Swimming muscle helps warm the brain of lamnid sharks

Wolf, Nancy G.; Swift, Peter R.; Carey, Francis G.

doi:10.1007/bf00691001

Cited by 32 publications

(34 citation statements)

References 16 publications

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“…The shortfin mako (I. oxyrinchus Lamniformes: Lamnidae) is a regionally endothermic, high-speed predator of marlin, tuna and other pelagic bony fishes (Block and Carey, 1985;Wolf et al, 1988). It is believed to be the fastest swimming shark (Carey and Teal, 1969).…”

Section: Methodsmentioning

confidence: 99%

Material properties and biochemical composition of mineralized vertebral cartilage in seven elasmobranch species (Chondrichthyes)

Porter

Beltran

Koob³

et al. 2006

Journal of Experimental Biology

100

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SUMMARY Elasmobranchs, particularly sharks, function at speed and size extremes,exerting large forces on their cartilaginous skeletons while swimming. This casts doubt on the generalization that cartilaginous skeletons are mechanically inferior to bony skeletons, a proposition that has never been experimentally verified. We tested mineralized vertebral centra from seven species of elasmobranch fishes: six sharks and one axially undulating electric ray. Species were chosen to represent a variety of morphologies, inferred swimming speeds and ecological niches. We found vertebral cartilage to be as stiff and strong as mammalian trabecular bone. Inferred swimming speed was a good, but not infallible, predictor of stiffness and strength. Collagen content was also a good predictor of material stiffness and strength, although proteoglycan was not. The mineral fraction in vertebral cartilage was similar to that in mammalian trabecular bone and was a significant predictor of material properties.

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Section: Methodsmentioning

confidence: 99%

Material properties and biochemical composition of mineralized vertebral cartilage in seven elasmobranch species (Chondrichthyes)

Porter

Beltran

Koob³

et al. 2006

Journal of Experimental Biology

100

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“…In the other tuna species, there is no evidence of modified extraocular muscle (Block et al, 1982;Block, 1990;Sepulveda et al, 2007), and contraction of the extraocular muscles (Block and Finnerty, 1994) or active metabolism within the brain (Block, 1987b;Block et al, 1982) have been proposed as possible sources of heat for cranial endothermy in those species. In lamnid sharks, heat produced within the slow-oxidative myotomal muscle is transferred to the cranial area via the unique red muscle vein and the myelonal vein (Block and Carey, 1985;Carey et al, 1985;Wolf et al, 1988;Alexander, 1998;Tubbesing and Block, 2000). In addition, contraction of extraocular muscles may also contribute to heat production in these sharks (Wolf et al, 1988;Alexander, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…In lamnid sharks, heat produced within the slow-oxidative myotomal muscle is transferred to the cranial area via the unique red muscle vein and the myelonal vein (Block and Carey, 1985;Carey et al, 1985;Wolf et al, 1988;Alexander, 1998;Tubbesing and Block, 2000). In addition, contraction of extraocular muscles may also contribute to heat production in these sharks (Wolf et al, 1988;Alexander, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…To reduce conduction, the eyes and brain of billfishes and tunas, but not lamnid sharks, are insulated by a layer of adipose tissue (Carey, 1982;Wolf et al, 1988;Block, 1990;Fritsches et al, 2005;Sepulveda et al, 2007). To reduce convection of heat to the gills, vascular counter-current heat exchangers (retia mirabilia) perfuse the cranial region in all fish species with cranial endothermy but retia morphology differs among the fish groups.…”

Section: Introductionmentioning

confidence: 99%

“…The lamnid sharks have paired orbital retia, each made of an arterial plexus branching from the highly coiled pseudobranchial and efferent hyoidean arteries surrounded by warm blood within the orbital venous sinus (Block and Carey, 1985;Carey et al, 1985;Alexander, 1998;Tubbesing and Block, 2000). The red muscle vein supplies warm blood to the orbital sinus via the myelonal vein (Wolf et al, 1988;Tubbesing and Block, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Evidence for cranial endothermy in the opah (Lampris guttatus)

Runcie

Dewar

Hawn

et al. 2009

Journal of Experimental Biology

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SUMMARYCranial endothermy evolved independently in lamnid sharks, billfishes and tunas, and is thought to minimize the effects of ambient temperature change on both vision and neural function during deep dives. The opah, Lampris guttatus, is a large epipelagic-mesopelagic predator that makes repeated dives into cool waters to forage. To determine if L. guttatus exhibits cranial endothermy, we measured cranial temperatures in live, decked fish and identified potential sources of heat and mechanisms to conserve heat. In 40 opah (95.1±7.6 cm fork length), the temperature of the tissue behind the eye was elevated by a mean (±s.e.m.) of 2.1±0.3°C and a maximum of 6.3°C above myotomal muscle temperature (T m ), used as a proxy for ambient temperature. Cranial temperature varied significantly with T m and temperature elevation was greater at lower T m . The proximal region of the paired lateral rectus extraocular muscle appears to be the primary source of heat. This muscle is the largest extraocular muscle, is adjacent to the optic nerve and brain and is separated from the brain only by a thin layer of bone. The proximal lateral rectus muscle is darker red in color and has a higher citrate synthase activity, indicating a higher capacity for aerobic heat production, than all other extraocular muscles. Furthermore, this muscle has a layer of fat insulating it from the gill cavity and is perfused by a network of arteries and veins that forms a putative counter-current heat exchanger. Taken together, these results support the hypothesis that the opah can maintain elevated cranial temperatures.

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Aquatic Locomotion: Environmental Constraints That Drive Convergent Evolution

Fish

2023

Fascinating Life Sciences

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Swimming muscle helps warm the brain of lamnid sharks

Cited by 32 publications

References 16 publications

Material properties and biochemical composition of mineralized vertebral cartilage in seven elasmobranch species (Chondrichthyes)

Material properties and biochemical composition of mineralized vertebral cartilage in seven elasmobranch species (Chondrichthyes)

Evidence for cranial endothermy in the opah (Lampris guttatus)

Aquatic Locomotion: Environmental Constraints That Drive Convergent Evolution

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