Ugo Laudani

The establishment of intracellular symbiosis in an ancestor of cockroaches and termites

All cockroaches examined so far have been found to harbour a bacterial endosymbiont in specialized cells of the fat body, whereas Mastotermes darwiniensis is the only termite currently known to intracellular symbiont. The localization and mode of transmission of these bacteria are surprisingly similar, but so far no data have been published on their phylogenetic relationships. To address this issue, molecular sequence data were obtained from the genes encoding the small subunit ribosomal RNA of the M. darwiniensis endosymbiont, and compared with those obtained from endosymbionts of seven species of cockroaches. Molecular phylogenetic analysis unambiguously placed all these bacteria among the flavobacteria-bacteroides, indicating that the endosymbiont of M. darwiniensis is the sister group to the cockroach endosymbionts examined. Additionally, nucleotide divergence between the endosymbionts appears to be congruent with the palaeontological data on the hosts’s evolution. These results support previous claims that the original infection occurred in an ancestor common to cockroaches and termites. A loss of endosymbionts should subsequently have occurred in all termite lineages, except that which gave rise to M. darwiniensis.

The fate of the endocytobionts of Blattella germanica (Blattaria: Blattellidae) and periplaneta Americana (Blattaria: Blattidae) during embryo development

Abstract In this paper we describe the behaviour of the symbiotic bacteria of Blattella germanica and Periplaneta americana during embryo development using transmission and scanning electron microscopy. In Blattella germanica, the bacteria are transferred by endocytosis to the egg cell and are sited in its peripheral cytoplasm; thence they begin to internalize in the yolk, using cytoskeletic structures which are probably only synthesized at this particular phase of their migration. In the 6–7‐day‐old embryo, the bacteria are in close contact with the vitellophages scattered in the yolk, where some of them appear to be in a degenerative phase. In Periplaneta americana, after the internalization of the bacteria, there is the formation of the mycetome which appears to be made up of a syncytial envelope, probably formed by the vitellophages, that contains a ball of symbionts of considerable number. During development, there is a progressive decline in the bacterial population, caused by complex lytic processe...

Mortality and tissue damage by heavy metal contamination in the German cockroach, Blattella germanica (Blattaria, Blattellidae)

Abstract The accumulation of lead, cadmium, mercury, and chromium, supplied in the diet under experimental conditions, was studied in adult German cockroaches. Chronic heavy‐metal exposure de termined different rates of mortality, higher in males than in fe males. In both sexes, Hg, Pb, and Cr bioaccumulated in time, whereas Cd remained at constant low concentrations. Histological studies showed that in some organs and structures, such as the ovary, the testis, the alimentary canal and the fat bodies, there were profound and irreversible pathological anomalies in their tis sues. Also the embryos of some treated females suffered heavy damage during development, and the symbiotic relationships be tween bacteria and fat body cells were deeply altered.

Effects of heat treatment on the symbiotic system of Blattoidea: Morphofunctional alterations of bacteriocytes

Abstract The purpose of the research was to study the morphological alterations that were produced in the symbiotic equilibrium of individuals of Leucophaea maderae, Periplaneta americana and Nauphoeta cinerea heat‐treated at + 39° C. The bacteria localized in the bacteriophorous vacuoles in the bacteriocytes of the samples treated underwent a series of structural modifications that led to protoplast formation. This phenomenon is similar to that which occurs in free‐living bacteria. The protoplasts were then further digested into the bacteriophorous vacuoles which had become cytolysosomes, to the point that they became residual bodies. When the process of endocellular lysis involved the whole symbiotic complement, the nucleus and the cytoplasmatic organelles of the bacteriocyte began to degenerate. These alterations were irreversible and could lead to the death of the cell. As a result, the number of bacteriocytes diminished. Heat treatment, which had lethal effects on the bacteria, altered the equilibriu...

