Enlarge (credit: CHOKSAWATDIKORN / SCIENCE PHOTO LIBRARY)

The hydra is a Lovecraftian-looking microorganism with a mouth surrounded by tentacles on one end, an elongated body, and a foot on the other end. It has no brain or centralized nervous system. Despite the lack of either of those things, it can still feel hunger and fullness. How can these creatures know when they are hungry and realize when they have had enough?

While they lack brains, hydra do have a nervous system. Researchers from Kiel University in Germany found they have an endodermal (in the digestive tract) and ectodermal (in the outermost layer of the animal) neuronal population, both of which help them react to food stimuli. Ectodermal neurons control physiological functions such as moving toward food, while endodermal neurons are associated with feeding behavior such as opening the mouth—which also vomits out anything indigestible.

Even such a limited nervous system is capable of some surprisingly complex functions. Hydras might even give us some insights into how appetite evolved and what the early evolutionary stages of a central nervous system were like.

Enlarge (credit: Buena Vista Images)

Lots of animals communicate with each other, from tiny mice to enormous whales. But none of those forms of communication share even a small fraction of the richness of human language. Still, finding new examples of complex communications can tell us things about the evolution of language and what cognitive capabilities are needed for it.

On Monday, researchers report what may be the first instance of a human-like language ability in another species. They report that elephants refer to each other by individual names, and the elephant being referred to recognizes when it's being mentioned. The work could be replicated with a larger population and number of calls, but the finding is consistent with what we know about the sophisticated social interactions of these creatures.

What’s in a name?

We use names to refer to each other so often that it's possible to forget just how involved their use is. We recognize formal and informal names that refer to the same individual, even though those names often have nothing to do with the features or history of that person. We easily handle hundreds of names, including those of people we haven't interacted with in decades. And we do this in parallel with the names of thousands of places, products, items, and so on.