Excretion in an oribatid mite Phthiracams sp. (Arachnida: Acari)



Phthiracams sp. has one pair of coxal glands. Each gland comprises a thin-walled sacculus which is specialized for the ultrafiltration of the haemolymph and a tubular labyrinth the ultrastructure of which indicates a specialization for the active resorption of material from the lumen.

In addition to its digestive function, the alimentary canal of this mite is also involved in excretion. Excretory material accumulates at the haemocoelic surface of the gut wall and, after endocytosis, passes through the cytoplasm of the cells as discrete bodies which appear in the faecal pellet.

The faecal pellet is covered with a peritrophic layer 250–500 nm thick which has no discernible structure and disintegrates in water.