Summary
The midgut of female Anophelinae and Culicinae comprises a narrow anterior (A-part) and a wide posterior part (P-part, stomach). Both are lined by a singlelayered epithelium, and in both parts regenerative cells are found between the epithelial cells. “Clear cells”, possibly with an endocrine function, are only found in the P-part.
The epithelial cells of the mosquito species investigated display close ultrastructural similarities. No significant differences are found between Anopheles gambiae and A. stephensi which differ markedly in origin and habitat.
In all species investigated the cellular organization suggests that both midgut parts are able to carry out processes of synthesis and secretion as well as of absorption and transport. On the other hand, in the A-part more microvilli, a higher density of membranes of the smooth endoplasmic reticulum and a tendency for more membranes of the basal labyrinth are seen by comparison with the P-part. The P-part is characterized by more rough endoplasmic reticulum (rer) and mitochondria.
As a working hypothesis it is proposed that absorption of sugar-containing solutions and the formation of mucus-like material occurs in A. The P-part is postulated to be responsible for synthesis and release of precursors of the peritrophic membrane and digestive enzymes as well as for the main absorption, transport and temporary storage of metabolites resulting from blood digestion.
Ultrastructural differences between mosquito species mainly consist of the following:
-
a)
less surface density of rer in the P-part of Culex and Anopheles as compared with Aedes; more rer in P than in A of Anopheles only present from 1st blood meal onwards,
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b)
an additional rer cisterna in Culex forms a “halo” around the nucleus,
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c)
apical granules in the P-part of Anopheles,
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d)
storage deposits — in Aedes primarily as lipids — in Anopheles as carbohydrates and lipids,
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e)
no maculae adhaerentes in the P-part of Anopheles.
Zusammenfassung
Der Mitteldarm der untersuchten Anophelinae und Culicinae-Weibchen ist in einen engen vordem (A-part) und in einen weiten hintern Abschnitt (P-part, Magen) gegliedert. Das Epithel ist einschichtig. Regenerationszellen findet man im A- und P-part. “Helle Zellen” (“clear cells”) mit möglicherweise endokriner Funktion kommen lediglich im P-part vor.
In vielen strukturellen Parametern gleichen sich die Epithelzellen der verschiedenen Mückenarten. Keine wesentlichen Unterschiede bestehen zwischen Anopheles gambiae (“Wildfänge”) und A. stephensi (Laborstamm).
Die Zellstruktur läßt vermuten, daß in beiden Mitteldarmabschnitten sowohl Synthese und Sekretionsvorgänge als auch Resorptionsund Transportprozesse ablaufen können. Daneben enthält der A-part mehr Mikrovilli, einen größeren Anteil an glattem endoplasmatischem Retikulum und an Membranen des basalen Labyrinths. Der P-part ist gekennzeichnet durch einen höheren Anteil an rauhem endoplasmatischem Retikulum (rer) und an Mitochondrien.
Als Arbeitshypothese wurde dem A-part aller untersuchten Culiciden die Bildung und Sekretion von Mucus-ähnlichen Substanzen und die Resorption von Zucker zugeordnet. Dementsprechend sollte im P-part sowohl Synthese und Sekretion der peritrophen Membran und der Enzyme für die Blutverdauung als auch zu wesentlichen Teilen Resorption, Transport und temporäre Speicherung von Blutabbauprodukten stattfinden.
Strukturelle Unterschiede zwischen den untersuchten Mückenarten bestehen zur Hauptsache im Folgenden:
-
a)
weniger Oberflächendichte des rer im P-part von Culex und Anopheles verglichen mit Aedes; erst während und nach der Verdauung des 1. Blutmahls mehr rer in P als in A,
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b)
eine zusätzliche rer Cisterne bildet bei Culex einen “Kernhof”,
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c)
apicale Granula im P-part von Anopheles,
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d)
Reserveprodukte bei Aedes als Lipide gespeichert, bei Anopheles als Kohlenhydrate und Lipide,
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e)
keine Maculae adhaerentes im P-part von Anopheles.
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I thank Prof. T.A. Freyvogel for his practical instructions in collecting, determining and breeding A. gambiae in Ifakara, Tanzania. The critical discussion of the manuscript by my collegues Drs. S. Böhringer, P.H. Burri and W. Rudin as well as English language corrections by Dr. R. Yeates and by the Copy-editor of “Cell and Tissue Research” are gratefully acknowledged. I thank Mr. P. Bauer for preparing the C.p.fatigans material, Miss C. Fauser for skillful technical assistance, and Miss U. Steffen for ty** the manuscript
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Hecker, H. Structure and function of midgut epithelial cells in culicidae mosquitoes (insecta, diptera). Cell Tissue Res. 184, 321–341 (1977). https://doi.org/10.1007/BF00219894
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DOI: https://doi.org/10.1007/BF00219894