Reduced Performance of Prey Targeting in Pit Vipers with Contralaterally Occluded Infrared and Visual Senses

Qin Chen,Steven E Brauth,Yezhong Tang,Li Ding,Huanhuan Deng,Andrew Iwaniuk

doi:10.1371/journal.pone.0034989

Abstract

Both visual and infrared (IR) senses are utilized in prey targeting by pit vipers. Visual and IR inputs project to the contralateral optic tectum where they activate both multimodal and bimodal neurons. A series of ocular and pit organ occlusion experiments using the short-tailed pit viper (Gloydius brevicaudus) were conducted to investigate the role of visual and IR information during prey targeting. Compared with unoccluded controls, snakes with either both eyes or pit organs occluded performed more poorly in hunting prey although such subjects still captured prey on 75% of trials. Subjects with one eye and one pit occluded on the same side of the face performed as well as those with bilateral occlusion although these subjects showed a significant targeting angle bias toward the unoccluded side. Performance was significantly poorer when only a single eye or pit was available. Interestingly, when one eye and one pit organ were occluded on opposite sides of the face, performance was poorest, the snakes striking prey on no more than half the trials. These results indicate that, visual and infrared information are both effective in prey targeting in this species, although interference between the two modalities occurs if visual and IR information is restricted to opposite sides of the brain.

Highlights

The pit organs of crotaline and boid snakes are unique sensory structures that can ‘‘see’’ targets through infrared (IR) receptors
In pit vipers, blocking both the visual and IR sensory organs simultaneously disrupts predatory behavior, consistent with the idea that visual and/or infrared cues are necessary for optimal prey targeting [9]
Other studies show that the infrared organ are as important as the eyes for orientation towards prey before strike initiation [10,11]

Summary

Introduction

The pit organs of crotaline and boid snakes are unique sensory structures that can ‘‘see’’ targets through infrared (IR) receptors. Some other species have been shown to detect IR radiation [3], the snake IR sensory system is the only known biological structure to form images using IR information [4,5,6]. In pit vipers, blocking both the visual and IR sensory organs simultaneously disrupts predatory behavior, consistent with the idea that visual and/or infrared cues are necessary for optimal prey targeting [9]. Neuroanatomical studies have shown that visual and IR information are both projected to the contralateral midbrain tectum, converging on bimodal neurons in IR-sensitive snakes [12,13,14] raising the question of whether these sensory inputs work in a complementary way [15]

Methods

Results

Conclusion