Functional genital morphology of armored spiders (Arachnida: Araneae: Tetrablemmidae)

Abstract

This study describes the female genitalia of the tetrablemmid spiders Brignoliella acuminata, Monoblemma muchmorei, Caraimatta sbordonii, Tetrablemma magister, and Ablemma unicornis by means of serial semi-thin sections and scanning electron microscopy and compares the results with previous findings on Indicoblemma lannaianum. Furthermore, the male palps and chelicerae are briefly described. The general vulval organization of females is complex and shows similarities in all of the investigated species. The copulatory orifice is situated near the posterior margin of the pulmonary plate. The opening of the uterus externus lies between the pulmonary and the postgenital plate. Paired copulatory ducts lead to sac-like receptacula. Except for A. unicornis, the male emboli of all investigated species are elongated and thread-like. However, they are too short to reach the receptacula. Hence, the spermatozoa have to be deposited inside the copulatory ducts. The same situation was also found in I. lannaianum. Females of this species store sperm encapsulated in secretory balls in their receptacula. The secretion is produced by glands adjoining the receptacula. The presence of paired fertilization ducts and spermatozoa in the uterus internus suggested that fertilization takes place internally in I. lannaianum. Secretory balls in the receptacula are found in all of the investigated species in this study, showing that sperm are stored in the same way. The place of fertilization may also be identical since dark particles, presumably spermatozoa, are located in the uterus internus of all investigated species except for T. magister. However, fertilization ducts are only found in B. acuminata and M. muchmorei. A sclerotized central process with attached muscles is present in A. unicornis, M. muchmorei, C. sbordonii and T. magister. Only in A. unicornis does the central process show an internal lumen and hold spermatozoa. In the other species, it could be used to lock the uterus during copulation in order to prevent sperm from getting into it as suggested for certain oonopid species. The uterus externus of all investigated species shows a sclerotized dorsal fold with attached muscles, previously described as "inner vulval plate." Contractions of the muscles lead to a widening of the dorsal fold, thus creating enough space for the large oocytes to pass the narrow uterus externus. The males of all investigated species have apophyses on their chelicerae. At least in B. acuminata and A. unicornis, where females have paired grooves on the preanal plate, these apophyses allow males to grasp the female during copulation as described for I. lannaianum.

Complex female genitalia indicate sperm dumping in armored goblin spiders (Arachnida, Araneae, Oonopidae)

“…Based on the observation of a sperm flagellum close to the oocytes, Suzuki (1995) proposed that fertilization in Parasteatoda tepidariorum takes place in the ovary. In tetrablemmids, activated spermatozoa were found inside the uterus internus, indicating that fertilization takes place internally, meaning in the uterus internus or even the ovary (Burger et al, 2006b;Burger, 2008). The present study shows that sperm are also present in the uterus internus of Myrmopopaea sp.…”

“…Oonopidae comprise a variety of species with a peculiar organization of the internal female genitalia (Saaristo, 2001;Burger et al, 2003Burger et al, , 2006aBurger, 2007;Fannes and Jocqué , 2008). Especially in species where live material for direct observations of the mating behavior is difficult to obtain, fine morphological details of the genitalia have large potential for the understanding of their function and evolution (Eberhard, 1985(Eberhard, , 1996(Eberhard, , 2004Galis, 1996;Hellriegel and Ward, 1998;Uhl, 2002;Huber, 2005;Burger, 2008).…”

“…Secretions around the sperm inside the female sperm storage site are found in different spider species, e.g., Pholcidae and Tetrablemmidae (Uhl, 1994;Burger et al, 2006b;Burger, 2008). In the oonopid Silhouettella loricatula it was suggested that the main function of sperm enclosure in a secretory sac is enabling females to dump the ejaculate of a male (Burger, 2007).…”

Copulatory and Post-copulatory Sexual Selection in Haplogyne Spiders, with Emphasis on Pholcidae and Oonopidae

“…In this way, they are able to influence sperm priority patterns (Burger et al 2003;Eberhard 1985Eberhard , 1996Eberhard , 2004Hellriegel and Ward 1998). The morphological differences between haplogyne and entelegyne have been questioned by studies on various haplogyne taxa, which have revealed a complexity in female genital morphology (Burger 2007(Burger , 2008(Burger , 2009(Burger , 2010Burger et al 2003Burger et al , 2006a, and by the genital morphology defined for haplogyne in species of several Entelegynae families (Dimitrov et al 2007;Griswold et al 1998;Platnick and Forster 1989). These species are considered secondarily haplogyne.…”

“…Such complex morphology could function to lock one area of the female's reproductive tract, to pack a male's ejaculate in a secretion preventing sperm mixing, and eject it from her body as a single mass (Burger 2007(Burger , 2008Burger et al 2006b). All of these strategies may enable females to influence the fate of transferred sperm (Burger 2007;Burger et al 2003Burger et al , 2006aEberhard 1985Eberhard , 1996.…”