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Evaluation of Dicyphus hersperus (Heteroptera: Miridae) for biological control of Frankliniella occidentalis (Thysanoptera: Thripidae) on greenhouse tomato.

The effectiveness of inoculative releases of the mirid predator Dicyphus hesperus Knight for control of Frankliniella occidentalis (Pergande) on greenhouse tomatoes was evaluated in terms of suppression of the population densities of F. occidentalis and associated fruit damage in the presence of the predator over two seasonal trials. An inoculative release of one D. hesperus per plant (approximately 0.1:10 predator:prey ratio) at a high F. occidentalis population density (140 thrips per plant) suppressed the thrips population density to a significantly lower level, compared with the nonrelease greenhouse, but not below a thrips level that caused economic fruit damage. As the predator:prey ratio increased to approximately 0.5:10 D. hesperus:F. occidentalis, the mean percentage of the thrips-damaged fruit in the D. hesperus release greenhouse decreased to 1.6%. However, the amount of fruit feeding by D. hesperus was highly correlated to the availability of prey (or predator:prey ratio) under greenhouse conditions. D. hesperus-induced fruit damage occurred when the predator:prey ratio was >1:10 D. hesperus:F. occidentalis. Considering the potential risk of fruit damage by D. hesperus and the need for effective control of F. occidentalis, a 0.5-1:10 D. hesperus:F. occidentalis ratio is recommended when the thrips population density is in the range of 60-150 thrips per plant.

Animals↗

Blood host sources of Mepraia spinolai (Heteroptera: Reduviidae), wild vector of chagas disease in Chile.

There are two vectors of the Chagas' disease in Chile: Triatoma infestans Klug the domestic vector and Mepraia spinolai Porter the sylvatic vector. The alimentary profile of M. spinolai has been poorly studied. In this work we study the participation of humans, goats, dogs, cats, rodents, rabbits, birds (hens) and reptiles in the diet of M. spinolai by analyzing the intestinal content through immunoradiometric assay. To put our results in a general context, we also compared the diet with that described for T. infestans. In decreasing order, we detected blood of rabbits, dogs, goats, rodents, humans, and birds (hens). There were 12.3% of insects infected with T. cruzi, but this fact was not significant for diet variance. In warm weather there was a larger diversity of alimentary sources than in a cold one. The niche breadth increased from 0.029 in cold weather to 0.464 in warm weather. The niche overlap of T. infestans and M. spinolai was 0.23.

Animals↗

Development of Triatoma rubida sonoriana, Triatoma barberi, and Meccus mazzottii (Heteroptera, Reduviidae) under laboratory conditions.

The objective of this study was to determine some of the most important bionomic parameters related to the capacity of transmission of Trypanosoma cruzi and to estimate the potential transmission capacity and role of 3 groups of recent colonized Mexican Triatoma barberi, T. rubida sonoriana, and Meccus (formerly Triatoma) mazzottii in the prevalence of Chagas disease cases based on the distribution area of each species. Among the studied Triatominae species, the life cycle was shorter in T. r. sonoriana and longer in T. barberi, by as much as 4 times. The 1st and 5th instars had the highest rates of mortality in most of the studied species. Statistically significant shorter duration of feeding of instars was observed for T. r. sonoriana and longer duration was found for M. mazzottii when the species were compared. The mean number of blood meals per nymphal stadium was statistically greater in T. barberi than in T. r. sonoriana and M. mazzottii. Triatoma r. sonoriana and M. mazzotti had shorter defecation delay than in T. barberi and the delay was uniform in all instars. Most of the studied parameters showed that T. r. sonoriana and M. mazzotti could have an important potential role in the prevalence of Chagas disease cases where these species are commonly found.

Animals↗

Electron microscopic study of the differentiation and development of trophocytes and oocytes in Gerris najas (Heteroptera).

The differentiation of oogonia and oocytes, and of trophocytes, from undifferentiated germ line cells has been studied in Gerris najas, a pond skater, from the fourth instar to the adult animal. For the first time criteria have been obtained which allow the distinction between poorly differentiated early oogonia and nurse cells. The most important criteria are the size, shape, and structure of nuclei and mucleoli. This is consistent with the different function of these cell types, which is primarily a different nuclear function: meiosis in the oocytes, and RNA synthesis to support the trophic core and the oocytes in the trophocytes.

Animals↗

A canonical discriminant analysis of post-embryonic development in Notonecta Maculata fabricius (Insecta:Heteroptera).

