Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Insecta”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2001

Molecular systematics of Goniodidae (Insecta: Phthiraptera).

The higher level phylogenetic relationships within the avian feather lice (Insecta: Phthiraptera: Ischnocera) are extremely problematic. Here we investigate the relationships of 1 family (Goniodidae), sometimes recognized as distinct within Ischnocera, using parsimony and likelihood analyses of nuclear and mitochondrial DNA sequences. These data support monophyly for a restricted definition of traditional Goniodidae, but recognition of this family would result in paraphyly of the large heterogeneous family Philopteridae. We show that the New World Chelopistes is not related to other members of Goniodidae, despite similarities in morphology, but rather is the sister taxon to Oxylipeurus. Within Goniodidae, genera are divided into those occurring on Galliformes (the Goniodes complex) and those occurring on Columbiformes (the Coloceras complex). Within the well-sampled Coloceras complex, or Physconelloidinae, several groups are identified. However, traditionally recognized genera such as Coloceras and Phvsconelloides appear to be paraphyletic. Whereas the phylogeny of Goniodidae reflects some aspects of host relationships, biogeography also influences coevolutionary history.

Animals↗
PubMed2001

Critical evaluation of five methods for quantifying chewing lice (Insecta: Phthiraptera).

Five methods for estimating the abundance of chewing lice (Insecta: Phthiraptera) were tested. To evaluate the methods, feral pigeons (Columba livia) and 2 species of ischnoceran lice were used. The fraction of lice removed by each method was compared, and least squares linear regression was used to determine how well each method predicted total abundance. Total abundance was assessed in most cases using KOH dissolution. The 2 methods involving dead birds (body washing and post-mortem-ruffling) provided better results than 3 methods involving live birds (dust-ruffling, fumigation chambers, and visual examination). Body washing removed the largest fraction of lice (>82%) and was an extremely accurate predictor of total abundance (r2 = 0.99). Post-mortem-ruffling was also an accurate predictor of total abundance (r2 > or = 0.88), even though it removed a smaller proportion of lice (<70%) than body washing. Dust-ruffling and fumigation chambers removed even fewer lice, but were still reasonably accurate predictors of total abundance, except in the case of data sets restricted to birds with relatively few lice. Visual examination, the only method not requiring that lice be removed from the host, was an accurate predictor of louse abundance, except in the case of wing lice on lightly parasitized birds.

Animals↗
PubMed2005

Structure of the ovary and the differentiation of follicular epithelium in the pig louse, Haematopinus suis (Insecta: Phthiraptera).

The female reproductive system of the pig louse, Haematopinus suis (Insecta: Phthiraptera) is composed of paired ovaries, lateral oviducts, and a common oviduct that leads into a vagina. Clusters of mycetocytes (= cells filled with symbiotic organisms) are associated with lateral oviducts. Each ovary is composed of five loosely arranged ovarioles of the polytrophic-meroistic type. An individual ovariole is covered by a basal lamina and is composed of a terminal filament, germarium, and vitellarium. The terminal filament is composed of large, disc-shaped cells that are orientated perpendicularly to the long axis ofthe ovariole. The basal part of the terminal filament is separated from the germarium by a well-developed transverse septum. The germarium is short and filled with clusters of oogonial cells. In each cluster the cells arejoined by intercellular bridges, filled with fusomal material. Within the cluster, only one cell, the future oocyte, enters the prophase of the first meiotic division; the other cells differentiate into nurse cells. The basal part ofthe germarium is filled with the somatic prefollicular cells. The boundary between the germarium and the vitellarium is not distinct. The vitellarium contains linearly arranged ovarian follicles in subsequent stages of oogenesis (previtellogenesis, vitellogenesis and choriogenesis). Each follicle consists of an oocyte and 7 nurse cells and is surrounded by follicular cells. During oogenesis the follicular cells diversify, so that ultimately, five morphologically distinct subpopulations of these cells can be distinguished: (1) cells in contact with the nurse cells, (2) anterior cells, (3) mainbody cells, (4) posterior cells, and (5) interfollicular cells. Interestingly, the follicular cells associated with the anterior part of the oocyte, i.e. located in space at the oocyte/nurse cell border (fold cells) are mitotically active throughout previtellogenesis. It might be suggested, in this context, that the separation of the oocyte from the nurse cell compartment is brought about by mitotic divisions, consequent multiplication and centripetal migration of these cells.

Animals↗
PubMed2006

Microsporidia infect the Liophloeus lentus (Insecta, Colepotera) ovarioles, developing oocytes and eggs.

