Evaluation of the vertical transmission of microsporidian N. ceranae in stingless bees: histological and histochemical diagnosis of the workers midgut

• Grant number: 19/24218-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: August 01, 2020
• End date: December 31, 2020
• Field of knowledge: Biological Sciences - Zoology - Applied Zoology
• Principal Investigator: Elaine Cristina Mathias da Silva
• Grantee: Isabelle Christine Corrêa de Araújo
• Host Institution: Centro de Ciências Humanas e Biológicas (CCHB). Universidade Federal de São Carlos (UFSCAR). Sorocaba , SP, Brazil

Abstract

Bees are important pollinators of plants because they need nectar and pollen from flowers to complete their life cycle. The Africanized honeybee (Apis mellifera) is the best-known managed species in Brazil and one of the most important species for pollination of many agricultural crops. Due to the worldwide decline in bee populations over the years, which is attributed to a number of factors, such as Nosema ceranae microsporidium infection, increased pesticide use and nutritional poverty, studies with stingless native bees were highlighted in this context. An example of a stingless bee species is Tetragonisca angustula, which has great efficiency in pollinating native plants and is widely distributed in Brazil, as well as Scaptotrigona postica and Melipona quadrifasciata. These bee species can pollinate the same floral resources and thus be infected by the same diseases by vertical contamination, such as nosemose, a disease reported in A. mellifera, but with cases identified in other non-Apis bee species. Thus, this study aims to evaluate the in vitro inoculation of stingless bees with N. ceranae spores in order to detect the occurrence or absence of infection of this intestinal endoparasite in non-Apis species, through histological and histochemical diagnosis, to prove or refute the hypothesis of vertical transmission of this microsporidium. The organ analyzed will be the intestine extracted from the bees at two collection times (7 days and 15 days after in vitro inoculation). The intestines will be fixed and routinely processed for inclusion in historesin. After microtomy, slides containing the histological sections of the intestine will be stained with Hematoxylin-Eosin for histological analysis, and histochemical techniques such as Feulgen and Toluidine Blue Reaction to detect spore DNA in infected intestinal cells, as well as Xilidine Ponceau and Bromophenol Blue for total protein analysis. The histological and histochemical diagnosis of the presence of spores will allow their identification in the midgut epithelium confirming the infection. In the absence of infection, the spores can be found in the intestinal lumen or posterior gut. Therefore, this study aims to understand the process of vertical contamination of different species of stingless bees with N. ceranae spores from Africanized A. mellifera.