Consequences of sexual size dimorphism on energetics and locomotor performance ofGrammostola rosea(Araneae; Teraphosidae)

Abstract

Most male spiders are smaller than females; during sexual maturity, males change their behaviour, abandoning their web or nest to seek out receptive females actively, whereas females stalk prey near their web or nest and tend not to move away from it. Considering this behavioural difference to be associated with increased locomotor activity at maturity, it may be hypothesized that males will have traits that increase locomotor performance. The present study examines the kinetics and energetics of the movements of the mygalomorph spider Grammostola rosea Walckenaer, a large spider with sexual size dimorphism. It is found that males have a higher maximum aerobic speed, average speed, distance travelled and critical angle of climbing than females, indicating better performance. Males also have lower costs of transport than females. These results support the hypothesis that sexual dimorphism in wandering spiders with active males, which are characterized by smaller body size and longer legs than the larger and more static females, is associated with low transport cost, high velocity and better locomotor performance.

Variation in movement: multiple locomotor gaits in Neotropical harvestmen

“…We did not find evidence that any measured intrinsic factors predicted the gaits performed. No morphological features (leg length or body area) predicted gait type, as has been shown for other animals (Heglund et al, 1974;Pontzer, 2007;Grossi et al, 2016). Males and females performed gaits with similar frequency, providing evidence that sex did not influence locomotion.…”

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“…CoT) recorded in Theraphosidae was comparable to that of other species of the same mass (Herreid & Full, 1980;Anderson & Prestwich, 1985;Shillington & Peterson, 2002;Grossi et al, 2016a). Therefore the mechanical efficiency (mechanical work / metabolic cost) should be lower than in other species of comparable mass.…”

“…The hardness of the components make difficult to modify the L S with the participation of other body parts, as happens in animals with endoskeleton (Griffin, Main & Farley, 2004). Considering that the F S is related with muscular work (Heglund & Taylor, 1988), and limited by the muscular physiology (Alexander, 2003), higher maximum speeds are achieved by spider species (or genders, in case of sexual dimorphism) with longer legs (Grossi & Canals, 2015;Grossi et al, 2016a).…”

“…The low magnitude of mechanical energy involved in locomotion would facilitate long displacements without feeding (Pérez-Miles et al, 2005). Indeed, there is a relationship between the mechanical work of locomotion and the metabolic energy expenditure, and low metabolic cost of transport is one of the characteristics associated to the lifestyle of wandering spider males (Grossi et al, 2016a). However, the low cost underlined these authors is an absolute value, influenced by the lower body mass of wandering males with respect to females.…”

“…However, the contribution of these features to climbing is subject to controversy (Pérez-Miles, Perafán & Santamaría, 2015;Pérez-Miles et al, 2017). There are few studies of spider locomotion on incline, mainly focused on the performance at maximum speed (Moya-Laraño et al, 2009;Prenter, Pérez-Staples & Taylor, 2010;Prenter, Fanson & Taylor, 2012;Grossi et al, 2016a;Grossi et al, 2016b). Pérez-Miles, Perafán & Santamaría (2015) analysed the role of adhesive setae to improve locomotion, on level and at different gradients of incline, in different species, using glass and Teflon as substrate for their trials.…”