Neoichnology of the burrowing spiders Gorgyrella inermis (Mygalomorphae: Idiopidae) and Hogna lenta(Araneomorphae: Lycosidae)

Abstract

Burrowing arachnids are important to modern soil ecosystems, but knowledge of these animals in ancient soil ecosystems is limited. In this study, two species of burrowing spiders were studied: Gorgyrella inermis (South African trapdoor spider) and Hogna lenta (field wolf spider). Individuals of each species were studied to investigate their burrowing techniques and behaviors and to categorize the morphologies of their burrows. Experiments were run with variations in sediment density and sediment moisture to evaluate the effects of environmental conditions on burrow morphology. Seven burrow architectures were produced by the spiders: vertical shafts, vertical shafts with terminal chambers, subvertical shafts, subvertical shafts with terminal chambers, Jshaped burrows, Y-shaped burrows, and isolated chambers. All burrow architectures share common features that make them identifiable as spider burrows. Sediment density and moisture had little influence on burrow morphology, but architecture diversity was greatest in sediments of moderate density and moisture. Results from this study show that spiders produce unique biogenic structures that can be distinguished from the burrows of other soil organisms. Data collected from this study can be used to better interpret the paleoecology and evolutionary history of spiders and soil arthropods.

Neoichnology of tarantulas (Araneae: Theraphosidae): Criteria for recognizing spider burrows in the fossil recor

“…Spiders have several types of appendages including eight walking legs, two chelicerae with fangs for delivering venom, and two pedipalps. The pedipalps are used to grab and kill prey, assist in reproduction, and to excavate burrows (Pechenik, 1991;Hils and Hembree, 2015). Silk is produced and manipulated using spinnerets at the posterior of the opisthosoma.…”

“…Spiders use burrows as temporary to permanent dwellings that serve as protection from predators and extreme weather conditions as well as for sites for ambush predation and brooding (Gertsch, 1949;Kotzman, 1990;Pérez-Miles et al, 2005;Machkour M'Rabet et al, 2007;Ferretti and Ferrero, 2008;Hamilton et al, 2012;Hils and Hembree, 2015). Spiders excavate their burrows using both the chelicerae and pedipalps, removing sediment and either carrying and depositing it on the surface or flinging it from the burrow opening (Gertsch, 1949;Hils and Hembree, 2015).…”

“…Spiders excavate their burrows using both the chelicerae and pedipalps, removing sediment and either carrying and depositing it on the surface or flinging it from the burrow opening (Gertsch, 1949;Hils and Hembree, 2015). Burrow walls may be lined with thin to thick sheets of silk depending on the species and the cohesiveness of the sediment (Gertsch, 1949;Pérez-Miles et al, 2005;Hils and Hembree, 2015). The dimensions of the burrow and its complexity also depend on the species, the size of the individual, and the associated behaviors (Gertsch, 1949;Kotzman, 1990;Pérez-Miles et al, 2005;Machkour M'Rabet et al, 2007;Hils and Hembree, 2015).…”

“…Burrow walls may be lined with thin to thick sheets of silk depending on the species and the cohesiveness of the sediment (Gertsch, 1949;Pérez-Miles et al, 2005;Hils and Hembree, 2015). The dimensions of the burrow and its complexity also depend on the species, the size of the individual, and the associated behaviors (Gertsch, 1949;Kotzman, 1990;Pérez-Miles et al, 2005;Machkour M'Rabet et al, 2007;Hils and Hembree, 2015).…”

“…Neoichnological studies of various spiders, scorpions, and whip scorpions have shown that not only do arachnids produce recognizable and distinct biogenic structures, but they are also active agents in soil formation (i.e., Sadler, 1993;Hembree et al, 2012;Schmerge et al, 2013;Hembree, 2013Hembree, , 2014Hils and Hembree, 2015). Mygalomorph spiders appear in the fossil record approximately 240 million years ago, yet they are rarer than fossils of other groups of spiders (Dunlop et al, 2008).…”