Allometry of Male Grasping Apparatus in Odonates Does Not Suggest Physical Coercion of Females

Abstract

Male abdominal grasping apparatus that are used to secure a female prior, during and after mating, are widespread in arthropods. The scarce evidence regarding its selective regime suggests that they are male adaptations to circumvent female mating decisions, as predicted by the sexual conflict hypothesis. A recent discussion regarding this way of selection suggests that, similar to weapons and traits that have to do with physical endurance, grasping apparatus should show hyperallometry (proportionally larger compared to body size) as an indication of selection towards increased size. We have tested this idea by measuring the length, width and area of the grasping apparatus of five dragonfly species (Anax junius, Rhionaeschna multicolor, Dythemis nigrescens, D. sterilis and Phyllogomphoides pacificus). We used two proxies of body size (wing and body length). Our measures did not indicate any pattern of hyperallometry. Thus, the grasping apparatus in these animals does not seem to be positively selected for increased size as would be expected if they were forcing females to mate. Given this, we discuss three other explanations for the maintenance of the grasping apparatus in odonates: 1) a firm grip that secures the tandem and mating position; 2) courtship devices subject to female choice; and, 3) isolation structures that mechanically prevent interspecific matings. The first hypothesis, however, could not J Insect Behav (2015) 28:15-25 explain the highly elaborated and species specific morphology of grasping apparatus in these animals. Support for the second hypothesis comes from the fact that odonate females have mechanoreceptor sensilla embedded in their mesostigmal plates (the place grabbed by the grasping apparatus). For the third hypothesis, coevolutionary patterns in morphology in the grasping apparatus and mesostigmal plates in some Zygoptera can also be used as support.

Let's mate here and now – seasonal constraints increase mating efficiency

“…Northern populations of this species have previously been found to have evolved higher growth rate and faster development than central and southern populations, suggesting that northern populations compensate for shorter growth season in terms of emergence time (Sniegula et al, 2016a). The grasping apparatus may be an armament affecting mating success (Emlen, 2008), but see Córdoba-Aguilar et al (2015). Interestingly, northern males of these populations also showed a longer grasping apparatus compared with males from lower latitudes (Sniegula et al, 2017).…”

“…Interestingly, northern males of these populations also showed a longer grasping apparatus compared with males from lower latitudes (Sniegula et al, 2017). The grasping apparatus may be an armament affecting mating success (Emlen, 2008), but see Córdoba-Aguilar et al (2015).…”

Copulatory courtship by bushcricket genital titillators revealed by functional morphology, μCT scanning for 3D reconstruction and female sense structures

“…Sakai, 2001a, 2001b ;Acebes et al, 2003;Gaino et al, 2009) and the single study in bushcrickets is restricted to the sensilla on the external male postabdomen (Faucheux, 2012). Limited data exist for sensilla on genitalia of both sexes (Rossignol and McIver, 1977;Kim and Teiji 2004;Düngelhoef and Schmitt, 2010;Córdoba-Aguilar et al, 2015). The many campaniform sensilla on the inner side of the female subgenital plate are comparable to mechanoreceptors found on other insect body structures (Altner, 1977;Keil, 1997;Keil and Steinbrecht, 1984), however without further analysis of the sensilla a contact chemoreception can not be excluded.…”

One size fits all? Determinants of sperm transfer in a highly dimorphic orb‐web spider

“…These observations indicate that male genital allometry in Argiope aurantia follows the trend observed in other invertebrates regarding intromittent structures (Tatsuta et al ., ; Bernstein & Bernstein, ; Ohno et al ., ; Hosken et al ., ; Mutanen & Kaitala, ; Mutanen et al ., ; Bonduriansky , Eberhard, ). Exceptions to this trend where invertebrate genitalia exhibit isometry or hyperallometry often occur in structures that are used in display (Hosken et al ., ; Outomuro & Cordero‐Rivera, ) or physical contests (Córdoba‐Aguilar & López‐Valenzuela, ; Nava‐Bolaños et al ., ; Córdoba‐Aguilar et al ., ), which is not believed to be the case for the analysed structures in this study (Uhl et al ., ).…”