Determination of pH in Regions of the Midguts of Acaridid Mites

Abstract

The pH of the guts of mites strongly affects their digestive processes. This study was carried out to determine the pH in the guts of 12 species of stored product and house dust mites. Eighteen pH indicators were chosen and offered to the mites in the feeding biotest. Based on the color changes of the indicators, the gut contents of acaridid mites were determined to be within a pH range of 4 to neutral. The gut contents showed a gradient in pH from the anterior to the posterior part. The anterior midgut (ventriculus and caeca) of most species had a pH ranging from 4.5 to 5, or slightly more alkaline for most of the species, while the middle midgut (intercolon/colon) had a pH of 5 to 6. Finally, the pH of the posterior midgut (postcolon) was between 5.5 and 7. Except for Dermatophagoides spp., no remarkable differences in the pH of the gut were observed among the tested species. Dermatophagoides spp. had a more acidic anterior midgut (a pH of 4 to 5) and colon (a pH of 5) with postcolon (a pH of below 6). The results characterizing in vivo conditions in the mite gut offer useful information to study the activity of mite digestive enzymes including their inhibitors and gut microflora.

Comparative analyses of proteolytic activities in seven species of synanthropic acaridid mites

“…This anomaly corresponds with in vivo pH conditions in gut of Dermatophagoides spp. (Erban and Hubert, 2010).…”

“…A trypsin allergen Der f3 was recently localized in the postcolon (posterior midgut; Zhan et al, 2010), indicating that the pH optima should correspond to pH 6 (Erban and Hubert, 2010). Nevertheless, the low activity toward BApNA suggests that the possible function of trypsin-like proteases, as digestive enzymes is very limited.…”

“…Previously, the pH conditions of the gut of acaridid mites have been described. There is a pH gradient from the anterior to the posterior mesodeum ranging from pH 4.5 to 7 in all species that were compared (Erban and Hubert, 2010).…”

Der p 1 is the primary activator of Der p 3, Der p 6 and Der p 9 the proteolytic allergens produced by the house dust mite Dermatophagoides pteronyssinus

“…Previous observations of the digestive tract of the mite showed that cells lining the anterior midgut, where pH is comprised between 4 and 5, would be gradually detached in the gut lumen and would then be taken in the faecal pellets in the posterior midgut and the hindgut, where pH reaches 6 [28][29][30]. It is thus likely that the auto-activation of proDer p 1 occurring at acidic pH proceeds in the anterior midgut, thereby providing active protease Der p 1.…”

Understanding the biology and control of the poultry red miteDermanyssus gallinae: a review

“…The mite digestive tract is a comparatively well-studied part of the anatomy of several species including the storage mite Lepidoglyphus destructor (Erban & Hubert, 2011), the house dust mite Dermatophagoides farinae (Dumez et al, 2014), the sheep scab mite Psoroptes ovis (Hamilton et al, 2003) and a range of synanthropic species (Erban & Hubert, 2010). In combination these studies provide an outline of the general anatomy of mites (Mehlhorn, 2001), although the specific physiology of PRM, which are haematophagous mites, may be substantially different.…”