Morphophysiological study of digestive system litter-feeding termite Cornitermes cumulans (Kollar, 1832).

Termites are the major decomposers of lignocellulosic biomass on Earth and are commonly considered as biological reactor models for lignocellulose degradation. Despite their biotechnological potential, few studies have focused on the morphophysiological aspects of the termite digestive system. We therefore analyze the morphology, ultrastructure and gut luminal pH of the digestive system in workers of the litter-feeding termite Cornitermes cumulans (Blattodea: Termitidae). Their digestive system is composed of salivary glands and an alimentary canal with a pH ranging from neutral to alkaline. The salivary glands have an acinar structure and present cells with secretory characteristics. The alimentary canal is differentiated into the foregut, midgut, mixed segment and hindgut, which comprises the ileum (p1), enteric valve (p2), paunch (p3), colon (p4) and rectum (p5) segments. The foregut has a well-developed chewing system. The midgut possesses a tubular peritrophic membrane and two cell types: digestive cells with secretory and absorptive features and several regenerative cells in mitosis, both cell types being organized into regenerative crypts. The mixed segment exhibits cells rich in glycogen granules. Hindgut p1, p4 and p5 segments have flattened cells with a few apical invaginations related to mitochondria and a thick cuticular lining. Conversely, the hindgut p3 segment contains large cuboid cells with extensive apical invaginations associated with numerous mitochondria. These new insights into the morphophysiology of the digestive system of C. cumulans reveal that it mobilizes lignocellulose components as a nutritional source by means of a highly compartmentalized organization with specialized segments and complex microenvironments.

Adaptations to haematophagy: Investigations on how male and female Culex quinquefasciatus (Diptera: Culicidae) deal with human complement activation after a blood meal.

Culex quinquefasciatus is a mosquito species with an anthropophilic habit, often associated with areas with poor sanitation in tropical and urban regions. Adult males and females feed on sugars but only females feed on blood in natural conditions for egg maturation. During haematophagy, female C. quinquefasciatus transmit pathogens such as the West Nile virus, Oropouche virus, various encephalitis viruses, and Wuchereria bancrofti to human hosts. It has been observed in laboratory conditions that male C. quinquefasciatus may feed on blood during an artificial feed. Experiments were carried out to understand how males and females of this species deal with human complement activation. Our results showed that female C. quinquefasciatus, but not males, withstand the stress caused by the ingestion of normal human serum. It was observed that the salivary gland extracts from female mosquitoes were able to inhibit the classical and lectin pathways, whereas male salivary gland extracts only inhibited the lectin pathway. The male and female intestinal contents inhibited the classical and lectin pathways. Neither the salivary glands nor the intestinal contents from males and females showed inhibitory activity towards the alternative pathway. However, the guts of male and female C. quinquefasciatus captured factor H from the human serum, permitting C3b inactivation to its inactive form iC3b, and preventing the formation of the C3 convertase. The activity of the antioxidant enzyme catalase is similar in C. quinquefasciatus females and males. This article shows for the first time that males from a haematophagous arthropod species present human anti-complement activity in their salivary gland extracts and gut contents. The finding of an activity that helps to protect the damage caused by blood ingestion in sugar-feeding male mosquitoes suggests that this may be a pre-adaptation to blood-feeding.

Canine visceral leishmaniasis: relationships between clinical status, humoral immune response, haematology and Lutzomyia (Lutzomyia) longipalpis infectivity.

The main source of Leishmania infantum infection in humans is a naturally infected dog. This study reports on the infectivity to phlebotomine sandflies (Lutzomyia longipalpis) of serologically positive mongrel dogs that differed in clinical status, haematology and humoral responses to immunoglobulin (Ig) G(T) (total anti-Leishmania IgG), IgG(1) and IgG(2) subclasses of antibody to crude antigen of L. infantum. Forty-five female L. longipalpis were allowed to feed directly on the ears of dogs classified as asymptomatic, oligosymptomatic or symptomatic before being dissected five days later. Promastigotes were detected in 88% of the dissected sandflies. The highest rate of infectivity to sandflies was found in symptomatic dogs, followed by oligosymptomatic and asymptomatic animals. The results suggest that dogs naturally infected with L. infantum with higher total IgG and IgG(2) concentrations and lower haematocrit levels were able to infect the highest proportion of L. longipalpis. No correlation was observed between anaemia and the intensity of clinical signs. Symptomatic dogs presented the highest infection rate and intensity of infection.

Feeding behaviour of morphologically similar Rhodnius species: influence of mechanical characteristics and salivary function.

Despite their morphological similarities, very similar Rhodnius species (R. prolixus, R. robustus, R. nasutus and R. neglectus) displayed a distinct feeding behaviour when fed on artificial feeder, pigeon or mouse. On pigeon hosts, these species showed distinct groups in terms of cumulative probing time - quicker species (R. prolixus and R. neglectus) followed by R. nasutus and finally a much slower species (R. robustus). On mouse hosts, R. nasutus showed quicker probing time compared to the other three species. Moreover, R. prolixus displayed quicker probing time compared to R. robustus and R. neglectus. Except for R. nasutus, the mean total ingestion rate tended to have different values between feeding sources (artificial feeder>pigeon>mouse). The volume ingested by each cibarial pump contraction and maximum frequency obtained using the artificial feeder are expected to be related to intrinsic mechanical characteristics of the insect feeding apparatus. However, probing time and the modulation of cibarial pump frequency on live hosts may be related to salivary function. R. prolixus showed high mechanical and salivary efficiency, achieving high values of total ingestion rate when fed on artificial feeder or either of the hosts. Comparative analysis suggests that species which possess higher total ingestion rates tend to achieve higher nutritional status, allowing them to reach higher densities.