Department of Biology, Texas State University, Aquatic Station, San Marcos, TX 78666, USA.
Department of Earth Sciences, Dartmouth College, Hanover, NH 03755, USA.
Sci Total Environ. 2020 Dec 20;749:141350. doi: 10.1016/j.scitotenv.2020.141350. Epub 2020 Aug 2.
Odontocetes are apex predators that, despite accumulating mercury (Hg) to high concentrations in their tissues, show few signs of Hg toxicity. One method of Hg detoxification in odontocetes includes the sequestering of Hg in toxicologically inert mercury selenide (HgSe) compounds. To explore the tissue-specific accumulation of Hg and Se and the potential protective role of Se against Hg toxicity, we measured the concentrations of total mercury (THg) and selenium (Se) in multiple tissues from 11 species of odontocetes that stranded along the northern Gulf of Mexico coast [Florida (FL) and Louisiana (LA)]. Tissues were collected primarily from bottlenose dolphins (Tursiops truncatus; n = 93); however, individuals from species in the following 8 genera were also sampled: Feresa (n = 1), Globicephala (n = 1), Grampus (n = 2), Kogia (n = 5), Mesoplodon (n = 1), Peponocephala (n = 4), Stenella (n = 9), and Steno (n = 1). In all species, mean THg concentrations were greatest in the liver and lowest in the blubber, lung, or skin. In contrast, in most species, mean Se concentrations were greatest in the liver, lung, or skin, and lowest in the blubber. For all species combined, Se:Hg molar ratios decreased with increasing THg concentration in the blubber, kidney, liver, lung, and skin following an exponential decay relationship. In bottlenose dolphins, THg concentrations in the kidney, liver, and lung were significantly greater in FL dolphins compared to LA dolphins. On average, in bottlenose dolphins, Se:Hg molar ratios were approximately 1:1 in the liver and >1:1 in blubber, kidney, lung, and skin, suggesting that Se likely protects against Hg toxicity. However, more research is necessary to understand the variation in Hg accumulation within and among species and to assess how Hg, in combination with other environmental stressors, influences odontocete population health.
齿鲸是顶级掠食者，尽管它们的组织中积累了高浓度的汞 (Hg)，但几乎没有表现出汞毒性的迹象。齿鲸体内汞解毒的一种方法是将汞螯合到毒理学上惰性的汞硒化物 (HgSe) 化合物中。为了探究 Hg 和 Se 在组织中的特异性积累以及 Se 对 Hg 毒性的潜在保护作用，我们测量了沿墨西哥湾北部海岸（佛罗里达州 (FL) 和路易斯安那州 (LA)）搁浅的 11 种齿鲸的多种组织中的总汞 (THg) 和硒 (Se) 浓度。组织主要取自宽吻海豚 (Tursiops truncatus；n=93)；然而，也从以下 8 个属的个体中采样：Feresa (n=1)、Globicephala (n=1)、Grampus (n=2)、Kogia (n=5)、Mesoplodon (n=1)、Peponocephala (n=4)、 Stenella (n=9) 和 Steno (n=1)。在所有物种中，肝脏中的平均 THg 浓度最高，而在鲸脂、肺或皮肤中最低。相比之下，在大多数物种中，肝脏、肺或皮肤中的平均 Se 浓度最高，而在鲸脂中最低。对于所有物种的组合，在鲸脂、肾脏、肝脏、肺和皮肤中，随着 THg 浓度的增加，Se:Hg 摩尔比呈指数衰减关系而降低。在宽吻海豚中，佛罗里达州海豚的肾脏、肝脏和肺中的 THg 浓度明显高于路易斯安那州海豚。平均而言，在宽吻海豚中，肝脏中的 Se:Hg 摩尔比约为 1:1，而在鲸脂、肾脏、肺和皮肤中大于 1:1，表明 Se 可能对 Hg 毒性具有保护作用。然而，还需要更多的研究来了解物种内和物种间 Hg 积累的差异，并评估 Hg 与其他环境胁迫因素相结合如何影响齿鲸种群健康。
