Complex genital system of a haplogyne spider (Arachnida, Araneae, Tetrablemmidae) indicates internal fertilization and full female control over transferred sperm

Abstract

The female genital organs of the tetrablemmid Indicoblemma lannaianum are astonishingly complex. The copulatory orifice lies anterior to the opening of the uterus externus and leads into a narrow insertion duct that ends in a genital cavity. The genital cavity continues laterally in paired tube-like copulatory ducts, which lead into paired, large, sac-like receptacula. Each receptaculum has a sclerotized pore plate with associated gland cells. Paired small fertilization ducts originate in the receptacula and take their curved course inside the copulatory ducts. The fertilization ducts end in slit-like openings in the sclerotized posterior walls of the copulatory ducts. Huge masses of secretions forming large balls are detectable in the female receptacula. An important function of these secretory balls seems to be the encapsulation of spermatozoa in discrete packages in order to avoid the mixing of sperm from different males. In this way, sperm competition may be completely prevented or at least severely limited. Females seem to have full control over transferred sperm and be able to express preference for spermatozoa of certain males. The lumen of the sperm containing secretory balls is connected with the fertilization duct. Activated spermatozoa are only found in the uterus internus of females, which is an indication of internal fertilization. The sperm cells in the uterus internus are characterized by an extensive cytoplasm and an elongated, cone-shaped nucleus. The male genital system of I. lannaianum consists of thick testes and thin convoluted vasa deferentia that open into the wide ductus ejaculatorius. The voluminous globular palpal bulb is filled with seminal fluid consisting of a globular secretion in which only a few spermatozoa are embedded. The spermatozoa are encapsulated by a sheath produced in the genital system. The secretions in females may at least partly consist of male secretions that could be involved in the building of the secretory balls or play a role in sperm activation. The male secretions could also afford nutriments to the spermatozoa.

A double role of sperm in scorpions: The mating plug of Euscorpius italicus (Scorpiones: Euscorpiidae) consists of sperm

“…This is probably due to the activation of the sperm only in contact with the female genital condition: The spermatozoa were activated only in insect Ringer's and not in human Ringer's solution. The possibility that females are able to activate spermatozoa in arachnids was suggested in several studies Burger et al, 2006;Eberhard and Huber, 1998;Peretti and Battá n-Horenstein, 2003). The female genital atrium is equipped with glands, which could produce secretions that activate sperm (Peretti, 2003;Peretti and Battá n-Horenstein, 2003).…”

Development of Loxosceles intermedia Mello-Leitão (1934) (Araneae, Sicariidae) genital tract

“…There are consistent descriptions of the genital apparatus morphology in adult L. intermedia and other spider species (Alberti, 1991;Uhl, 2000;Uhl and Gunnarsson, 2001;Klann et al, 2005;Costa-Ayub and Faraco, 2007;Burger et al, 2006aBurger et al, , 2006bBurger and Kropf, 2007;Talarico et al, 2008;Simeó et al, 2009).…”

Fine structural reconstruction on the testicular cyst of the furrow orb weaver,Larinioides cornutusby 3D volume rendering

“…As a result, a large amount of data are accumulated in the field, providing a wealth of information, particularly on the genitalia and germ-cell development (Burger et al 2006;Michalik & Ramirez 2014). However, when it comes to germ-cell development, most of the studies are focused on the spermiogenesis, covering acrosome formation (Michalik & Huber 2006;CostaAyub & Faraco 2007), mitochondria and filament arrangement in flagellum (Baccetti et al 1970;Phillips 1974;Zizzari et al 2008) as a potential phylogenetic inference.…”