Cytogenetic Features of Human Head and Body Lice (Phthiraptera: Pediculidae).

The genus Pediculus L. that parasitize humans comprise two subspecies: the head lice Pediculus humanus capitis De Geer and the body lice Pediculus humanus humanus De Geer. Despite the 200 yr of the first description of these two species, there is still a long debate about their taxonomic status.

Complementary sex determination in the parasitic wasp Diachasmimorpha longicaudata.

We studied the sex determination in Diachasmimorpha longicaudata, a parasitoid braconid wasp widely used as biological control agent of fruit pest tephritid flies. We tested the complementary sex determination hypothesis (CSD) known in at least 60 species of Hymenoptera. According to CSD, male or female development depends on the allelic composition of one sex locus (single-locus CSD) or multiple sex loci (multiple-locus CSD).

Heterochromatin characterization and ribosomal gene location in two monotypic genera of bloodsucker bugs (Cimicidae, Heteroptera) with holokinetic chromosomes and achiasmatic male meiosis.

Members of the family Cimicidae (Heteroptera: Cimicomorpha) are temporary bloodsuckers on birds and bats as primary hosts and humans as secondary hosts. Acanthocrios furnarii (2n=12=10+XY, male) and Psitticimex uritui (2n=31=28+X1X2Y, male) are two monotypic genera of the subfamily Haematosiphoninae, which have achiasmatic male meiosis of collochore type. Here, we examined chromatin organization and constitution of cimicid holokinetic chromosomes by determining the amount, composition and distribution of constitutive heterochromatin, and number and location of nucleolus organizer regions (NORs) in both species.

The significance of cytogenetics for the study of karyotype evolution and taxonomy of water bugs (Heteroptera, Belostomatidae) native to Argentina.

Male meiosis behaviour and heterochromatin characterization of three big water bug species were studied. Belostoma dentatum (Mayr, 1863), Belostoma elongatum Montandon, 1908 and Belostoma gestroi Montandon, 1903 possess 2n = 26 + X1X2Y (male). In these species, male meiosis is similar to that previously observed in Belostoma Latreille, 1807.

Cytogenetic study in a mutant of Triatoma infestans (Hemiptera: Reduviidae) carrying a spontaneous autosomal fusion and an extra chromosome.

Triatomainfestans (2n = 20 A + XY, male) is a blood-sucking bug and the most important vector of Chagas disease in the Southern Cone countries. A cytogenetic analysis of 14 individuals from the Argentine Gran Chaco has revealed the presence of a naturally heterozygous for an autosomal fusion. The fusion heterozygote (2n = 19 A + 1 extra chromosome + XY, male) presented an autosomal trivalent, 8 bivalents, the X and Y sex univalents, and a minute extra chromosome at meiosis I.

Male meiosis, heterochromatin characterization and chromosomal location of rDNA in Microtomus lunifer (Berg, 1900) (Hemiptera: Reduviidae: Hammacerinae).

In the present work, we analysed the male meiosis, the content and distribution of heterochromatin and the number and location of nucleolus organizing regions in Microtomus lunifer (Berg, 1900) by means of standard technique, C- and fluorescent bandings, and fluorescent in situ hybridization with an 18S rDNA probe. This species is the second one cytogenetically analysed within the Hammacerinae. Its male diploid chromosome number is 31 (2n=28+X1X2Y), including a minute pair of m-chromosomes.

Immature stages of development in the parasitoid wasp, Diachasmimorpha longicaudata.

The morphological changes experienced during the immature stages of the solitary parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae: Opiinae) were studied. This natural enemy of several species of tephritid fruit flies is widely used in biological control strategies. Immature stages are poorly understood in endoparasitoids because they exist within the host.

Sex chromosome evolution in cotton stainers of the genus Dysdercus (Heteroptera: Pyrrhocoridae).

The neo-X and neo-Y sex chromosomes of Dysdercus albofasciatus represent a unique model for the study of early stages of sex chromosome evolution since they retained the ability to pair and recombine, in contrast to sex chromosomes in most Heteroptera. Here we examined structure, molecular differentiation, and meiotic behaviour of the D. albofasciatus neo-sex chromosomes.

Cytogenetic analysis of three species of Pseudacteon (Diptera, Phoridae) parasitoids of the fire ants using standard and molecular techniques.

Pseudacteon flies, parasitoids of worker ants, are being intensively studied as potentially effective agents in the biological control of the invasive pest fire ant genus Solenopsis (Hymenoptera: Formicidae). This is the first attempt to describe the karyotype of P. curvatus Borgmeier, P.

