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PubMed2002

Comparative morphological assessment of the psyllid pleuron (Insecta, Hemiptera, Sternorrhyncha).

A unique set of morphological characters based on the hemipteran (sensu lato) thorax are used to define the pleuron of Psylloidea. New external and internal topographical descriptions of pleurites of all three thoracic segments are provided based on observations of specimens from various genera representing the current taxonomic arrangement of Psylloidea. Variations in propleurite morphology and the anteroventral angle of the episternum among taxa are clarified. The mesothoracic pleural sulcus is found to be a distinct groove formed by the deep fossa of the pleural apophysis and is not a secondary structure, as assigned by previous authors. A newly discovered internal apodeme of the metathoracic trochantin and a serially homologous structure in the mesothorax isolate the trochantinal territory of the second segment. The metathoracic pleural sulcus appears to be pressed against the ventral edge of the metepimeron, as previously described for the mesothorax of certain species of other insects having a strongly developed meron. Use of morphological interpretations and newly discovered apodemes to assess primary homology of structures for phylogenetic and taxonomic studies is discussed. A glossary of standardized morphological terms for thoracic structures of non-heteropteran Hemiptera based on this study and other recent and former dissertations on the insect thorax is provided.

Animals↗

PubMed2002

Embryogenesis of the glowworm Rhagophthalmus ohbai Wittmer (Insecta: Coleoptera, Rhagophthalmidae), with emphasis on the germ rudiment formation.

The early embryonic development and features of the developing embryo of the glowworm Rhagophthalmus ohbai are described chiefly by light microscopy, with emphasis on the germ rudiment formation and its phylogenetic implication. The egg period is 30-34 days at about 23 degrees C. The newly laid egg is a short ellipsoid, 1.09 by 0.78 mm in size, and the size increases to 1.15 by 0.95 mm by 17 days after oviposition. Cleavage is of the typical superficial type. The germ disk is formed by cell aggregation of the embryonic area at the anterior end of the egg. The central part of the germ disk then sinks into the yolk and the spherical germ rudiment is formed by fusion of the amnioserosal folds extended from all margins of the germ disk. The inner region of the germ rudiment soon becomes slender and develops into the short embryo, whereas the outer region facing the anterior end is extended to form the thin amnion. The embryo then rapidly elongates, the elongation being accompanied by embryo segmentation and formation of appendages. The submerged condition of the embryo persists until about 17 days after oviposition (about 1 day before embryonic revolution) and thereafter the embryo becomes superficial in position. The presence of the following embryonic characters in R. ohbai supports the molecular data placing it within the Lampyridae: 1) formation of a spherical germ rudiment near the anterior end of the egg, and 2) the submerged condition of the developing embryo persists until shortly before revolution.

Animals↗

PubMed2005

Mass spectrometric analysis of head ganglia and neuroendocrine tissue of larval Galleria mellonella (Arthropoda, Insecta).

A brain-retrocerebral complex-subesophageal ganglion acidified methanolic extract of 100 larval Galleria mellonella (greater wax moth) was prepared for the isolation and identification of (neuro)peptides. To reduce sample complexity, the isolated peptides were roughly separated using a single, conventional chromatographic separation step. Subsequently, screening of these fractions with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry in combination with nanoflow electrospray ionization quadrupole time-of-flight tandem mass spectrometry resulted in the identification of 12 lepidopteran peptides. None of these had been previously isolated or characterized within this species. VIFTPKLamide encoded by the diapause hormone-pheromone biosynthesis activating neuropeptide precursor was for the first time isolated and biochemically identified in a tissue extract, providing irrefutable evidence of its expression in larval nervous tissue. Another pentapeptide, AMVRFamide, with no resemblance to other lepidopteran peptides, was de novo sequenced and is most related to the neuropeptide F peptide family.

Amino Acid Sequence↗

PubMed2002

Centrosome dynamics and inheritance in related sexual and parthenogenetic Bacillus (Insecta Phasmatodea).

