Visual odometry in the wolf spider Lycosa tarantula (Araneae: Lycosidae)

Abstract

The wolf spider Lycosa tarantula homes using path integration. The angular component of the displacement is measured using a polarized-light compass associated with the functioning of the anterior median eyes. However, how L. tarantula estimates the linear component of the displacement was not known prior to this investigation. The ability of L. tarantula to gauge the distance walked after being displaced from its burrow was investigated using experimental channels placed in an indoor setup. Firstly, we manipulated the perception of visual stimuli by covering all the spider's eyes. Secondly, we changed the optic flow supplied by a black-and-white grating (λ=2 cm) perceived either in the lateral or in the ventral field of view. Finally, the period of the lateral or ventral grating was changed from λ=2 cm to λ=1 cm. Our results indicate that visual information contributes to distance estimation because when the spider's eyes were covered, the spiders tended to search for the burrow at very variable distances. This visual information is created by the motion of the image as the spider walks, the motion in the lateral field of view being the most important. The preference of a lateral optic flow over the ventral flow can be explained by the difference in the resolution capacity of the posterior lateral eyes and the anterior lateral eyes.

The behavioral ecology of amblypygids

“…The distances over which amblypygids have been shown to home, in combination with the complex habitats through which they travel (e.g., lowland tropical rainforests), make these feats quite impressive. Similar homing activities have been studied extensively in the wolf spider Lycosa tarantula (Linnaeus, 1758) (Ortega-Escobar 2002Reyes-Alcubilla et al 2009;Ortega-Escobar & Ruiz 2014) and the wandering desert spider Leucorchestris arenicola Lawrence, 1962 (Norgaard et al 2003(Norgaard et al , 2007(Norgaard et al , 2008(Norgaard et al , 2012Norgaard 2005). Like many of their arthropod relatives (e.g., ants, bees, crabs, etc.…”

“…Like many of their arthropod relatives (e.g., ants, bees, crabs, etc. ; reviewed in Cheng (Ortega-Escobar 2002Norgaard et al 2007Norgaard et al , 2008Norgaard et al , 2012Reyes-Alcubilla et al 2009;Ortega-Escobar & Ruiz 2014). In contrast to their spider relatives, however, neither path integration nor vision appears necessary for amblypygid homing, though more work is needed to further explore the putative role of vision (Hebets et al 2014a, b).…”

Role of the different eyes in the visual odometry in the wolf spider Lycosa tarantula (Araneae, Lycosidae)

“…The required sample size was determined from previous data gathered in comparable conditions (Ortega-Escobar and Ruiz, 2014). Assuming a nominal significance level α=0.05 and a power level of (1−β)=0.80, the need to detect differences corresponding to an effect size of 0.348 with a correlation between repeated measures of 0.56, and using repeated measures ANOVA with two groups and 10 repeated measurements, the total number of measurements needed would be n=8.…”

“…How do they do this? In our previous study (Ortega-Escobar and Ruiz, 2014), female L. tarantula were placed in an experimental channel in an indoor setup and were made to walk from their burrow to a point 30 cm from the superior part of it. They were then transferred to an experimental channel (from which all silk cues had been removed) at the same distance from the burrow.…”

“…In control experiments, spiders were made to walk through channels with plain white walls and substratum and with all eyes uncovered or all eyes covered. When all eyes were covered and the spiders could use only proprioceptive information, there was more variation in the distance walked before they began searching for the burrow or making Turner's loops (Ortega-Escobar and Ruiz, 2014;Wehner, 2016), also called 'search loops' (Wehner and Srinivasan, 1981). The optic flow induced by a grating (λ=2 cm) perpendicular to the direction of walking had a great influence on the distance walked by L. tarantula but the effect was more apparent when the grating was lateral than when it was over the substratum.…”