A multivariate method, canonical discriminant analysis, was used to discern a pattern of growth in Notonecta maculata. A stepwise procedure reduced the 11 metrical characters measured on individuals of both sexes, from the 1st larval stage to the adult, to 4 significant variates which were used in the canonical analysis. The four canonical variates accounted for the meaningful part of the variablity. Relying on bivariate allometry and on an experimentation with a juvenile hormone analogue, each independent direction of variation was related to combined effects of such biological factors as a general growth trend, sex and juvenile hormone.

Analysis of Variance↗

Ribosome crystals in the oocyte of Gerris najas (Heteroptera).

Oocytes of the pond skater, Gerris najas, display ribosome tetramers that are arranged in the form of sheets in the vicinity of the nucleus. This is the first finding of ribosome crystals in an insect and suggests that ribosome crystallization may be a common phenomenon of cells that are inactive in protein synthesis.

Animals↗

Localization of rDNA sites in holocentric chromosomes of three species of triatomines (Heteroptera, Triatominae).

Chromatin organization in the holocentric chromosomes of three triatomines species was cytologically studied by fluorescent in situ hybridization with a 45S rDNA probe of Drosophila melanogaster to localize ribosomal genes. In Triatoma tibiamaculata, metaphases I showed telomeric highlights in a single, larger bivalent. In T. protacta, hybridization was detected in one of the telomeres of an autosomal chromosome. In T. platensis, there were highlights in a single, smaller chromosome (X chromosome). The results obtained did not agree with the expected localization of rDNA genes in the sex chromosomes of triatomines, as demonstrated by silver impregnation, and suggest that the chromosome reorganization that occurred in this group during evolution may be a more important mechanism involved in rDNA distribution.

Animals↗

Effect of actinomycin-D on the fat body RNA content in Dysdercus koenigii (Heteroptera: Pyrrhocoridae).

The effect of actinomycin-D on the RNA content of the total fat body was studied on day 3, 4, 5 and 6 of the first reproductive cycle in the females. Actinomycin-D exhibited its highest inhibitory effect in insects injected on day 4 and a lower degree of the effect was seen in insects injected on day 5. These results suggest that by the end of day 4, a major quantity of DNA-dependent RNA, necessary for vitellogenin synthesis, has already been synthesised and accumulated.

Adipose Tissue↗

Acrosome formation during spermiogenesis in Notonecta glauca L. (Heteroptera).

The giant spermatozoon of Notonecta glauca has a 1 mm long acrosome. It has the shape of a stiff needle with round cross section and contains several different components. Morphogenesis of this simple form proceeds by very complex changes of both the internal structure and the outer shape. Surrounded by a great number of individual dictyosomes the acrosome is attached to the anterior nuclear pole where it grows to a sphere measuring about 20 microns in diameter. In its interior differentiations consisting of several components become visible which develop independently and may be characterized as basal and lateral complexes. At the end of the growing phase these two complexes come in contact with each other. After the dictyosomes have detached from the acrosome, the cell membrane surrounds the acrosome very closely so that cytoplasmic structures temporarily disappear completely from the narrow space in between. The tip of the acrosome grows out of the sphere as a slender lateral process which becomes increasingly spiralized. It shows a deep lateral groove, its contents consist of components of the basal complex. Parts of the lateral complex form a baso-lateral protuberance. Between these two structures a narrow channel extends from the subacrosomal space to the base of the lateral process. During elongation the acrosome attains spindle shape, the lateral process gradually becoming its anterior part. The distance between acrosome and cell membrane broadens again and cytoplasmic structures reappear among them about 1000 microtubules which are not surrounded by a sleeve membrane. In the posterior part cell membrane and acrosomal membrane are connected by two lines of weld spots where acrosomal membrane is eliminated as small vesicles. In the anterior part the groove becomes deeper. One leg of its initially U-shaped cross section becomes longer and is wrapped around the shorter one. The two legs subsequently fuse with the consequence that membrane and cytoplasmic components of the former groove become secondarily incorporated into the acrosome. The subacrosomal channel obliterates and the cross section of the acrosome showing acute angles in later stages finally gets round. Anterior and posterior part of the acrosome can be differentiated due to structural details even in the mature sperm.

Acrosome↗

[A new plasminogen activator isolated from the saliva of Rhapactor biparticeps (Heteroptera, Reduviidae): biological and physicochemical properties].

A new plasminogen activator has been isolated from the saliva of Rhapactor biparticeps. This product is 5% of salivary proteins and acts at an optimal pH of 7.8.P.D.F which results from its action on human fibrinogen are similar to those which are obtained with streptokinase. The modalities of action of this plasminogen activator on the fibrinogen are discussed.

Animals↗