In the ovarioles of Liophloeus lentus (Insecta, Coleoptera, Curculionidae) two types of bacteria and parasitic microorganisms belonging to Microsporidia have been found. This study shows that the different microsporidian life stages (meronts, sporonts, sporoblasts and spores) infect the outer ovariole sheath, trophic chambers, follicular cells, late previtellogenic and vitellogenic oocytes and eggs. In trophic chambers the parasites are very abundant and are distributed unevenly, i.e. their large mass occupies the syncytial cytoplasm between the nurse cell nuclei, whereas the neck region of the trophic chamber (which houses young oocytes, prefollicular cells and trophic cords) is almost free of parasites. The developing oocytes and eggs contain a lower number of parasites which are usually distributed in the cortical ooplasm. The gross morphology of the ovaries is similar in infected and non-infected specimens. Similarly, the presence of a parasite seems to not disturb the course of oogensis. The only difference was found in the ultrastructure of mitochondria in young previtellogenic oocytes. In the infected females they are unusual i.e. bigger and spherical with tubullar cristae, whereas in the non-infected insects they are elongated and have lamellar cristae. As oogenesis progresses the unusual mitochondria rapidly change their morphology and become similar to the mitochondria in non-infected females. Taking into account the distribution of parasites within the ovarioles, it is suggested that they infect growing oocytes via outer ovariole sheath and follicular epithelium rather than via trophic cords.

Animals↗
PubMed1996

Evolution of Tribolium madens (Insecta, Coleoptera) satellite DNA through DNA inversion and insertion.

Two different satellite DNAs from tenebrionid species Tribolium madens (Insecta, Coleoptera) have been detected, cloned, and sequenced. Satellite I comprises 30% of the genome; it has a monomer size of 225 bp and a high A + T content of 74%. Satellite II, with a monomer size of 711 bp and A + T content of 70%, is less abundant, making 4% of the total DNA. Sequence variability of the monomers relative to consensus sequence is 4.1% and 1.2% for satellite I and II, respectively. Both satellites are localized in the heterochromatic regions of all chromosomes. A search for internal motifs showed that both satellites contain a related subsequences, about 100 bp long. The creation of satellite I monomer is explained by duplication of the basic subunit, followed by subsequent divergence by single point mutations, deletions, and gene conversion. Inversion of the subsequence in addition to its duplication has occurred in satellite II. The result of this inversion is possible formation of a long, stable dyad structure. The 408-bp sequence, inserted within satellite II monomer, shares no similarity with a basic subunit. Frequent direct repeats found within the inserted sequence point to its evolution by duplication of shorter motifs. It is proposed that both satellites have been derived from a common ancestral sequence whose duplication played a major role in the formation of satellite I monomer, while insertion of a new sequence together with inversion of an ancestral one induced the occurrence of satellite II.

Animals↗
PubMedDate not supplied

Porous channels in the cuticle of the head-arrester system in dragon/damselflies (Insecta:Odonata).

The ultrastructure of the porous channels (PC) of the postcervical sclerite (SPC), which provides additional head fixation to the neck in adult odonates, was studied using TEM and high resolution SEM microscopy. Single chitin-protein microfibrils, about 0.14 micron thick, are arranged into channels with cylinder-like shapes. The axial rod of the chitin fiber (0.04 micron thick) is located in the center of the cylinder. The orientation of the axial rods was three-dimensionally demonstrated after dissolving the protein cover with NaOH. The PCs are arranged vertically to the surface and pass from the epidermal cells through all the cuticular layers to the surface of the cuticle. In the exo- and endocuticle, the PCs are usually oval in cross-section and about 0.3 micron thick. In the endocuticle, the cross-sectional area of the PCs varies widely, from 0.01-0.15 micron2. The shape of the PC is determined by the macromolecular organization of the chitin-protein microfibrils: the long axis of the channel is orientated parallel to the axis of the preferred orientation of the cuticular microfibrils. The microfibrils tend to follow the line of the channel very closely. In fractures orientated perpendicular to the surface, the PC resembles a ribbon-like construction, which was clearly demonstrated by casts. The strongly parallel orientation of PCs in the deep layers of the cuticle changes within the microtrichia (MT), and they begin to be curved. Numerous PCs pass through the microtrichium, and most of them end on its side wall. PCs usually contain channel filaments about 0.09 micron thick. Usually, a single channel contained one filament, but channels located in the deep layers of the endocuticle have from one to five single filaments. The filaments were observed in the intact cuticle and in the cuticle enzymatically treated with chitinase, while in the cuticle treated with NaOH filaments were absent. The porous channel system of the odonate arrester is interpreted as a device transporting adhesive excretions from the epidermal cells to the cuticular surface.

