Ectotherm & Heart Rate
Many animals rely on external environmental temperature to keep their internal body temperature within healthy levels. There are many intrinsic as well as extrinsic factors that influence the heart rates of ectotherms, both over time and between species. Of all the variables, environmental temperature is the most influential in determining heart rate. As a result, many species of ectotherms have developed physiological as well as behavioral patterns to regulate their body temperature and maintain optimal health and the appropriate heart rate at any given time.
Other People Are Reading
-
Ectotherms Defined
-
The term ectotherm comes from the Greek "ectos," meaning "outside," and "therm," meaning "hot." As the name implies, ectotherms are animals with internal body temperatures that are determined by the temperature of the environment around them. Ectotherms are commonly referred to as cold-blooded, but the more appropriate term for most of these animals is poikilothermic, coming from the Greek "poikilos," meaning "varied," and "thermos," meaning "warm."
Ectotherm Cardiovascular System
-
Because ectotherms do not need to consistently exert energy to maintain their body temperature, they require much less energy to survive and function. Some ectotherms require only one-half to one-tenth of the energy needed by mammals of the same size. The cardiovascular system is no different. As ectotherms bask in the sun to raise their body temperature, all of the components of the body become more active. Cells that operate the muscles in the heart warm and are able to pump faster, and blood vessels dilate and allow larger volumes of blood flow within the animal. This, when coupled with increased respiratory rates, enable ectotherms to become more active than at cooler temperatures.
-
Temperature Adaptations in Ectotherms
-
Many reptiles, for example, have evolved physical as well as behavioral adaptations that help them regulate their body temperature. Dark coloration, activity at times that are temperature-appropriate in the surrounding environment, and body shape and size are all variables that ectotherms have evolved to fit into a wide range of ecological niches.
Example of Temperature and Heart Rate Regulation
-
Marine iguanas of the Galapagos Islands feed on marine algae that grows in the cold waters of the Pacific. In order to maneuver the chilly waters effectively, they spend a large amount of time basking on black rocks, soaking up the thermal radiation from the sun above and the rocks below. When in the water, they regulate their heartbeat and blood flow to minimize heat lost at its surface. In addition, their dark black coloration aids them in absorbing heat. If they become too hot, they suck in their belly and raise their body off the rocks, allowing the coastal winds to cool them on all sides.
Interesting Facts
-
Some turtles exhibit heart rates as low as 1 beat per minute when lying dormant at the bottom of cold ponds through winter.
Many ectotherms that live in extremely cold environments survive thanks to a natural antifreeze within their body that lowers the freezing point of the liquids in their body.
Some particularly large ectotherms, such as great white sharks and sea turtles, are referred to more specifically as gigantotherms. These large ectotherms are able to maintain a relatively stable internal temperature due to their large body mass and volume-to-surface-area ratio, which make their absorption and loss of heat much slower than smaller ectotherms.
-
References
- Photo Credit reptile image by Oleg Leshchev from Fotolia.com
