Blaptica Dubia Research Articles

Animals as sentinels of human health hazards of environmental chemicals.

A workshop titled "Using Sentinel Species Data to Address the Potential Human Health Effects of Chemicals in the Environment," sponsored by the U.S. Army Center for Environmental Health Research, the National Center for Environmental Assessment of the EPA, and the Agency for Toxic Substances and Disease Registry, was held to consider the use of sentinel and surrogate animal species data for evaluating the potential human health effects of chemicals in the environment. The workshop took a broad view of the sentinel species concept, and included mammalian and nonmammalian species, companion animals, food animals, fish, amphibians, and other wildlife. Sentinel species data included observations of wild animals in field situations as well as experimental animal data. Workshop participants identified potential applications for sentinel species data derived from monitoring programs or serendipitous observations and explored the potential use of such information in human health hazard and risk assessments and for evaluating causes or mechanisms of effect. Although it is unlikely that sentinel species data will be used as the sole determinative factor in evaluating human health concerns, such data can be useful as for additional weight of evidence in a risk assessment, for providing early warning of situations requiring further study, or for monitoring the course of remedial activities. Attention was given to the factors impeding the application of sentinel species approaches and their acceptance in the scientific and regulatory communities. Workshop participants identified a number of critical research needs and opportunities for interagency collaboration that could help advance the use of sentinel species approaches.

Hypertrehalosaemic neuropeptides decrease levels of the glycolytic signal fructose 2,6-bisphosphate in cockroach fat body

In cockroach fat body, trehalogenesis and glycolysis compete for glucose phosphates as common substrates. During trehalogenesis, glycolysis is inhibited, although the mechanism responsible for this is not known. Incubation of the isolated fat body from the Argentine cockroach Blaptica dubia with an extract of the corpora cardiaca containing as little as 0.005 gland equivalents ml-1 of incubation medium increased the release of trehalose (anthrone-positive material) from the tissue by more than 100 %. The content of the glycolytic activator fructose 2,6-bisphosphate was decreased by up to 50 %. A decapeptide was isolated from the corpora cardiaca of B. dubia and shown to be identical to the naturally occurring Blaberus discoidalis hypertrehalosaemic peptide (Bld HrTH), which was also found in the corpora cardiaca. Synthetic Bld HrTH at 2 nmol l-1 and above increased trehalose production and decreased the content of fructose 2,6-bisphosphate to the same extent as did corpus cardiacum extract. The octapeptides Periplaneta americana cardioacceleratory hormones I and II (Pea CAH-I and Pea CAH-II) also had a significant effect on both parameters. Fructose 2,6-bisphosphate is a potent activator of phosphofructokinase from cockroach fat body if the enzyme is assayed at near-physiological concentrations of substrates and effectors. It is suggested that, because of the decrease in fructose 2,6-bisphosphate levels in the fat body, the activity of the key glycolytic enzyme phosphofructokinase is diminished. This can explain the inhibition of glycolytic flux by hypertrehalosaemic peptides which alters the balance of glucose metabolism in favour of trehalose formation.

Signal transduction in isolated fat body from the cockroach Blaptica dubia exposed to hypertrehalosaemic neuropeptide

Hypertrehalosaemic hormones stimulate trehalogenesis while inhibiting glycolysis in cockroach fat body. Signal transduction of the hypertrehalosaemic peptide Bld HrTH was examined in isolated fat body of the Argentine cockroach Blaptica dubia with respect to its effects on the increase in trehalose production and decrease in the content of the glycolytic activator fructose 2,6-bisphosphate in the tissue. Cyclic AMP does not seem to be involved in these processes as the cAMP analogue cpt-cAMP and the phosphodiesterase inhibitor IBMX, which both permeate cell membranes, had no effect on either parameter. Octopamine at physiological concentrations (10−7 mol · l−1) was also ineffective, but at 10−5 mol · l−1 or above, octopamine stimulated trehalose production although the content of fructose 2,6-bisphosphate in fat body was not affected. Both calcium entry and the release of Ca2+ from intracellular stores seem to be involved in the action of the hormone. If Ca2+ was omitted from the incubation medium, the hormone stimulated trehalose production less, though still significantly, whereas the hormone effect on fructose 2,6-bisphosphate was completely abolished in the absence of extracellular Ca2+. With Ca2+ present in the medium, the effect of the hormone on fructose 2,6-bisphosphate could be fully mimicked by the calcium ionophore A23187, suggesting that calcium entry is a␣decisive step in this signalling pathway. Trehalose production, on the other hand, was increased by thimerosal and thapsigargin which increase cytosolic Ca2+ from intracellular stores, whereas thimerosal in the absence of extracellular Ca2+ increased rather than decreased the content of fructose 2,6-bisphosphate, thus dissociating the two effects, which are normally coordinated by the hormone. Trehalose production and the content of fructose 2,6-bisphosphate were not significantly affected by mepacrine and mellitin, which are known to inhibit, respectively stimulate, phospholipase A2. Our data suggest that the effects of Bld HrTH on the stimulation of trehalose production and reduction of fructose 2,6-bisphosphate content in fat body are mediated by Ca2+, but that different signalling pathways are involved, suggesting that the two processes, although they are functionally linked, could be regulated separately.