Animals↗
PubMed1999

Chromosome elimination and sex determination in springtails (Insecta, Collembola).

A post-zygotic mechanism of sex determination is described in the two symphypleonans Dicyrtomina ornata (Nicolet) and Ptenothrix italica Dallai. The process consists of the loss of two sex chromosomes from the male embryo. At the end of the first meiotic division of spermatogenesis, a second chromosome elimination occurs, allowing half the secondary spermatocytes, later transformed into spermatids, to receive a complete haploid set of chromosomes. The secondary spermatocytes, which receive an incomplete set of chromosomes, degenerate. Males of the two collembolan species, therefore, produce a reduced number (50%) of spermatozoa. Females of D. ornata have 2n = 12 and males 2n = 10 chromosomes; females of P. italica have 2n = 14 and males 2n = 12 chromosomes. In both species, oogenesis proceeds normally and chromosomes pair and form chiasmata in meiotic prophase. The adaptive significance of this post-zygotic mechanism of sex determination is discussed. The mechanism seems to be a characteristic feature of the suborder Symphypleona. The neanurid Arthropleona Anurida maritima (Guérin), which was studied for comparative analysis, has 2n = 8 chromosomes and normal spermatogenesis producing haploid nuclei with four chromosomes. J. Exp. Zool. (Mol. Dev. Evol.) 285:215-225, 1999.

Animals↗
PubMed2004

Morphometric analysis of the larval branchial chamber in the dragonfly Aeshna cyanea Müller (Insecta, Odonata, Anisoptera).

The aquatic larvae of anisopteran dragonflies possess tracheal gills located in the rectum. Using stereological methods, we estimated the morphometric diffusing capacity for oxygen (D(MO2)) across the gill epithelium, i.e., from rectal water to the gill tracheoles, in the larvae of Aeshna cyanea. A 271-mg larva has a total branchial surface area of approximately 12 cm(2). Tracheoles make up 6% of the epithelial volume of the gills; the harmonic mean thickness of the water-tracheolar diffusion barrier is 0.27 microm and consists mainly of cuticle. The calculated D(MO2) is 23.0 microl min(-1) g(-1) kPa(-1), which, using published values for oxygen consumption in a similar species, would result in a mean driving pressure of 0.2 kPa at rest and 1.3 kPa during activity. Since these driving pressures are similar to those reported for other arthropods, we conclude that the D(MO2) of the gill is not rate-limiting for aerobic metabolism in Aeshna cyanea larvae. J Morphol. 261:81-91, 2004.

Animals↗
PubMed2005

Mating of Xenos vesparum (Rossi) (Strepsiptera, Insecta) revisited.

The controversial mating of the strepsipteran Xenos vesparum was studied to investigate the possible sperm routes for fertilization. The female, which is a neotenic permanent endoparasite of Polistes wasps, extrudes only its anterior region, the "cephalothorax," from the host abdomen. This region has an opening where both mating and larval escape occur. Observations with scanning and transmission electron microscopy revealed spermatozoa not only in the hemocoel, but also in the "ventral canal" (an extragenital duct peculiar to strepsipteran females) and in the "genital ducts" (ectodermal invaginations connecting the ventral canal to the hemocoel) of recently mated females. Xenos vesparum spermatozoa can reach the oocytes either through the hemocoel as a result of a hypodermic insemination, or by moving along the extragenital ducts, which are later used by first instar larvae to escape. The hypothesis of hypodermic insemination is reconsidered in the light of behavioral and ultrastructural evidence.

Animals↗
PubMed2005

Embryonic development of Galloisiana yuasai Asahina, with special reference to external morphology (insecta: Grylloblattodea).

