Image from Karen Osborn, Smithsonian
Alright gang, we’re on a deep sea kick (it’s wonderful for the pores) over here at JV HQ so buckle your bathysphere and ready for descent. Last week I highlighted Kathy Sullivan, only woman to walk in space AND visit the deepest part of the ocean. Now, let’s talk about what she might have seen down there, or rather, what she almost certainly didn’t see because it’s goddamn invisible in the light-less depths. And let me be clear, lack of light is not the issue – these newly-identified fish have such a perfectly black hue that they absorb more than 99.95% of any available light.
That’s nutso. In practice it means they might escape notice even under the bright sub lights, but, more importantly, they avoid detection by predator and prey in the glow of bioluminescence. I misspoke a bit earlier when I said the deep sea is light-less – in reality it’s just sunlight-less. Bioluminescence is fairly common in the marine world from ultra-black anglerfish in the deepest depths all the way to luminescing phytoplankton at the surface. Thus, even in an environment devoid of sunlight, camouflage is of great value.
What really chuffs me about this study (besides the lead author admitting that the researchers only got lucky and adding “We basically just drop nets and see what we get”) is the way these ultra-black fish produce the effect. They use the same pigment building block we all do – melanin – but rather than spread it out (in a layer of collagen) they super saturate. With all that melanin packed together, any light that does manage to get reflected is just trapped by the melanin right next door. Turns out, this method is way more efficient than what other animals (birds, spiders, butterflies) employ to create their ultra-blacks which involves complex surface geometries and trapping photons. Simple is better when you’re trying to survive crushing pressure, near-zero food, and the absence of sunlight. Or so I’ve always said. Always.