Hormonal Control of Courtship Behavior and Reproductive Cycle in the Cockroach Species Blaptica dubia (Blattoidea: Blaberoidea: Blaberidae)

Blaptica dubia (Serville 1839) was reared at 26°C ± 2° with a 12 :12 L/D photoperiod. Under these conditions mating was first detected 5± 2 days after imaginal ecdysis. The pregnancy of this ovoviviparous cockroach lasts 48 - 64 days. Neuroendocrine and other humoral factors (juvenile hormone [JH]) stimulate oocyte growth, the activity of colleterial glands, and receptivity of FF. The ovulation of the 1rst gonotropic cycle occurs on d-17 (±3) after adult ecdysis. This period is correlated with high activity of corpora allata [CA] and corpora cardiaca [CC]. Thereafter and throughout most of pregnancy, the CA are generally inactive, rising in size again shortly before oviposition in association with the second gonotropic cycle. Allatectomy as well as cauterization of the median neurosecretory cells [m.ns.c]or decapitation prevent receptivity of the FF, mating behavior and oocyte maturation. Implantation of the retrocerebral complex and/or JH injections cancel the inhibition. The inhibitory influence of the extirpations depends on their timing during the reproductive cycle.

Sexualdimorphismus der Flügel bei der ovoviviparen Schaben-Art Blaptica dubia (Blattoidea: Blaberoidea: Blaberidae)

Both sexes, males [MM]and females [FF], of the cockroach species Blaptica dubia (Serville 1839) are distinguished, among other characteristics, by pronounced wing dimorphism : the MM have long wings covering the abdomen entirely, whereas the FF have strongly reduced wings. These differences and their formation were investigated using adult wings and wing pads. - Newly hatched larvae [L 1 ] already have small wing pads and the main tracheae with the same secondary ramifications characteristic for the wings of the adults. Up to L 4 , the wing anlagen continually grow in MM and FF likewise. Starting in L 5 , the form of the wings allows to identify the sexes. In FF, the tip growth of the wing remains behind that in the MM. The main growth of the prospective wings of the M and of the tegmina of the F takes part in the last larval instar [L 7 ]. In both cases, the growth is based on the elongation of the remigial parts as well as on the enlargement of the anal region. The alae of the F, by contrast become strongly reduced. In the adult F, they match the wing anlagen of L 4 as to size and anatomy ; its form and tracheal pattern predominantly show larval features. Thus, these reduced wings may be interpreted as larval features persisting in the adult, rather than as a result of growth inhibition with the typical adult wing stage.

Ecology of Triatoma rubrovaria (Hemiptera, Triatominae) in wild and peridomestic environments of Uruguay.

This paper describes population structure, spatial distribution and habitat selection of wild and peridomestic populations of Triatoma rubrovaria (Blanchard, 1843). Field studies were carried out at Las Piedras and La Bolsa in the Northern Department of Artigas, Uruguay. A semicircular sampling area, divided in seven or eight triangular sectors was sequentially examined from October 1990 to November 1991. At Las Piedras (typical wild habitat) 1063 T. rubrovaria bugs were collected from 84% of the rocky outcroops ("pedregales"). Abundance varied by season peaking in October-November (spring). Throughout the year, most of the population was made up of third, fourth and fifth instar nymphs; adults were found from October to March. In the peridomestic environment of La Bolsa, however T. rubrovaria was less common and showed a more irregular instar distribution. Colonized ecotopes, were those close to houses. In both sites T. rubrovaria was mainly associated with the geckonid Homonota uruguayensis and the cockroach Blaptica dubia.

Fine structure of meiotic chromosomes. Comparative study of nine species of insects.

A comparative electron microscope study at magnifications ranging from about 80,000 up to 800,000 x was carried out in nine species of insects (Gryllus argentinus, Myogryllus verticalis, undetermined species of Gryllus; Blaptica dubia, Periplaneta americana, Blattella germanica; Laplatacris dispar, Aleua lineata and Omexechae servillei). Particular attention was paid: a) to the elementary components of the s. complexes and b) to the structure of their medial ribbon. - a) In all the species examined the basic element found is a curled filament some 15–20 A thick. Filaments of this kind integrate: the 100 A fibrils of the chromosome body, the compacts layers of the s. complexes (lateral arms) and the slender planes of the pairing space. The filaments are similar to those described in metaphase chromosomes and their kinetochores (Wettstein and Sotelo, 1965). A difference in density between the filaments of the lateral arms and those of the medial planes is sometimes noticed. - b) Three structural patterns were found in the pairing space. In crickets, the medial ribbon is composed of three parallel, longitudinal planes of filaments, interconnected and connected with the lateral arms by means of bridges. The latter are constituted by fibrils or by single filaments. In cockroaches only two longitudinal planes were found. The distribution of components in these planes follows a plan similar to the one found in crickets. In the electron-micrographs the medial component of both groups of Insecta appears as composed of three (crickets) or two (cockroaches) lines in the longitudinal frontal views, and ladder-like striated in lateral views. The latter striae correspond to filaments or groups of filaments running in antero-posterior direction. - The pattern of structure of grasshoppers differs completely from those mentioned above. Bridging between the homologues is made of regularly spaced transversal planes of filaments. No longitudinal array was observed.

Electron microscope study on spermatogenesis

The morphogenesis of chromosomes at early prophase of spermatocytes I is studied in three ortoptherian species: Grillus argentinus (Grillidae), Laplatacris dispar (Acrididae) and Blaptica dubia (Blaptidae).