Securing paternity in spiders? A review on occurrence and effects of mating plugs and male genital mutilation

Abstract

Low female mating frequencies often appear to be cases of direct male induction that can oppose female interests. Mating plugs are most obvious means leading to low degrees of multiple mating in females. In spiders, mating plugs are formed by a variety of amorphous materials, by the breakage of the male sperm transferring organ, or by the whole male that functions as a mating barrier. Our compilation of the available information on the presence of the various types of mating plugs suggests that plugs predominantly occur in entelegyne spiders. In this group, plugs do not interfere with oviposition since separate openings for insemination and oviposition are present. In contrast, mating plugs seem to be rare in haplogyne spiders that do not possess separate openings. The available experimental studies on the function of the different types of plugs suggest that plugs can be considered as male adaptations to avoid sperm competition. However, females in some cases were shown to have evolved means to prevent or control male manipulation or may selectively favour plug production in specific males, an aspect which has largely been neglected. In order to understand plug evolution and function we need to explore the morphological, behavioural and biochemical aspects involved and extend our approach to interactions between the sexes.

Obligate male death and sexual cannibalism in dark fishing spiders

“…In only two cases during experiment 2 was the first male still attached to the female when the second male was introduced. Regardless, even after the removal of the male, there were no obvious palpal fragments remaining in the female's epigynum that would have inhibited subsequent mating (reviewed in Uhl, Nessler, & Schneider, 2010).…”

Copulatory Wounding and Traumatic Insemination

“…In contrast to self-infliction caused by partner resistance, in several species, the intromittent organs routinely break and the whole or parts thereof remain in the female (nudibranchs: Sekizawa et al 2013;spiders: Uhl et al 2010;Izquierdio and Rubio 2011;earwigs: Kamimura 2003;bees: Franck et al 2002). This self-inflicted CW can acquire adaptive function (such as preventing remating of the partner: Nessler et al 2007;Uhl et al 2010), in which case the term "wound inflictor" would,again, beambiguous,evenmoreso if specific break-off points evolved (e.g., Uhl et al 2010;Sekizawa et al 2013) that no longer result in wounding. In other species, injuries to the intromittent organs happen occasionally rather than routinely (moths: Cordero and Miller 2012; humans: the section Case Studies) and their adaptive function, if any, is unknown (but, see Cordero and Miller 2012).…”

“…Copulatory organs evolved from a diverse set of developmental structures, representing penises, ectodermal appendages (such as parameres in the insects : Carayon 1966b), mouthparts (such as the pedipalps in spiders: Uhl et al 2010), and a range of structures collectively known as spermatophores of various origins (Davey 1960;Mann 1984). Such frequent developmental reorganizations may increase the likelihood of copulatory mismatches and, hence, CW.…”

Revalidation of Acanthinozodium Denis, 1966 with description of three new species and discovery of a remarkable male palpal character (Araneae, Zodariidae)

“…Epigynes of Acanthinozodium have large atria that are often filled with a large sticky plug that protrudes above the surrounding tegument ( Figs 1A, 5H, 12A). Epigyne plugs are not uncommon in spiders (Uhl et al 2010). The most commonly mentioned plugs are parts of the palp, more precisely of the embolus.…”