In animals, some general features of centrosome dynamics and inheritance have been widely recognized. The most acknowledged model assigns to sperm the contribution of a centriole to the fertilized egg, which in turn provides the pericentriolar materials, including gamma-tubulin, recruiting them from the cytoplasm: the main zygote microtubule organizing center (MTOC) is thus reconstituted to organize first the spermaster and then the full first embryonic spindle. Obviously the model cannot apply to parthenogenetic systems, which actually rely on egg components alone. In stick insects of the Bacillus genus, the spindle of both somatic and germ cells is clearly anastral, therefore we have been investigating their centrosome in sexual and parthenogenetic taxa by analyzing its component dynamics and transmission through the use of monoclonal beta- and gamma-tubulin antibodies and transmission electron microscopy (TEM). It has been shown that in sexually reproducing species the spermatozoon does not contribute the centriole, so that the egg wholly provides the MTOC and the ensuing anastral spindle of the embryo: MTs appear to derive from pronuclear chromatin surroundings and no asters are observed. The parthenogenetic embryo development is the same as the sexual one if syngamy is excepted. The parthenogenetic mechanism realized by these panoistic insects appears to differ from that observed in the meroistic hymenopteran and drosophilid species, where the embryo spindle derives from asters formed in the egg cortex. In stick insects, the lack of sperm contribution to embryonic centrosome appears to be a major trait accounting for the widespread occurrence of facultative and obligate parthenogenesis within the order.

Animals↗

PubMed1992

Genome exclusion and gametic DAPI-DNA content in the hybridogenetic Bacillus rossius-grandii benazzii complex (Insecta Phasmatodea).

Among Sicilian stick insects, two hybridogenetic complexes have been discovered: Bacillus rossius-grandii benazzii and B. rossius-grandii grandii, which also produce androgenetic offspring. The egg maturation of the former is analyzed here through DAPI fluorometry, which, besides the assessment of the meiotic stages, also allows their DNA measurements and the analysis of sperm-head evolution into male pronuclei in these polyspermic eggs. Hybridogenetic eggs undergo an extrasynthesis of chromosomes, because two groups of n autobivalents (4C each) are segregated at metaphase 1st; the two groups must correspond to the pure parental species haplosets. Then the grandii chromosomes degenerate (1st polar body), while the rossius chromosomes divide further to produce two groups of n autodiads (2C each); one of them degenerates (2nd polar body), and the other is ready to perform syngamy (female pronucleus). Meanwhile, several B. grandii sperm evolve into male pronuclei by doubling their DNA (from 1C to 2C content) and assuming an interphase nucleus appearance. If regular mixis occurs, the F1 hybrid constitution is restored but, if it fails, a fusion between two sperms may occur, originating fully paternal descendants (natural androgenesis). The genome exclusion mechanism of stick-insect hybridogens appears to be more primitive than those observed in the already known hybridogenetic complexes of Poeciliopsis and Rana esculenta. Unfertilized eggs of hybridogens are capable of self-activation, but the cytology of the related clonally reproducing B. whitei indicates that its parthenogenetic mechanism stems from the hybridization event (hybrid theory) rather than from tychoparthenogenetic potentialities (spontaneous theory).

Animals↗

PubMed1993

Spermatid nucleus of Megaselia scalaris Loew (Insecta, Diptera, Phoridae): a study using anti-histone antibodies, scanning electron microscopy, and a centromere-specific oligonucleotide.

