Midgut of the diplopod Urostreptus atrobrunneus: structure, function, and redefinition of hepatic cells

Abstract

Diplopods are considered important macroarthropods the soil as part of its maintenance and balance. These animals usually do not occur in high densities, but population explosions caused by environmental disturbances, climate changes, and use of pesticides that eliminate possible competitors, have been reported. The millipede Urostreptus atrobrunneus Pierozzi and Fontanetti, 2006 have become a nuisance to humans in infestation sites in urban centers of the state of Sao Paulo, Brazil. As a contribution to the understanding of this potential pest, this study describes the histology, histochemistry, and ultrastructure of the U. atrobrunneus midgut, and presents the redefinition of hepatic cells somewhat controversial in the literature. The region of the midgut is characterized by the absence of a cuticular intima, and composed of a pseudostratified epithelium on a thick basal membrane, followed by a muscle layer, a layer of hepatic cells, lined by an external membrane. The morphology observed in U. atrobrunneus is similar to that reported for other species of diplopods. The hepatic cells have been previously described as randomly without forming a layer, however, the present results clearly demonstrate that these cells form a continuous layer over the whole midgut.Keywords: histology, histochemistry, ultrastructure, Diplopoda, digestive tract. Intestino médio do diplópodo Urostreptus atrobrunneus: estrutura, função e redefinição das células hepáticas ResumoDiplópodos são considerados importantes macro-artrópodes do solo, uma vez que participam de sua manutenção e equilíbrio. Comumente estes animais não apresentam população numerosa, porém há relatos de explosões populacionais ocasionadas por desequilíbrios ambientais, mudanças climáticas e utilização de pesticidas que eliminam possíveis competidores. O milípede Urostreptus atrobrunneus Pierozzi e Fontanetti, 2006, têm apresentado pontos de infestação em centros urbanos, do estado de São Paulo, Brasil, causando muitos transtornos à população humana. Com objetivo de contribuir para o conhecimento desta potencial praga, este trabalho apresenta a descrição histológica, histoquímica e ultra-estrutural do intestino médio do milípede U. atrobrunneus, bem como apresenta a redefinição das células hepáticas, um tanto controversa na literatura pertinente. A região do intestino médio é caracterizada pela ausência da íntima cuticular, sendo formado por um epitélio pseudoestratificado, apoiado por uma membrana basal espessa, seguido de uma camada muscular, uma camada de células hepáticas, revestido por uma membrana externa. A morfologia observada neste trabalho assemelha-se bastante com as descrições de outras espécies de diplópodos estudadas até o momento. As células hepáticas foram previamente descritas como dispostas aleatoriamente sem a formação de uma camada, contudo, os presentes resultados demonstram claramente que estas células formam uma camada contínua ao longo de todo o intestino médio.

Structure of the midgut epithelium in four diplopod species: histology, histochemistry and ultrastructure

“…The similar type of epithelium in centipedes has been described previously (Kaufman 1961a, 1961b, 1962, Chajec et al 2012. The principal cells which form the midgut epithelium are the digestive cells, the cytoplasm of which shows distinct regionalization in organelle distribution; thus the apical (with the cortical layer), perinuclear and basal regions could be distinguished (Nunez and Crawford 1977;Camargo-Mathias et al 2004;Fonanetti et al 2006Fonanetti et al , 2015Sosinka et al 2014;Moreira-de-Sousa et al 2017;Rost-Roszkowska et al 2018). The apical cytoplasm is characterized by microvilli formed by the apical cell membrane and internal actin filaments.…”

“…They resemble A and B granules described for insects (Hopkin 1989), where zinc, lead, cadmium and/or copper can be stored. The accumulation of spherites that contain all of the organic and inorganic chemical compounds is connected with feeding on decaying leaves, feces and organic matter mixed with soil (Hubert 1979;Köhler and Alberti 1992;Köhler et al 1995;Köhler 2002;Nogarol and Fontanetti 2010;Godoy and Fontanetti 2010) or even calcium (Hubert 1988;Hopkin and Read 1992;Fantazzini et al 2002;Fontanetti et al 2006;Moreira-de-Sousa et al 2017). These structures may be utilized in the digestive cells of the millipede midgut inside autophagosomes (Rost-Roszkowska et al 2019).…”

Histologic lesions of giant African millipedes (Archispirostreptus gigas) from a zoological institution

“…The secretions of each part of the gut have been studied in detail to understand organic matter transformation, animal-microbial interactions, and compartmentalization of digestion, and these secretions may be investigated further in the context of millipede health. 21,31,32,37 Indeed, there were several millipedes in this population that had histologic evidence of gut necrosis and hemocoelic inflammation with bacterial invasion and dissemination. Large numbers of fungal organisms often accompanied bacteria in these lesions and could represent postmortem proliferation and opportunistic infection versus true pathogens.…”

Influence of herbicides, insecticides and fungicides on food consumption and body weight of Rossiulus kessleri (Diplopoda, Julidae)

“…This means that during several vegetation seasons, this species can accumulate various types of pesticides introduced by farmers in different years to various plants of field crop rotations. At the same time, accumulation of pesticides in R. kessleri can cause dysbalance in the compositions of gut microbiota or parasites of its intestine (Guzev & Byzov, 2006;Brygadyrenko & Svyrydchenko, 2015;Moreira-de-Sousa et al, 2017;Reshetniak et al, 2017). This can change the extent of digestion of food in the organism of R. kessleri, as we observed in the experiment: food consumption slows (1), as well as evacuation of feces from the intestine (2) or consumption of food and digestion (3), causing decrease in the total body weight of the animals throughout the experiment.…”