Evidence for cranial endothermy in the opah (Lampris guttatus)
Evidence for cranial endothermy in the opah (Lampris guttatus)
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DOI：
10.1242/jeb.022814
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发表时间：
2009-02-15
影响因子：
2.8
通讯作者：
Dickson, Kathryn A.
中科院分区：
文献类型：
--
作者：
Runcie, Rosa M.;Dewar, Heidi;Dickson, Kathryn A.
颅骨植物植物在兰尼德鲨鱼，比尔鱼和金枪鱼中独立演变，被认为可以最大程度地减少周围温度变化对深度潜水期间视力和神经功能的影响。 Opah，Lampris Guttatus是一种大型的表皮中质捕食者，使重复的潜水进入凉爽的水中。为了确定l. guttatus是否表现出颅骨对吸水剂，我们测量了活的，甲板上的颅骨温度，并确定了潜在的热和机制来源以节省热量。在40个Opah（95.1 +/- 7.6厘米叉长）中，眼睛后面的组织温度的平均（+/- S.E.M.）为2.1 +/- 0.3摄氏度，最大为6.3摄氏度。肌肉温度（T-M），用作环境温度的代理。在较低的TM时，随着TM的颅骨温度显着变化，温度升高更大。配对的外侧直肠外肌的近端区域似乎是热的主要来源。该肌肉是最大的眼外肌肉，与视神经和大脑相邻，仅通过薄薄的骨头与大脑分离。与所有其他眼外肌肉相比，近端侧直肠肌肉的颜色更深，柠檬酸合酶活性更高，表明有氧热量产生的能力更高。此外，这种肌肉具有一层脂肪从g腔中绝缘，并且被形成推定的反电流热交换器的动脉和静脉网络所灌注。综上所述，这些结果支持这样的假设，即Opah可以维持颅骨温度升高。
Cranial 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 degrees C and a maximum of 6.3 degrees C above myotomal muscle temperature (T-m), used as a proxy for ambient temperature. Cranial temperature varied significantly with Tm and temperature elevation was greater at lower Tm. 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.