Pattern of bacteriocyte formation in Periplaneta americana (L.) (Blattaria: Blattidae)

Abstract In the embryos of Periplaneta americana (L.) (Blattaria: Blattidae), bacterial symbionts, together with vitellophages, form a mycetomic structure inside the deutoplasm; this regresses between the 15th and 16th day after deposition of the ootheca. In this article we describe the migration of bacteria across the wall of the midgut from the mycetome, and the topographic distribution of pre-bacteriocyte cells. We also report that the pre-bacteriocytes are present only on the lateral surface of the internal abdominal fat bodies. We discuss the possible embryological origin and evolution of these cells, and put forward the hypothesis that pre-bacteriocytes are derived from oenocytes activated to perform phagocytosis.

Membrane systems in endocytobiosis I. Specializations of the vacuolar membrane in bacteriocytes of Blattella germanica (L.) (Dictyoptera: Blattellidae)☆

Abstract In bacteriocytes of Blattella germanica the symbionts are enveloped by the vacuolar membrane which is produced by the eukaryotic host cell. A study of serial thin sections shows the presence of vesicles originated from a blebbing process of the vacuolar membrane. Also, the presence of close adhesion sites between the vacuolar membrane and the prokaryotic cell envelope is revealed. Freeze-fracture replicas evidence aggregates of intramembrane particles on the vacuolar membrane while no corresponding membrane differentiation is present on the symbiont cell envelope. These observations are discussed in relation to the peculiarity of the interaction which involves both eukaryotic and prokaryotic cell membranes.

On the mycetome formation in Periplaneta americana (Blattaria, Blattidae)

Abstract The behaviour of the symbiont bacteria of Periplaneta americana during the different phases of embryogenesis is described. The succession of events that determine an interaction between the vitellophagic energids and the symbionts is analysed, with the successive formation of a mycetome that at first envelops the bacteria and from which they then migrate to colonize the plasmatocytes that will become bacteriocytes. We suggest that the mycetome is the primary site of symbiotic population growth.

Occurrence of apoptosis in serosa of Periplaneta americana l. (Blattaria: blattidae): ultrastructural and biochemical features.

In 16-17-day-old embryos of Periplaneta americana, the amnion-serosa penetrates the cavity of the middle intestine, where it forms a cluster of compressed roundish cells. We demonstrated that these cells degenerate throughout apoptosis. The programmed cell death revealed by morphological and biochemical approaches showed all the apoptotic steps: chromatin fragmentation and pyknosis, cytoplasm condensation, karyorrhexis, cytoplasm cleavage. Nevertheless, some ultrastructural peculiarities (atypical heterochromatin arrangement, appearance of nuclear envelope protrusions, absence of nucleolar structures) suggest that the apoptotic expression partially depends on the biological situation (type of organism and inducing factors) in which the programmed cell death takes place. The presence of histiocytic cells internalizing cell debris, of apoptotic and non-apototic derivation, may be correlated with the importance of recycling substances useful for embryo growth.

La consommation d'oxygène de la glande prothoracique de Leucophea maderae et Periplaneta americana d'après l'aspect histologique des organes endocrines

Abstract The oxygen consumption of the prothoracic gland of young larvae, final-instar larvae, and adults of Leucophaea maderae and Periplaneta americana has been found to have cyclical variations. The maximum oxygen consumption is attained before ecdysis and the minimum 24 hr after ecdysis. These results are discussed in relation to the histology of the endocrine organs.

STUDY OF ACID PHOSPHATASES IN THORACIC MUSCLES OF MUSCA DOMESTICA L.

SUMMARY The activity of acid phosphatases was tested in thoracic muscles of Musca domestica L. (WHO/IN/Musca domestical/1) at pH 4.8 and at 38°C. p-nitrophenylphosphate (NPP) was used as substrate. The course of the enzymatic reaction in function with the time and in function with the different substrate concentrations was examined. The activity of these enzymes in the course of the adult life of the two sexes was analyzed: this decreases with time being greater in the females up until the 9th day. After this, the males present a greater activity which reaches its maximum point on the 15th day. The decrease in activity for both sexes is greatest within the first 9 days of adult life.