidoptera) and outgroup taxa. Relationships among basal Lepidoptera are well established by morphological analysis, providing a strong test for the utility of a gene which has not previously been used in systematics. Parsimony and other phylogenetic analyses were conducted on nucleotides by codon positions (nt1, nt2, nt3) separately and in combination, and on amino acids, for comparison to the test phylogeny. The highest concordance was achieved with nt1 + nt2, for which one of two most-parsimonious trees was identical to the test phylogeny, and with all nucleotides when nt3 was down-weighted sevenfold or higher, for which a single most-parsimonious tree identical to the test phylogeny resulted. Substitutions in nt3 approached saturation in many, but not all, pairwise comparisons and their exclusion or severe downweighting greatly increased the degree of concordance with the test phylogeny. Neighbor-joining analysis confirms this finding. The utility of PEPCK for phylogenetics is demonstrated over a time span for which few other suitable genes are currently available.

Amino Acid Sequence↗
PubMed1998

Satellite sequence turnover in parthenogenetic systems: the apomictic triploid hybrid Bacillus lynceorum (Insecta, Phasmatodea).

In the genus Bacillus (Insecta, Phasmatodea) the Bag320 satellite DNA family is present in the bisexual B. grandii and in the related automictic nonhybrid B. atticus; it is lacking in the other bisexual taxon of the genus, B. rossius. This family of highly repeated sequences was analyzed for 11 populations of the apomictic triploid hybrid B. lynceorum. In the neighbor-joining dendrogram, B. lynceorum nucleotide sequences distribute, regardless of geographical origin, among two clusters, one also including all clones of the three B. atticus races, and the other including sequences of the B. grandii grandii subspecies. Thus, B. lynceorum is a trihybrid taxon: as the molecular approach definitively demonstrates, it embodies one haploid complement each of both B. grandii grandii and B. atticus, which must be added to that of B. rossius. The contribution of the latter species has already been assessed on karyological and allozymic grounds. A statistical analysis performed on p-distances shows that for the parental taxa, nucleotide substitution values are of comparable magnitudes at the population level but differ at the subspecific level, being higher for the bisexual taxon. In the apomictic hybrid, atticus- and grandii grandii- like sequences coexist with significantly different p-distance values. For three clones, the nucleotide compositions at the diagnostic loci suggest that gene conversion can occur between atticus- and grandii grandii-like monomers. On the whole, this supports bisexuality as a driving force in variant fixation and suggests that in Bacillus, different gametogenetic processes and different origins of the unisexuals are mirrored in genomic turnover rates of satellite DNA.

Africa, Northern↗
PubMed1995

[Analysis of the variable structure of a cluster of ribosomal genes in the Insecta class].

General estimation of ribosomal DNA variation within the Insecta class is presented. It is shown that, using blot-hybridization, one can detect differences in the structure of the ribosomal gene cluster not only between genera within an order, but also between species within a genera, including sibling species. Structure of the ribosomal gene cluster of the Coccinelidae family (ladybirds) is analyzed. It is shown that cloned highly conservative regions of ribosomal DNA of Tetrahymena pyriformis can be used as probes for analyzing ribosomal genes in insects.

Animals↗
PubMed2000

Participation of testicular spermatids in development upon intracytoplasmic injection into eggs of the sawfly, Athalia rosae (Insecta, hymenoptera).

Fertilization by intracytoplasmic injection of mature sperm into mature eggs has previously been achieved in the sawfly, Athalia rosae (Insecta, Hymenoptera). In the present study, we examined the potential of spermatids, premature male gametes, for participating in development. When round spermatids and elongating spermatids from pupal testes were injected into the anterior end of mature eggs, about 5% of the total injected eggs developed into chimeric embryos (independent participation in development of the egg and spermatid nuclei). Some of them developed further, hatched, and pupated, with 1-2% of the total injected eggs becoming haploid chimeric male adults in which both the egg-derived and injected spermatid-derived nuclei contributed to the germline. No fertilized embryos were obtained by these injections. Elongated spermatids (immature sperm) from newly eclosed adult male testes upon injection did produce fertilized embryos that developed into normal diploid females (about 7% of the total injected). These results indicate that insect spermatids (round and elongating) have the potential to participate in development, but only independently of the egg nucleus. J. Exp. Zool. 286:181-192, 2000.