The structure of elongated spermatid nuclei was examined in the fly Megaselia scalaris using indirect immunofluorescence with anti-histone antibodies, scanning electron microscopy, and in situ hybridization with a centromere-specific oligonucleotide. The immunofluorescence experiments showed that, in keeping with the situation in most animals, histones are hyperacetylated prior to their displacement from the nucleus in the course of spermiogenesis. Scanning electron microscopy revealed that grooves run parallel to the long axis of the spermatid nuclei. The chromatin is segmented into blocks lateral to the grooves. This finding most probably indicates that the chromatin is not yet maximally condensed at this stage. The retarded chromatin condensation may be correlated with the export of somatic histones from the nucleus. The location of the centromeres could not be identified using scanning electron microscopy, but in situ hybridization showed that a centromere-specific oligonucleotide mapped to the central or close to the central areas within the spermatid nucleus. Possibly, the chromosomes are extended and arranged parallel to the long axis of the spermatid nucleus.

Animals↗

PubMed1985

The central morphology of the giant interneurons and their spatial relationship with the thoracic motorneurons in the cockroach, Periplaneta americana (Insecta).

Three groups of giant fibers are found in the cockroach ventral nerve cord. A latero-dorsal group (dorsal GIs), a latero-ventral group (ventral GIs) and a medio-ventral group. The morphology of all three groups of fibers within the thoracic ganglia is described. The morphology of the dorsal and ventral GI pathways in the abdominal and suboesophageal ganglia is also described. The projection patterns of the neurons in each ganglion are remarkably similar which suggests a common function. When motorneurons 5rl (depressor) and 6Br4 (levator) are stained simultaneously with the dorsal and ventral GI groups, some branches from both motor and giant neurons converge. The branching of the remaining medio-ventral group of fibers and their proximity to areas receiving motorneuronal input suggests that these are the small diameter axons described by Dagan and Parnas (1970).

Animals↗

PubMed1985

The central morphology of mechanoreceptor afferents in the metathoracic leg of the cockroach, Periplaneta americana (Insecta).

The sensory arborizations of the femoral chordotonal organ (FECO), trochanteral campaniform sensilla (CS) and the trochanteral hairplate (THP) are restricted to the ipsilateral hemiganglion and possess large dendritic fields in the dorsal and ventral neuropiles. The efferent projections of the fast (Df) and the slow (Ds) depressor motoneurons project into the same areas. Three groups of trichoid sensilla located on the coxal and trochanteral cuticular walls have central contralateral projections and in one case intersegmental projections. All sensory projections terminate either just lateral of or in the Ventral Association Centre (VAC). Comparisons with the mechanoreceptors of other insects reveal similar projection patterns for some proprioceptors and non-homologous central configurations for others.

Afferent Pathways↗

PubMed1998

Age-related changes in the dendrites of olfactory receptor neurons in the male silkmoth Antheraea peryni (Insecta, Lepidoptera: Saturniidae).

A study was conducted to evaluate the changes that occur with aging at the dendrite level of the olfactory receptor neuron in the male silkmoth Antheraea pernyi. Using calcein AM/ethidium homodimer-1 solutions, we found increased numbers of dendrites with damaged membrane with aging. Correspondingly there was an overall decrease in the electrophysiological activity as evidenced by the decreased number of cells discharging nerve impulse in response to female pheromone. It was also seen that the number of membrane swellings increased with age. In young animals aged 1-4 days, swellings showed intact membrane, and in older animals aged 5-15 days, they showed damaged membranes. With TUNEL assay that detects fragmented DNA in dying cells, an increased number of dendrites showing cytoplasmic labelling with age was found. The presence of fragmented DNA within aged dendrites was also confirmed in polyacrylamide gels after DNA extraction and PCR amplification. When tested for reversal of phosphatidylserine from the inner leaflet to the outer leaflet of plasma membrane no reactivity was seen. It appears that changes that occur during aging of dendrites may reflect some of the recognized symptoms of both apoptosis and necrosis.

Animals↗

PubMed2001

Ultrastructural variations in Lethocerus niloticum (Insecta: Hemiptera) caused by pollution in Lake Mariut, Alexandria, Egypt.

