Female secondary sexual traits in spiders: Adaptive interpretations of the sternum projection in the pholcid Holocnemus pluchei

Calbacho‐Rosa, Lucía; Cargnelutti, Franco; Peretti, Alfredo V.; Costa-Schmidt, Luiz Ernesto

doi:10.1016/j.zool.2019.125694

Cited by 8 publications

(6 citation statements)

References 35 publications

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“…Judging from the positions of similarly textured cuticle (e.g., on the carapace), these areas are here interpreted as muscle attachment sites. In Holocnemus pluchei males, this is what Calbacho-Rosa et al (2019b) proposed to correspond functionally with the female sternum projection. An alternative that these authors did not consider is that the female sternum process might primarily function in a different context (i.e., not intersexual but intrasexual or allospecific).…”

Section: Sexual Dimorphismsmentioning

confidence: 69%

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Revisions of Holocnemus and Crossopriza: the spotted-leg clade of Smeringopinae (Araneae, Pholcidae)

Huber

2022

EJT

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The genera Holocnemus Simon, 1873 and Crossopriza Simon, 1893 are revised. Together with Stygopholcus Kratochvíl, 1932 (revised recently) and the newly described genus Maghreba gen. nov., they constitute the spotted-leg clade within the northern clade of Smeringopinae. Males and females in this group are characterized by dark marks on the leg femora and tibiae. The native area of the spotted-leg clade ranges from northern Africa and the Mediterranean to Central Asia and NW India. A morphological cladistic analysis suggests that Holocnemus is paraphyletic while Crossopriza is monophyletic, but morphology seems only partly adequate to resolve phylogenetic relationships convincingly. The genus Holocnemus includes four species, all of which are redescribed: H. pluchei (Scopoli, 1763); H. reini (C. Koch, 1873) comb. nov. (transferred from Pholcus); H. caudatus (Dufour, 1820); and H. hispanicus Wiehle, 1933. The genus Maghreba gen. nov. includes eight species from NW Africa: M. aurouxi (Barrientos, 2019) gen. et comb. nov. (transferred from Holocnemus; redescribed, female newly described) and seven newly described species. The genus Crossopriza includes six previously described species (of which five are redescribed), and 18 newly described species. The Madagascan C. nigrescens Millot, 1946 is synonymized with C. lyoni (Blackwall, 1867). All new species are described on the basis of both sexes.

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Section: Sexual Dimorphismsmentioning

confidence: 69%

“…The projection on the female sternum has been interpreted as a structure that controls the intensity and range of male palpal movements during copulation (Calbacho-Rosa et al 2019b). These authors support their conclusion mainly by the fact that the projection contacts the male clypeus at the moment of maximum palpal contraction.…”

Section: Natural Historymentioning

confidence: 79%

Revisions of Holocnemus and Crossopriza: the spotted-leg clade of Smeringopinae (Araneae, Pholcidae)

Huber

2022

EJT

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“…For its quantification, we followed the guidelines established in Calbacho‐Rosa et al (2013): each contraction that males perform with their pedipalps, squeezing females' abdomen, followed by pedipalp relaxation and return to their initial posture, was considered a pedipalp movement (Video S1). The length of the tibia‐patella segments of the first pair of legs was measured to have an estimate of the body size, as it is common in pholcid spiders (Calbacho‐Rosa et al, 2010, 2012, 2019; Huber, 1996; Jakob, 1994). For this purpose, a picture of each individual's tibia‐patella segment was taken over a graph paper and under a dissecting microscope (Nikon SMZ 1500), with the same magnification which was later used to measure in the ImageJ software (Schneider et al, 2012).…”

Section: Methodsmentioning

confidence: 99%

Genital movements are not restricted to spermatozoa transfer in a haplogyne spider

