The gnathosoma of the Eriophyoidea (Acari, Trombidiformes, Prostigmata): a review and update with particular emphasis on external morphology

A review with an update from a comparative study of the external morphology of the eriophyoid gnathosoma, with notes on the anatomy, are presented. It includes information largely published after the review of Lindquist (1996), and Nuzzaci and Alberti (1996), with the addition of new data from a study of 70 eriophyoid species from all three eriophyoid families using various microscopy techniques, including low-temperature and variable pressure scanning electron microscopy (SEM), transmission electron microscopy (TEM), light microscopy (LM) and confocal laser scanning microscopy (CLSM). The study revealed the presence of unknown gnathosomal structures and provided further structural data of known characteristics. Functions of these structures in feeding and resting position of the gnathosoma are extrapolated from the data. This combined knowledge of the gnathosoma is compared with published phylogenetic hypotheses, and appraised for use in the taxonomy of eriophyoids.