Rodcells were the most common types of photoreceptor found in all 17 shark species, which means the predators should be able to see within a wide range of light levels.
在17种鲨鱼的视网膜中，最常见的感光体是视杆细胞，这意味着鲨鱼在不同的亮度环境下都可以看得到外界。
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Retinas use two main types of light-sensitive cells to allow animals to see: Rodcells help measure brightness, while various types of cone cells help distinguish colors.
In all 17 species, the commonest kind of light receptors were "rod" cells, which are highly sensitive to light and allow night vision but cannot tell colors apart, they found.