Striges

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Jacob Riglin

lachryphagy is the term used to describe the behaviour of tear drinking in nature, typically in environments - like the purvian amazon shown here - where sodium and other micronutrients are hard to find. 

bees and butterflies need sodium for egg production and metabolic purposes, but their diets of nectar are low in salt. so the orange julia and sulfur yellow butterflies you see here turn to the salty tears of often stationary turtles and caiman. 

and though the caiman and turtles seem to receive no reciprocal benefit from the interaction, they’re apparently happy enough to just help out. (x, x, x, x, x, x)

https://www.protobacillus.com

Are colour-changing octopuses really colourblind? 

Cephalopods, including octopuses and squid, have some of the most incredible colour-changing abilities in nature. 

They can almost instantly blend in with their surroundings to evade predators or lay in wait, and put on colourful displays to attract mates or dazzle potential prey.

This is impressive enough on its own, but becomes even more amazing when you discover these creatures are in fact colourblind – they only have one type of light receptor in their eyes, meaning they can only see in black and white.

So how do they know what colours to change to at all?

This has puzzled biologists for decades but a father/son team of scientists from the University of California, Berkeley, and Harvard University think the unusual shape of their pupils holds the key, and they can see colour after all.

Cephalopods have wide U-shaped or dumbbell-shaped pupils, which allow light into the lens from many directions.

When light enters the pupils in human eyes it gets focused on one spot, cutting down on blur from the light being split into its constituent colours.

The scientists believe cephalopod eyes work the opposite way – the wide pupils split the light up and then individual colours can be focused on the retina by changing the depth of the eyeball and moving the pupil around.  

The price for this is blurry vision, but it does mean they could make out colours in a unique way to any other animals.

Processing colour this way is more computationally intensive than other types of colour vision and likely requires a lot of brainpower, which might explain in part why cephalopods are the most intelligent invertebrates on Earth.

Read the paper

Images:  Roy Caldwell, Klaus Stiefel, Alexander Stubbs

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by  NI Yipeng