Animals↗
PubMed1993

Actin, alpha-actinin, and vinculin are associated with septate junctions in Insecta.

Cytoskeletal elements associated with the smooth septate junctions linking the midgut columnar cells of Manduca sexta larvae (Insecta, Lepidoptera) were characterized. Myosin subfragment 1 decoration and immunostaining for actin demonstrated that the filaments associated with the septate junctions were constituted of actin. Moreover, using a combination of immunochemical and immunolocalization techniques, evidence is presented that alpha-actinin, myosin II, and vinculin are localized close to the specialized plasma membranes. The insertion of microfilament bundles into submembranous F-actin/alpha-actinin/vinculin complexes, previously described in vertebrate junctions of adherens type, appears to be a more general organization, including the insect septate junction here examined.

Actin Cytoskeleton↗
PubMed2005

Absence asymmetry: the evolution of monorchid beetles (Insecta: Coleoptera: Carabidae).

Asymmetrical monorchy, or the complete absence of one testis coupled with the presence of its bilateral counterpart, is reported for 174 species of the carabid beetle tribes Abacetini, Harpalini, and Platynini (Insecta: Coleoptera: Carabidae) based on a survey of over 820 species from throughout the family. This condition was not found in examined individuals of any other carabid beetle tribes, or of other adephagan beetle families. One monorchid taxon within Platynini exhibits symmetrical vasa deferentia at the beginning of the pupal stadium, suggesting that developmental arrest of the underdeveloped vas deferens takes place in pupation. The point at which development of the testis is interrupted is unknown. Complete absence of one organ of a bilateral pair--absence asymmetry--is rarely found in any animal clade and among insects is otherwise only known for testes in the minute-sized beetles of the family Ptiliidae, ovaries in Scarabaeinae dung beetles, and ovaries of some aphids. Based on current phylogenetic hypotheses for Carabidae, testis loss has occurred independently at least three times, and up to five origins are possible, given the variation within Abacetini. Clear phylogenetic evidence for multiple independent origins suggests an adaptive or functional cause for this asymmetry. A previously posited taxon-specific hypothesis wherein herbivory in the tribe Harpalini led to testis loss is rejected. Optimal visceral packing of the beetle abdomen is suggested as a general explanation. Specifically, based on the function of various organ systems, we hypothesize that interaction of internal organs and pressure to optimize organ size and space usage in each system led to the multiple origins and maintenance of the monorchid condition. Testes are the only redundant and symmetrically paired structures not thought to be developmentally linked to other symmetrical structures in the abdomen. Among all possible organs, they are the most likely--although the observed frequency is very small--to bypass constraints that maintain bilateral symmetry, resulting in absence asymmetry. However, based solely on our observations of gross morphology of internal organs, no function conclusively explains the ontogenetic loss of one testis in these taxa. Unlike the analogous absence asymmetry of organs in other animal groups, no dramatic body-form constraint--e.g., snakes and lung loss, ptiliid beetles' small body-size and relatively giant sperm--or adaptive scenario of improved locomotory performance--e.g., birds and ovary loss due to flight constraints-applies to these carabid beetles. We tentatively suggest that testis loss is driven wholly by an interaction among the internal organs of these beetles, possibly due to selective pressure to maximize the comparatively large accessory glands found in these taxa. However, as the ordering of these evolutionary events of testis loss and accessory gland size increase is not known, large accessory glands might have secondarily evolved to compensate for a decreased testicular output.

Adaptation, Physiological↗