A human case of otoacariasis involving a histiostomatid mite (Acari: Histiostomatidae).

A 31-year-old Saudi man was seen at an ear, nose, and throat clinic at Riyadh, Saudi Arabia, with bilateral itching in the external auditory canal. On otoscopic examination, the skin lining the ear canal was thickened with whitish sheets of sloughed cells and thick discharge. Large numbers of mites of an undescribed species closely related to members of the genus Loxanoetus (Histiostomatidae) were present. The patient underwent successive washings of the ear canal with saline and 70% ethanol at intervals of 2-3 months and was treated with antibiotics. Treatment with Eurax (crotamiton) ear drops for one week cleared the mite infestation. This represents the first reported case of human otoacariasis involving a histiostomatid mite. Based on the known biology of histiostomatid mites and the associated hosts of Loxanoetus and related genera, there is reason to speculate that the patient acquired the infestation while swimming in a lake or pond where this mite was present.

Pit membranes in tracheary elements of Rosaceae and related families: new records of tori and pseudotori.

The micromorphology of pits in tracheary elements was examined in 35 species representing 29 genera of Rosaceae and related families to evaluate the assumption that angiosperm pits are largely invariant. In most Rosaceae, pit membranes between fibers and tracheids frequently appear to have amorphous thickenings with an irregular distribution. Although these structures are torus-like under the light microscope, observations by electron microscopy illustrate that they represent "pseudotori" or plasmodesmata-associated thickenings. These thickenings frequently extend from the periphery of the pit membrane and form a cap-like, hollow structure. Pseudotori are occasionally found in few Elaeagnaceae and Rhamnaceae and appear to be related to species with fiber-tracheids and/or tracheids. True tori are strongly associated with round to oval pit apertures and are consistently present in narrow tracheary elements of Cercocarpus (Rosaceae), Planera (Ulmaceae), and ring-porous species of Ulmus and Zelkova (Ulmaceae). Vestured pits with homogenous pit membranes are reported for Hemiptelea (Ulmaceae). The homoplastic nature of pit membrane characteristics may be related to functional adaptations in terms of safety and efficiency of water transport or may reflect different developmental processes of xylem elements. These observations illustrate that there is more variation in angiosperm pits than previously thought.