Ultrastructure of the Excretory Organs ofBombus morio(Hymenoptera: Bombini): Bee Without Rectal Pads

Abstract

Bumblebees need to keep bodily homeostasis and for that have an efficient system of excretion formed by the Malpighian tubules, ileum, and rectum. We analyzed the excretory organs of Bombus morio, a bee without rectal pads. In addition, we analyzed the rectal epithelium of Melipona quadrifasciata anthidioides which has rectal pads. The Malpighian tubules exhibited two cell types and the ileum four types. However, comparative analysis of the rectum showed that only cells of the anterior region of the rectal epithelium of B. morio are structurally distinct. We suggest that cells of the Malpighian tubules of B. morio have an excretory feature and that cells of ileum have different functions, such as ion absorption and water, organic compound, and protein secretion. In addition, only the anterior region of the rectum of B. morio showed characteristic absorption. We suggest that Malpighian tubules participate in the excretion of solutes and that the ileum and rectal epithelium are responsible for homeostasis of water and solutes, compensating for the absence of rectal papillae. These results contribute to our understanding of the morphophysiology of the excretory organs of bees without rectal pads.

Fine structure of the Malpighian tubules in Gryllus campestris(Linnaeus, 1758) (Orthoptera, Gryllidae)

“…Its proximal region opens into the alimentary canal at the junction of the midgut and hindgut, and the distal region lies free in the abdominal cavity (Acar, 2009;Amutkan et al, 2015). The structure of the Malpighian tubules in Gryllus campestris displays significant similarities and differences compared with those of species investigated previously (Ramsay, 1954;Beams et al, 1955;Taylor, 1971;Acar, 2009;Pal and Kumar, 2012;Gonçalves et al, 2014;Amutkan et al, 2015;Zhong et al, 2015). While the numbers of the Malpighian tubules in Gryllus campestris range from 90 to 150, this number is 4 in Graphosoma lineatum (Heteroptera, Pentatomidae) and Sarcophaga ruficornis (Diptera, Sarcophagidae) (Pal and Kumar, 2014;Amutkan et al, 2015).…”

Comparative physiology of Malpighian tubules: form and function

“…Type II cells are more related to the selective endocytosis, because they show a little amount of mitochondria associated with an apical membrane with shorter and irregular projections. 23 In many insects, the Malpighian cells are polytene, and the nuclei of the cells are large. 9 In Dinoponera australis, organs related to digestion and excretion present the much higher levels of endopolyploidy when compared with other organs such as brain and muscle.…”

“…22 However, this regionalization is not observed in Bombus morio, where the epithelium has two cell types that are interspersed throughout the tubule. 23 The ultrastructure of the cells is variable throughout the species. In Musca domestica (Diptera), 24 Frankliniella occidentalis (Thysanoptera), 25 and Calpodes ethlius ( Lepidoptera), 26 the MT layer is uniform, while, in other insects, it can be observed in different cell types, functionally and morphologically.…”

“…In Musca domestica (Diptera), 24 Frankliniella occidentalis (Thysanoptera), 25 and Calpodes ethlius ( Lepidoptera), 26 the MT layer is uniform, while, in other insects, it can be observed in different cell types, functionally and morphologically. 3,9,23 In adults, MTs are composed of two cell types: the principal cells and the stellate cells, which play different roles in the process of excretion. 12 Malpighian tubules of the yellow fever mosquito differ morphologically from other epithelia in two ways: the abundance of intracellular concretions (metallo-organic aggregates of Ca 2+ , Mg…”

“…33 However, in Bombus morio, the two cell types I and II have crystals in their cytoplasm crystals. 23 These crystals are generally supposed to serve as a form of storage excretion, and the most common are the "laminate spheres" or spherocrystals, which have unclear origin.…”