Ultrastructure of the digestive tract in Acarus siro (Acari: Acaridida)

Abstract

The gut of the mite Acarus siro is characterized on the ultrastructural level. It consists of the foregut (pharynx, esophagus), midgut (ventriculus, caeca, colon, intercolon, postcolonic diverticula, postcolon), and hindgut (anal atrium). The gut wall is formed by a singlelayered epithelium; only regenerative cells are located basally and these have no contact with the lumen. Eight cell types form the whole gut: (i) simple epithelial cells forming fore-and hindgut; (ii) cells that probably produce the peritrophic membrane; (iii) regenerative cells occurring in the ventriculus, caeca, colon, and intercolon; (iv) spherite cells and (v) digestive cells forming the ventriculus and caeca; (vi) colonic cells and (vii) intercolonic cells; and (viii) cells forming the walls of postcolonic diverticula and postcolon. Spherite and digestive cells change in structure during secretory cycles, which are described and discussed. The cycle of spherite, colonic, and intercolonic cells is terminated by apoptosis. Ingested food is packed into a food bolus surrounded by a single homogeneous peritrophic membrane formed by addition of lamellae that subsequently fuse together. The postcolonic diverticula serve as a shelter for filamentous bacteria, which also are abundant in the intercolon.

Molecular physiology of digestion in arachnida: functional and comparative-evolutionary approaches.

“…Peritrophin was identified in fasting animals (0.55‰) and in the DJ (0.31‰). It was observed in spiders that the peritrophic membrane was surrounding the fecal pellets (19) and also in mites (16). The fact that it was found in the DJ remains unclear but finding it in only in fasting and not in fed animals agrees with the literature information about fecal involucre.…”

“…Only in Acari some major differences are observed (5). In (Acari-) Anactinotrichida, for example the predatory tick Pergamasus longicornus and the blood-sucking ticks (15), the secretory cells are absent whereas in other cases more cell types are present like in Acarus siro (16). Acari families both types of EOD can be observed, however Araneae presenting EOD type I are refluxers and Acari EOD type I are non refluxers.…”

“…Acari families both types of EOD can be observed, however Araneae presenting EOD type I are refluxers and Acari EOD type I are non refluxers. Opiliones are the only arachnid group that does not do any EOD type (1) and together with some Acari (Oribatida, Acaridida) are the only arachnids that ingest solid food (16,17). Probably due to this fact peritrophic membranes can be found in these two groups (16,18).…”

Visualization of protein digestion in the midgut of the acarid mite Lepidoglyphus destructor

“…Generally, the gut morphology of L. destructor is similar to that of Acarus siro (Sobotnik et al, 2008). The foregut is formed from the pharynx and the esophagus.…”

“…The sizes of the structures were measured for at least five specimens, and the mean is presented. The nomenclature of the gut was adopted from Sobotnik et al (2008).…”