Tarantulas (Araneae: Theraphosidae) use different adhesive pads complementarily during climbing on smooth surfaces: experimental approach in eight arboreal and burrower species

Abstract

Tarantulas are large spiders with adhesive setae on their legs, which enable them to climb on smooth vertical surfaces. The mechanism proposed to explain adhesion in tarantulas is anisotropic friction, where friction is higher when the leg pushes than when it pulls. However, previous studies and measurements of adhesion in theraphosids were performed using dead specimens. To test their ability to climb, we studied static friction of live theraphosid spiders on different surfaces and at different inclines. We compared burrower with arboreal species to test the hypothesis of higher friction in arboreal tarantulas. We found a complementary participation of claw tufts and scopula of anterior and posterior legs when the tarantula climbs. The mechanics of climbing in association with the biological characteristics of the species are discussed.

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

“…Male G. rosea have a higher α c than females. This result does not agree with results obtained with the white collared tarantula Eupalaestrus weijenberghi in which males have lower friction than females on glass, which is interpreted because the intense locomotion of males produces body deterioration and, consequently, wastage of adhesive pads when reducing friction values (Pérez-Miles et al, 2015). Also, no differences are found in α c among sexes in the eight other species examined, although the number of individuals studied for each species is low.…”

“…Considering only α c < π/2 radians and estimating the friction coefficient by a force diagram (Hecht, ), values of 9.96 ± 9.76 are obtained for male G. rosea and 2.43 ± 1.88 for female G. rosea . The angle values in the present study are similar to those reported by Pérez‐Miles et al () for several Theraphosidae spiders on a glass surface but do not agree with those reported for Aphonopelma seemanni (Theraphosidae), with values lower than 1.0 (Niederegger & Gorb, ). However, the study by Niederegger & Gorb () uses dead spiders and the friction coefficient is estimated only for isolated metatarsi connected to force transductors.…”

Morphology and evolution of scopula, pseudoscopula and claw tufts in Mygalomorphae (Araneae)

“…Pulling adhesion is expected in claw tufts or the extreme of tarsal scopula, so these features could be involved in both prey capture and adhesion for locomotion. When the spider climbs vertically upward, the adhesion may be produced by apical adhesive setae of forelegs pulling and proximal scopula of hind legs pushing (Pérez-Miles et al 2015) with a similar dynamics as proposed by and Wohlfart et al (2014), for Cupiennius salei (Keyserling 1877). Inversely, when the locomotion is oriented downward, anterior scopulae push and posterior claw tufts (or distal scopulae) pull.…”

“…The presence of adhesive setae strongly suggests the importance of adhesive setae in locomotion and mainly to climb on inclined or vertical surfaces. Mygalomorphs walk on horizontal surfaces using their tarsal tips, but when climbing on vertical surfaces a close contact is observed between most part of tarsi which push on the surface (Pérez-Miles et al 2015). Arboreal species of Mygalomorphae (e.g.…”

“…The morphology of sticky setae, functions, mechanics and association with lifestyle was exhaustively studied (Homann 1957;Foelix and Chu-Wang 1975;Hill 1977;Rovner 1978;Kesel et al 2003Kesel et al , 2004Niederegger andGorb 2006, Varenberg et al 2010;Foelix 2011;Foelix et al 2012;Keane et al 2012;Gorb 2012a, b, 2015;Niederegger 2013;Wohlfart et al 2014;Lapinski et al 2015;Pérez-Miles et al 2015); these studies mostly focused on Araneomorphae. However, fine structure and function of adhesive setae in mygalomorphs are severely understudied.…”