Physiological thermoregulation of mature alligators

En, Smith; Ea, Standora; Sl, Robertson

doi:10.1016/0300-9629(84)90033-1

Cited by 17 publications

(8 citation statements)

References 18 publications

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“…Studies of lizards have shown that many species heat faster than they cool (Bartholomew & Tucker 1963, 1964Bartholomew & Lasiewski 1965;Weathers 1970Weathers , 1971Wilson & Lee 1970;Spellerberg 1972;Oaussen & Art 1981;Fraser 1985). Similar results were obtained with crocodiles and alligators (Grigg & Alchin 1976;Smith 1976;Boland & Bell 1980;Chater 1984;Smith, Standora & Robertson 1984). However, the terrapins do not follow this general pattern.…”

supporting

confidence: 63%

Heating and cooling rates and their effects upon heart rate in the angulate tortoise,Chersina angulate

Els¹,

Erasmus²,

Winter³

1988

South African Journal of Zoology

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supporting

confidence: 63%

Heating and cooling rates and their effects upon heart rate in the angulate tortoise,Chersina angulate

Els¹,

Erasmus²,

Winter³

1988

South African Journal of Zoology

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“…This heating-cooling ''hysteresis'' is associated with increased heart rate and perfusion of the skin with blood during warming, and a reduction in heart rate and perfusion of the skin during cooling (Bartholomew and Tucker 1963;Bartholomew and Lasiewski 1965;Weathers and White 1971;White 1973;Grigg and Alchin 1976;Smith 1976Smith , 1979Smith and Adams 1978;Smith et al , 1984Grigg et al 1979;Robertson and Smith 1981;Grigg and Seebacher 1999;Seebacher 2000;Seebacher and Franklin 2007). However, if subjected to heat stress, the reptile can use ''reverse hysteresis'' to deliver extra blood to the skin for dumping excess heat to heat sinks (shaded parts of the body, parts exposed to the wind or a cool substrate : White 1973;Grigg and Seebacher 1999).…”

Section: Blood Circulation and Temperature Regulation In Amniotesmentioning

confidence: 99%

Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora)

2010

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X-ray computed tomography and petrographic thin sectioning were used to study internal features of the plates of the thyreophoran dinosaur Stegosaurus and the osteoderms of Alligator. Infrared thermographic imaging of basking caimans was used to examine possible differential blood flow to osteoderms and other parts of the skin. Multiple large openings in the Stegosaurus plate base lead to a linear, mesiodistally oriented vestibule, which in turn apically sends off multiply branching ''pipes''. The pipes are best developed in the basal half of the plate, and communicate with cancellous regions (some of which presumably were vascular spaces) throughout the plate interior. Some internal vascular features also connect with vascular pits and grooves on the plate surface. Alligator osteoderms show a similar internal vascularity. In crocodylians, the osteoderms serve as armor and help to stiffen the back for terrestrial locomotion, but their vascularity enables them to be used as sources of calcium for egg shelling, as sites of lactate sequestration, and possibly for heat exchange with the external environment, as suggested by our infrared thermographic imaging of basking caimans. Thyreophoran osteoderms presumably had multiple functions as well. In Stegosaurus the potential thermoregulatory role of the plates may have been greater than in other thyreophorans, by virtue of their extensive external and internal vascularity, their large size, thin cross-sections above the plate base, dorsal position, and alternating arrangement.

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“…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%

“…For example, crocodilians display a dramatic facial rotation that flattens the skull (Witmer, 1995b(Witmer, , 1997, a reduction of the antorbital sinus (Witmer, 1995b), a secondary bony palate that extends from the nasal cavity into the pterygoid bone (Ferguson, 1981), and suturing of the quadrate and pterygoid to the braincase (Witmer, 1995b;Sedlmayr, 2002). Moreover, there are documented differences among crocodilians in thermoregulatory abilities that relate to body size (Smith, 1979;Fraser & Grigg, 1984;Smith et al 1984). Thus, crocodilians may have a bearing for inferring some of the effects of size on dinosaur thermoregulatory strategies, in that these studies may provide insight into both the problems and solutions of how large and small nonavian dinosaurs thermoregulated (Seebacher et al 1999).…”

Section: Introductionmentioning

confidence: 99%

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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Physiological thermoregulation of mature alligators

Cited by 17 publications

References 18 publications

Heating and cooling rates and their effects upon heart rate in the angulate tortoise,Chersina angulate

Heating and cooling rates and their effects upon heart rate in the angulate tortoise,Chersina angulate

Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora)

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

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