Fine structure of the spermatheca and of the accessory glands inOrchesella villosa(Collembola, Hexapoda)

Abstract

The spermatheca and the accessory glands of the collembolan Orchesella villosa are described for the first time. Both organs exhibit ultrastructural differences, according to the time of the intermolt in which the specimens were observed. A thick cuticular layer lines the epithelial cells of the accessory glands. In the reproductive phase, they are involved in secretory activity; a moderately dense secretion found in the apical cell region opens into the gland lumen. Cells with an extracellular cistern are intermingled with the secretory cells. These cells could be involved in fluid secretion, with the secretory product opening into the cistern which is filled with an electron-transparent material. After the reproductive phase, the gland lumen becomes filled with a dense secretion. The accessory gland secretion may play a protective role towards the eggs. The spermatheca is located between the accessory glands; its epithelium is lined by a thin cuticle forming spine-like projections into the lumen and consists of cells provided with an extracellular cistern. Secretory cells, similar to those seen in the accessory glands, are missing. Cells with a cistern could be involved in the production of a fluid secretion determining sperm unrolling and sperm motility.

The ultrastructure of the spermathecae in the Collembola Symphypleona (Hexapoda)

“…This great difference, with respect to Arthropleona, is worthy of discussion. In the Arthropleona Orchesella villosa (and in Pogonognathellus flavescens, personal observations) only one spermatheca is present and it is flanked by two accessory glands (Dallai et al, 2008). The function of these glands in Collembola is not yet known, but considering that they are very close to the genital opening and that females that have picked up spermatophores lay eggs within 1 h Fig.…”

“…The male deposits spermatophores on the soil and the female picks them up to fertilize her eggs. In a recent paper we described the spermatheca and two accessory glands in the collembolan Arthropleona Orchesella villosa (Dallai et al, 2008). We clarified the nature of the lateral ectodermal pockets [the so called ''accessory organs'' of Tullberg (1872)] close to the female genital opening, establishing that they are true accessory glands.…”

“…The two species of Collembola Symphypleona do not have accessory glands. Compared with the Arthropleona Orchesella villosa, which has a single spermatheca and two accessory glands (Dallai et al [2008] J Morphol 269:464-478), a great difference has occurred in the organization of the female genital system of these species. The results are discussed in light of the implications for reproductive behavior and egg protection in Symphypleona.…”

Male–male competition leads to less abundant but more attractive sperm

“…Females subsequently choose among male ejaculates for internal fertilization, similar to female-biased sperm use in conventional mating systems. But in dissociated systems, fertilization choice takes place outside the female tract, making it easy to observe a male's ejaculate fertilization success [12,13].…”

“…Females of the genus Orchesella pick up only one spermatophore [12,13] and do not store sperm [13]; hence, postcopulatory cryptic choice is absent. Earlier work on O. cincta has demonstrated that female choice based exclusively on assessment of spermatophores provides the females with indirect benefits [16].…”