Seeing in the Dark and the Green: How Eyes and Leaves Share a Lighty Secret

The world of biology reveals surprising connections, and the human eye and a seemingly ordinary leaf share a fascinating one. Both organs rely on sophisticated light-sensing mechanisms to function effectively in their environments, despite their vastly different purposes.

Within the human eye, the retina houses two crucial photoreceptor cell types: rods and cones. Rods, responsible for low-light vision, utilize rhodopsin, a specialized protein, to capture even the faintest light signals. Cones, responsible for color vision, rely on various forms of iodopsin to differentiate colors in bright light conditions. Both rhodopsin and iodopsin function by undergoing a shape change upon encountering light, triggering a biochemical cascade that ultimately translates light energy into electrical signals the brain interprets as vision.

Plants exhibit a similar strategy. Nestled within their leaves lies phytochrome, a remarkable molecule that, like its counterparts in the eye, acts as a light receptor. Phytochrome exists in several states depending on the specific wavelengths of light it absorbs. By sensing variations in light intensity and spectrum, phytochrome provides the plant with vital information about its surrounding environment. This information plays a critical role in processes like photosynthesis, where plants utilize sunlight as an energy source, and regulates growth patterns based on light availability.

In both the eye and the plant, the photosensors function together with chromophores: retinal in the eye and phytochromobilin in the plant.

This unexpected parallel between the human eye and the leaf underscores a fundamental principle in biology – the ability to detect light is a powerful evolutionary advantage. By harnessing the power of light, both humans and plants gain the ability to navigate their environments, grow, and thrive.

Molting of my Chilean fire tarantula (Grammostola rosea), last July. ✨

Under increased blood pressure, the tarantula begins to transport a molting hormone (hydroxylated ecdysone/ecdysterone) from the rear to the front of the body. This causes pressure to build up and the carapace (back shield) to burst open. This extends over the entire body, so that the tarantula can now gradually free itself from the old exoskeleton. This can sometimes take several hours and is therefore very exhausting for the tarantula, so that it remains lying on its back even after it has successfully moulted. In this state, the spider has not yet hardened and can therefore easily become a victim. That's why spiders create a somewhat safer place with silk threads beforehand. I've increased the speed of the video eight times because you all don't have as much patience as I do 🤪 and it makes the rhythmic movement sequences clearer.

Ecdysterone is a hormone that triggers moulting in molting animals (arthropods, tardigrades, nematodes, etc.). It is also found in plants to protect against plant pests. In mammals, it only occurs through ingestion or parasitic infestation. It also has an effect on mammals and influences lipid metabolism and protein biosynthesis. It is believed to have an anabolic effect on the muscles, which is why it is also used in competitive sports. It is believed to have no harmful effects because it is a natural part of our diet. 💪😋🥬

African Penguin
(Spheniscus demersus)
2004 @dallaszoo 🏙️

The only penguin species of Africa. 🌍

It's expected to be extinct in the wild in a few years.⚰️

I wish we could just put a band-aid on everything... 🩹

Check @sanccob 🌠

Coypu,
Myocastor coypus

There's a very stable population of this invasive species along the Nidda river.
It's not good to pet or feed them. They can get pushy, but don't give in! It harms nature. Water pollution is increasing and native species are endangered. Children can be bitten. Just enjoy it as long as it's here.❤️

So what is that? Weird animal! This is not a human being! 😲
I smell flowers! 🌻💕
Weird animal and flowers... I have to go there! ❤
⠀ ⠀

Kalusho is the only black rhino at Frankfurt Zoo.
His female companion Tsororo died of a complication of the uterus in 2016.
Together they had three daughters. All of their daughters were released into the wild in Africa.
The eldest daughter Akura became a grandmother four years ago in the Marakele National Park.


Kalusho, now 33 years old and originally from Zimbabwe,
should actually be released together with Tsororo 8 years ago.
However, it failed.


For most of the 20th century the continental black rhino was the most numerous of all rhino species.
Around 1900 there were probably several hundred thousand living in Africa.
In the early 1990s the number dipped below 2,500, and in 2004 it was reported that only 2,410 black rhinos remained.
By 2019 the population of 5,500 was either steady or slowly increasing.



🎼Music: "African meditation dance" by Stefan Kartenberg (2017 - Licensed under Creative Commons Attribution Noncommercial 3.0, creativecommons.org/licenses/by-nc/3.0/)

🔎🐧💡 At Centro de Interpretación, Paracas, Peru:
In the coastal desert around Paracas, numerous fossils were found. Including various penguin species, such as the Inkayacu pictured here. It lived around 36 million years ago. The 2008 discovered skeleton is the first one with fossilized feathers attached to it. The feathers are so well preserved that it's even possible to draw conclusions about the coloring. They had similar feathers as modern penguins, but more gray or brownish.


The other prehistoric bird in the picture is a pseudotooth bird (pelagornithid). These birds reached a wing span of up to 6 meters and were thus about twice as large as the Andean condor. They were probably related to pelicans or storks and lived all around the world. The fossils found around Paracas are attributed to the same era as the Inkayacu.

💕🐧🐧🐧💕 African penguins (Spheniscus demersus) are the only penguin species of Africa. Their wild population has decreased by 90 percent since 1956. At this rate of decline, the African Penguin is expected to be extinct in the wild by 2026. You can help the Southern African Foundation for the Conservation of Coastal Birds (@sanccob , sanccob.co.za) with a donation.

Barramunda / Australian lungfish
(Neoceratodus forsteri) in the Frankfurt Zoological Garden.

There are 6 species of lungfish in the world, of which the Australian is the most primitive. The lungfish morphology has hardly changed in the last 100 million years and therefore, like the closely related coelacanths, are considered living fossils.

Genetic studies, as well as the skull structure, the arrangement and shape of the fins, the approach of separation of oxygen-rich blood from the lungs and oxygen-poor blood from the body, suggest a close relationship to the tetrapods, to which we also belong.

Netherless, the lungfish aren't considered our ancestors, but are closely related to them.

Mata mata! 😄🐢
A nocturnal freshwater turtle that is found mainly in the Amazon and Orinoco basins. There it prefers shallow waters, where it remains motionless until a fish comes close. Only small fish are eaten by creating a vacuum that sucks the prey into its mouth. The fish is swallowed whole, the structure of the mouth makes it impossible to chew.

Weird horse! 🐪