Deep-sea fish vision pushing limits of the vertebrate eye

Deep-sea fishes are known for extraordinary adaptations including enhanced sensory systems. They have eyes often modified in shape, anatomy or at the molecular level. Fascinatingly, some deep-sea fishes have evolved unique vision to potentially see colours.

Here I propose to study functional evolution of this visual system, and to target the crucial question – can deep-sea fish see in colours?

To perceive light, vertebrate retina has two types of photoreceptor cells, the rods for dim-light vision and cones for daylight colour vision. Many deep-sea fish lack cones, which makes them colour blind.

The novel visual system based purely on multiple different rod opsins possibly overcomes this limit, and it is not found in any other vertebrate.

In SensingDEEP I aim to “zoom” into the level of single rod/cone cells to understand deep-sea molecular adaptations of vision.

I will target species with 1) the novel multiple-rhodopsin visual system and test if it has a potential to serve for colour discrimination.

With multiple rhodopsins expressed in the retina, single-cell transcriptomics will either reveal rod cells sensitive to different colours, or alternatively, “superpowerful” rods sensing along the entire light spectrum. Both options would be unique among vertebrates.

Further I aim to focus on the deep-sea species with 2) challenged rod and cone cell identity with mismatch of molecular machinery of both (rod and cone) types.

Lastly, I will also test 3) how rare these extreme adaptations are in deep-sea fish diversity using the high-quality whole-genome sequencing.

In the species with multiple rhodopsins, I will specifically focus on their genomic architecture and gene regulation by applying single-cell multiomics. SensingDEEP combines modern genomic tools with rare and unique samples.

Given that vertebrate eye is a conserved structure, the deep-sea fish with extreme adaptations will, therefore, serve as a model to explore (and push) the limits of vertebrate vision.