Ultrastructure of the eggs of Reduviidae: III. Eggs of Triatominae and Echtrichodiinae (Insecta-Heteroptera)

Psyttala horrida (Stål, 1865) (Hemiptera: Reduviidae: Reduviinae)-A Morphological Study of Eggs and Nymphs

In terms of body size, species of the genus Psyttala Stål, 1859, are the largest known representatives of the subfamily Reduviinae. Among the species belonging to this genus, Psyttala horrida (Stål, 1865) is the most popular, mainly because it is a laboratory breeding species. Individuals of this species were bred in the laboratory of the Zoology Team at the University of Silesia in Katowice, Poland. A description of the morphology of the nymphs and eggs is presented. In addition to descriptions, photos of the successive immature stages are provided and scanning electron microscopy (SEM) images are included to show morphological details and compare the developmental changes in subsequent stages.

Checklist and phenetics studies of nymphs of two species of triatomines: Triatoma lenti Sherlock & Serafim, 1967 and Triatoma sherlocki Papa, Jurberg, Carcavallo, Cerqueira, Barata, 2002 (Hemiptera: Reduviidae: Triatominae)

INTRODUCTION

Triatoma lenti and Triatoma sherlocki are endemic species of the State of Bahia, located in northeastern Brazil, where they have records of domiciliation in the human environment. In view of the epidemiological aspect and taxonomic importance of these species for the systematics of the Triatoma genus, a study was carried out with nymphs of all five instars.

METHODS

An extensive review of studies on nymphs from the subfamily Triatominae is presented. Morphology was studied using a scanning electron microscope and morphometric analyses.

RESULTS

The morphological study allowed us to characterize and discriminate species by means of scanning electron microscope of the last abdominal segment. In addition, the results show morphometric variability, with the total size of the head that best discriminates the species.

CONCLUSIONS

Studies on nymphs are fundamental to the ecosystem; however, the literature on the immature forms of certain groups is scarce, difficult to use, or nonexistent. Therefore, this study includes morphological and morphometric data of the nymphal instars of T. lenti and T. sherlocki, corroborating the specific taxonomy of these species.

Eggshell ultrastructure and delivery of pharmacological inhibitors to the early embryo of R. prolixus by ethanol permeabilization of the extraembryonic layers

Most vectors of arthropod-borne diseases produce large eggs with hard and opaque eggshells. In several species, it is still not possible to induce molecular perturbations to the embryo by delivery of molecules using microinjections or eggshell permeabilization without losing embryo viability, which impairs basic studies regarding development and population control. Here we tested the properties and permeability of the eggshell of R. prolixus, a Chagas disease vector, with the aim to deliver pharmacological inhibitors to the egg cytoplasm and allow controlled molecular changes to the embryo. Using field emission scanning and transmission electron microscopy we found that R. prolixus egg is coated by three main layers: exochorion, vitelline layer and the plasma membrane, and that the pores that allow gas exchange (aeropiles) have an average diameter of 10 μm and are found in the rim of the operculum at the anterior pole of the egg. We tested if different solvents could permeate through the aeropiles and reach the egg cytoplasm/embryo and found that immersions of the eggs in ethanol lead to its prompt penetration through the aeropiles. A single five minute-immersion of the eggs/embryos in pharmacological inhibitors, such as azide, cyanide and cycloheximide, solubilized in ethanol resulted in impairment of embryogenesis in a dose dependent manner and DAPI-ethanol solutions were also able to label the embryo cells, showing that ethanol penetration was able to deliver those molecules to the embryo cells. Multiple immersions of the embryo in the same solutions increased the effect and tests using bafilomycin A1 and Pepstatin A, known inhibitors of the yolk proteolysis, were also able to impair embryogenesis and the yolk protein degradation. Additionally, we found that ethanol pre-treatments of the egg make the aeropiles more permeable to aqueous solutions, so drugs diluted in water can be carried after the eggs are pre-treated with ethanol. Thus, we found that delivery of pharmacological inhibitors to the embryo of R. prolixus can be performed simply by submersing the fertilized eggs in ethanol with no need for additional methods such as microinjections or electroporation. We discuss the potential importance of this methodology to the study of this vector developmental biology and population control.

Morphological study of the eggs and nymphs of Triatoma dimidiata (Latreille, 1811) observed by light and scanning electron microscopy (Hemiptera: Reduviidae: Triatominae)

Eggs and nymphs of Triatoma dimidiata were described using both light and scanning electron microscopy. The egg body and operculum have an exochorion formed by irregular juxtaposed polygonal cells; these cells are without sculpture and the majority of them are hexagonal in shape. The five instars of T. dimidiatacan be distinguished from each other by characteristics of the pre, meso and metanotum. The number of setiferous tubercles increases progressively among instars. The sulcus stridulatorium of 1st instar nymphs is amorphous, showing median parallel grooves; from the 2nd instar on the sulcus is, progressively, elongate, deep and posteriorly pointed with stretched parallel grooves. All instars have a trichobothrium on the apical 1/3 of segment II of the antenna. The opening of the Brindley's gland is on the mesopleura. Fifth instar nymphs have an apical ctenidium on the ventral surface of the fore tibia. Dorsal glabrous patches are found on the lateral 1/3 of abdomen. Bright oval patches are found on the ventral median line of the abdomen, from segment IV-VI; 1st instar nymphs lack these patches. Abdominal dorsal plates are present from the 1st-5th instars; the 1st instar also contains a rectangular plate in segment IX. From the 2nd instar on, variably-shaped plates are present on segments VII to IX. Morphometric data were also obtained and proved to be useful for distinguishing T. dimidiata instars.

Why are the subfamily relationships of Triatominae (Hemiptera: Reduviidae) important?

Why are the subfamily relationships of Triatominae (Hemiptera: Reduviidae) important?-This question is really two: Is Triatominae a phylogenetically valid monophyletic subfamily; and, if it is, to what other reduviid subfamilies is it most closely related? If the answer to the first question is Yes, then what one knows about one member of Triatominae may be true for other members; if the answer is No, then no such prediction can be made. Because many members of Triatominae are of medical importance, such predictions are vitally (literally) important. For the same reason, knowledge of the subfamily relatives of medically important triatomines is important: For here too predictions about one related member can be based on knowledge of others. These points are discussed here, and the evidence for and against (especially against) monophyly of Triatominae is also discussed. The status of Linshcosteus, the only Old World genus of Triatominae, is also discussed.

[Morphology of the eggs of Triatoma circummaculata and Triatoma rubrovaria (Hemiptera, Reduviidae)]

OBJECTIVE

To study morphologically the eggs of T. circummaculata and T. rubrovaria.

METHODS

Forty eggs of the two species were measured through Nikon model 6C profile projector. Student test was utilized for the statistical analysis and scanning electron microscopy for the morphological study of the eggs.

RESULTS/CONCLUSIONS

The statistical analysis shows that the T. rubrovaria eggs are larger that those of T. circummaculata. Microscopical observations revealed that the chorial rim and the spermatic groove are less evident in T. circummaculata than in T. rubrovaria. Both species, the majority of exochorion cells are hexagonal. It was also observed the embryo eclosion and details of the embryonic molt.