I’ve heard of albinism since I was young, and knew that common examples were white mice and white rabbits, with their characteristic red eyes. But it wasn’t until today that I read about the opposite condition, called melanism.
I’ve seen black panthers in zoos, similar to these at the Philadelphia Zoo. (I haven’t seen the ones pictured here, since they came to that zoo since I moved out of the Philadelphia area, but a zoo near where I live now has one also.) Like many people, I always thought of them as a separate species, but in fact they simply have a particular gene that makes their fur dark. They are usually either jaguars or leopards, and their spotted pattern is still visible in the right light.
I was also surprised to learn that the distinctive appearance of Siamese cats is due to partial albinism. Moreover, it is a temperature-sensitive sort of albinism, where the melanin is produced normally in parts of the body which are coolest – the legs and feet, tail, and face (the face is cooled by air going through the sinuses). That is what gives Siamese their unusual pattern of light and dark fur.
The photo that got my attention, though, is one of an all-black penguin. Partial melanism is rare enough in penguins – about four out of a million. But an all-black penguin is “one in a zillion” according to an ornithologist at the University of Toronto.