20:
143:
241:. This is consistent with the very thin pit membrane, which would allow incoming infrared radiation to quickly and precisely warm a given ion channel and trigger a nerve impulse, as well as the vascularization of the pit membrane in order to rapidly cool the ion channel back to its original temperature state. While the molecular precursors of this mechanism are found in other snakes, the protein is both expressed to a much lower degree and much less sensitive to heat.
1295:
215:, wherein the location of a source of thermal radiation is determined by the location of the radiation on the membrane of the heat pit. However, studies that have visualized the thermal images seen by the facial pit using computer analysis have suggested that the resolution is extremely poor. The size of the opening of the pit results in poor resolution of small, warm objects, and coupled with the pit's small size and subsequent poor
139:. The purpose of the vasculature, in addition to providing oxygen to the receptor terminals, is to rapidly cool the receptors to their thermo-neutral state after being heated by thermal radiation from a stimulus. Were it not for this vasculature, the receptor would remain in a warm state after being exposed to a warm stimulus, and would present the animal with afterimages even after the stimulus was removed.
1307:
254:
infrared detection of prey. It was previously assumed that the organ evolved specifically for prey capture. However, recent evidence suggests that the pit organ is also used for thermoregulation. In an experiment that tested snakes' abilities to locate a cool thermal refuge in an uncomfortably hot maze, all pit vipers were able to locate the refuge quickly and easily, while
208:
and the firing rate of the nerves in the pit organ will return to normal. If that warm object is then removed, the pit organ will now register the space that it used to occupy as being colder, and as such the firing rate will be depressed until it adapts to the removal of the object. The latency period of adaptation is approximately 50 to 150 ms.
58:. The more advanced infrared sense of pit vipers allows these animals to strike prey accurately even in the absence of light, and detect warm objects from several meters away. It was previously thought that the organs evolved primarily as prey detectors, but recent evidence suggests that it may also be used in
219:, the image produced is of extremely low resolution and contrast. It is known that some focusing and sharpening of the image occurs in the lateral descending trigeminal tract, and it is possible that the visual and infrared integration that occurs in the tectum is also used to help sharpen the image.
194:
in the tectum respond to visual or infrared stimulation alone; others respond more strongly to combined visual and infrared stimulation, and still others respond only to a combination of visual and infrared. Some neurons appear to be tuned to detect movement in one direction. It has been found that
207:
The pit organ will adapt to a repeated stimulus; if an adapted stimulus is removed, there will be a fluctuation in the opposite direction. For example, if a warm object is placed in front of the snake, the organ will increase in firing rate at first, but after a while will adapt to the warm object
253:
prey such as rodents and birds. Blind or blindfolded rattlesnakes can strike prey accurately in the complete absence of visible light, though it does not appear that they assess prey animals based on their body temperature. In addition, snakes may deliberately choose ambush sites that facilitate
203:
of the organ. The thermal radiation above a given threshold causes an increase in the temperature of the nerve fiber, resulting in stimulation of the nerve and subsequent firing, with increased temperature resulting in increased firing rate. The sensitivity of the nerve fibers is estimated to be
258:
were unable to do so. This finding suggests that the pit vipers were using their pit organs to aid in thermoregulatory decisions. It is also possible that the organ even evolved as a defensive adaptation rather than a predatory one, or that multiple pressures have contributed to the organ's
236:
which is a temperature sensitive ion channel. It senses infrared signals through a mechanism involving warming of the pit organ, rather than chemical reaction to light. In structure and function it resembles a biological version of warmth-sensing instrument called a
102:), while boas and pythons have three or more smaller pits lining the upper and sometimes the lower lip, in or between the scales (labial pits). Those of the pitvipers are the more advanced, having a suspended sensory membrane as opposed to a simple pit structure.
118:
stretched across it. Behind the membrane, an air-filled chamber provides air contact on either side of the membrane. The pit membrane is highly vascular and heavily innervated with numerous heat-sensitive receptors formed from terminal masses of the
198:
The nerve fibers in the pit organ are constantly firing at a very low rate. Objects that are within a neutral temperature range do not change the rate of firing; the neutral range is determined by the average thermal radiation of all objects in the
227:
In spite of its detection of infrared light, the infrared detection mechanism is not similar to photoreceptors - while photoreceptors detect light via photochemical reactions, the protein in the pits of snakes is a type of
718:
Gracheva, Elena O.; Nicholas T. Ingolia; Yvonne M. Kelly; Julio F. Cordero-Morales; Gunther
Hollopeter; Alexander T. Chesler; Elda E. Sánchez; John C. Perez; Jonathan S. Weissman; David Julius (15 April 2010).
