Patterns of heating in the body trunk and tail of Crocodylus porosus

Drane, C.R.; Webb, Grahame J. W.; Heuer, Paige

doi:10.1016/0306-4565(77)90017-1

Cited by 7 publications

(8 citation statements)

References 5 publications

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“…Crocodilians are a highly apomorphic group yet show conserved vascular patterns that have, to a limited degree, been tested for involvement in thermoregulatory processes. Physiological processes such as heart rate hysteresis and shunting blood to either the periphery or core have received the most attention (Smith, 1976(Smith, , 1979Drane et al 1977;Smith et al 1978;Franklin & Seebacher, 2003;Seebacher & Franklin, 2004, 2007. Unfortunately, selective head or brain cooling has not been tested in crocodilians as it has been in mammals, birds, and squamates, although the findings presented here suggest that such studies are warranted.…”

Section: Discussionmentioning

confidence: 95%

“…Whereas the behavioral thermoregulatory strategies of crocodilians are well known (e.g. sliding into the water when overheated; Smith, 1976Smith, , 1979Drane et al 1977;Smith et al 1978Smith et al , 1984Fraser & Grigg, 1984;Franklin & Seebacher, 2003;Seebacher & Franklin, 2004, 2007, it is possible that the study of such behaviors may have resulted in more strictly physiological thermoregulatory strategies being overlooked. The anatomical findings on blood flow though the nasal, oral, and orbital regions need to be investigated by experimental physiologists to determine the role and efficiency of evaporative cooling and its pathways to neurosensory tissues.…”

Section: Discussionmentioning

confidence: 99%

“…For example, Johnson (1974) reported that a temperature differential between the head and body occurs in crocodilians such that, similar to other reptiles (Crawford, 1972), the head warms slower than the body under certain conditions, especially during gaping. The number of publications focusing on behavioral thermoregulation in crocodilians is high (Smith, 1976(Smith, , 1979Drane et al 1977;Smith et al 1978Smith et al , 1984Fraser & Grigg, 1984;Franklin & Seebacher, 2003;Seebacher & Franklin, 2004, 2007 and it is well understood how crocodilians control body temperature during warming and cooling. Yet, similar to squamates, crocodilians have distinct vascular abilities that are directly related to adjusting body temperatures and, like other reptiles, may have evolved a circulatory system that elevates a function in thermoregulation over oxygen delivery (Pough, 1980;Seebacher & Franklin, 2004, 2007.…”

Section: Introductionmentioning

confidence: 99%

“…Yet, similar to squamates, crocodilians have distinct vascular abilities that are directly related to adjusting body temperatures and, like other reptiles, may have evolved a circulatory system that elevates a function in thermoregulation over oxygen delivery (Pough, 1980;Seebacher & Franklin, 2004, 2007. Crocodilians have also been shown to vasodilate peripheral blood vessels and increase heart rate to increase temperature quickly and to vasoconstrict peripheral blood vessels and reduce heart rate to slow the shedding of heat and maintain body temperature (Smith, 1976(Smith, , 1979Drane et al 1977;Smith et al 1978;Franklin & Seebacher, 2003;Seebacher & Franklin, 2004, 2007. The number of publications investigating physiological sites of heat exchange is small.…”

Section: Introductionmentioning

confidence: 99%

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Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