Water bugs, Lethocerus niloticum (Hemiptera: Belostomatidae), were collected from polluted and unpolluted areas of Lake Mariut to study ultrastructural alterations of different organs as a response to mainly heavy metal water pollution in the lake. Malpighian tubules are described by light, scanning, and transmission electron microscopy. L. niloticum has four Malpighian tubules floating in the hemolymph. Each tubule opens separately into the hindgut, consisting of one type of epithelium cells, and is divided into four regions. Structural changes in cells of the third distinctive region are examined. The most prominent pathological changes are the occurrence of pleomorphic mitochondria, the presence of enlarged irregular laminated concretions, an increase in lysosomes, and lysis of cytoplasm. Indentations of the nucleus and chromatin clumping are observed. These results allowed determination of the impact of pollutants in Malpighian tubule cells of L. niloticum, and thus this insect can be used as a biomonitor.

Animals↗

PubMed1996

Intracytoplasmic Bacteria in Male Germ Cells of Philudoria potatoria L. (Lasiocampidae, Lepidoptera, Insecta)

The fine structure of bacteria, detected in the cytoplasm of spermatogonia, spermatocytes, and spermatids of a Lepidoptera species, Philudoria potatoria L. (Lasiocampidae), was described using transmission electron microscopy of ultrathin sections through testes. The effects of the bacteria on the germ cells were studied in semithin sections using light microscopy and in ultrathin sections using transmission electron microscopy. Larvae of the animal were collected in the field at the same location in two subsequent summers and the picture was very similar in both preparations. We examined a total of five animals and all were infected. The intracytoplasmic bacteria were usually rod-shaped, up to 1.7 μm long, and about 0.5 μm thick. They lay in intracellular cavities of the germ cells and were separated from the host cell by a membrane. The envelope of the bacteria consisted of two thin electron-dense layers interspersed by a transparent zone which represent the plasma membrane and the cell wall, respectively. Thus, the bacteria are most probably gram-negative. When the cells contained a small number of intracytoplasmic bacteria, pachytene spermatocytes and the development and structure of the meiotic spindles appeared regular. A prominent layer of perispindle membranes that is typical of male meiosis in the Lepidoptera (Wolf, 1994) was, however, missing in the infected animals. A low number of bacteria apparently does not interfere with the onset of spermiogenesis and it is possible that the microorganisms are transmitted into the next generation via the male germ line. In contrast, high numbers of intracytoplasmic bacteria result in cell degeneration in late prophase I of meiosis. Under these circumstances, electron-dense bodies formed within the nuclei and the nucleoplasm became transparent. The most prominent event in the cytoplasm was the aggregation of the mitochondria into large clusters. Finally, the nuclear envelope dissolved and the germ cells degenerated. The intracytoplasmic bacteria of P. potatoria are interpreted as parasites.

Journal Article↗

PubMed2001

Differential infectivity of two Pseudomonas species and the immune response in the milkweed bug, Oncopeltus fasciatus (Insecta: Hemiptera).

Pseudomonas aeruginosa and Pseudomonas putida show a profound differential infectivity after inoculation in Oncopeltus fasciatus. Whereas P. putida has no significant impact on nymphs, P. aeruginosa kills all experimental animals within 48 h. Both Pseudomonas species, however, induce the same four hemolymph peptides in O. fasciatus. Also injection of saline solution and injury induced these peptides. In general peptide induction was stronger in nymphs than in adult males. A significantly higher number of nymphs survived a challenge with P. aeruginosa when an immunization with P. putida preceded. The antibacterial properties of the hemolymph were demonstrated in inhibition experiments with P. putida. Two of the four inducible peptides (peptides 1 and 4) could be partially sequenced after Edman degradation and were compared with known antibacterial peptides. Peptide 1, of 15 kDa, showed 47.1% identity with the glycine-rich hemiptericin of Pyrrhocoris apterus. Peptide 4, of 2 kDa, had a 77.8% identity with the proline-rich pyrrhocoricin of P. apterus and a 76.9% identity with metalnikowin 1 of Palomena prasina. Peptides 2 and 3 are also small, with molecular weights of 8 and 5 kDa.