175:, information from the labial pit is sent directly to the contralateral optic tectum via the lateral descending trigeminal tract, bypassing the nucleus reticularus caloris.
679:
Bakken, George S.; Krochmal, Aaron R. (2007), "The imaging properties and sensitivity of the facial pits of pitvipers as determined by optical and heat-transfer analysis",
178:
It is the optic tectum of the brain which eventually processes these infrared cues. This portion of the brain receives other sensory information as well, most notably
131:
lacks the suspended membrane and consists more simply of a pit lined with a membrane that is similarly innervated and vascular, though the morphology of the
952:
Shine, R; Sun, L; Kearny, M; Fitzgerald, M (2002). "Thermal correlates of foraging-site selection by
Chinese pit-vipers (Gloydius shedaoensis, Viperidae)".
23:
A python (top) and rattlesnake illustrating the positions of the pit organs. Arrows pointing to the pit organs are red; a black arrow points to the nostril.
195:
the snake's visual and infrared maps of the world are overlaid in the optic tectum. This combined information is relayed via the tectum to the forebrain.
123:(terminal nerve masses, or TNMs). The receptors are therefore not discrete cells, but a part of the trigeminal nerve itself. The labial pit found in
359:
Goris, RC; Terashima, S (1973). "Central response to infra-red stimulation of the pit receptors in a crotaline snake, Trimeresurus flavoviridis".
1335:
394:
425:"Heat in evolution's kitchen: evolutionary perspectives on the functions and origin of the facial pit of pitvipers (Viperidae: Crotalinae)"
579:
Hartline, PH; L Kass; MS Loop (1978-03-17). "Merging of modalities in the optic tectum: infrared and visual integration in rattlesnakes".
259:
development. The use of the heat pit to direct thermoregulation or other behaviors in pythons and boas has not yet been determined.
999:
1027:
536:
Newman, EA; Gruberg, ER; Hartline, PH (1980). "The infrared trigemino-tectal pathway in the rattlesnake and in the python".
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98:. Most superficially, pitvipers possess one large pit organ on either side of the head, between the eye and the nostril (
1350:
1044:
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273:
501:
Goris, CR; et al. (2003). "The microvasculature of python pit organs: morphology and blood flow kinetics".
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Schraft, HA; Goodman, C; Clark, RW (2017). "Do free-ranging rattlesnakes use thermal cues to evaluate prey?".
992:
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Bullock, TH; Cowles, RB (1952). "Physiology of an infrared receptor: the facial pit of pit vipers".
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304:"Integration of visual and infrared information in bimodal neurons in the rattlesnake optic tectum"
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778:"The thermal background determines how the infrared and visual systems interact in pit vipers"
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817:
Kardong, KV; Mackessy, SP (1991). "The strike behavior of a congenitally blind rattlesnake".
470:
Campbell JA, Brodie ED Jr. 1992. Biology of the
Pitvipers. Texas: Selva. 467 pp. 17 plates.
211:
The facial pit actually visualizes thermal radiation using the same optical principles as a
163:
via the lateral descending trigeminal tract. From there, it is relayed to the contralateral
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of the structure is similar between the two lineages, but they differ in gross structural
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evolved independently in three different groups of snakes, consisting of the families of
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1992. Herpetology: Third
Edition. Pearson Prentice Hall: Pearson Education, Inc., 2002.
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897:"Infrared-sensing snakes select ambush orientation based on thermal backgrounds"
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Greene HW. 1992. The ecological and behavioral context for pitviper evolution.
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detection, making it a more general-purpose sensory organ than was supposed.
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90:. It evolved once in pitvipers and multiple times in boas and pythons. The
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Krochmal, Aaron R.; George S. Bakken; Travis J. LaDuc (15 November 2004).