Synapsis with and without recombination in the male meiosis of the leaf-footed bug Holhymenia rubiginosa (Coreidae, Heteroptera).

In organisms with chiasmatic meiosis two different relationships have been described between crossing over and synapsis: in one group of organisms synapsis depends on the initiation of meiotic recombination while in the other group it is independent of this initiation. These patterns have been observed mainly in organisms where all meiotic bivalents in the set have similar behaviors. In some heteropteran insects a pair of chromosomes named m chromosomes is known to behave differently from autosomes regarding synapsis and recombination.

Heterochromatin characterization in five species of Heteroptera.

The amount, composition and location of heterochromatin in Athaumastus haematicus (Stål, 1859), Leptoglossus impictus (Stål, 1859), Phthia picta (Drury, 1770) (Coreidae), Largus rufipennis Laporte, 1832 (Largidae) and Jadera sanguinolenta (Fabricius, 1775) (Rhopalidae) are analyzed by C-banding and DAPI/ CMA fluorescent banding. As the rule for Heteroptera the possession of holokinetic chromosomes and a pre-reductional type of meiosis cytogenetically characterize these five species. Besides, all of them (except L.

Achiasmatic male meiosis in Tenagobia (Fuscagobia) fuscata (Stål) (Heteroptera, Corixoidea, Micronectidae).

Male karyotype and meiosis of Tenagobia fuscata (Corixoidea, Micronectidae) are studied. The species possesses a male diploid chromosome number 2n = 28 + XY, holokinetic chromosomes, absence of m chromosomes and an achiasmatic male meiosis. Autosomes divide pre-reductionally while the sex chromosomes do so post-reductionally.

Cytogenetic and nucleolar meiotic cycle analyses in Dysdercus imitator Blöte, 1931 (Pyrrhocoridae, Heteroptera) from Argentina.

So far, only seven and five species of Dysdercus from the Old and New Worlds, respectively, have been cytogenetically analysed. They all have holokinetic chromosomes and a pre-reductional type of meiosis. In the present study the chromosome complement, male meiosis and nucleolar meiotic cycle of Dysdercus imitator were analyzed.

Nucleolus organizing regions and semi-persistent nucleolus during meiosis in Spartocera fusca (Thunberg) (Coreidae, Heteroptera).

The Coreidae are cytogenetically characterized by possessing holokinetic chromosomes and a pre-reductional type of meiosis. The modal diploid chromosome number of the family is 21, with a pair of m chromosomes and an XO/XX sex chromosome determining system. Spartocera fusca presents 2n=23/24=20+2m+XO/20+2m+XX (male/female).

Behaviour of ring bivalents in holokinetic systems: alternative sites of spindle attachment in Pachylis argentinus and Nezara viridula (Heteroptera).

Heteropteran chromosomes are holokinetic; during mitosis, sister chromatids segregate parallel to each other but, during meiosis, kinetic activity is restricted to one pair of telomeric regions. This meiotic behaviour has been corroborated for all rod bivalents. For ring bivalents, we have previously proposed that one of the two chiasmata releases first, and a telokinetic activity is also achieved.

Cytogenetic proof that the brine shrimp Artemia franciscana (Crustacea, Branchiopoda) is found in Argentina.

Artemia brine shrimps are commercially important and they have been extensively studied. This branchiopod crustacean is extensively used in aquaculture and other commercial and applied practices. The genus also awakes an increasing interest worldwide as an experimental model in other basic areas of research such as evolution and cytogenetics.

Meiotic studies in Dysdercus Guérin Meneville 1831 (Heteroptera: Pyrrhocoridae). I. Neo-XY in Dysdercus albofasciatus Berg 1878, a new sex chromosome determining system in Heteroptera.

The genus Dysdercus Guérin Méneville 1831 represents the only taxon within the family Pyrrhocoridae in the New World. Based on morphological features, it has been suggested that American species derived from immigrants from the Old World, most probably from the Ethiopian Region. So far, 10 species from Dysdercus, including six species from the Old World and four species from the Neotropical Region have been cytogenetically analyzed.

Comparative meiotic studies in Triatoma sordida (Stål) and T. guasayana Wygodzinsky & Abalos (Reduviidae, Heteroptera).

Triatoma sordida and T. guasayana are competent Trypanosoma cruzi vectors, with overlapping distribution areas in Argentina. Both species are morphologically similar, and their immature stages are hard to discriminate.