Amino Acid Sequence↗

PubMed1997

Molecular phylogenetic study of Tephritidae (Insecta: Diptera) using partial sequences of the mitochondrial 16S ribosomal DNA.

We analyzed sequence data from 925 base pairs within the mitochondrial 16S ribosomal DNA from 34 tephritid species and two outgroup taxa. DNA sequences were amplified by the polymerase chain reaction and sequenced by the dideoxy chain-termination method. Patterns of nucleotide composition and substitution were assessed based on sequence comparison. Phylogenetic relationships among the included taxa were inferred using neighbor-joining and maximum parsimony methods. The trees were congruent with the morphological classification and suggested the following phylogenetic relationships: (1) monophyly of the tribe Trypetini, s. str., excluding Parastenopa; (2) a possible sister group relationship between Platyparea and the subfamily Tephritinae; (3) a sister group relationship between Hexachaeta and the tribe Toxotrypanini; (4) monophyly of the Dacinae and possible relationship of Oedicarena to this subfamily; (5) monophyly of the tribe Adramini; and (6) the nonmonophyletic nature of the genus Rhagoletis. We propose that the 16S rDNA shows great promise for helping to create a phylogenetically based higher classification of the Tephritidae.

Animals↗

PubMed1997

The phylogeny of the Caelifera (Insecta, Orthoptera) as deduced from mtrRNA gene sequences.

Fragments of both mitochondrial ribosomal RNA genes of 32 caeliferan taxa (representing six of the seven superfamilies) and six outgroup Orthopteroids were sequenced. The combined alignment length was 630 bp after removal of all ambiguously aligned positions. Separation for the basal taxa was problematic and analysis using the LogDet transformation indicated that shared base composition biases were a confounding factor. The suborder Caelifera and all traditional caeliferan superfamilies except the Pamphagoidea are retrieved as monophyletic groups, though the Eumastacoidea lack significant bootstrap support. Of the traditional pamphagoid taxa, the Pamphagidae is embedded between classically acridid subfamilies, whereas Pyrgomorphidae is placed close to the Pneumoroidea. The morphological similarities of the Pyrgomorphidae and Pamphagidae may thus be homoplasic. A consensus tree based on five different methods of analysis indicated the following order: (Tridactyloidea, Tetrigoidea (Eumastacidae, Proscopiidae (Pneumoridae, Pyrgomorphidae (Acrididae + Pamphagidae)))).

Algorithms↗

PubMed1999

The major opsin in bees (Insecta: Hymenoptera): A promising nuclear gene for higher level phylogenetics.

We report the phylogenetic utility of the nuclear gene encoding the long-wavelength opsin (LW Rh) for tribes of bees. Aligned nucleotide sequences were examined in multiple taxa from the four tribes comprising the corbiculate bees within the subfamily Apinae. Phylogenetic analyses of sequence variation in a 502-bp fragment (approx 40% of the coding region) strongly supported the monophyly of each of the four tribes, which are well established from previous studies of morphology and DNA. Trees estimated from parsimony and maximum likelihood analyses of LW Rh sequences show a strongly supported relationship between the tribes Meliponini and Bombini, a relationship that has been found uniformly in studies of other genes (28S, 16S, and cytochrome b). All of the tribal clades as well as relationships among the tribes are supported by high bootstrap values, suggesting the utility of LW Rh in estimating tribal and subfamily rank for these bees. The sequences exhibit minimal base composition bias. Both 1st + 2nd and 3rd position sites provide information for estimating a reliable tree topology. These results suggest that LW Rh, which has not been reported previously in studies of organismal phylogenetics, could provide important new data from the nuclear genome for phylogeny reconstruction.

