Abstract
Friesella schrottkyi is a small stingless bee (3-mm long) important for agricultural and native forest pollination. This study describes the morphology and morphometry of the midgut in F. schrottkyi forager workers. The F. schrottkyi midgut presents a single-layered epithelium with digestive, regenerative and endocrine cells. The digestive cells are similar along the entire midgut length with a spherical nucleus, apex with long striated border, cytoplasmic granules in the apical region and well-developed basal labyrinth associated with mitochondria, suggesting they are multifunctional, synthesizing digestive enzymes and peritrophic matrix compounds and absorbing nutrients. Regenerative cells are located around the basal region organized in nests with some cells with a spherical nucleus. Phe-Met-Arg-Phe-NH2-amide (FMRFamide) positive endocrine cells are restricted to the posterior midgut region, suggesting a paracrine function in the midgut. This is the first morphological description of the F. schrottkyi midgut contributing to the comprehension of the digestive process of this bee.
Highlights
Friesella schrottkyi (Friese) is a monotypic exceedingly small neotropical stingless bee (3 mm in length) inhabiting a small region of the fragmented Atlantic rain forest of Southeast Brazil [1]with ecological and economic importance, pollinating native and cultivated plants [2,3].Pollination occurs during food collection in the flowers for the bee colony performed by forager workers [4]
The midgut of bees is a tubular organ with a single-layered epithelium having three cell types: (i) digestive cells, which are responsible for the synthesis of digestive enzymes and nutrient absorption [10,11]; (ii) endocrine cells that synthesize hormonal peptides controlling digestion, Insects 2019, 10, 73; doi:10.3390/insects10030073
Friesella schrottkyi workers returning from foraging activity were collected in two nests located at the apiary of the Federal University of Viçosa (UFV), Viçosa, state of Minas Gerais, Brazil
Summary
Pollination occurs during food collection (nectar and pollen) in the flowers for the bee colony performed by forager workers [4] Because these workers leave the hive, they can be exposed to toxic compounds, such as pesticides, which may affect the alimentary canal [5,6,7,8]. Those studies have been used for the honey bee Apis mellifera, whereas stingless bees have different life histories, such as small colony population The midgut of bees is a tubular organ with a single-layered epithelium having three cell types: (i) digestive cells, which are responsible for the synthesis of digestive enzymes and nutrient absorption [10,11]; (ii) endocrine cells that synthesize hormonal peptides controlling digestion, Insects 2019, 10, 73; doi:10.3390/insects10030073 www.mdpi.com/journal/insects
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