What does it mean to be an endothermic or an ectothermic animal?
- endothermy: body heat derived from inside (metabolic processes)
- ectothermy: body heat derived from outside (the environment)
Provide some examples of endothermic and ectothermic animals.
- endotherms: mammals, birds
- ectotherms: reptiles, amphibians, fish, invertebrates
What are the major advantages and disadvantages of each strategy? (endothermism vs. ectothermism)
- endotherms: can maintain more optimal temperature for physiological processes and less subject to changes in environmental temperature BUT energetically expensive
- ectotherms: energetically cheap BUT cannot maintain optimal temperatures for physiological processes and subject to changes in environmental temperature
What are “temporal” and “regional” endotherms?
-regional endothermy: internal production of heat allowing for certain organs or parts of the body to be warmed
How do “surface to volume ratio” and “countercurrent heat exchangers” contribute to thermoregulation?
- countercurrent heat exchange helps to minimize heat lost to the environment
- low surface area to volume ratio decreases amount of heat that diffuses out by decreasing how much of body is in contact with water, which heats up more slowly than air and would take more heat from the organism than air does
What are the different body regions that some fish are able to preferentially warm? What are the advantages in each case?
- red aerobic swimming muscles: increases muscle contraction rates and power output (swims faster)
- brains: increase visual resolution and neurological response times
- viscera (gut): digest food more quickly to receive energy more quickly
What are three requirements that are essential for achieving regional endothermia in fishes?
- Heat source (constantly contracting/heat producing muscle)
- Heat source must be insulated to minimize convective heat loss
- Counter-current heat exchanger to minimize heat loss at the gills
How is the thermoregulatory strategy of the opah unique among fishes?
- allows it to spend long periods of time at depth instead of needing to surface constantly to reheat body, causes deep diving behavior
- regional endotherm instead of ectotherm
Describe the adaptations in the opah’s muscle, adipose/connective tissue, and gills that are essential for its thermoregulatory strategy.
- an extensive rete mirabile in each gill arch conserves heat which allows for warm blood to be distributed throughout the body (countercurrent heat exchange in gills, tight coupling of aerated and anaerated vessels)
- Thick layer of adipose and connective tissue covering the pectoral muscle to insulate the heat, not normal
- pectoral muscle provides heat to body
