Specificity of the female’s local cellular immune response in genital plug producing scorpion species

Abstract

Immune defense is a key feature in the life history of organisms, expensive to maintain, highly regulated by individuals and exposed to physiological and evolutionary trade-offs. In chelicerates, relatively scarce are the studies that relate postcopulatory mechanisms and immune response parameters. This work makes an approximation to the female’s immunological consequences produced after the placement of a foreign body in the genitalia of three scorpions species, two species that normally receive genital plugs during mating (Urophonius brachycentrus and U. achalensis) and one that does not (Zabius fuscus). Here we performed the first morphological description of the natural plugs of the two Urophonius species. We described complex three zoned structure anchored to the female genital atrium and based on this information we placed implants in the genitalia (for eliciting the local immune response) of virgin females of the three species and measured the immune encapsulation response to this foreign body. We found a greater and heterogeneous response in different zones of the implants in the plug producing species. To corroborate the specificity of this immune response, we compared the local genital reaction with the triggered response at a systemic level by inserting implants into the female body cavity of U. brachycentrus and Zabius fuscus. We found that the systemic response did not differ between species and that only in the plug producing species the local response in the genitalia was higher than the systemic one. We also compared the total hemocyte load before and after the genital implantation to see if this parameter was compromised by the immunological challenge. We confirmed that in Urophonius species the presence of a strange body in the genitalia caused a decrease in the hemocyte load. Besides, we find correlations between the body weight and the immunological parameters, as well as between different immunological parameters with each other. Complementarily, we characterized the hemocytes of the three scorpion species for the first time. This comparative study can help to provide a wider framework of the immunological characteristics of the species, their differences and their relationship with the particular postcopulatory mechanism such as the genital plugs.

The morphology of mating plugs and its formation in scorpions: Implications for intersexual participation

“…In the laboratory, each individual was weighted with a digital balance (Ohaus Pioneer PA114), classified (following Ojanguren Affilastro, 2005) and sexed using a stereomicroscope (Nikon SMZ1500). Following Oviedo‐Diego et al (2019) and Romero‐Lebrón et al (2019), the reproductive status of the females was determined according to whether the mating plug was present (i.e., mated female) or absent (i.e., virgin female) under the genital operculum (Figure 1), which was inspected by lifting it with straight tweezers. Inseminated females always had a mating plug.…”

“…The vast majority of plugs have been described as male‐derived structures, formed by coagulation of the ejaculate and/or glandular secretions (Althaus et al, 2010; Baer, Morgan, & Schmid‐Hempel, 2001; Duvoisin, Baer, & Schmid‐Hempel, 1999; Townsend Jr et al, 2019; Uhl, Kunz, Vöcking, & Lipke, 2014), hard structures like portions of spermatophores (Contreras‐Garduño, Peretti, & Córdoba‐Aguilar, 2005; Mattoni & Peretti, 2004; Orr & Rutowski, 1991; Peretti, 2003; Peretti & Battán‐Horenstein, 2003), or even by parts of the male's body or genitalia (Foellmer, 2008; Fromhage & Schneider, 2006; Kuntner et al, 2015). However, there is growing evidence that females are involved in the formation or degradation of the plug through secretions or changes produced by the internal genitalia, involving complex physiological processes (Aisenberg & Barrantes, 2011; Aisenberg & Eberhard, 2009; Alonso‐Pimentel, Tolbert, & Heed, 1994; Giglioli & Mason, 1966; Hernández, Aisenberg, & Molina, 2018; Knoflach, 1998; Kuntner, Gregorič, Zhang, Kralj‐Fišer, & Li, 2012; Oviedo‐Diego, Mattoni, & Peretti, 2019). Other instances of female control may occur, such as preventing the placement of a plug (Andrade & MacLeod, 2015; Schneider, 2014; Snow & Andrade, 2005), regulating the duration of mating (Aisenberg & Barrantes, 2011; Herberstein, Wignall, Nessler, Harmer, & Schneider, 2012), or actively removing or expelling the plug (Eberhard, 1996; Knoflach & van Harten, 2002; Lee et al, 2015; Lorch, Wilkinson, & Reillo, 1993).…”

“…A more complex type is the “cone‐shaped” plug, which derives from the fusion of the hemispermatophores basal lobes and fills the female genital atrium anchoring to the cuticular wall of the atrium with microspines (Mattoni & Peretti, 2004). A “mixed” plug has been proposed for Urophonius Pocock, 1893 and Phoniocercus Pocock, 1893, species in which the plug consists of detachable sclerotized portions of the spermatophore and glandular substances (Mattoni & Peretti, 2004; Oviedo‐Diego et al, 2019; Peretti, 2010). Some authors suggested that females participate in the formation and degradation of the mating plugs and, even though it has not been studied in detail, there is some evidence that the plug undergoes progressive changes inside the female's genitalia (Althaus et al, 2010; Contreras‐Garduño et al, 2005; Mattoni & Peretti, 2004; Oviedo‐Diego et al, 2019; Polis & Sissom, 1990).…”

“…A “mixed” plug has been proposed for Urophonius Pocock, 1893 and Phoniocercus Pocock, 1893, species in which the plug consists of detachable sclerotized portions of the spermatophore and glandular substances (Mattoni & Peretti, 2004; Oviedo‐Diego et al, 2019; Peretti, 2010). Some authors suggested that females participate in the formation and degradation of the mating plugs and, even though it has not been studied in detail, there is some evidence that the plug undergoes progressive changes inside the female's genitalia (Althaus et al, 2010; Contreras‐Garduño et al, 2005; Mattoni & Peretti, 2004; Oviedo‐Diego et al, 2019; Polis & Sissom, 1990). Occasionally, plugs can degrade completely, although the expulsion of plug fragments before parturition has also been described (Castelvetri & Peretti, 1999; Contreras‐Garduño et al, 2005; Mattoni & Peretti, 2004; Varela, 1961).…”

“…Thus, it is a suitable model for the study of morpho‐functional characteristics of the mating plugs. Oviedo‐Diego et al (2019) provided a preliminary and basic description of the mating plug of Urophonius achalensis and Urophonius brachycentrus , and highlighted the putative female role in its formation. However, there is still no detailed morphological description to confirm this possibility.…”