Tunas can elevate their red (slow-twitch, oxidative) skeletal muscle, visceral and cranial temperatures significantly above the ambient water temperature (Ta) with the aid of specialized blood vessels (retia mirabilia) that conserve metabolic heat. The ontogeny of this phenomenon, known as regional endothermy, was studied in young [18.5–62.5 cm fork length (FL), 71–5350 g body mass, 2–16 months of age] Pacific bluefin tuna (Thunnus orientalis). Maximal red muscle, visceral and cranial temperatures were measured in parallel with measuring red muscle mass and the size of the red muscle and visceral retia. The maximal thermal excess (maximal tissue temperature – Ta) increased from 1.1 ± 0.3 °C (mean ± SD) to 11.1 ± 3.4 °C in the red muscle, from 0.6 ± 0.3 °C to 3.5 ± 1.4 °C in the viscera and from 0.5 ± 0.4 °C to 2.0 ± 0.6 °C in the cranium in the smallest individuals compared with the largest. Thus, red muscle endothermy was well developed, but visceral and cranial endothermy were still developing, in the largest individuals studied. The scaling coefficients, relative to body mass, for total red muscle mass (0.90 ± 0.03, mean ± SE), red muscle rete (RMR) length (0.84 ± 0.06), maximum number of RMR blood vessel rows (0.43 ± 0.04) and visceral rete cross-sectional area (0.90 ± 0.08), indicated negative allometry for total red muscle mass ( 0.33) and the area of the visceral rete (> 0.67).

中文翻译：

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太平洋蓝鳍金枪鱼（Thunnus orientalis）区域吸热的个体发育

金枪鱼可以借助保存代谢热量的特殊血管（奇异视网膜）将它们的红色（慢肌、氧化性）骨骼肌、内脏和颅骨温度显着高于环境水温 (Ta)。这种现象的个体发育，被称为区域性吸热，在年轻的 [18.5-62.5 厘米叉长 (FL)，71-5350 克体重，2-16 个月大] 太平洋蓝鳍金枪鱼 (Thunnus orientalis) 中进行了研究。与测量红肌质量以及红肌和内脏视网膜的大小同时测量最大红肌、内脏和颅骨温度。最大热量过剩（最大组织温度 - Ta）从红肌的 1.1 ± 0.3 °C（平均值 ± SD）增加到 11.1 ± 3.4 °C，内脏从 0.6 ± 0.3 °C 增加到 3.5 ± 1.4 °C，以及从 0.5 ± 0.4 °C 到 2.0 ± 0。与最大个体相比，最小个体的颅骨温度为 6°C。因此，在研究的最大个体中，红肌吸热发育良好，但内脏和颅骨吸热仍在发育。相对于体重，总红肌质量 (0.90 ± 0.03，平均值 ± SE)、红肌网 (RMR) 长度 (0.84 ± 0.06)、最大 RMR 血管行数 (0.43 ± 0.04) 和内脏网横截面积 (0.90 ± 0.08)，表明总红肌质量 (0.33) 和内脏网面积 (> 0.67) 为负异速生长。