A spider in motion: facets of sensory guidance

Abstract

Spiders show a broad range of motions in addition to walking and running with their eight coordinated legs taking them towards their resources and away from danger. The usefulness of all these motions depends on the ability to control and adjust them to changing environmental conditions. A remarkable wealth of sensory receptors guarantees the necessary guidance. Many facets of such guidance have emerged from neuroethological research on the wandering spider Cupiennius salei and its allies, although sensori-motor control was not the main focus of this work. The present review may serve as a springboard for future studies aiming towards a more complete understanding of the spider's control of its different types of motion. Among the topics shortly addressed are the involvement of lyriform slit sensilla in path integration, muscle reflexes in the walking legs, the monitoring of joint movement, the neuromuscular control of body raising, the generation of vibratory courtship signals, the sensory guidance of the jump to flying prey and the triggering of spiderling dispersal behavior. Finally, the interaction of sensors on different legs in oriented turning behavior and that of the sensory systems for substrate vibration and medium flow are addressed.

Keywords: Mechanoreception; Neuroethology; Sensory control; Sensory ecology; Spider motion.

Fig. 1

The three large Cupiennius species which turned out be perfect “model spiders “. a Cupiennius salei, b C. getazi, c C. coccineus (fotos FG Barth; with permission of SpringerNature; modified from a Barth 2015a; c Barth 2002b.)

Fig. 2

An early experiment on kinesthetic (idiothetic) orientation of C.salei. Example of a return path of C. salei from “start “ to the site of prey capture after the relocation of the fly. a Intact animal, successful return; b animal with all tibial lyriform organs destroyed, unsuccessful return. At point 1–12 the spider paused and/or turned. (modified: a, b. From Seyfarth and Barth ; with permission of SpringerNature)

Fig. 3

Proprioreceptive hair sensilla of C. salei at the tibia-metatarsus joint. a Movement of the joint (note joint angle β) during slow locomotion at a speed of 2 cm/s; frame-to-frame video analysis. Red line indicates the mean angle at which the hair sensilla start to deflect each other. b Position of the proprioreceptive hair sensilla ventro-laterally on tibia and metatarsus (see red circles). c SEM picture showing the microtrichs on the hair shaft of the tibial (top) and metatarsal sensilla (below) at a joint angle β of 135° (with permission of SpringerNature; modified from Schaber and Barth 2015)

Fig. 4

Body raising upon tactile stimulation by an obstacle. a The spider approaches (arrow) the obstacle (above green symbol) from the left side. b It raises its body upon tactile stimulation of mechanosensitive hair sensilla located ventrally on its legs and prosoma. (With permission from Aarhus University Press; modified from Seyfarth 2002)

Fig. 5

Vibratory courtship signals. a, b Movements (arrows) of the opisthosoma (C. getazi) of a courting male. Note that the opisthosoma does not touch the substrate. c Vibrations introduced by the spider into the substrate (leaf of a bromeliad). (with permission of SpringerNature (a, b) and Birkhäuser (c); a, b. Dierkes and Barth 1995; c Barth 1997)

Fig. 6

Catching flying prey. a A tethered humming fly approaches (arrow) a juvenile C. salei sitting on a bromeliad leaf with its front (green asterix) oriented away from the fly (above). The spider turns towards the approaching fly when it is still a few centimeters away (middle). It finally jumps into the air to catch the fly when its position is above the closest tarsus (below). b Airflow measured above the spider tarsus and showing the abrupt change in flow turbulence which triggers the spider’s timely jump. (with permission of SpringerNature; modified from a Barth ; b Klopsch et al. 2013)

Fig. 7

Drop and swing dispersal behavior. a Upon exposure to adequate airflow (arrows) spiderlings drop from their dwelling plant and swing on a lengthening thread in the wind (1,2,3). When touching a nearby substrate they attach to it. Inset: C. getazi spiderling, 9 days after leaving the egg sac. b Trichobothria of a spiderling (C.salei) at the age of 9 days after leaving the egg sac. c Spiderlings in a tangle of silken threads spun by the female at the time of the spiderlings leaving the egg sac. Scale bars in a and b 1 mm (with permission of SpringerNature; modified from a Barth et al. ; b Barth ; c foto FG Barth)

Fig. 8

Turning towards or away from a stimulus source. a Turning movement (arrow) of C. salei towards a vibratory stimulus applied to the tarsus of its right hindleg. Quantification of the spider’s motion by measuring the parameters indicated. α stimulus angle, B site of stimulation, β turning angle, γ error angle, A center of prosoma. b Behavioral thresholds of C. salei for its approach (prey capture) and withdrawal (escape) reaction to stimulation with substrate vibrations. The approach reaction has a considerably lower threshold than the escape reaction and is lower for band-limited noise stimulation (bars) than for sinusoidal stimulation (circles). (With permission of SpringerNature; from Hergenröder and Barth 1983a, b)