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Humans have red green and blue photoreceptors allowing them to sense colours in the spectrum of about 400-700nm. Certain proteins allow for the extending of wavelength range in the RGB receptors, this however is only perceived as more shades of the colour in question. Additional photoreceptors are necessary to sense a new colour, explicitly separate from RGB.

Organisms such as mantis shrimp can sense infrared light as they have 12-16 cones, allowing them to see into the infrared spectrum.

The issue is that there seems to be no information detailing the the structure of mantis shrimp eyes, specifically regarding the the aspects of which are responsible for vision into the near infrared spectrum (roughly 700-1000nm).

What would the cones of an organism that saw exclusively in infrared look like? (assuming the organism had eyes like a human)

Would they be differently coloured or structurally different to our own?

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  • $\begingroup$ Are you asking what the photoreceptors of a mantis shrimp look like? $\endgroup$
    – AliceD ♦
    Mar 20, 2018 at 14:03
  • $\begingroup$ @AliceD Infrared light sensing photoreceptors in general, although mantis shrimp would be a good example. $\endgroup$
    – Lutro
    Mar 20, 2018 at 14:09

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The photoreceptors of the mantis shrimp (Fig. 1) are quite different from that of the human retina (Fig. 2).

Importantly, when light enters the units in the shrimp's eye, it must first pass through a crystalline cone, which lies over the receptors. These crystalline cones contain frequency-specific light-blocking substances called MAAs (mycosporine-like amino acids). These filters help to filter the spectrum and this means that less different opsins are necessary tod etect different wavelengths. In other words, a mantis shrimp does not feature 16 different opsins. Instead it utilizes the same opsins for various wavelengths by putting a filter on top of the cone (source: National Geographic).

mantis
Fig. 1. Mantis shrimp photoreceptors. source: Physiologizing

human
Fig. 2. Human cone cell. source: Wikipedia

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  • $\begingroup$ Interesting. Do the Crystalline cones of the mantis shrimp have set colours which they detect such as a humans red, green and blue? $\endgroup$
    – Lutro
    Mar 20, 2018 at 14:36
  • $\begingroup$ Yes they do; each class is devoted to a specific [range of] wavelength[s] $\endgroup$
    – AliceD ♦
    Mar 20, 2018 at 14:52
  • $\begingroup$ I know i'm asking a bit much, but would you happen to have any information regarding how they are devoted to different ranges of wavelengths? E.g. different colours or lengths. Also, could you please define what you mean by 'class'. $\endgroup$
    – Lutro
    Mar 20, 2018 at 15:04

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