Ultrastructure features of the midgut of the female adult Amblyomma cajennense ticks Fabricius, 1787 (Acari: Ixodidae) in several feeding stages and subjected to three infestations.

The digestive tract of Amblyomma cajennense, as well as other species of ticks, is divided into the anterior, medium and posterior intestines and is the organ responsible for digestion of blood ingested during the meal on the host. The anterior and posterior regions are derived from the ectoderm and the medium one from the endoderm. In the present ultrastructural study, we analyzed the midgut of females in a semi- and fully engorged stages, on the rabbit host, which was subjected to three infestations, where were analyzed the changes that the epithelial cells went through. The results showed that during the feeding period the outermost layer the intestine is composed of muscle fibres, as observed in those semi-engorged and engorged ones in the 1st infestation and semi-engorged in the 2nd infestation. The cytoplasm of digestive cells of feeding females, and those of the semi-engorged and fully engorged in the 1st, 2nd and 3rd infestations showed some intact regions (preserved organelles) with others were disorganized. Large lipid droplets and protein granules were observed in the cytoplasm of the cells of the intestine in all phases of feeding process. Cytoplasmic spherocrystals were only observed in the semi-engorged and engorged females in the 1st and 2nd infestations. Intense vacuolation was observed in the digestive cells of the midgut of semi-engorged and engorged A. cajennense females in the 2nd infestation and those engorged in the 3rd infestation. The data showed that the gut of the females of the A. cajennense tick is actually going through big changes during the feeding period, which become more pronounced when reinfesting. These changes are probably due to the host immune response that returns antibodies to the ectoparasite and thus acquires resistance to their secreted products.

Histopathology and ultrastructure features of the midgut of adult females of the tick Amblyomma cajennense Fabricius, 1787 (Acari: Ixodidae) in various feeding stages and submitted to three infestations.

The digestive tube of the tick Amblyomma cajennense is responsible for the digestion during feeding on the host. This study analyzed the midgut of unfed, partially engorged, and fully engorged fed females as well as three infestations in rabbits. In A. cajennense, the digestive tube is long and from the midgut, two pairs of diverticula ramify and lead to a blind end. In some midgut regions were observed for the first time in ticks, structures termed here "nodules." The midgut of unfed females possesses a pseudostratified epithelium composed of digestive and generative cells. In partially engorged and engorged females at 1st infestation and partially engorged at 2nd infestation, the epithelium becomes stratified. In partially engorged females at 2nd infestation, the epithelium exhibits a third cell type: secretory cell. So the intestinal epithelium undergoes several changes during the feeding process in ticks at subsequent infestations. As infestations progress in the same host, the latter becomes more resistant and female ticks require more days to complete their feeding cycle, which in A. cajennense is 25 days.

Female reproductive system of the sugarcane spittlebug Mahanarva fimbriolata (Auchenorrhyncha): vitellogenesis dynamics and protein quantification.

The present study aimed describing the ovaries of the sugarcane spittlebug Mahanarva fimbriolata which are meroistic telotrophic with nurse cells and oocytes located in the tropharium. SEM revealed paired ovaries located dorsolaterally around the intestine, and oocytes exhibiting shapes ranging from round (less developed) to elliptic (more developed), suggesting a simultaneous, although, asynchronous development. Based on histological data we classified the oocytes in stages from I to V. Stage I oocytes exhibit follicular epithelium with cubic and/or prismatic cells, fine cytoplasmic granules. Stage II oocytes present intercellular spaces in the follicular epithelium due to the incorporation of yolk elements from the hemolymph. Small granules are present in the periphery of oocytes while larger granules are observed in the center. Stage III oocytes are larger and intercellular spaces in the follicular epithelium are evident, as well as the interface between follicular epithelium and oocyte. Yolk granules of different sizes are present in the cytoplasm. During this stage, chorion deposition initiates. Stage IV oocytes exhibit squamous follicular cells and larger intercellular spaces when compared to those observed in the previous stage. The oocyte cytoplasm present granular and viscous yolk, the latter is the result of the breakdown of granules. Stage V oocytes exhibit a follicular epithelium almost completely degenerated, smaller quantities of granular yolk and large amounts of viscous yolk. Based on our findings we established the sequence of yolk deposition in M. fimbriolata oocyte as follows: proteins and lipids, which are first produced by endogenous processes in stages I and II oocytes. Exogenous incorporation begins in stage III. In stages I and II oocytes, lipids are also produced by follicular epithelial cells. The third element to be deposited is polysaccharides, mainly found as complexes. Therefore, the yolk present in the oocytes of this species consists of glycolipoproteins. Molecular weights of proteins present in M. fimbriolata oocytes ranged from 10 to 92 KDa, differently from vitellogenin, the most common protein present in insect oocytes, weighing approximately 180 KDa.

Ultrastructural study of the ovary of the sugarcane spittlebug Mahanarva fimbriolata (Hemiptera).

The present study describes the ultrastructure of meroistic telotrophic ovaries of the sugarcane spittlebug Mahanarva fimbriolata. In this type of ovary, nurse cells, oogonia, and prefollicular tissue are located at the terminal (distal) regions or tropharium of ovarioles. Oocytes in different developmental stages, classified from I to V, are observed in the vitellarium. Stage I oocytes do not exhibit intercellular spaces in the follicular epithelium, suggesting that synthesis and production of yolk during this stage occurs only through endogenous processes. Small yolk granules of different electron densities are present in the cytoplasm. Few lipid droplets are observed. Stage II oocytes exhibit small intercellular spaces in the follicular epithelium. More protein as well as lipid yolk granules are observed in the cytoplasm. In stage III oocytes, intercellular spaces in the follicular epithelium are larger than those observed in the previous stage. Electrondense protein granules of various sizes, larger than those observed in stage II oocytes predominate in the cytoplasm. Smaller lipid droplets are also present. In stage IV oocytes, the follicular epithelium exhibits large intercellular spaces. Our data clearly indicate that the opening of these spaces in the follicular epithelium of M. fimbriolata oocytes increases as the intake of exogenous proteins intensifies, that is, in stages IV and V oocytes. During these stages, granular yolk becomes viscous due to the lysis of granules. In stage V oocytes, viscous yolk predominates in the cytoplasm. This type of yolk, however, has not been described for other orders of insects. The chorion of M. fimbriolata oocytes consists of an external layer (exochorion) and an internal one (endochorion), which is in direct contact with the oocyte. Numerous small pores that probably facilitate oxygenation of the internal structures inside the eggs are observed in the exochorion.