The retinal pigments of the whale shark (Rhincodon typus) and their role in visual foraging ecology.
The retinal pigments of the whale shark (Rhincodon typus) and their role in visual foraging ecology.
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DOI：
10.1017/s0952523819000105
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发表时间：
2019-11-13
影响因子：
1.9
通讯作者：
Robinson, Phyllis R
中科院分区：
文献类型：
--
作者：
Fasick, Jeffry I;Algrain, Haya;Robinson, Phyllis R
鲸鲨（Rhincodon typus）视杆细胞（视紫红质或Rh1）和长波长敏感（LWS）视锥细胞色素的光谱调谐特性进行了检查，以确定这些视网膜色素是否已适应宽带光谱可用于表面觅食或窄带蓝移光谱可在深度。最近发表的鲸鲨基因组已经确定了鲸鲨Rh1和LWS视锥蛋白的orthopathic基因，这表明双重视网膜。在这里，鲸鲨Rh1和LWS锥视蛋白序列进行了检查，以确定氨基酸残基光谱调谐的关键。令人惊讶的是，鲸鲨Rh1和LWS视色素的预测吸光度最大值（λ max）接近500 nm。虽然Rh1的蓝移值在500 nm附近是陆生脊椎动物和水面觅食鱼类的典型特征，但脊椎动物LWS视锥色素蓝移如此之大是不常见的。我们建议，鲸鲨Rh1和LWS锥色素的光谱调谐特性是最有可能适应的宽带光谱在表面。研究鲸鲨黑视蛋白（Opn4）失活动力学，以更好地理解瞳孔光反射的潜在分子机制。结果表明，鲸鲨Opn4的失活速率与具有双重视网膜的脊椎动物的Opn4失活速率相似，并且显著快于缺乏功能性视锥光感受器的水生杆状单色者的Opn4失活速率。鲸鲨Opn4的快速失活率与功能性视锥类一致，并且当从明视光条件过渡到暗视光条件时，会为动物提供光感受器信号传导所需的光子数量的指数增加，就像潜水时的情况一样。
The spectral tuning properties of the whale shark (Rhincodon typus) rod (rhodopsin or Rh1) and long-wavelength-sensitive (LWS) cone visual pigments were examined to determine whether these retinal pigments have adapted to the broadband light spectrum available for surface foraging or to the narrowband blue-shifted light spectrum available at depth. Recently published whale shark genomes have identified orthologous genes for both the whale shark Rh1 and LWS cone opsins suggesting a duplex retina. Here, the whale shark Rh1 and LWS cone opsin sequences were examined to identify amino acid residues critical for spectral tuning. Surprisingly, the predicted absorbance maximum (lambdamax) for both the whale shark Rh1 and LWS visual pigments is near 500 nm. Although Rh1 lambdamax values near 500 nm are typical of terrestrial vertebrates, as well as surface foraging fish, it is uncommon for a vertebrate LWS cone pigment to be so greatly blue-shifted. We propose that the spectral tuning properties of both the whale shark Rh1 and LWS cone pigments are most likely adaptations to the broadband light spectrum available at the surface. Whale shark melanopsin (Opn4) deactivation kinetics was examined to better understand the underlying molecular mechanisms of the pupillary light reflex. Results show that the deactivation rate of whale shark Opn4 is similar to the Opn4 deactivation rate from vertebrates possessing duplex retinae and is significantly faster than the Opn4 deactivation rate from an aquatic rod monochromat lacking functional cone photoreceptors. The rapid deactivation rate of whale shark Opn4 is consistent with a functional cone class and would provide the animal with an exponential increase in the number of photons required for photoreceptor signaling when transitioning from photopic to scotopic light conditions, as is the case when diving.