Box jellyfish stable-eyes vision to hunt prey

Ernst Haeckel’s Kunstformen der Natur (Artforms of Nature) was a landmark in biological illustration. Published in 1904, it was lavishly illustrated with 100 exquisitely detailed lithographic plates, including the one above, showing different species of cubomedusae, or box jellyfish. Since around the time that Haeckel’s masterpiece was published, we’ve known that box jellyfish have a unique visual system which is more sophisticated than that of other jellyfish species. They boast an impressive set of 24 eyes of four different types, which are clustered within bizarre sensory appendages that dangle from the cube-shaped umbrella.

The known light-guided behaviours of these organisms are, however, relatively simple, so exactly why they possess such an elaborate array of eyes was somewhat puzzling. A group of Scandinavian researchers working in the Caribbean now report that one of the box jelly’s eye types is highly specialized to peer up towards the water surface at all times, so that it can use terrestrial landmarks to navigate towards its prey.

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Gut bacteria may influence thoughts and behaviour

The human gut contains a diverse community of bacteria which colonize the large intestine in the days following birth and vastly outnumber our own cells. These intestinal microflora constitute a virtual organ within an organ and influence many bodily functions. Among other things, they aid in the uptake and metabolism of nutrients, modulate the inflammatory response to infection, and protect the gut from other, harmful micro-organisms. A new study by researchers at McMaster University in Hamilton, Ontario now suggests that gut bacteria may also influence behaviour and cognitive processes such as memory by exerting an effect on gene activity during brain development.

Jane Foster and her colleagues compared the performance of germ-free mice, which lack gut bacteria, with normal animals on the elevated plus maze, which is used to test anxiety-like behaviours. This consists of a plus-shaped apparatus with two open and two closed arms, with an open roof and raised up off the floor. Ordinarily, mice will avoid open spaces to minimize the risk of being seen by predators, and spend far more time in the closed than in the open arms when placed in the elevated plus maze.

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