The embryogenesis of Grylloblattodea, one of the most primitive of the polyneopteran orders, is described using Galloisiana yuasai with special reference to external morphology. The egg membranes are characterized by an endochorion crossed by numerous vertical aeropyles and a fairly thin vitelline membrane, features shared by Mantophasmatodea. The inner layer formation is of the fault type. Serosal elements in the amnioserosal fold differentiate into hydropylar cells, to function in water absorption together with specialized amniotic structures, i.e., an amniotic strand and a thickened amnion. The germ band is of the short germ type. The germ band immerses deep into the yolk after its full elongation along the egg surface, and in this respect blastokinesis closely resembles that of Mantophasmatodea. The embryological features, i.e., those on egg membranes and blastokinesis, may suggest a closer affinity of Grylloblattodea and Mantophasmatodea. Appendages, ectodermal invaginations, and sternal and pleural sclerites are discussed in the light of serial homology, to provide a new basis for elucidating the insect body plan. Appendages are divided into the proximal coxopodite and distal telopodite, the former being divided further into the subcoxa and coxa. Subcoxal and coxal elements are identified in the mandible as well as in the abdominal appendages. The subcoxa is divided into the epimeron and episternum by the pleural suture in thoracic segments. Likewise, in the abdominal segments the subcoxa is divided into two, although the homologs of the epimeron and episternum are not sclerotized, and in the labial segment the subcoxal derivative or the postmentum is divided into the submentum and mentum. Two coxal endites bulge out from the medial side of the gnathal appendages. The mandibular molar and incisor, maxillary lacinia and galea, and labial glossa and paraglossa are serially homologous with each other. In the thoracic segments the original embryonic sternum or "protosternum" is largely replaced by subcoxal elements, and merely remains as a small anterior presternum and a posterior spinasternum. A major part of the venter is represented by the derivatives of the episternum such as an extensive basisternum, katepisternum, and trochantin and the medial element of the epimeron. The pleuron is derived from the episternal elements or the anepisternum and preepisternum, which bears a spiracle in the mesothorax and metathorax, and the lateral element of the epimeron. The homolog of the preepisternum in the prothorax is the cervical sclerite, but with no spiracle developed. A median ventral invagination arises in the thoracic segments as a spina, and the homolog of the spina develops into the eversible sac in the first abdominal segment.

Animals↗
PubMed2006

Right-handed penises of the earwig Labidura riparia (Insecta, Dermaptera, Labiduridae): evolutionary relationships between structural and behavioral asymmetries.

The number of penises vary in the insect suborder Forficulina (order Dermaptera; earwigs). Males of the families Diplatyidae, Pigidicranidae, Anisolabididae, Apachyidae, and Labiduridae have two penises (right and left), while those of the Spongipohridae, Chelisochidae, and Forficulidae have a single penis. The proposed phylogenetic relationships among these families suggest that the single-penis families evolved from an ancestor possessing two penises. To date, examinations of double-penis earwig species have found that only a single penis is used per single copulation. These diversities in structural and behavioral aspects of genitalia raises the following intriguing questions: How are the two penises used? Why did a penis degenerate in several earwig families, and which one was lost? To address these questions, structural and behavioral asymmetries were examined in detail for a representative species Labidura riparia (Labiduridae). Although there was no detectable morphological differentiation between the right and left penises, male L. riparia predominantly used the right one for insemination. This significant "right-handedness" developed without any experience of mating and was also manifested in the resting postures of the two penises when not engaged in copulation. However, surgical ablation of the right penis did not influence the insemination capacity of males. In wild-caught males, only about 10% were left-handed; within this group, abnormalities were frequently observed in the right penis. These lines of evidence indicate that the left penis is merely a spare intromittent organ, which most L. riparia males are likely never to use. Additional observations of five species of single-penis families revealed that the left penis degenerated in the common ancestor of this group. Considering the proposed sister relationship between the Labiduridae and the single-penis families, it is possible that such behavioral asymmetries in penis' use, as observed in L. riparia, are parental to the evolutionary degeneration of the infrequently used left penis.

Animals↗
PubMed1977

Comparative analysis of the hindgut in two species of protura (Insecta, Apterygota).

The proturan hindgut consists of two regions, with different ultrastructure. The anterior region is organized into three primary longitudinal folds alternating with three smaller, secondary ones. In Acerentomon each primary fold in a cross section contains one or two cells showing all the structures which are involved in water reabsorption. The cells of the secondary folds do not seem engaged in a similar function. In Eosentomon the primary folds present a more complicated organization. Each of them consists of one central cell concerned with reabsorption and two lateral ones. Beneath these cells, on both sides of the fold there is a longitudinal muscle fiber. The posterior region of the hindgut does not seem capable of modifying the gut contents.

Animals↗
PubMed1977

Sense organs on the antennal flagellum of psocids (Insecta, Psocoptera).

