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.

A new monotypic Theraphosidae genus, Kankuamo Perafán, Galvis & Pérez-Miles, gen. n., is described from Colombia, with a new type of urticating setae. These setae differ from others principally by having a small distal oval patch of lanceolate reversed barbs. Males of Kankuamo gen. n. additionally differ by having a palpal bulb organ very divergent from all known species, with many conspicuous keels dispersed across the median tegulum to the tip, mostly with serrated edges. Females differ by having spermathecae with a single notched receptacle, with two granulated lobes and several irregular sclerotized longitudinal striations. The new urticating setae, type VII, is characterized, illustrated and its releasing mechanism is discussed. It is hypothesized that these setae are the first in Theraphosinae subfamily whose release mechanism is by direct contact. Kankuamo gen. n. is described and illustrated on the basis of the type species Kankuamo marquezi Perafán, Galvis & Gutiérrez, sp. n., and their remarkable characteristics, morphological affinities and cladistic relationship are analyzed.

We studied the morphology of scopula, claw tufts and a scopula-like feature (pseudoscopula) of tarsi on representatives of all Mygalomorphae spider families. The pseudoscopula is constituted by groups of non-microtriched conical setae. The taxonomic distribution of all these features was studied and mapped on a recent phylogeny of Mygalomorphae and the association of them with the lifestyles of the spiders was analyzed. Adhesive setae, as well as some other setal types found on ventral tarsi are described and characterized. The adhesive face of setae varied in the orientation in different parts of the tarsi, and this variation is more conspicuous in the spiders which only have claw tufts or scopula. We found an association of adhesive scopulae and claw tufts with burrower/cursorial or thin wafer lid trapdoor mygalomorphs as suggested for free hunter spiders, but we found that the pseudoscopula is associated with males of some trap-door and some weavers mygalomorphs. The presence of pseudoscopula widely extended among Mygalomorphae seems to be ancestral for the infraorder. The setal morphology of pseudoscopula suggests chemosensorial function; sparse chemosensory setae were also found in almost all Mygalomorphae. The morphology, functions and evolution of scopula, claw tufts and pseudoscopula are discussed.

No abstract

No abstract