2021

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Internally fertilized animals are characterized by the transfer of their spermatozoa during copulation. However, the duration of copulation is highly variable, which suggests that they may serve for other functions apart from spermatozoa transfer. For example, during copulation, males can stimulate the female by using genitalic movements and/or by positioning their spermatozoa adequately within the female genitalia. In the spider Holocnemus pluchei, males perform strong squeezes and torsion movements with their pedipalps (part of their genitalia actively related to copulation) inside the female genitalia and transfer their spermatozoa during Phase I of copulation. However, the exact moment in which such transfer occurs and its relation to the pedipalp movements are still unknown. Herein, we first have identified the precise moment when the spermatozoa transfer occurs during phase I and its relation to genital movements by interrupting mating couples at the beginning, at middle and at end of this phase. Subsequently, the spermatozoa number remaining in male genitalia and stored in female genitalia were counted. We detected no relation between the number of genital movements and the spermatozoa number present in both, female and male genitalia and body size. As stated above, male genital movements serve another role during copulation in addition to spermatozoa transfer in a context of post‐copulatory sexual selection; most likely, they stimulate the female in a cryptic female choice framework.

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“…Arachnids have proven to be exceptional models, although morphological quanti cation techniques have generally been applied mainly in systematic or ecomorphological studies (Costa-Schmidt & de Araújo, 2010; Kallal et Bellvert et al, 2022). Some studies have demonstrated the usefulness of these techniques in addressing sexual dimorphism (Fernández-Montraveta et al, 2017; Kallal et al, 2019), as well as the combination with other approaches such as the analysis of phenotypic variation (by the coe cient of variation -CV) of certain characters in some arachnids (Eberhard et al, 1998;Peretti et al, 2001;Calbacho-Rosa et al, 2019;Lai et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Mosaic evolution of grasping and genitalic traits in two sympatric scorpion species with reproductive interference

Oviedo-Diego

Mattoni

Bollatti

et al. 2023

Preprint

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Reproductive interference (RI) can occur when two related species coexist in sympatry, involving sexual attraction, mating, and even hybridization between heterospecifics. Consequently, reproductive key characters of these species may suffer morphological shifts in sympatry to avoid the success of heterospecific sexual interactions, a phenomenon known as reproductive character displacement (RCD). RCD can be promoted by natural selection, although sexual selection pressures can act synergistically or agonistically so that phenotypic variation can respond in different directions and magnitudes to these forces. In turn, the size and shape of characters may respond differentially (mosaic evolution) to these pressures, so the analysis of multiple dimensions in traits is essential to understand the complexity of their phenotypic variability. To date, there are no studies evaluating this topic in scorpions, and two species (Urophonius brachycentrus and U. achalensis) sympatric and synchronous with RI represent an ideal model to evaluate the phenotypic variation and occurrence of RCD. In addition, the populations of these species are found in an altitudinal cline, so environmental factors may also be responsible for explaining their morphological variation. We compared the intra-specific variation, the size and shape of multiple characters involved in courtship, and sperm transfer in individuals from sympatric and allopatric populations using geometric morphometrics. We found asymmetric RCD of several sexual characters for courtship success (grasping structures) and sperm transfer (genital characters). This would evidence the action of natural selection pressures and the existence of a possible mechanism to avoid heterospecific mating success. In addition, we found a pattern of asymmetric morphological variation where one species in the sympatric zone suffered an increase in size in several characters due to environmental factors (pattern of morphological convergence). The convergence of characters combined with RI and a scramble competition mating system could intensify sexual selection pressures on specific characters, which was reflected in their high coefficients of variation. Our results suggest that in this sympatric zone, several selective regimes act differentially on various dimensions of the characters evaluated, which would support a possible mosaic evolution. This comprehensive study illuminates the complexity inherent in the evolution of multi-functional traits in a previously unexplored model, providing novel insights for evaluating traits under multiple selective pressures in animal systems experimenting RI.

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Female secondary sexual traits in spiders: Adaptive interpretations of the sternum projection in the pholcid Holocnemus pluchei

Cited by 8 publications

References 35 publications

Revisions of Holocnemus and Crossopriza: the spotted-leg clade of Smeringopinae (Araneae, Pholcidae)

Revisions of Holocnemus and Crossopriza: the spotted-leg clade of Smeringopinae (Araneae, Pholcidae)

Genital movements are not restricted to spermatozoa transfer in a haplogyne spider

Mosaic evolution of grasping and genitalic traits in two sympatric scorpion species with reproductive interference

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