The sense organs on the antennal flagella of five species of winged psocids belonging to two families of Psocoptera, Psocidae and Leptopsocidae, have been examined, All agree in possessing tactile hairs, thick-walled chemoreceptors and long, porous chemoreceptors. Thin-walled chemoreceptors were identified in all species except Metylophorous novaescotiae. Coeloconic chemoreceptors were present in all species except Echmepteryx hageni. Campaniform sense organs were found only in Metylophorus novaescotiae and Psocus leidyi.

Animals↗
PubMed2001

New DAPI and FISH findings on egg maturation processes in related hybridogenetic and parthenogenetic Bacillus hybrids (Insecta, Phasmatodea).

Bacillus stick insects have proved adequate for studying a wide array of reproductive modes: sexual, parthenogenetic, hybridogenetic, androgenetic. Hybridogenetic strains (B. rossius-grandii) were thought to discard the paternal "grandii" haploset during first meiotic division and keep the "rossius" hemiclone, whereas the clonal B. whitei (=rossius/grandii) would maintain its hybrid structure by fusing back two nonsister nuclei-each derived from previously segregated heterospecific complements-by the end of the 2(nd) meiotic division. New investigations on laid eggs and ovariole squashes, either DAPI stained or FISH labeled, revealed that in hybridogens the "grandii" set is excluded from the germ line prior to meiosis and that a DNA extra-synthesis should occur to produce hemiclonal eggs after two cytologically normal meiotic divisions. On the other hand, in B. whitei eggs no genome segregation appears to occur and an intrameiotic DNA extra-synthesis must take place to produce 2n tetrachromatidic oocytes I; these divide twice and give unreduced clonal eggs. The new findings bring hybridogenetic oogenesis of Bacillus to be coincident with that of the known hemiclonal organisms and point to an independent onset of B. whitei from hemiclonal strains. In addition, B. whitei gains a closer resemblance to B. lynceorum owing to the sharing of a cytologically identical egg maturation mechanism, of the same maternal ancestor and of peculiar chromosomal features. It is here suggested that B. lynceorum originated from the incorporation of an "atticus" genome into a B. whitei egg, according to a pathway of repeated hybridization often occurred with other polyploid hybrids.

Animals↗
PubMed2001

Continuous monitoring of Folsomia candida (Insecta: Collembola) in a metal exposure test.

Current recommended ecotoxicological tests with the parthenogenetic springtail Folsomia candida using standard OECD soil do not allow for continuous monitoring during the exposure period. Effects of chemicals cannot be determined until the end of the experiment (typically after 4 weeks), since the animals stay below the soil surface. In this study, F. candida were maintained on a plaster of Paris/graphite substrate for 7 weeks and were supplied with an aqueous suspension of yeast contaminated with Cd, Cu, Pb, and Zn as nitrate salts. Growth rate, time to first batch of eggs, quantity of food consumed, and the presence of graphite in the gut (a sign of avoidance of yeast) were all affected by metal contaminated diets. The relative toxicities of Cd:Cu:Pb:Zn in the yeast were 1.0:1.07:12.0:4.3, respectively (on a weight basis) with Cd being the most toxic. Internal body concentrations increased, and the concentration factor (metal concentration in F. candida/metal concentration in yeast) decreased with increasing metal exposure. In general, metals are much less toxic when added to the food of F. candida than when incorporated into soil in standard tests. It is suggested that Collembola have a greater tolerance of metals in the diet since they avoid contaminated food, and are able to excrete assimilated metals at moulting via exfoliation of the midgut epithelium where the elements are retained as part of a storage--detoxification system. The methodology described in this article allows effects on growth to be observed as early as 7 days after the beginning of the experiment.

Animals↗
PubMed2000

Large amounts of genetic divergence among Italian species of the genus Orchesella (Insecta, collembola) and the relationships of two new species.

The phylogenetic position of two putative new species of the collembolan genus Orchesella was investigated by comparison with four other Italian species of the genus using a fragment of the mitochondrial gene encoding for subunit I of cytochrome c oxidase (COI). The gene showed the well-known A + T bias, typical of insect mitochondrial DNA, although A + T content was not as high as that observed in species belonging to more derived insect orders. The large number of variable sites in 3rd codon positions (85.2% variable) suggested that these sites contain significant homoplasy due to multiple hits. Despite the lack of morphological differentiation, the COI portion examined shows remarkable levels of genetic divergence between the putative species and their closest relatives. Phylogenetic analysis suggests that one of the putative new species is related to O. villosa, whereas the other is included in a clade with O. cincta and O. ranzii. The species O. chiantica appears to be related to O. villosa, agreeing with previous allozyme data.

Animals↗