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Infrared sensing snakes use pit organs extensively to detect and target
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In all cases, the facial pit is innervated by the trigeminal nerve. In
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114:, the heat pit consists of a deep pocket in the rostrum with a
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1336:
Infrared vision in snakes summary article (archived 7/15/2013)
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50:
allows these animals to essentially "see" radiant heat at
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Chen, Q; Liu, Y; Brauth, SE; Fang, G; Tang, Y (2017).
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721:"Molecular basis of infrared detection by snakes"
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1331:Physorg article on Infrared vision in snakes
895:Schraft, HA; Bakken, GS; Clark, RW (2019).
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46:(pit vipers). What is commonly called a
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245:Behavioral and ecological implications
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395:"Snake infrared detection unravelled"
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538:The Journal of Comparative Neurology
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230:transient receptor potential channel
854:Journal of Comparative Physiology A
146:Diagram of the Crotaline pit organ.
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302:Newman, EA; Hartline, PH (1981).
135:differs between these snakes and
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274:Infrared sensing in vampire bats
1050:Central pattern generator (CPG)
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888:
845:
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782:Journal of Experimental Biology
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681:Journal of Experimental Biology
429:Journal of Experimental Biology
361:Journal of Experimental Biology
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1244:Frog hearing and communication
647:10.1126/science.115.2994.541-a
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295:
1:
966:10.1016/S0306-4565(02)00009-8
515:10.1016/s0026-2862(03)00003-7
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182:stimulation, but also motor,
42:(pythons), and the subfamily
7:
262:
16:Sensory abilities in snakes
10:
1392:
1249:Infrared sensing in snakes
1234:Jamming avoidance response
954:Journal of Thermal Biology
921:10.1038/s41598-019-40466-0
105:
1351:Electromagnetic radiation
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1216:
1195:
1099:
1015:
866:10.1007/s00359-017-1239-8
74:The facial pit underwent
1254:Caridoid escape reaction
1107:Theodore Holmes Bullock
328:10.1126/science.7256281
70:Phylogeny and evolution
1264:Surface wave detection
941:– via in review.
819:Journal of Herpetology
601:10.1126/science.628839
503:Microvascular Research
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54:between 5 and 30
24:
1080:Anti-Hebbian learning
550:10.1002/cne.901910309
145:
27:The ability to sense
22:
1157:Bernhard Hassenstein
1090:Ultrasound avoidance
1065:Fixed action pattern
1028:Coincidence detector
788:(Pt 17): 3103–3109.
435:(Pt 24): 4231–4238.
1224:Animal echolocation
1162:Werner E. Reichardt
1112:Walter Heiligenberg
913:2019NatSR...9.3950S
745:10.1038/nature08943
737:2010Natur.464.1006G
731:(7291): 1006–1011.
639:1952Sci...115..541B
593:1978Sci...199.1225H
587:(4334): 1225–1229.
401:on 28 December 2016
373:10.1242/jeb.58.1.59
320:1981Sci...213..789N
223:Molecular mechanism
204:<0.001 °C.
1187:Fernando Nottebohm
1085:Sound localization
1060:Lateral inhibition
901:Scientific Reports
795:10.1242/jeb.155382
694:10.1242/jeb.006965
148:
76:parallel evolution
25:
1321:
1320:
1208:Slice preparation
1070:Krogh's Principle
1045:Feature detection
687:(16): 2801–2810,
633:(2994): 541–543.
442:10.1242/jeb.01278
92:electrophysiology
32:thermal radiation
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1274:Mechanoreception
1269:Electroreception
1182:Masakazu Konishi
1147:Jörg-Peter Ewert
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399:the original
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165:optic tectum
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151:Neuroanatomy
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1203:Patch clamp
1172:Eric Kandel
1152:Franz Huber
1023:Feedforward
907:(1): 3950.
256:true vipers
133:vasculature
100:loreal pits
52:wavelengths
1345:Categories
1177:Nobuo Suga
1092:in insects
405:20 January
290:References
269:Crotalinae
157:crotalines
137:crotalines
112:pit vipers
44:Crotalinae
40:Pythonidae
239:bolometer
82:and some
80:pitvipers
48:pit organ
1356:Ethology
1300:Category
1040:Instinct
1016:Concepts
939:30850649
874:29218413
804:28855322
763:20228791
703:17690227
663:30122231
655:17731960
566:10279222
523:12711259
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