Ultrastructure of the male accessory glands of Allacma fusca (Insecta, Collembola)

The accessory glands of Allacma fusca (L.) (Insecta, Collembola, Sminthurid ae) consist of a series of secretory units that are arranged in parallel an d open into the ejaculatory duct. Each unit is composed of microvillate cel ls stacked around a common cavity, Basal cells are involved in ion-control of fluids from the hemocoel to the cavity, The intermediate and apical cell s, which have a laminar appearance and contain many microtubules, are invol ved in the structural integrity of the unit. Supporting cells ensheath the most apical cells, Large openings in the cuticle allow the gland secretion to flow into the ejaculatory duct lumen. These openings are protected by a porous cuticle different from that lining the epithelium of the ejaculatory duct. Conspicuous muscle fibers run along the lateroventral side of the ej aculatory duct beneath the insertion of the accessory glands. The fine stru cture of the accessory glands indicates that they are type I ectodermic gla nds as defined by Noirot & Quennedey (1974), Their function could be to con trol the fluidity of the material for spermatophore formation and to ensure the proper physiological conditions for spermatozoa stored in the ejaculat ory duct lumen.