Transecting and contrasting the feeding designs of the astigmatan community from bird nests

The chelal moveable digit patterns of seventeen free-living astigmatan mites commonly found in bird nests is decomposed (for the first time) into functional groups using standardised profiles. Contrasts along the mastication surface are used to detect trophic features so as to explain the coexistence of different species in that community. Variation in profiles in general track geometric similarity changes in chelicerae and chelae, except in the moveable digit design transition between Thyreophagus entomophagus TH3 and Lepidoglyphus destructor G6. Full-kerf (Aleuroglyphus ovatus AL2 and Chortoglyphus arcuatus CH1) and particularly thin-kerf (Acarus farris A17) species are found. Both the moveable 'digit tip angle' and the angular bluntness of the anterior region (on which the tip sits, denoted the 'distal digit angle'), mirror digit robustification.Ventral surface intrinsic curvature of the moveable digit appears common across species. Acarus gracilis A4, Glycyphagus domesticus G5 and Lepidoglyphus destructor G6 have more than expected strengthened digit tips compared to other taxa. Rates of this strengthening with chelal occlusive force varies across species. With respect to the whole moveable digit profile a design transition from glycyphagids through acarids to pyroglyphids is found, along with an evolutionary path amongst pest species (Rhizoglyphus robini R1, through Tyrophagus longior T40, to Tyrophagus putrescentiae T13). Acarus gracilis A4 appears unique. In particular Tyrophagus palmarum T17 & T32 and Tyrophagus similis T21 & T44 are indistinguishable from replicates of each other and typify a basal form Tyrophagus longior T40, Tyrophagus putrescentiae T13, Acarus immobilis A1, Tyrolichus casei T62 and Acarus farris A17 are only mildly different from the observed scale of sampling variation of the basal overall profile form in this study Two design groups of ever increasing post-horizontal ramus investment are clear, with the basal rami of Chortoglyphus arcuatus CH1, Thyreophagus entomophagus TH3, Rhizoglyphus robini R1, Glycometrus hugheseae G3 and Dermatophagoides pteronyssinus D3 being taller and sometimes more rounded than those of the distinct group Acarus gracilis A4, Suidasia pontifica S5, Glycyphagus domesticus G5, Lepidoglyphus destructor G6 and Aleuroglyphus ovatus AL2. The bulk of the bird nest astigmatan species have a common profile pattern of apparent asperities on their mastication surface. Although, two species, Rhizoglyphus robini R1 and Chortoglyphus arcuatus CH1, have somewhat exaggerated features on this common 'Bauplan' (perhaps scaled for greater adductive force). Certain species: Acarus immobilis A1, Dermatophagoides pteronyssinus D3, Glycometrus hugheseae G3, Glycyphagus domesticus G5, Lepidoglyphus destructor G6 and Tyrophagus putrescentiae T13, have an individualised distinctly featured mastication surface. These species must each feed differently or on different material in bird nests. Basal ramus and chelal leverage differences are discussed. More work on the ascending ramus and specific dentition in future work is needed to explain certain remaining mite coexistences in this habitat.