The structure and function of the facial pit of the pit vipers

Lynn, W. Gardner

doi:10.1002/aja.1000490105

Cited by 60 publications

(37 citation statements)

References 18 publications

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“…The facial pit innervation has been described by Lynn (1931). There are three branches of the trigeminal nerve, the ophthalmic from which we have never recorded, the superficial and the deep branches of the supramaxillary division, both of which we have used but chiefly the former.…”

Section: Infra-red Receptor 49supporting

confidence: 43%

Properties of an infra‐red receptor

Bullock¹,

Diecke²

1956

The Journal of Physiology

225

130

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Section: Infra-red Receptor 49supporting

confidence: 43%

Properties of an infra‐red receptor

Bullock¹,

Diecke²

1956

The Journal of Physiology

225

130

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“…Warm receptors in the pit membrane have a largely phasic/accommodative response, and primarily detect temperature contrasts (Bullock and Diecke, 1956;Van Dyke and Grace, 2010). Sensory output is transmitted to the brain via the trigeminal nerve (Lynn, 1931). Behaviorally, the facial pit appears to function as an 'eye' because it can compensate for visual deprivation (Kardong and Berkhoudt, 1999;Kardong and Mackessy, 1991).…”

Section: Introductioncontrasting

confidence: 38%

Analytical methods for the geometric optics of thermal vision illustrated with four species of pitvipers

Bakken

Colayori

Duong

2012

Journal of Experimental Biology

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SUMMARYThe pitviper facial pit is a pinhole camera-like sensory organ consisting of a flask-shaped cavity divided into two chambers by a suspended membrane. Neurophysiological studies and simplified optical models suggest that facial pits detect thermal radiation and form an image that is combined with visual input in the optic tectum to form a single multispectral image. External pit anatomy varies markedly among taxonomic groups. However, optical function depends on unknown internal anatomy. Therefore, we developed methods for relating anatomy to optical performance. To illustrate, we constructed detailed anatomical models of the internal anatomy of the facial pits of four individuals of four pitviper species using X-ray tomography sections of fresh material. We used these models to define the point spread function, i.e. the distribution of radiation from a point source over the pit membrane, for each species. We then used optical physics, heat transfer physics and computational image processing to define the thermal image formed on the pit membrane for each species. Our computed pit membrane images are consistent with behavioral observations if the sensitivity of membrane receptors equals the most sensitive (ca. 0.001°C) laboratory estimates. Vignetting (variation in optical aperture size with view angle) and differences between body and environmental temperatures can create temperature variation across the membrane that greatly exceeds image temperature contrasts, potentially impairing imaging. Spread functions plotted versus source point azimuth and elevation show distinct patterns that suggest new research directions into the relationships among the optical anatomy, ecology, behavior and sensory neurophysiology of pitvipers. Supplementary material available online at

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“…In addition, although it is known that the pit membrane is innervated by three branches of the trigeminal nerve, the ophthalmic nerve (V1), the superficial branch of the maxillary nerve (V2s), and the deep branch of the maxillary nerve (V2d) (Lynn, 1931;Kishida et al, 1982), and that each branch innervates a discrete area of the pit membrane (Goris et al, 1989; cf. Fig.…”

mentioning

confidence: 47%

Microvasculature of crotaline snake pit organs: Possible function as a heat exchange mechanism

et al. 1999

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The infrared sensory membranes of the pit organs of pit vipers have an extremely rich capillary vasculature, which has been noted passim in the literature, but never illustrated or studied in detail. We rendered the pit vasculature visible in various ways, namely, by microinjection of India ink, by a combination of ink and succinate dehydroge-nase staining, and by making resin casts for scanning electron microscope study. We also used transmission electron microscopy for identifying the types (arterioles, venules, capillaries) of blood vessels. Then we compared the pit vasculature with that of the retina and the dermis. Good visualization of the vasculature was obtained with both ink and resin injection. Arterioles, venules, and capillaries could be distinguished with all methods used. The monolayer vasculature was denser in the pit membrane than in the retina or skin. Each loop of the network enclosed a small number of infrared receptors so that all receptors were in contact with a capillary on at least one side. The forward-looking areas of the pit had a denser network than side-looking areas. Since infrared rays cause nerve impulses by raising the temperature of individual receptors, the capillary network functions not only as a supplier of energy but also as a cooling mechanism to reduce afterimages. Thus the denser network in the forward-looking areas causes these areas to be more sensitive and have better image resolution than the rest of the membrane.

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The structure and function of the facial pit of the pit vipers

Cited by 60 publications

References 18 publications

Properties of an infra‐red receptor

Properties of an infra‐red receptor

Analytical methods for the geometric optics of thermal vision illustrated with four species of pitvipers

Microvasculature of crotaline snake pit organs: Possible function as a heat exchange mechanism

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