Animals↗

PubMed2000

Phylogenetic utility of the nuclear gene dopa decarboxylase in noctuoid moths (Insecta: Lepidoptera: noctuoidea).

Phylogenetic utility for the nuclear gene encoding dopa decarboxylase (DDC), little used in systematics, was recently demonstrated within the noctuid moth subfamily Heliothinae. Here we extend the test of the utility of a 709-bp DDC fragment to deeper levels, analyzing 49 species representing major groups across the superfamily Noctuoidea. Parsimony, distance, and maximum-likelihood analyses recover all or nearly all of a set of "test clades" supported by clear morphological synapomorphies, spanning a wide range of taxonomic levels. DDC also upholds a recent proposal that the Noctuidae are paraphyletic. Nt3 contributes a majority of the signal and recovers the basal split between Notodontidae and all other noctuoids, despite a plateau of nt3 divergence at this level. However, nonsynonymous changes also support groups at all levels, and in contrast to nt3, amino acid divergence shows no plateau. The utility of DDC promises to extend back to the early Tertiary and Cretaceous, a time span for which few suitable genes have been identified.

Animals↗

PubMed2000

18S rRNA secondary structure and phylogenetic position of Peloridiidae (Insecta, hemiptera).

A secondary structure model for 18S rRNA of peloridiids, relict insects with a present-day circumantarctic distribution, is constructed using comparative sequence analysis, thermodynamic folding, a consensus method using 18S rRNA models of other taxa, and support of helices based on compensatory substitutions. Results show that probable in vivo configuration of 18S rRNA is not predictable using current free-energy models to fold the entire molecule concurrently. This suggests that refinements in free-energy minimization algorithms are needed. Molecular phylogenetic datasets were created using 18S rRNA nucleotide alignments produced by CLUSTAL and rigorous interpretation of homologous position based on certain secondary substructures. Phylogenetic analysis of a hemipteran data matrix of 18S rDNA sequences placed peloridiids sister to Heteroptera. Resolution of affiliations between the three main euhemipteran lineages was unresolved. The peloridiid 18S RNA model presented here provides the most accurate template to date for aligning homologous nucleotides of hemipteran taxa. Using folded 18S rRNA to infer homology of character as morpho-molecular structures or nucleotides and scoring particular sites or substructures is discussed.

Animals↗

PubMed2000

Phylogeny of the treehoppers (Insecta: Hemiptera: Membracidae): evidence from two nuclear genes.

We present a molecular systematic investigation of relationships among family-group taxa of Membracidae, comprising nearly 3.5 kb of nucleotide sequence data from the nuclear genes elongation factor-1alpha (EF-1alpha: 958 bp) and 28S ribosomal DNA (28S rDNA: 2363 bp); data partitions are analyzed separately and in combination for 79 taxa. Analysis of the combined sequence data provided a better-resolved and more robust hypothesis of membracid phylogeny than did separate analyses of the individual genes. Results support the monophyly of the family Membracidae and indicate the presence of two major lineages (Centrotinae + Stegaspidinae + Centrodontinae and Darninae + Membracinae + Smiliinae). Within Membracidae, molecular data support the following assertions: (1) the previously unplaced genera Antillotolania and Deiroderes form a monophyletic group with Microcentrini; (2) Centrodontini and Nessorhinini are monophyletic clades that arise independently from within the Centrotinae; (3) Centrotinae is paraphyletic with respect to Centrodontinae; (4) the subfamily Membracinae is monophyletic and possibly allied with the darnine tribe Cymbomorphini; (5) the subfamily Darninae is paraphyletic; (6) the subfamily Smiliinae is paraphyletic, with molecular evidence indicating the exclusion of Micrutalini and perhaps Acutalini and Ceresini; and (7) Membracidae arose and diversified in the New World with multiple subsequent colonizations of the Old World. Our phylogenetic results suggest that morphology-based classifications of the Membracidae need to be reevaluated in light of emerging molecular evidence.

Animals↗