By Rebecca McCauley

Of all colours visible to the human eye red light has the longest wavelength. Underwater, as depth increases and the ability of light to penetrate water lessens, red light is the first to be lost.

In 1994 my mother submitted her PhD thesis in the Department of Marine Biology, examining changes in the visual systems of fishes during their lifespan. In what was a world first, she was able to show that the eyesight of certain species can change over their lifetime in adaptation to the environments they inhabit. For example, larval fish feeding at the ocean surface may initially have eyes sensitive to blue light. The structure of the eye may change over time, developing increased sensitivity to red light as the fish matures and moves deeper in search of prey, and the available underwater light changes. Visual, lived evolutions.Unique underwater environments, where light and colours dim and quickly change from the surface, place highly specialised ecological demands on different species, impacting their visual colour ranges. Fish that live in environments such as shallow freshwater where green and red light are most prevalent have developed colour receptors suited to this, while some have developed to see colour ranges which the human eye cannot detect, such as ultraviolet. Later in my mother’s research it was found that a certain type of seahorse, the zebra-snout seahorse, can actually see five colour channels (humans can see three).

Hers was a unique and highly specialised world, populated by the mysterious visual systems of animals we know relatively little about. A world where clues into these systems are gained from machines called microspectrophotometers, and where concepts like bands, channels, spectrums, cones and rods are the cornerstones to understanding.

These ideas balance extremely complex explanations with the most basic lived reality. For those of us born with vision, we see what we see. The idea that there are more or less colours in the objects and environments around us than what we can envision seems absurd, as we have no comparative lived experiences to measure this against. To understand that some animals lose and gain certain colour spectrums throughout a lifetime requires both a suspension of understanding and an extension of it.

To reflect on vision is not only to question how we see, but also to question what we believe and perceive. Colours shape our understandings of the world, just as memories and lived experiences enter into images and visions of things we have not partaken in. The flickering light of the sun through the fingers of a hand, or seeping through the vinyl on a doorway – it is what it suggests – but it is also what we project our own perception of the world onto. Those fingers – are they my mother’s hands playing with light on the wall? Flesh becomes a filter, and pink noise echoes the womb-like sensation of immersion; inside and outside – eyelids, windows, blood vessels, skin surfaces. Light is an emotive signifier. We enter the space, the cone cells in our eyes respond, the lens and cornea block shorter wavelengths reducing our sensitivity to blue and violets, our eyes adjust; we become immersed.

REFERENCES
Ireland, Steve; Looking through a fish eye darkly. Western Fisheries, 2007, p 44-47.

Shand, Julia; Changes in the visual system of teleost fishes during growth and settlement: an ecological perspective. PhD thesis, James Cook University, 1994.

This writing was originally developed with the assistance of Kings Emerging Writers Program, 2017.

Tara O'Conal's 'Filter' runs 21 November—9 December, 2017.

Tara O’Conal, Pink Noise (2017), two-channel digital video with stereo sound, 9mins. Courtesy the artist.