2016

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Extant crocodilians are a highly apomorphic archosaur clade that is ectothermic, yet often achieve large body sizes that can be subject to higher heat loads. Therefore, the anatomical and physiological roles that blood vessels play in crocodilian thermoregulation need further investigation to better understand how crocodilians establish and maintain cephalic temperatures and regulate neurosensory tissue temperatures during basking and normal activities. The cephalic vascular anatomy of extant crocodilians, particularly American alligator (Alligator mississippiensis) was investigated using a differential-contrast, dual-vascular injection technique and high resolution X-ray micro-computed tomography (μCT). Blood vessels were digitally isolated to create representations of vascular pathways. The specimens were then dissected to confirm CT results. Sites of thermal exchange, consisting of the oral, nasal, and orbital regions, were given special attention due to their role in evaporative cooling and cephalic thermoregulation in other diapsids. Blood vessels to and from sites of thermal exchange were studied to detect conserved vascular patterns and to assess their ability to deliver cooled blood to neurosensory tissues. Within the orbital region, both the arteries and veins demonstrated consistent branching patterns, with the supraorbital, infraorbital, and ophthalmotemporal vessels supplying and draining the orbit. The venous drainage of the orbital region showed connections to the dural sinuses via the orbital veins and cavernous sinus. The palatal region demonstrated a vast plexus that comprised both arteries and veins. The most direct route of venous drainage of the palatal plexus was through the palatomaxillary veins, essentially bypassing neurosensory tissues. Anastomotic connections with the nasal region, however, may provide an alternative route for palatal venous blood to reach neurosensory tissues. The nasal region in crocodilians is probably the most prominent site of thermal exchange, as it offers a substantial surface area and is completely surrounded by blood vessels. The venous drainage routes from the nasal region offer routes directly to the dural venous sinuses and the orbit, offering evidence of the potential to directly affect neurosensory tissue temperatures. The evolutionary history of crocodilians is complex, with large-bodied, terrestrial, and possibly endothermic taxa that may have had to deal with thermal loads that likely provided the anatomical building-blocks for such an extensive vascularization of sites of thermal exchange. A clear understanding of the physiological abilities and the role of blood vessels in the thermoregulation of crocodilians neurosensory tissues is not available but vascular anatomical patterns of crocodilian sites of thermal exchange indicate possible physiological abilities that may be more sophisticated than in other extant diapsids.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

2016

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“…Head–body temperature differences are also known for snakes (Webb & Heatwole, ; Heatwole & Johnson, ; Gregory, ; Dorcas & Peterson, ), turtles (Webb & Johnson, ; Morgareide & Hammel, ) and crocodilians (Grigg & Alchin, ; Drane, Webb & Heuer, ). Some authors explained heterothermy by means of different surface/volume ratio between the head and the body (Pough & MacFarland, ), while others demonstrated that reptiles can actively maintain their heads and bodies at different temperatures with a combination of physiological and behavioural mechanisms like panting (Webb et al ., ), gaping (Spotila, Terpin & Dodson, ), countercurrent vascular systems (Heath, ; Tattersall, Cadena & Skinner, ), controlling the regional blood flow (Amiel et al ., ) or exposure of certain body parts to solar radiation (Gregory, ).…”

Section: Introductionmentioning

confidence: 99%

Keeping a cool mind: head–body temperature differences in the common wall lizard

2014

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Evidence of head-body temperature differences are known for many species of medium-to large-sized reptiles, but are scanty for small lacertid lizards. In this study, we heated 48 individuals of Podarcis muralis (19 males and 29 females) in order to investigate their ability to achieve and maintain local temperature differences between body parts. Lizards were put into polystyrene boxes and heated with incandescent lamps. Temperatures were measured with both an infrared thermometer and an infrared camera at four different body points every 20 min for 2 h. We found a statistically significant thermal gradient from the tip of the nose, the coolest part of the body, to the trunk, the warmest area, whereas the head achieved an intermediate temperature. We therefore hypothesize that P. muralis is able to physiologically regulate the heat distribution across its body. Podarcis muralis is sexually dimorphic, but neither sex nor body size are associated with temperature differences between individuals. The two measurement devices used responded differently to insulating material and to living animals, possibly indicating that infrared camera is able to detect dermal heat, while infrared thermometer detects mainly epidermal heat. This study shows for the first time that P. muralis can achieve and maintain temperature differences between the head and the body.

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Long Range Tracking of Crocodylus porosus in Arnhem Land, Northern Australia

Yerbury

1980

A Handbook on Biotelemetry and Radio Tracking

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Patterns of heating in the body trunk and tail of Crocodylus porosus

Cited by 7 publications

References 5 publications

Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

Vascular patterns in the heads of crocodilians: blood vessels and sites of thermal exchange

Keeping a cool mind: head–body temperature differences in the common wall lizard

Long Range Tracking of Crocodylus porosus in Arnhem Land, Northern Australia

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