Endothermy in Fishes

Dear Colleagues,

I am pleased to call for papers dealing with the ecology, physiology and molecular biology of endothermy in fishes. Endothermy, the ability to warm the body using metabolically-derived heat, is unusual in fishes. It is found only in tunas, certain shark species and a select few other fish species. In tunas, which have a larval stage, endothermy develops gradually during the first year of life whereas in sharks it is most likely present at birth. This makes these fishes powerful tools for studying the physiological and molecular basis of this important highlight in vertebrate evolution. Unlike in mammals, it is only the red (oxidative myotomal) muscle, the cranium (eye/brain), and, in some species, the viscera that are warmed metabolically in fishes. Three key characteristics permit this. The first is the presence of heat exchanging blood vessels forming retia mirabilia (“wonderful nets”), which allow heat transfer from the warm blood exiting the endothermic tissue to the cool blood entering the tissue from the gills. Thus, the retia mirabilia reduce heat loss due to convection. The second characteristic is continuous swimming. This, powered by the repeated contraction of the red muscle, generates metabolic heat, which is conserved by the red muscle retia and possibly also the cranial and visceral retia. In the viscera, the conserved heat is generated as a by-product of specific dynamic action, i.e., the processes associated with digestion and in the cranium there are highly metabolically active extraocular muscles that in some species are modified as heater organs. The third characteristic associated with endothermy in fishes is the more internal (i.e., closer to the vertebral column) location of the red muscle. This contrasts with the more superficial (i.e., just under the skin) location of the red muscle in typical ectothermic fish species and it reduces heat loss across the body surface as a result of conduction.

I am pleased to solicit manuscripts pertaining to original research, as well as mini and full reviews and short communications, which address any aspect of endothermy in fishes.

Submissions are invited that include the following topics, but this list is by no means exhaustive:

• Ecological implications of endothermy in fishes in relation to climate change
• Evolutionary origins of endothermy in fishes
• Anatomical and physiological requirements for endothermy in fishes
• Ontogeny of endothermy in fishes.

Dr. Kathryn A. Schuller
Guest Editor

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• endothermy
• evolution
• ontogeny
• anatomy
• climate change
• ecology
• physiology