Sperm storage by spermatodoses in the spermatheca of Trioza alacris (Hemiptera, Psylloidea, Triozidae): a structural and ultrastructural study

Female insects generally store sperm received during mating in specific organs of their reproductive tract, i.e., the spermathecae, which keep the sperm alive for a long time until fertilization occurs. We investigated spermatheca morphology and ultrastructure in the psylloidean insect Trioza alacris (Flor,1861) in which spheroidal sperm packets that we refer to as spermatodoses are found after mating. The ectoderm-derived epithelium of the sac-shaped spermatheca that has a proximal neck, consists of large secretory and flat cuticle-forming cells. Secretory cells are characterized by a wide extracellular cavity, bordered by microvilli, in which electron-dense secretion accumulates before discharge into the spermathecal lumen. The cuticle-forming cells produce the cuticular intima of the organ and a peculiar specialized apical structure, through which secretion flows into the lumen. At mating, the male transfers bundles of sperm cells embedded in seminal fluid into the spermathecal neck. Sperm cells proceed towards the spermathecal sac lumen, where they are progressively compacted and surrounded with an envelope that also encloses secretions of both male and female origin. We describe the formation of these sperm containing structures and document the contribution of the female secretion to spermatodose or female-determined spermatophore construction. We also discuss the choice of the term spermatodose for T. alacris and suggest it be used to refer to sperm masses constructed in the female reproductive organs, at least when they involve the contribution of female secretion.