Abstract
Storage of sperm inside the female genital tract is an integral phase of reproduction in many animal species. The sperm storage site constitutes the arena for sperm activation, sperm competition and female sperm choice. Consequently, to understand animal mating systems information on the processes that occur from sperm transfer to fertilization is required. Here, we focus on sperm activation in spiders. Male spiders produce sperm whose cell components are coiled within the sperm cell and that are surrounded by a proteinaceous sheath. These inactive and encapsulated sperm are transferred to the female spermathecae where they are stored for later fertilization. We analyzed the ultrastructural changes of sperm cells during residency time in the female genital system of the orb-web spider Argiope bruennichi. We found three clearly distinguishable sperm conditions: encapsulated sperm (secretion sheath present), decapsulated (secretion sheath absent) and uncoiled sperm (cell components uncoiled, presumably activated). After insemination, sperm remain in the encapsulated condition for several days and become decapsulated after variable periods of time. A variable portion of the decapsulated sperm transforms rapidly to the uncoiled condition resulting in a simultaneous occurrence of decapsulated and uncoiled sperm. After oviposition, only decapsulated and uncoiled sperm are left in the spermathecae, strongly suggesting that the activation process is not reversible. Furthermore, we found four different types of secretion in the spermathecae which might play a role in the decapsulation and activation process.
Highlights
A key adaptation to terrestrial life is internal fertilization
Since the processes transfer of sperm to the female and fertilization of the ova are generally separated in time, with hours, months or even years between the two events [1], sperm storage inside the female genital tract is an integral phase of reproduction
We chose the spider Argiope bruennichi (Araneae: Araneidae), a model species for sexual selection [10], and addressed the following questions: (1) in which condition is sperm transferred to the female? (2) when is the sperm capsule lysed, (3) when do sperm uncoil? (3) what is the condition of sperm after oviposition? In addition, we provide information on the morphology of the female sperm storage organs and morphological information on female secretion as potential activation triggers
Summary
A key adaptation to terrestrial life is internal fertilization. Since the processes transfer of sperm to the female and fertilization of the ova are generally separated in time, with hours, months or even years between the two events [1], sperm storage inside the female genital tract is an integral phase of reproduction. The sperm storage phase entails adaptations to keep the sperm viable until fertilization but at the same time opens the possibility for sperm competition and female sperm choice [2,3]. In particular arthropods show a high diversity in reproductive strategies and morphology ranging from species with external fertilization with simple ‘‘aquasperm’’ to species with internal fertilization and complex sperm and sperm storage organs [4,6,7]. In many cases sperm cells can conjugate/aggregate and be transferred as packages, spermatophores or spermatodesms [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
