Effect of heavy metals on chromatin supraorgnization, nuclear phenotypes, and survival of Triatoma infestans

The nuclear phenotypes and survival of the hemipteran, Triatoma infestans (Hemiptera, Reduviidae), were studied in specimens treated with copper sulfate and methyl mercury. The objective was to determine whether changes in chromatin supraorganization and insect survival similar to those promoted by other stressing agents could also be induced by heavy metals. At the concentrations used, copper sulfate and methyl mercy were toxic to the cell, mainly inducing nuclear degeneration in the Malpighian tubules and being lethal to a large part of the insect population. Although some individual resistance was found, especially in fasted in fasted specimens, heavy metals were found to be much more lethal than was, for instance, a thermal shock at 0 oC for 12 h. The nuclear phenotypes detected after heavy metal treatment were similar to those reported under other stressing conditions. However, the frequency at which nuclei exhibited aspects of heterochromatin unraveling was much higher than that found in fasted and thermal-shocked specimens, and was independent of the heavy metal type used. If this phenotype represents an attempt to improve opportunities for extensive cell and insect survival, it was not sufficiently effective. In 5th instar nymphs, the effect of CuSO4 on chromatin supraorganization was detected at early steps of spermatogenesis but not in the cells which were at late spermiogenesis when the metal was administered. This is probably due to changes in nuclear protein composition and to the tightly packed state of DNA-protein complexes occurring at spermiogenesis, which may protect chromatin from damages. However, when CuSO4 was supplied to 4th instar nymphs, it slowed down the spermiogenesis proves, possibly due to several factors including Cu2+ binding to DNA phosphates.

Number of chromosomes, Feulgen-DNA content, and nuclear phenotypes in domestic and wild specimens of Panstrongylus megistus

Specimens of Panstrongylus megistus with different levels of adaptation to a domestic way of life had some of their nuclear and chromosomal characteristics compared, in an attempt to differentiate them by cytological means. The number of chromosomes in male testes was found not to differ. The nuclear frequency and phenotypes of the Malpighian tubules were also found to be the same. On the other hand, Feulgen-DNA values, however, may no represent real differences in DNA content, but may possibly be due differences in DNA-protein complexes.

Viral infection in Blood-Sucking hemipterans

Blood-Sucking reduviid specimens reared in the laboratory were found to develop swollen and translucent abdomens at the same time as they acquire physiological disturbances. They die within a few days after the carly observations of swelling symptoms. Light and electron microscopy of their Malpighian tubules and midgut showed some cell disintegration and an accelerated elimination of laminated “concretions”. Non-occluded virus-like particles were found free in the cytoplasm or inside cytoplasmic globules an nuclei and outside the cells. Spheroidal inclusions were also found in the nuclei. It is possible this virus may by related to the inserct’s general pathological state. However, experimental data are required support to this hypothesis.